Nutritional value of duckweeds (Lemnaceae) as human food

Cytotoxicity, chemical, and nutritional profile evaluation of biomass extracts of the Lemna aequinoctialis (duckweed) aquatic plant

Lemna aequinoctialis (duckweed) is the smallest and fast-growing aquatic plant species producing protein-rich biomass with high protein nutritional value, phytoremediation capacity, and nutrient removal from wastewater. Duckweed may also be used as a new potential bioreactor for biological products, such as vaccines, antibodies, and pharmaceutical proteins. Based upon the potential importanc of L. aequinoctialis in phytoremediation and as a bioreactor the aim of this study was to (1) characterize the chemical and nutritional profiles of L. aequinoctialis biomass utilizing an integrated multi-trophic aquaculture system (IMTA) and a pond, and (2) investigate the cytotoxic potential of different concentrations of organic extracts and fractions using the MTT bioassay. EDXRF and ICP-MS analyses indicated the presence of trace elements in lower amounts in relation to the biomass of L. aequinoctialis in the lagoon, emphasizing the importance of plant inclusion management to reduce bioaccumulation of these elements. Analysis of mineral profiles, fatty acids, and amino acids indicated a satisfactory nutritional composition for the use of biomass as a bioproduct. Pigment analysis showed a high concentration of carotenoids, especially astaxanthin. After standardizing the controls, the MTT cell viability test was carried out utilizing rat hepatoma cell line (HTC), which are metabolizing cells that were treated with aqueous or ethanolic extracts and the dichloromethane, ethyl acetate, and methanol fractions at different concentrations. No apparent cytotoxic potential was observed following treatments, since there was no significant reduction in cell viability. Therefore, this study provides information regarding the biomass of L. aequinoctialis derived from the IMTA system, which might support further research into the application of this species as a bioproduct.

Duckweed protein: Extraction, modification, and potential application

Discovering alternative protein sources that are both nutritious and environmentally friendly is essential to meet the growing global population's needs. Duckweed offers promise due to its cosmopolitan distribution, rapid growth, high protein content, and scalability from household tanks to large lagoons without requiring arable land that competes for the major crops. Rich in essential amino acids, particularly branched-chain amino acids, duckweed supports human health. Extraction methods, such as ultrasound and enzymatic techniques, enhance protein yield compared to traditional methods. However, low protein solubility remains a challenge, addressed by protein modification techniques (physical, chemical, and biological) to broaden its applications. Duckweed proteins hold potential as functional food ingredients due to their unique physicochemical properties. This review also includes patents and regulations related to duckweed protein, filling a gap in current literature. Overall, duckweed presents a sustainable protein source with a lower environmental impact compared to conventional crops.

Screening potential antileukemia agents from duckweed: Integration of chemical profiling, network pharmacology, and experimental validation

INTRODUCTION

The identification of active dietary flavonoids in food is promising for novel drug discovery. The active ingredients of duckweed (a widely recognized food and herb with abundant flavonoids) that are associated with acute myeloid leukemia (AML) have yet to be identified, and their underlying mechanisms have not been elucidated.

OBJECTIVES

The objective of this study was to identify novel constituents exhibiting antileukemia activity in duckweed through the integration of chemical profiling, network pharmacology, and experimental validation.

METHODS

First, high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was used to characterize the primary constituents of duckweed. Subsequently, AML cell-xenograft tumor models were used to validate the anticancer effect of duckweed extract. Furthermore, network pharmacology analysis was conducted to predict the potential active compounds and drug targets against AML. Lastly, based on these findings, two monomers (apiin and luteoloside) were selected for experimental validation.

RESULTS

A total of 17 compounds, all of which are apigenin and luteolin derivatives, were identified in duckweed. The duckweed extract significantly inhibited AML cell growth in vivo. Furthermore, a total of 88 targets for duckweed against AML were predicted, with key targets including PTGS2, MYC, MDM2, VEGFA, CTNNB1, CASP3, EGFR, TP53, HSP90AA1, CCND1, MMP9, TNF, and MAPK1. GO and KEGG pathway enrichment analyses indicated that these targets were primarily involved in the apoptotic signaling pathway. Lastly, both apiin and luteoloside effectively induced apoptosis through CASP3 activation, and this effect could be partially reversed by a caspase inhibitor (Z-VAD).

CONCLUSION

Duckweed extract has an antileukemic effect, and apiin derived from duckweed shows potential as a treatment for AML.

Optimization of Hoagland solution macro-elements as a culture media, for increasing protein content of duckweeds (Lemna minor)

This study aimed to increase the protein content of duckweed, a promising alternative to animal proteins and a sustainable source of plant protein cultivated via soilless agriculture, by manipulating the culture medium conditions (Hoagland solution). The contribution percentages of KH2PO4 and Ca(NO3)2, pivotal macro-elements in Hoagland solution affecting duckweed protein content, were determined using Plackett-Burman factorial design as 33.06 % and 36.61 %, respectively. Additionally, optimization was conducted employing response surface methodology, incorporating pH alongside KH2PO4 and Ca(NO3)2. Under optimal conditions of 3.92 mM KH2PO4, 7.95 mM Ca(NO3)2, and 7.22 pH, the protein content of duckweed increased significantly, reaching 51.09 % from 39.81 %. The duckweed cultivated in modified Hoagland solution exhibited protein content of 41.74 %, while duckweed grown in commercial Hoagland solution displayed protein content of 33.01 %. This study showed protein content of duckweed could significantly increase according to the growth medium and showcasing its potential as a sustainable source of plant protein.

A review and outlook on expression of animal proteins in plants

This review delves into the multifaceted technologies, benefits and considerations surrounding the expression of animal proteins in plants, emphasizing its potential role in advancing global nutrition, enhancing sustainability, while being mindful of the safety considerations. As the world's population continues to grow and is projected to reach 9 billion people by 2050, there is a growing need for alternative protein sources that can meet nutritional demands while minimizing environmental impact. Plant expression of animal proteins is a cutting-edge biotechnology approach that allows crops to produce proteins traditionally derived from animals, offering a sustainable and resource-efficient manner of producing these proteins that diversifies protein production and increases food security. In the United States, it will be important for there to be clear guidance in order for these technologies to reach consumers. As consumer demand for sustainable and alternative food sources rise, biotechnologies can offer economic opportunities, making this emerging technology a key player in the market landscape.

Duckweed: Beyond an Efficient Plant Model System

Duckweed (Lemnaceae) rises as a crucial model system due to its unique characteristics and wide-ranging utility. The significance of physiological research and phytoremediation highlights the intricate potential of duckweed in the current era of plant biology. Special attention to duckweed has been brought due to its distinctive features of nutrient uptake, ion transport dynamics, detoxification, intricate signaling, and stress tolerance. In addition, duckweed can alleviate environmental pollutants and enhance sustainability by participating in bioremediation processes and wastewater treatment. Furthermore, insights into the genomic complexity of Lemnaceae species and the flourishing field of transgenic development highlight the opportunities for genetic manipulation and biotechnological innovations. Novel methods for the germplasm conservation of duckweed can be adopted to preserve genetic diversity for future research endeavors and breeding programs. This review centers around prospects in duckweed research promoting interdisciplinary collaborations and technological advancements to drive its full potential as a model organism.

An Ionic Liquid-Based Biorefinery Approach for Duckweed Utilization

This study establishes a foundation for the ionic liquid (IL) pretreatment of duckweed biomass. An optimized IL-based process was designed to exploit the unique properties of duckweed including efficient metal removal, potential starch accumulation, and protein accumulation. Two ILs, namely, dimethylethanolammonium formate ([DMEtA][HCOO]) and N,N-dimethylbutylammonium hydrogen sulfate ([DMBA][HSO4]), were investigated for the pretreatment of two duckweed species (Spirodela polyrhiza and Lemna minor). The evaluation focused on starch recovery, sugar release, protein recovery, and metal extraction capabilities. [DMEtA][HCOO] demonstrated near-quantitative starch recoveries at 120 °C, while [DMBA][HSO4] showed similar performance at 90 °C within a reaction time of 2 h. Saccharification yields for most pulps exceeded 90% after 8 h of hydrolysis, outperforming "traditional" lignocellulosic biomasses such as miscanthus or sugarcane bagasse. Approximately 50 and 80 wt % of the protein were solubilized in [DMEtA][HCOO] and [DMBA][HSO4], respectively, while the remaining protein distributed between the pulp and lignin. However, the solubilized protein in the IL could not be recovered due to its low molecular weight. Regarding metal extraction, [DMEtA][HCOO] demonstrated higher efficiency, achieving 81% removal of Ni from Lemna minor's pulps, whereas [DMBA][HSO4] extracted only 28% of Ni with slightly higher pulp concentrations. These findings indicate the need for further optimization in concurrent metal extraction using ILs.

Cellulose Nanocrystals and Lignin Nanoparticles Extraction from Lemna minor L.: Acid Hydrolysis of Bleached and Ionic Liquid-Treated Biomass

Using biomass to develop and obtain environmentally friendly and industrially applicable biomaterials is increasingly attracting global interest. Herein, cellulose nanocrystals (CNCs) and lignin nanoparticles (LNPs) were extracted from Lemna minor L., a freshwater free-floating aquatic species commonly called duckweed. To obtain CNCs and LNPs, two different procedures and biomass treatment processes based on bleaching or on the use of an ionic liquid composed of triethylammonium and sulfuric acid ([TEA][HSO4]), followed by acid hydrolysis, were carried out. Then, the effects of these treatments in terms of the thermal, morphological, and chemical properties of the CNCs and LNPs were assessed. The resulting nanostructured materials were characterized by using Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) spectroscopy, thermo-gravimetric analysis (TGA), and scanning electron microscopy (SEM). The results showed that the two methodologies applied resulted in both CNCs and LNPs. However, the bleaching-based treatment produced CNCs with a rod-like shape, length of 100-300 nm and width in the range of 10-30 nm, and higher purity than those obtained with ILs that were spherical in shape. In contrast, regarding lignin, IL made it possible to obtain spherical nanoparticles, as in the case of the other treatment, but they were characterized by higher purity and thermal stability. In conclusion, this research highlights the possibility of obtaining nanostructured biopolymers from an invasive aquatic species that is largely available in nature and how it is possible, by modifying experimental procedures, to obtain nanomaterials with different morphological, purity, and thermal resistance characteristics.

The evolution of the duckweed ionome mirrors losses in structural complexity

BACKGROUND AND AIMS

The duckweeds (Lemnaceae) consist of 36 species exhibiting impressive phenotypic variation, including the progressive evolutionary loss of a fundamental plant organ, the root. Loss of roots and reduction of vascular tissues in recently derived taxa occur in concert with genome expansions of ≤14-fold. Given the paired loss of roots and reduction in structural complexity in derived taxa, we focus on the evolution of the ionome (whole-plant elemental contents) in the context of these fundamental changes in body plan. We expect that progressive vestigiality and eventual loss of roots might have both adaptive and maladaptive consequences that are hitherto unknown.

METHODS

We quantified the ionomes of 34 accessions in 21 species across all duckweed genera, spanning 70 Myr in this rapidly cycling plant (doubling times are as rapid as ~24 h). We related both micro- and macroevolutionary ionome contrasts to body plan remodelling and showed nimble microevolutionary shifts in elemental accumulation and exclusion in novel accessions.

KEY RESULTS

We observed a robust directional trend in calcium and magnesium levels, decreasing from the ancestral representative Spirodela genus towards the derived rootless Wolffia, with the latter also accumulating cadmium. We also identified abundant within-species variation and hyperaccumulators of specific elements, with this extensive variation at the fine (as opposed to broad) scale.

CONCLUSIONS

These data underscore the impact of root loss and reveal the very fine scale of microevolutionary variation in hyperaccumulation and exclusion of a wide range of elements. Broadly, they might point to trade-offs not well recognized in ionomes.

Lemna minor: Unlocking the Value of This Duckweed for the Food and Feed Industry

Duckweed (Lemna minor L.) is a small floating aquatic plant that has an important economic impact in several industrial areas. With its high biomass production, reasonable protein content, and resilience to several climates, it has been attracting increasing interest for potential use in animal and human food systems. Historically consumed in southwest Asia, this duckweed is now gaining attention as a potential novel food in Europe. This manuscript explores the contributions of duckweed to various food and feed industries, including aquaculture and livestock, while also pointing out the incipient research carried out for human consumption. Most importantly, it highlights the potential of Lemna minor as a vegetable for future human consumption whether eaten whole or through extraction of its nutrients.

Characterization of Bioactive Metabolites and Antioxidant Activities in Solid and Liquid Fractions of Fresh Duckweed (Wolffia globosa) Subjected to Different Cell Wall Rupture Methods

Fresh Wolffia globosa, the smallest flowering plant well-known for its favorable nutrient composition and rich content of bioactive compounds, was subjected to boiling, freeze-thawing, and mechanical crushing to reduce its excessive (95-96%) moisture level and consequent drying time. The resultant three wolffia matrixes were filtered through a plankton net to fractionate into the residue and the filtrate. The proximate composition, bioactive metabolites, antioxidant activity, and characterization of bioactive metabolites by LC-ESI-QTOF-MS/MS and Fourier transform infrared spectroscopy were made from oven-dried residues and filtrates. Among residues, crude protein (29.84%), crude lipid (5.77%), total carotenoids (TCC; 722.8 μg/g), and vitamin C (70.02 mg/100 g) were the highest (p < 0.05) for freeze-thawing against higher ash (7.99%), total phenolic content (TPC; 191.47 mg GAE g-1 dry weight), total flavonoid content (TFC; 91.54 mg QE g-1 dry weight), DPPH activity (47.46%), and ferric reducing antioxidant power (FRAP) activity (570.19 μmol FeSO4 equiv/mg) for the crushed counterpart and Chl-b in residues from boiling. No significant variation was evident in the total tannin content (TTC). Among filtrates, higher total phenolic content (773.29 mg GAE g-1 dry weight), TFC (392.77 mg QE g-1 dry weight), TTC (22.51 mg TAE g-1), and antioxidant activity as DPPH activity (66.46%) and FRAP (891.62 μmol FeSO4 equiv/mg) were evident for boiling, while that from crushing exhibited the highest TCC (1997.38 μg/g DM). LC-ESI-QTOF-MS/MS analysis identified 72 phenolic compounds with the maximum in residue (33) and filtrate (33) from freeze-thawing, followed by crushing (18 and 19) and boiling (14 and 13) in order, respectively. The results indicated that the predrying cell rupturing method significantly impacted quantitative, as well as qualitative compositions of residues and filtrates from fresh wolffia.

Contrasting patterns of 5S rDNA repeats in European and Asian ecotypes of greater duckweed, Spirodela polyrhiza (Lemnaceae)

Ribosomal DNA (rDNA) contains highly conserved, specifically organized sequences encoding ribosomal RNAs (rRNAs) separated by variable non-transcribed intergenic spacers (NTSs) and is abundant in eukaryotic genomes. These characteristics make the rDNA an informative molecular target to study genome organization, molecular evolution, and phylogenetics. In this study, we characterized the 5S rDNA repeats in the greater duckweed Spiroldela polyrhiza, a species known for its small size, rapid growth, highly conserved genome organization, and low mutation rate. Sequence analysis of at least 12 individually cloned PCR fragments containing the 5S rDNA units for each of six ecotypes that originated from Europe (Ukraine) and Asia (China) revealed two distinct types of 5S rDNA repeats containing NTSs of different lengths and nucleotide compositions. The shorter 5S rDNA repeat units had a highly homogeneous 400-bp NTS, with few ecotype- or region-specific single-nucleotide polymorphisms (SNPs). The longer 5S rDNA units had NTSs of 1056-1084 bp with characteristic intra- and inter-genomic variants due to specific SNPs and insertions/deletions of 4-15-bp DNA elements. We also detected significant variability in the ratio of short/long 5S rDNA variants between ecotypes of S. polyrhiza. The contrasting dynamics of the two types of 5S rDNA units, combined with the unusually low repeat copy number (for plants) in S. polyrhiza (46-220 copies per genome), shows that this species could serve as an excellent model for examining the mechanisms of concerted evolution and functional significance of rDNA variability.

Duckweed application in nature-based system for water phytoremediation and high-value coproducts at family agrisystem from a circular economy perspective

Duckweeds are widely recognized for their efficiency in the phytoremediation of agricultural and industrial effluents. This study had two main objectives: 1) Implement a Nature-based Solutions (NBS) utilizing the environmental services of duckweeds to improve water quality through phytoremediation in small fish farms; 2) Analysis of duckweeds biomass produced in these fish farms to develop coproducts from a circular economy perspective in family agrisystem in Brazilian Atlantic Forest. The effectiveness of the phytoremediation system was assessed by the reduction of the Trophic State Index (TSI). Phytoremediation in small fish farming NBS was implemented using Clarias gariepinus, employing two different managements approaches: (i) System I - L. minor cultured every 15 days, with biomass harvest and effluent analysis conducted in each cycle over 60 days; (ii) System II - L. minor cultured every 30 days, following a similar cycle and analysis. Additionally, effluent from fish production underwent testing for phytoremediation in a batch system within a climate-controlled laboratory. L. minor demonstrated efficiency in System II, leading to a reduction of the TSI. The dry biomass of the plants emerged as a viable source of amino acid for application in functional foods and feed or nutraceuticals. The findings underscore the potential integration of L. minor into the NBS system and the generation of new co-products from circular production. In addition to its effective phyto- remediation properties, L. minor's dry biomass exhibited appealing characteristics, with elevated levels of crude protein, minerals, fatty acids, and carotenoids. This positions L. minor as a promising candidate for developing bioproducts tailored for functional foods and nutraceuticals. This underscores the potential of duckweeds to produce valuable nutritional compounds beyond their remediation capabilities.

Physiological adaptation to irradiance in duckweeds is species and accession specific and depends on light habitat niche

Duckweeds span 36 species of free-floating aquatic organisms with body sizes ranging from 2 mm to 10 mm, where each plant body plan is reduced to a largely leaf-like structure. As an emerging crop, their fast growth rates offer potential for cultivation in closed systems. We describe a novel UK collection derived from low light (dLL) or high light (dHL) habitats, profiled for growth, photosynthesis, and photoprotection (non-photochemical quenching, NPQ) responses. Twenty-three accessions of three Lemna species and one Spirodela polyrhiza were grown under relatively low light (LL: 100 μmol m-2 s-1) and high light (HL: 350 μmol m-2 s-1) intensities. We observed broad within- and between-species level variation in photosynthesis acclimation. Duckweeds grown under HL exhibited a lower growth rate, biomass, chlorophyll, and quantum yield of photosynthesis. In HL compared with LL, carotenoid de-epoxidation state and NPQ were higher, whilst PSII efficiency (φPSII) and Chl a:b ratios were unchanged. The dLL plants showed relatively stronger acclimation to HL compared with dHL plants, especially Lemna japonica accessions. These achieved faster growth in HL with concurrent higher carotenoid levels and NPQ, and less degradation of chlorophyll. We conclude that these data support local adaptation to the light environment in duckweed affecting acclimation in controlled conditions.

Enhancing biomass production and biochemical compositions of Spirodela polyrhiza through superhydrophobic cultivation platforms at low light intensity

Duckweed, a floating macrophyte, has attracted interest in various fields such as animal feedstocks and bioenergy productions. Its enriched nutritional content and rapid growth rate make it particularly promising. However, common laboratory cultures of duckweed often experience fronds layering, diminishing the efficiency of sunlight capturing due to limited surface area on conventional cultivation platforms. In this work, we aimed to address the issue of fronds layering by introducing a novel cultivation platform - a superhydrophobic coated acrylic sheet. The sheet was prepared by spray-coating a suspension of beeswax and ethanol, and its effectiveness was evaluated by comparing the growth performance of giant duckweed, Spirodela polyrhiza, on this platform with that on a modified version. The superhydrophobic coated acrylic sheet (SHPA) and its variant with a metal mesh added (SHPAM) were employed as growing platforms, with a glass jar serving as the control. The plantlets were grown for 7 days with similar growth conditions under low light stress (25 μmol/m2/s). SHPAM demonstrated superior growth performance, achieving a mass gain of 102.12 ± 17.18 %, surpassing both SHPA (89.67 ± 14.97 %) and the control (39.26 ± 8.94 %). For biochemical compositions, SHPAM outperformed in chlorophyll content, protein content and lipid content. The values obtained were 1.021 ± 0.076 mg/g FW, 14.59 ± 0.58 % DW and 6.21 ± 0.75 % DW respectively. Therefore, this work proved that incorporation of superhydrophobic coatings on a novel cultivation platform significantly enhanced the biomass production of S. polyrhiza. Simultaneously, the biochemical compositions of the duckweeds were well-maintained, showcasing the potential of this approach for optimized duckweed cultivation.

The Duckbot: A system for automated imaging and manipulation of duckweed

Laboratory automation can boost precision and reproducibility of science workflows. However, current laboratory automation systems are difficult to modify for custom applications. Automating new experiment workflows therefore requires development of one-off research platforms, a process which requires significant time, resources, and experience. In this work, we investigate systems to lower the threshold to automation for plant biologists. Our approach establishes a direct connection with a generic motion platform to support experiment development and execution from a computational notebook environment. Specifically, we investigate the use of the open-source tool-changing motion platform Jubilee controlled using Jupyter notebooks. We present the Duckbot, a machine customized for automating laboratory research workflows with duckweed, a common multicellular plant. The Duckbot comprises (1) a set of end-effectors relevant for plant biology, (2) software modules which provide flexible control of these tools, and (3) computational notebooks which make use of these tools to automate duckweed experiments. We demonstrate the Duckbot's functionality by automating a particular laboratory research workflow, namely, duckweed growth assays. The Duckbot supports setting up sample plates with duckweed and growth media, gathering image data, and conducting relevant data analysis. We discuss the opportunities and limitations for developing custom laboratory automation with this platform and provide instructions on usage and customization.

Enzymatic Hydrolysis of Water Lentil (Duckweed): An Emerging Source of Proteins for the Production of Antihypertensive Fractions

Water lentil (Duckweed), an emerging protein source, is a small floating aquatic plant with agronomic and compositional characteristics rendering it a potential source of bioactive peptides. However, enzymatic hydrolysis of duckweeds has only been carried out to assess the antioxidant and antimicrobial activities of the hydrolysates. The main objectives of this study were to perform enzymatic hydrolysis of duckweed powder utilizing several enzymes and to evaluate the final antihypertensive activity of the fractions. Duckweed powder was efficiently hydrolyzed by pepsin, chymotrypsin, papain and trypsin, with degree of hydrolysis ranging from 3% to 9%, even without prior extraction and concentration of proteins. A total of 485 peptide sequences were identified in the hydrolysates and only 51 were common to two or three hydrolysates. It appeared that phenolic compounds were released through enzymatic hydrolyses and primarily found in the supernatants after centrifugation at concentrations up to 11 mg gallic acid/g sample. The chymotryptic final hydrolysate, the chymotryptic supernatant and the papain supernatant increased the ACE inhibitory activity by more than 6- to 8-folds, resulting in IC50 values ranging between 0.55 to 0.70 mg peptides/mL. Depending on the fraction, the ACE-inhibition was attributed to either bioactive peptides, phenolic compounds or a synergistic effect of both. To the best of our knowledge, this was the first study to investigate the enzymatic hydrolysis of duckweed proteins to produce bioactive peptides with therapeutic applications in mind.

Selenite (IV) and selenate (VI) uptake and accumulation capacity of Lemna minor L. from an aquatic medium

The uptake of sodium selenite (Se(IV)) and sodium selenate (Se(VI)) from aqueous medium by Lemna minor L. and the influence of different Se concentrations on its growth, morphological and ultrastructural characteristics were studied. L. minor was grown at different concentrations (1, 3, 5 and 10 mg L-1) of Se(IV) and Se(IV). The Se(IV) concentration in the plant tissue ranged between 77.7 (± 4.3) to 453 (± 0) mg kg-1 DW. The Se(VI) concentration in plant tissues ranged between 117 (± 11) to 417 (± 2) mg kg-1 DW. The highest bioconcentration factor for Se(VI) was 127 (± 7) at 3 mg/L, with a Se removal efficiency of 44%. For Se(IV), the highest bioconcentration factor was 77.7 (± 4.3) at 1 mg L-1, which had a Se removal efficiency of 23%. Growth of L. minor was suppressed at 10 mg L-1 Se in both forms. The addition of Se promoted the formation of starch granules in L. minor which occupied a chloroplast area of 74% for Se(IV) and 77% for Se(VI). The efficient uptake of both Se forms by L. minor indicates the potential application of this species for phytoremediation of Se laden wastewaters and its use as an alternative feedstock in biofuel production.

Duckweed protein as an alternative plant-based protein source for dog and cat dry diets

Duckweed has attracted increasing attention as a high-quality and sustainable novel plant-based protein source. However, little research has been conducted in dogs and cats. We evaluated the effects of inclusion of duckweed protein (Lemna; MCSelect; Parabel; Vero Beach, FL) primarily in replacement of pea protein in dog diets at 0%, 5%, and 10% and cat diets at %, 10%, and 15% on stool quality, nutrient digestibility, and palatability. We hypothesized that duckweed protein would be a viable protein source in both dog and cat diets by showing no detriment to nutritional outcomes. All feeding tests were conducted at an independent research facility (Susquehanna, PA). A standard 2-bowl palatability test over a 2-d period was conducted with adult animals (n = 30 each) to determine intake ratio between test diets (duckweed-containing diets) and control diets (0% duckweed protein). Apparent total tract nutrient digestibility was conducted with 18 adult dogs and 21 adult cats (n = 6 to 7 per diet) with 5 d of diet acclimation followed by 5 d of total fecal collection. Stool quality was evaluated on a 1 to 5 scale where 1 = non-formed or diarrhea and 5 = hard, formed. Palatability data were analyzed using paired t-test (daily consumption) and chi-square test (first choice). All other data were analyzed by ANOVA and contrast (SAS version 9.4). For cats, 10% duckweed had greater (P < 0.05) palatability than control, while no difference was observed between 15% duckweed protein and control. For dogs, 5% and 10% duckweed protein had (P < 0.05) lower palatability, demonstrating a preference to control. Both cats and dogs fed duckweed diets had acceptable stool quality (Mean = 3.4 and 3.3, respectively). No detriments in nutrient digestibility were observed in dogs fed 5% and 10% duckweed protein; however, cats fed 10% and 15% duckweed protein had (P < 0.05) lower dry matter, protein, and energy digestibility vs. control. In conclusion, the data collected indicate that duckweed can be a viable replacement for other plant-based proteins in dog diets at inclusion levels up to 10%; more development is needed for duckweed protein inclusion into cat diets.

From bytes to bites: Advancing the food industry with three-dimensional food printing

The rapid advancement of three-dimensional (3D) printing (i.e., a type of additive manufacturing) technology has brought about significant advances in various industries, including the food industry. Among its many potential benefits, 3D food printing offers a promising solution to deliver products meeting the unique nutritional needs of diverse populations while also promoting sustainability within the food system. However, this is an emerging field, and there are several aspects to consider when planning for use of 3D food printing for large-scale food production. This comprehensive review explores the importance of food safety when using 3D printing to produce food products, including pathogens of concern, machine hygiene, and cleanability, as well as the role of macronutrients and storage conditions in microbial risks. Furthermore, postprocessing factors such as packaging, transportation, and dispensing of 3D-printed foods are discussed. Finally, this review delves into barriers of implementation of 3D food printers and presents both the limitations and opportunities of 3D food printing technology.

On the rise: Development of a multi-tiered, indoor duckweed cultivation system

Duckweed species (Lemnaceae) are suitable for remediation and valorization of agri-feed industry wastewaters and therefore can contribute to a more sustainable, circular economy where waste is a resource. Industrial applications will, however, require space efficient cultivation methods that are not affected by prevailing weather conditions. Here, the development and operation of a multi-tiered duckweed bioreactor is described. The developed prototype bioreactor depicted in this paper is composed of four cultivation layers (1 m2 each) with integrated LED lighting (generating up to 150 μmol m-2  s-1 ), a system of pumps and valves to manage the recirculatory flow (2.5 L min-1 ) of wastewater, and an automatic harvesting system. Using a nutrient poor medium, good growth of the duckweed species Lemna minor was achieved in the bioreactor, and this was matched by strong nutrient depletion from the medium, especially for phosphorus (45-mg total phosphorus [TP] removed per m-2  day-1 ). A fully automatic harvesting arm reliably captured similar amounts of duckweed biomass across multiple harvesting cycles, revealing a future scenario whereby labor and interventions by human operators are minimized. Further developments to advance the system towards fully automated operation will include, for example, the use of specific nutrient sensors to monitor and control medium composition. It is envisaged that multi-tiered, indoor bioreactors can be employed in the agri-feed industry where wastewaters are, in many cases, continuously generated throughout the year and need remediating immediately to avoid costly storage. Given the extensive use of automation technology in conventional wastewater treatment plants, multi-tiered duckweed bioreactors can be realistically integrated within the operating environment of such treatment plants. PRACTITIONER POINTS: Duckweed is suitable for remediation and valorization of agri-feed wastewater. Industrial duckweed applications require space efficient cultivation methods. Development and operation of a multi-tiered duckweed bioreactor is detailed. Flow dynamics and automatic harvesting in the bioreactor are optimized. It is concluded that a multi-tiered bioreactor can be used in industry.

Optimization of Water Lentil (Duckweed) Leaf Protein Purification: Identification, Structure, and Foaming Properties

Water lentil, commonly known as duckweed, is an aquatic plant with great agronomic potential, as it can double its biomass in less than 24 h and contains up to 45% leaf proteins on a dry matter basis. However, extracting proteins from leaves is an arduous process due to the complexity of the matrix, which limits their uses in the food industry. In this study, water lentil protein extraction by solubilization was maximized using response surface methodology. By heating at 80 °C at pH 11 with a water lentil powder concentration of 2% or 4% for 2 h, up to 77.8% of total proteins were solubilized. Then, by precipitating the solubilized proteins at pH 4, a protein purity of 57.6% combined with a total protein yield of 60.0% was achieved. To the best of our knowledge, this is the highest leaf protein extraction yield reported in the literature with such protein purity. Proteomics analyses showed that the protein concentrate was composed of around 85.0% RubisCO, and protein structure analyses using ATR-FTIR and DSC were linked to a high protein solubility in water at pH 7. Moreover, a 1.5% protein solution of the protein concentrate at pH 7 showed excellent foaming properties compared to a 10.3% protein egg white solution. It had a superior foaming capacity (194% vs. 122%, respectively) for the same foaming stability after 60 min, which confirms water lentil proteins' potential for human nutrition and food formulation.

Optimum aquaculture and drying conditions for Wolffia arrhiza (L.) Wimn

This study aimed to investigate the effects of aquaculture and the optimum conditions for drying duckweed plants to maintain the highest nutritional value and bioactive substances. Protein quantification was used to screen duckweed plants subjected to the 14 treatments under aquaculture conditions. Proximate analysis of three aquaculture conditions showed the highest quantification of protein. Moreover, these samples were analyzed for total phenolics, flavonoids, and chlorophylls. The optimal drying conditions for duckweed plants with the highest protein content were determined using a factorial design with three temperature and time parameters. The results showed that the duckweed under aquaculture conditions in an outdoor cement pond with hydroponic electrical conductivity (EC) of 0.5 mS/cm contained the highest protein at 41.81 ± 3.40%. Moreover, proximate analysis of this sample showed fat, fiber, moisture, ash, and carbohydrate contents of 1.99 ± 0.08%, 4.46 ± 0.71%, 3.29 ± 0.17%, 22.06 ± 0.07% and 14.12 ± 1.63%, respectively. In addition, the optimum drying conditions for this sample were 50 °C and a drying time of 6 h. Under optimum drying conditions, this sample showed total phenolics, flavonoids, and chlorophylls contents of 55.28 ± 1.35 (μg GAE/g dry weight), 159.84 ± 6.65 (μg catechin equivalent [QE]/g dry weight) and 22.91 ± 0.15 (mg/g dry weight), respectively. In conclusion, the dried duckweed under aquaculture conditions in an outdoor cement pond with hydroponic EC 0.5 mS/cm contained the highest contents of proteins, total phenolics, total flavonoids, and total chlorophyll, which could be used as functional ingredients in health food products.

Lemnaceae as Novel Crop Candidates for CO2 Sequestration and Additional Applications

Atmospheric carbon dioxide (CO2) is projected to be twice as high as the pre-industrial level by 2050. This review briefly highlights key responses of terrestrial plants to elevated CO2 and compares these with the responses of aquatic floating plants of the family Lemnaceae (duckweeds). Duckweeds are efficient at removing CO2 from the atmosphere, which we discuss in the context of their exceptionally high growth rates and capacity for starch storage in green tissue. In contrast to cultivation of terrestrial crops, duckweeds do not contribute to CO2 release from soils. We briefly review how this potential for contributions to stabilizing atmospheric CO2 levels is paired with multiple additional applications and services of duckweeds. These additional roles include wastewater phytoremediation, feedstock for biofuel production, and superior nutritional quality (for humans and livestock), while requiring minimal space and input of light and fertilizer. We, furthermore, elaborate on other environmental factors, such as nutrient availability, light supply, and the presence of a microbiome, that impact the response of duckweed to elevated CO2. Under a combination of elevated CO2 with low nutrient availability and moderate light supply, duckweeds' microbiome helps maintain CO2 sequestration and relative growth rate. When incident light intensity increases (in the presence of elevated CO2), the microbiome minimizes negative feedback on photosynthesis from increased sugar accumulation. In addition, duckweed shows a clear propensity for absorption of ammonium over nitrate, accepting ammonium from their endogenous N2-fixing Rhizobium symbionts, and production of large amounts of vegetative storage protein. Finally, cultivation of duckweed could be further optimized using hydroponic vertical farms where nutrients and water are recirculated, saving both resources, space, and energy to produce high-value products.

Wolffia globosa-Based Nutritious Snack Formulation with High Protein and Dietary Fiber Contents

Wolffia globosa (W. globosa) or duckweed is a small aquatic plant with high protein, dietary fiber, and lipid contents that can be combined with food products to develop nutritious snacks as one strategy to mitigate malnutrition. Here, response surface methodology (RSM) with mixture design was used to develop snacks from W. globosa freeze-dried powder (WP). The physical properties, proximate analysis, amino acid profiles, sensory evaluation, phytochemical analysis, antioxidant properties, and genotoxicity (Ames test) of the snacks were evaluated. The optimal W. globosa snack formula was 64% glutinous rice flour, 10% tapioca flour, and 26% WP, giving a highly desirable liking score of 1.00. Addition of WP increased crude protein, essential amino acids, and dietary fiber compared with the control snack by 51%, 147%, and 83%, respectively. According to the Thai recommended daily intakes, the developed W. globosa snack had high protein and dietary fiber. Phytochemical contents and antioxidant activities of the W. globosa snack such as total phenolic contents (TPCs), total flavonoid contents (TFCs), ferric ion reducing antioxidant power (FRAP) activity, and oxygen radical absorbance capacity (ORAC) activity were significantly higher than the control snack. The novel combination of WP with snack product ingredients greatly enhanced nutritional value.

Characterisation of a Spontaneous Mutant of Lemna gibba G3 (Lemnaceae)

A spontaneous mutant of the duckweed Lemna gibba clone no. 7796 (known as strain G3, WT) was discovered. In this mutant clone, L. gibba clone no. 9602 (mt), the morphological parameters (frond length, frond width, root length, root diameter) indicated an enlarged size. A change in the frond shape was indicated by the decreased frond length/width ratio, which could have taxonomic consequences. Several different cell types in both the frond and the root were also enlarged. Flow cytometric measurements disclosed the genome size of the WT as 557 Mbp/1C and that of the mt strain as 1153 Mbp/1C. This represents the results of polyploidisation of a diploid clone to a tetraploid one. The mutant clone flowered under the influence of long day-treatment in half-strength Hutner's medium in striking contrast to the diploid WT. Low concentration of salicylic acid (<1 µM) induced flowering in the tetraploid mutant but not in the diploid plants. The transcript levels of nuclear-encoded genes of the photosynthetic apparatus (CAB, RBCS) showed higher abundance in light and less dramatic decline in darkness in the mt than in WT, while this was not the case with plastid-encoded genes (RBCL, PSAA, PSBA, PSBC).

Sustainable Stress Management: Aquatic Plants vs. Terrestrial Plants

The Indo-German Science and Technology Centre (IGSTC) funded an Indo-German Workshop on Sustainable Stress Management: Aquatic plants vs. Terrestrial plants (IGW-SSMAT) which was jointly organized at the Friedrich Schiller University of Jena, Germany from 25 to 27 July 2022 by Prof. Dr. Ralf Oelmüller, Friedrich Schiller University of Jena, Germany as the German coordinator and Dr. K. Sowjanya Sree, Central University of Kerala, India as the Indian Coordinator. The workshop constituted researchers working in this field from both India and Germany and brought together these experts in the field of sustainable stress management for scientific discussions, brainstorming and networking.

Diversity of duckweed (Lemnaceae) associated yeasts and their plant growth promoting characteristics

The diversity of duckweed (Lemnaceae) associated yeasts was studied using a culture-dependent method. A total of 252 yeast strains were isolated from 53 duckweed samples out of the 72 samples collected from 16 provinces in Thailand. Yeast identification was conducted based on the D1/D2 region of the large subunit (LSU) rRNA gene sequence analysis. It revealed that 55.2% and 44.8% yeast species were Ascomycota and Basidiomycota duckweed associated yeasts, respectively. Among all, Papiliotrema laurentii, a basidiomycetous yeast, was found as the most prevalent species showing a relative of frequency and frequency of occurrence of 21.8% and 25%, respectively. In this study, high diversity index values were shown, indicated by the Shannon-Wiener index (H'), Shannon equitability index (EH) and Simpson diversity index (1-D) values of 3.48, 0.86 and 0.96, respectively. The present results revealed that the yeast community on duckweed had increased species diversity, with evenness among species. Principal coordinate analysis (PCoA) revealed no marked differences in yeast communities among duckweed genera. The species accumulation curve showed that the observed species richness was lower than expected. Investigation of the plant growth promoting traits of the isolated yeast on duckweed revealed that 178 yeast strains produced indole-3-acetic acid (IAA) at levels ranging from 0.08-688.93 mg/L. Moreover, siderophore production and phosphate solubilization were also studied. One hundred and seventy-three yeast strains produced siderophores and exhibited siderophores that showed 0.94-2.55 activity units (AU). One hundred six yeast strains showed phosphate solubilization activity, expressed as solubilization efficiency (SE) units, in the range of 0.32-2.13 SE. This work indicates that duckweed associated yeast is a potential microbial resource that can be used for plant growth promotion.

A holistic approach toward development of plant-based meat alternatives through incorporation of novel microalgae-based ingredients

This study explored the changes in the physiochemical, textural, sensory, and functional characteristics of plant-based meat (PBM) after incorporating novel plant-based ingredients including spirulina (SPI), duck Weed (DW), and yellow Chlorella (YC). In the chromaticity evaluation, the YC group (YCI YC2, and YC3%) displayed significant differences (p < 0.05) in lightness (L*) indices as compared to the control. Whereas, based on concertation gradient of SPI microalgae (SP0.5, SP0.7, and SP1%) incorporated into PBM patties demonstrated that SPI 1 had the lowest values (p < 0.05) in redness (a*) and yellowness (b*) followed by SPI 0.7 and SPI 0.5% concentration, respectively. The concentration gradient of the YC group indicated that YC3 was intended to be the highest crude fat value followed by YC2 and YCI. The ash content in PBM patties increased considerably (p < 0.05) as the concentration level of microalgae advanced in all treated groups. Based on the concentration level of YC incorporated microalgae into PBM patties indicated that YC 3 had the highest (p < 0.05) gumminess and chewiness while YC 1 had the lowest reported values in terms of gumminess and chewiness. Moreover, springiness and cohesiveness showed considerable differences between SPI and YC groups. In the sensory evaluation, SPI 1 showed the lowest value only in color and appearance (p < 0.05), conversely, the other sensory parameters were non-significant among all treatment groups (p > 0.05). The micronutrient in PBM presented an irregular pattern after incorporating various ingredients. However, levels were higher (p < 0.05) in the DW group (DW 0.5 DW 0.7, and DW% 1) than those in the other groups. Moreover, the SPI and YC groups showed detectable levels of diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity with, SP 1 showing the highest level of antioxidant activity. Acknowledging the limited research on PBM production, extraction technologies, and selecting various novel suitable ingredients in meat substitutes. Hence, to fill this knowledge gap an attempt has been made to incorporate various concentrations of microalgae including SPI, YC, and DW to enhance the quality and functionality of meat alternatives. To the best of our knowledge, this is the first report that describes the physiochemical, textural, sensory, and nutritional attributes of PBM incorporated with novel microalgae. Collectively these results indicate that the incorporation of SPI, DW, and YC may improve the quality of PBM without showing deleterious outcomes on the quality and functionality of the ultimate PBM products.

Terrestrial and Floating Aquatic Plants Differ in Acclimation to Light Environment

The ability of plants to respond to environmental fluctuations is supported by acclimatory adjustments in plant form and function that may require several days and development of a new leaf. We review adjustments in photosynthetic, photoprotective, and foliar vascular capacity in response to variation in light and temperature in terrestrial plants. The requirement for extensive acclimation to these environmental conditions in terrestrial plants is contrasted with an apparent lesser need for acclimation to different light environments, including rapid light fluctuations, in floating aquatic plants for the duckweed Lemna minor. Relevant features of L. minor include unusually high growth rates and photosynthetic capacities coupled with the ability to produce high levels of photoprotective xanthophylls across a wide range of growth light environments without compromising photosynthetic efficiency. These features also allow L. minor to maximize productivity and avoid problems during an abrupt experimental transfer of low-light-grown plants to high light. The contrasting responses of land plants and floating aquatic plants to the light environment further emphasize the need of land plants to, e.g., experience light fluctuations in their growth environment before they induce acclimatory adjustments that allow them to take full advantage of natural settings with such fluctuations.

A novel cultivation platform of duckweed (Lemna minor) via application of beeswax superhydrophobic coatings

Conventional establishment of laboratory cultures of duckweed Lemna minor are prepared in beakers, Erlenmeyer flasks or Schott bottles. These conventional cultivation methods limit the available surface area for growth which then causes layering of fronds that reduces the efficiency of plants in sunlight capturing. Here, acrylic sheets were spray-coated with a superhydrophobic (SHP) beeswax suspension and these coated acrylic sheets were used as a novel cultivation platform for L. minor. L. minor was grown for 7 days in conventional glass jar which acted as the control and were compared to SHP coated acrylic (SHPA) and SHP coated acrylic with aluminium mesh centrally placed (SHPAM) at similar duration and cultivation conditions. Addition of mesh was to entrap the plantlets and fixed the plantlets' position on the growing platform. The effects of cultivation platforms on growth rate and biochemical compositions of L. minor were monitored. The highest biomass growth was obtained from SHPA cultivation where the relative growth rate (RGR) was 0.0909 ± 0.014 day^-1 and the RGR was 2.17 times higher than the control. Moreover, L. minor harvested from SHPA displayed the highest values in total protein content, total carbohydrates content and crude lipid percentage. The values were 156.04 ± 12.13 mg/g, 94.75 ± 9.02 mg/g and 7.09 ± 1.14% respectively. However, the control showed the highest total chlorophyll content which was 0.7733 ± 0.042 mg/g FW. Although SHPA obtained a slightly lower chlorophyll content than the control, this growing platform is still promising as it displayed the highest growth rate as well as other biochemical composition. Hence, this study proved that the proposed method that applied superhydrophobic properties in cultivation of L. minor provided a larger surface area for L. minor to grow, which then resulted in a greater biomass production while simultaneously maintaining the quality of the biochemical compositions of duckweeds.

Safety of water lentil protein concentrate from a mixture of Lemna gibba and Lemna minor as a novel food pursuant to Regulation (EU) 2015/2283

Following a request from the European Commission, the EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA) was asked to deliver an opinion on water lentil protein concentrate from a mixture of Lemna gibba and Lemna minor as a novel food (NF) pursuant to Regulation (EU) 2015/2283. Water lentil protein concentrate is produced from two water lentil species (L. gibba and L. minor) by separation of the protein fraction of the plant material from fibres, followed by pasteurisation and spray drying. The NF consists mainly of protein, fibre, fat and ash. The applicant proposed to use the NF as a food ingredient in a variety of food categories and as a food supplement. The target population is the general population when used as a food ingredient and exclusively adults when used as a food supplement. The Panel considers that taking into account the composition of the NF and the proposed conditions of use, the consumption of the NF is not nutritionally disadvantageous. There are no concerns regarding genotoxicity of the NF. The Panel considers that the risk of the NF triggering allergic reactions is low. The Panel concludes that the NF, water lentil protein concentrate from a mixture of L. gibba and L. minor, is safe under the proposed conditions of use.

Evaluation of the Potential of Duckweed as a Human Food, Bioethanol Production Feedstock, and Antileukaemia Drug

This study evaluated the potential of duckweed as a human food, ethanol feedstock, and anticancer drug. First, the nutritional value of wild duckweed was reported for the first time. Its main composition was similar to that of artificially cultivated duckweed, and thus, wild duckweed can serve as a great human food source. In addition, high-starch duckweed induced by nutrient starvation was fermented into bioethanol. A yield of 0.262 g/g, the highest duckweed-ethanol yield reported thus far, was achieved, indicating that duckweed is an excellent feedstock for ethanol production. Finally, the anticancer effects of duckweed flavonoids (DFs) were assessed for the first time using acute myeloid leukaemia (AML) cells as models in vitro and in vivo. The results revealed that DFs possessed antileukaemia activity and were safe and effective for AML therapy. In conclusion, duckweed was demonstrated to be helpful for humans for food security, energy crisis remediation, and tumour treatment.

Duckweeds for Phytoremediation of Polluted Water

Tiny aquatic plants from the Lemnaceae family, commonly known as duckweeds, are often regarded as detrimental to the environment because of their ability to quickly populate and cover the surfaces of bodies of water. Due to their rapid vegetative propagation, duckweeds have one of the fastest growth rates among flowering plants and can accumulate large amounts of biomass in relatively short time periods. Due to the high yield of valuable biomass and ease of harvest, duckweeds can be used as feedstock for biofuels, animal feed, and other applications. Thanks to their efficient absorption of nitrogen- and phosphate-containing pollutants, duckweeds play an important role in the restorative ecology of water reservoirs. Moreover, compared to other species, duckweed species and ecotypes demonstrate exceptionally high adaptivity to a variety of environmental factors; indeed, duckweeds remove and convert many contaminants, such as nitrogen, into plant biomass. The global distribution of duckweeds and their tolerance of ammonia, heavy metals, other pollutants, and stresses are the major factors highlighting their potential for use in purifying agricultural, municipal, and some industrial wastewater. In summary, duckweeds are a powerful tool for bioremediation that can reduce anthropogenic pollution in aquatic ecosystems and prevent water eutrophication in a simple, inexpensive ecologically friendly way. Here we review the potential for using duckweeds in phytoremediation of several major water pollutants: mineral nitrogen and phosphorus, various organic chemicals, and heavy metals.

Machado L, R. Brande M, S. Heitzman B, D. Trombeta T. Bioprocess for mass production and feed utilization of Azolla pinnata in aquaculture ponds: a perspective of bioeconomy and eco-friendly technology for small farms

Aquatic plants have a high potential to be used as eco-friendly technology in fish farming effluent treatment systems. However, there is still a reduced use of the vegetable biomass produced in these treatment systems. Thus, the aim of this study was to develop an alternative feed with the aquatic plant Azolla pinnata to take advantage of plant biomass, reusing the plant to develop a new product and promote a circular economy. A. pinnata was implemented in decantation pond that receives effluents from fish farming. Samples were collected weekly at four times (0, 7, 14, and 21 days). Posteriorly, A. pinnata was processed to obtain the meal. Azolla meal was offered along with three commercial feed (24%, 28% and 32% of the crude protein) in an experiment to evaluate the zootechnical performance of tilapia in small tanks. The results indicated that A. pinnata was efficient to retention of phosphorus and nitrogen after seven days. In the experiment with animals, the treatment using commercial feed with 28% of the crude protein + Azolla showed the best efficiency rates for using the diet. Thus, the use of the A. pinnata meal was a viable alternative in the search for sustainable products to promote a bioeconomy in the small fish farms.

Broad-scale factors shaping the ecological niche and geographic distribution of Spirodela polyrhiza

The choice of appropriate independent variables to create models characterizing ecological niches of species is of critical importance in distributional ecology. This set of dimensions in which a niche is defined can inform about what factors limit the distributional potential of a species. We used a multistep approach to select relevant variables for modeling the ecological niche of the aquatic Spirodela polyrhiza, taking into account variability arising from using distinct algorithms, calibration areas, and spatial resolutions of variables. We found that, even after an initial selection of meaningful variables, the final set of variables selected based on statistical inference varied considerably depending on the combination of algorithm, calibration area, and spatial resolution used. However, variables representing extreme temperatures and dry periods were more consistently selected than others, despite the treatment used, highlighting their importance in shaping the distribution of this species. Other variables related to seasonality of solar radiation, summer solar radiation, and some soil proxies of nutrients in water, were selected commonly but not as frequently as the ones mentioned above. We suggest that these later variables are also important to understanding the distributional potential of the species, but that their effects may be less pronounced at the scale at which they are represented for the needs of this type of modeling. Our results suggest that an informed definition of an initial set of variables, a series of statistical steps for filtering and exploring these predictors, and model selection exercises that consider multiple sets of predictors, can improve determination of variables that shape the niche and distribution of the species, despite differences derived from factors related to data or modeling algorithms.

The effects of replacing wheat and soyabean meal with duckweed (Lemna minor) and including enzymes in the diet of laying hens on the yield and quality of eggs, biochemical parameters, and their antioxidant status

Duckweed is a rapidly growing aquatic plant, which could be used in the diet of laying hens to enhance carbon capture and improve land use efficiency. Digestion may be improved by supplementation with exogenous enzymes. We replaced soyabean meal and wheat with duckweed in a 10-week study with 432, 60-week-old Hy-Line W-36 layers, divided into six isocaloric and isonitrogenous dietary treatments, each with eight replicates. Two factors were investigated: first, duckweed substituted for wheat gluten meal and soyabean meal at 0, 7.5 and 15% of the diet, and second, with and without a multi-enzyme supplement (500 mg/kg). Duckweed did not affect egg output or weight, but it improved yolk color (P = 0.01) and reduced the liver enzymes aspartate aminotransferase (P = 0.04) and alanine aminotransferase (P = 0.02) in serum, suggesting hepatoprotective effects. Enzyme addition did not alter the effects of including duckweed in the diet, but it increased feed intake (P = 0.03). It is concluded that, as well as offering the potential to increase land productivity, inclusion of duckweed in the diet of laying hens enhances egg yolk color and hepatoprotection, without detrimental effects on performance.

Microbial Population Dynamics in Lemnaceae (Duckweed)-Based Wastewater Treatment System

The dynamic microflora associated within, and in the surrounding aquatic environment, has been found to be responsible for the functional properties of many aquatic plants. The aim of the current work was to evaluate the effectiveness of Lemnaceae-based wastewater treatment system under tropical conditions and investigate the changes in the aquatic microflora upon plant growth. A biological wastewater treatment system was designed and investigated using mixed Lemnaceae culture comprising Lemna minor and Spirodela polyrhiza in a batch mode. A significant reduction in total solids (31.8%), biochemical oxygen demand (93.5%), and chemical oxygen demand (73.2%) was observed after seven days of duckweed growth using a low inoculum. A preliminary study on the change in the microbial population diversity and functionality, in the wastewater before and after treatment, revealed an increase in the denitrifying microflora in wastewater post-Lemnaceae treatment. Dominance of 10 bacterial phyla, contributing for 98.3% of the total bacterial communities, was recorded, and ~ 50.6% loss of diversity post-treatment of wastewater was revealed by the Shannon Index. Among 16 bacterial families showing relative abundance of ≥ 1% in untreated wastewater, Methylobacteriaceae, Pseudomonadaceae, Brucellaceae, Rhodobacteraceae, and Acetobacteraceae prevailed in the water post-treatment by duckweeds. This is a novel work done on the dynamics of aquatic microflora associated with Lemnaceae under tropical Indian conditions. It confirms the application of Lemnaceae-based wastewater treatment system as effective biofilter and calls for further studies on the active involvement of the endophytic and aquatic microflora in the functions of these plant.

Modelling of Lemna minor L. growth as influenced by nutrient supply, supplemental light, CO2 and harvest intervals for a continuous indoor cultivation

Given the proper conditions, Lemna spp. rapidly produce a high amount of valuable biomass which is considered as an alternative source for feed and food. For a continuous and long-term indoor production under controlled conditions, environmental and harvest parameters have to be optimized to suppress algal growth and constantly yield a high-quality product. Experimentally assessing the effect of a larger number of parameters on the growth rate r_i is impossible due to the theoretically high number of parameter combinations. Thus, a SIMILE® - based model has been developed. This enables production parameters to be assessed individually for its effect on the growth rate r _i by a differential equation. Start values for numerical integration were taken from measured data and analytical solutions of the differential growth equation. At 400 ppm CO₂, the regrowth rate ri in an optimized laboratory set-up amounted to 216 g FM·m^-2d^-1, harvesting one third of the biomass at intervals of 5 days. In up-scaled set-ups, lower regrowth rates ri of about 173 g FM·m^-2d^-1 (Kalkar) and 190 g FM·m^-2d^-1 (Berlin) were obtained, because temperature and light conditions were below optimum. At 3,500 ppm CO₂, the regrowth rate ri in laboratory set-up increased to 323 g FM·m^-2d^-1 by shortening the harvest interval to three days. Maximum growth rates ri were obtained with an NH₄ ⁺/NO₃ ^- ratio of 1/9 at 1.14 mM total N concentration. The results indicate how to optimize culture conditions and harvest intervals. Model runs closely match the experimental data taken from the three different approaches and thus confirm the validity of the model.

Diversity and Differentiation of Duckweed Species from Israel

Duckweeds (Lemnaceae) are tiny plants that float on aquatic surfaces and are typically isolated from temperate and equatorial regions. Yet, duckweed diversity in Mediterranean and arid regions has been seldom explored. To address this gap in knowledge, we surveyed duckweed diversity in Israel, an ecological junction between Mediterranean and arid climates. We searched for duckweeds in the north and center of Israel on the surface of streams, ponds and waterholes. We collected and isolated 27 duckweeds and characterized their morphology, molecular barcodes (atpF-atpH and psbK-psbI) and biochemical features (protein content and fatty acids composition). Six species were identified-Lemna minor, L. gibba and Wolffia arrhiza dominated the duckweed populations, and together with past sightings, are suggested to be native to Israel. The fatty acid profiles and protein content further suggest that diverged functions have attributed to different haplotypes among the identified species. Spirodela polyrhiza, W. globosa and L. minuta were also identified but were rarer. S. polyrhiza was previously reported in our region, thus, its current low abundance should be revisited. However, L. minuta and W. globosa are native to America and Far East Asia, respectively, and are invasive in Europe. We hypothesize that they may be invasive species to our region as well, carried by migratory birds that disperse them through their migration routes. This study indicates that the duckweed population in Israel's aquatic environments consists of both native and transient species.

DNA barcoding and biomass accumulation rates of native Iranian duckweed species for biotechnological applications

The Lemnaceae family (duckweed) consists of at least three recognized genera with six reported species in Iran that are distributed in wetlands. Duckweeds are the simplest and smallest flowering aquatic monocots with free-floating fronds that can reproduce asexually every 2-3 days. Duckweed could be a major source of balanced amino acids and high protein content, which is increasingly promising for biotechnological applications. For molecular classification and species identification of the collected samples, DNA barcoding was performed using two standard chloroplast markers, the spacer region between the ATP synthase subunits F and H (atpF-atpH) and the intron region of the ribosomal protein S16 (rps16). The results confirm the presence of four species belonging to the two genera Lemna and Spirodela. In addition, L. turionifera was detected for the first time in Iran. Due to the high growth rates of duckweed, measurement of biomass accumulation and doubling time are important factors in determining growth potential, especially for native species. The relative growth rates (RGR), doubling times (DT), biomass accumulation, and relative weekly yields (RY) of 40 distinct duckweed clones were determined under standard cultivation conditions. The dry weight-based RGR ranged from 0.149 to more than 0.600 per day, DT from 1.12 to 9 days, and RY from 7 to 108.9 per week. All values are comparable with previous studies. RGR and RY of selected clones are higher than the growth potential for a wide range of wild plants and common crops. These data support that native duckweed has high productivity value and should be further investigated as a potentially rich protein source for alternative human food, livestock feed, and recombinant protein production.

Exogenous melatonin enhances the growth and production of bioactive metabolites in Lemna aequinoctialis culture by modulating metabolic and lipidomic profiles

BACKGROUND

Lemna species are cosmopolitan floating plants that have great application potential in the food/feed, pharmaceutical, phytoremediation, biofuel, and bioplastic industries. In this study, the effects of exogenous melatonin (0.1, 1, and 10 µM) on the growth and production of various bioactive metabolites and intact lipid species were investigated in Lemna aequinoctialis culture.

RESULTS

Melatonin treatment significantly enhanced the growth (total dry weight) of the Lemna aequinoctialis culture. Melatonin treatment also increased cellular production of metabolites including β-alanine, ascorbic acid, aspartic acid, citric acid, chlorophyll, glutamic acid, phytosterols, serotonin, and sucrose, and intact lipid species; digalactosyldiacylglycerols, monogalactosyldiacylglycerols, phosphatidylinositols, and sulfoquinovosyldiacylglycerols. Among those metabolites, the productivity of campesterol (1.79 mg/L) and stigmasterol (10.94 mg/L) were the highest at day 28, when 10 µM melatonin was treated at day 7.

CONCLUSION

These results suggest that melatonin treatment could be employed for enhanced production of biomass or various bioactive metabolites and intact lipid species in large-scale L. aequinoctialis cultivation as a resource for food, feed, and pharmaceutical industries.

Naturally grown duckweeds as quasi-hyperaccumulators of rare earth elements and yttrium in aquatic systems and the biounavailability of gadolinium-based MRI contrast agents

The use of rare earths and yttrium (REY) in high-technology products is accompanied by their increasing release into the environment. Concerns regarding the (eco-)toxicity and bioaccumulation of these emerging contaminants highlight the need for research on REY uptake by (aquatic) plants. Duckweeds are widespread macrophytes in lentic waters and receive increasing attention as a potential protein-rich food additive. We here provide a baseline dataset for the complete set of REY in naturally grown duckweed assemblages and ambient freshwater and coastal brackish seawater. Our results show that duckweeds strongly bioaccumulate REY and incorporate them at the μg/kg level (dry matter basis). Their shale-normalised (_SN) REY patterns are mildly fractionated relative to upper continental crust, regardless of sampling location and season. In contrast, the patterns of ambient waters increase from light to heavy REY (LREY and HREY, resp.) and may show prominent positive anthropogenic Gd_SN anomalies due to the presence of Gd-based contrast agents (Gd-CAs) applied for magnetic resonance imaging (MRI). The lack of Gd_SN anomalies in the duckweed assemblages reveals discrimination against the uptake of Gd-CAs by the macrophytes, providing further evidence for the conservative behaviour of these xenobiotics in the environment. High REY concentrations and apparent bulk distribution coefficients between duckweeds and ambient waters of up to 10⁵ show that duckweeds are quasi-hyperaccumulators of REY. Uptake of LREY is up to two orders of magnitude higher than of HREY, possibly due to stronger complexation of HREY with dissolved ligands. The REY closely correlate with Mn but not with Ca, suggesting that uptake of REY and Mn occurs via the same pathway and revealing the negligible role of calcium oxalates. Our study demonstrates that while duckweeds are quasi-hyperaccumulators of REY, there is currently no risk that anthropogenic Gd from MRI contrast agents may enter the food chain via consumption of duckweeds.

Automated imaging of duckweed growth and development

Duckweeds are the smallest angiosperms, possessing a simple body architecture and highest rates of biomass accumulation. They can grow near-exponentially via clonal propagation. Understanding their reproductive biology, growth, and development is essential to unlock their potential for phytoremediation, carbon capture, and nutrition. However, there is a lack of non-laborious and convenient methods for spatially and temporally imaging an array of duckweed plants and growth conditions in the same experiment. We developed an automated microscopy approach to record time-lapse images of duckweed plants growing in 12-well cell culture plates. As a proof-of-concept experiment, we grew duckweed on semi-solid media with and without sucrose and monitored its effect on their growth over 3 days. Using the PlantCV toolkit, we quantified the thallus area of individual plantlets over time, and showed that L. minor grown on sucrose had an average growth rate four times higher than without sucrose. This method will serve as a blueprint to perform automated high-throughput growth assays for studying the development patterns of duckweeds from different species, genotypes, and conditions.

Flow Rate and Water Depth Alters Biomass Production and Phytoremediation Capacity of Lemna minor

Given its high biomass production, phytoremediation capacity and suitability as a feedstock for animal and human nutrition, duckweeds are valuable multipurpose plants that can underpin circular economy applications. In recent years, the use of duckweeds to mitigate environmental pollution and valorise wastewaters through the removal of excess nitrogen and phosphate from wastewaters has gained considerable scientific attention. However, quantitative data on optimisation of duckweed performance in phytoremediation systems remain scant. In particular, a mechanistical understanding of how physical flows affect duckweed growth and remediation capacity within vertical indoor multi-tiered bioreactors is unknown. Here, effects of flow rate (0.5, 1.5 or 3.0 L min^-1) and medium depth (25 mm or 50 mm) on Lemna minor biomass production and phytoremediation capacity were investigated. Results show that flow rates and water depths significantly affect both parameters. L. minor grew best at 1.5 L min^-1 maintained at 50 mm, corresponding to a flow velocity of 0.0012 m s^-1. The data are interpreted to mean that flow velocities should be low enough not to physically disturb duckweed but still allow for adequate nutrient mixing. The data presented will considerably advance the optimisation of large-scale indoor (multi-tiered, stacked), as well as outdoor (pond, lagoon, canal), duckweed-based remediation of high nutrient wastewaters.

Ethnobotanical History: Duckweeds in Different Civilizations

This presentation examines the history of duckweeds in Chinese, Christian, Greek, Hebrew, Hindu, Japanese, Maya, Muslim, and Roman cultures and details the usage of these diminutive freshwater plants from ancient times through the Middle Ages. We find that duckweeds were widely distributed geographically already in antiquity and were integrated in classical cultures in the Americas, Europe, the Near East, and the Far East 2000 years ago. In ancient medicinal sources, duckweeds are encountered in procedures, concoctions, and incantations involving the reduction of high fever. In this regard, we discuss a potential case of ethnobotanical convergence between the Chinese Han and Classical Maya cultures. Duckweeds played a part in several ancient rituals. In one, the unsuitability of its roots to serve as a wick for Sabbath oil lamps. In another reference to its early use as human food during penitence. In a third, a prominent ingredient in a medicinal incantation, and in a fourth, as a crucial element in ritual body purifications. Unexpectedly, it emerged that in several ancient cultures, the floating duckweed plant featured prominently in the vernacular and religious poetry of the day.

A Machine-Learning Method to Assess Growth Patterns in Plants of the Family Lemnaceae

Numerous new technologies have been implemented in image analysis methods that help researchers draw scientific conclusions from biological phenomena. Plants of the family Lemnaceae (duckweeds) are the smallest flowering plants in the world, and biometric measurements of single plants and their growth rate are highly challenging. Although the use of software for digital image analysis has changed the way scientists extract phenomenological data (also for studies on duckweeds), the procedure is often not wholly automated and sometimes relies on the intervention of a human operator. Such a constraint can limit the objectivity of the measurements and generally slows down the time required to produce scientific data. Herein lies the need to implement image analysis software with artificial intelligence that can substitute the human operator. In this paper, we present a new method to study the growth rates of the plants of the Lemnaceae family based on the application of machine-learning procedures to digital image analysis. The method is compared to existing analogical and computer-operated procedures. The results showed that our method drastically reduces the time consumption of the human operator while retaining a high correlation in the growth rates measured with other procedures. As expected, machine-learning methods applied to digital image analysis can overcome the constraints of measuring growth rates of very small plants and might help duckweeds gain worldwide attention thanks to their strong nutritional qualities and biological plasticity.

Cyanobacteria as Candidates to Support Mars Colonization: Growth and Biofertilization Potential Using Mars Regolith as a Resource

Cyanobacteria are indicated as organisms that can possibly support Mars colonization, contributing to the production of oxygen and other commodities therein. In this general context, the aim of this work was to evaluate the ability of three species of cyanobacteria (Anabaena cylindrica, Nostoc muscorum, and Arthrospira platensis) and a green microalga (Chlorella vulgaris) to grow using only the resources existing in Mars, i.e., water and Martian regolith stimulant (MGS-1), under an Earth-like atmosphere. A Martian regolith extract was produced and used as a culture medium to grow these species. Their growth was assessed during a period of 25 days, using optical density and fluorometric parameters. After this period, the possible contribution of end-of-life cyanobacteria/microalga as biofertilizing agents was also assessed, using the macrophyte Lemna minor as a vegetable model. Among the three species, N. muscorum showed the best growth performance when compared to the other species, while A. platensis and C. vulgaris were not able to thrive on Mars regolith extract. Therefore, N. muscorum should be the target of future studies not only due to their role in oxygen production but also due to their possible use as a food source, as many members of the Nostoc genus. Cyanobacteria and microalgae (A. platensis and C. vulgaris) showed good abilities as biofertilizing agents, i.e., they stimulated biomass (i.e., dry weight) production at levels comparable to the plants that grew on standard synthetic medium. The highest yield was reached with A. platensis, while the lowest was achieved using the media with N. muscorum. FTIR-ATR (Fourier transform infrared with attenuated total reflectance) spectroscopy showed that the differences between the plants grown on media with or without Martian regolith seem to be related mainly to polysaccharides.

Interspecific divergence of circadian properties in duckweed plants

The circadian clock system is widely conserved in plants; however, divergence in circadian rhythm properties is poorly understood. We conducted a comparative analysis of the circadian properties of closely related duckweed species. Using a particle bombardment method, a circadian bioluminescent reporter was introduced into duckweed plants. We measured bioluminescence circadian rhythms of eight species of the genus Lemna and seven species of the genus Wolffiella at various temperatures (20, 25, and 30°C) and light conditions (constant light or constant dark). Wolffiella species inhabit relatively warm areas and lack some tissues/organs found in Lemna species. Lemna species tended to show robust bioluminescence circadian rhythms under all conditions, while Wolffiella species showed lower rhythm stability, especially at higher temperatures. For Lemna, two species (L. valdiviana and L. minuta) forming a clade showed relatively lower circadian stability. For Wolffiella, two species (W. hyalina and W. repanda) forming a clade showed extremely long period lengths. These analyses reveal that the circadian properties of species primarily reflect their phylogenetic positions. The relationships between geographical and morphological factors and circadian properties are also suggested.