Assessment of a Novel Oleaginous Filamentous Microalga Klebsormidium sp. Lgx80 (Streptophyta, Klebsormidiales) for Biomass and Lipid Production1

Unveiling potential of promising filamentous microalga Klebsormidium cf. nitens: Shear stress resilience and carotenoid-fatty acid dynamics in tubular photobioreactor

In this study, the effects of shear stress and different culture media on the growth of the filamentous microalga Klebsormidium cf. nitens were studied. The microalga's growth, carotenoids and fatty acids were further evaluated in a pump-driven tubular photobioreactor. The results show that this microalga had the ability to withstand high shear stress and the adaptability to grow in a culture medium that lacks certain trace elements. K. cf. nitens grew consistently in the tubular photobioreactor at different average light intensities although it did not grow well in a tall bubble column. The carotenoid analysis revealed that the xanthophyll cycle was activated to protect the cell photosynthetic system. The fatty acids increased with irradiance, with linoleic acid (C18:2n6) making up over 50 % of the total fatty acids. This study supports the potential of employing pump-driven tubular photobioreactors to produce the filamentous microalga K. cf nitens at the large scale.

Space-Efficient 3D Microalgae Farming with Optimized Resource Utilization for Regenerative Food

Photosynthetic microalgae produce valuable metabolites and are a source of sustainable food that supports life without compromising arable land. However, the light self-shading, excessive water supply, and insufficient space utilization in microalgae farming have limited its potential in the inland areas most in need of regenerative food solutions. Herein, this work develops a 3D polysaccharide-based hydrogel scaffold for vertically farming microalgae without needing liquid media. This liquid-free strategy is compatible with diverse microalgal species and enables the design of living microalgal frameworks with customizable architectures that enhance light and water utilization. This approach significantly increases microalgae yield per unit water consumption, with an 8.8-fold increase compared to traditional methods. Furthermore, the dehydrated hydrogels demonstrate a reduced size and weight (≈70% reduction), but readily recover their vitality upon rehydration. Importantly, valuable natural products can be produced in this system including proteins, carbohydrates, lipids, and carotenoids. This study streamlines microalgae regenerative farming for low-carbon biomanufacturing by minimizing light self-shading, relieving water supply, and reducing physical footprints, and democratizing access to efficient aquatic food production.

Reliable reference genes and abiotic stress marker genes in Klebsormidium nitens

Microalgae have recently emerged as a key research topic, especially as biological models. Among them, the green alga Klebsormidium nitens, thanks to its particular adaptation to environmental stresses, represents an interesting photosynthetic eukaryote for studying the transition stages leading to the colonization of terrestrial life. The tolerance to different stresses is manifested by changes in gene expression, which can be monitored by quantifying the amounts of transcripts by RT-qPCR. The identification of optimal reference genes for experiment normalization was therefore necessary. In this study, using four statistical algorithms followed by the RankAggreg package, we determined the best reference gene pairs suitable for normalizing RT-qPCR data in K. nitens in response to three abiotic stresses: high salinity, PEG-induced dehydration and heat shock. Based on these reference genes, we were able to identify marker genes in response to the three abiotic stresses in K. nitens.

Assessment of Eicosapentaenoic Acid (EPA) Production from Filamentous Microalga Tribonema aequale: From Laboratory to Pilot-Scale Study

It has long been explored to use EPA-rich unicellular microalgae as a fish oil alternative for production of the high-value omega-3 fatty acid eicosapentaenoic acid (EPA, 20:5, n-3). However, none of the efforts have ever reached commercial success. This study reported a filamentous yellow-green microalga Tribonema aequale that possesses the ability to grow rapidly and synthesize significant amounts of EPA. A series of studies were conducted in a glass column photobioreactor under laboratory culture conditions and in pilot-scale open raceway ponds outdoors. The emphasis was placed on the specific nutrient requirements and the key operational parameters in raceway ponds such as culture depth and mixing regimes. When optimized, T. aequale cells contained 2.9% of EPA (w/w) and reached a very high biomass concentration of 9.8 g L⁻¹ in the glass column photobioreactor. The cellular EPA content was increased further to 3.5% and the areal biomass and EPA productivities of 16.2 g m⁻² d⁻¹ and 542.5 mg m⁻² d⁻¹, respectively, were obtained from the outdoor pilot-scale open raceway ponds, which were the record high figures reported thus far from microalgae-based EPA production. It was also observed that T. aequale was highly resistant to microbial contamination and easy for harvesting and dewatering, which provide two additional competitive advantages of this filamentous microalga over the unicellular counterparts for potential commercial production of EPA and other derived co-products.

Dietary Klebsormidium sp. Supplementation Improves Growth Performance, Antioxidant and Anti-Inflammatory Status, Metabolism, and Mid-Intestine Morphology of Litopenaeus Vannamei

Filamentous microalga Klebsormidium sp. has huge potential to become a natural and healthy additive in aquatic feed since it contains various bioactive nutrients, such as linoleic acid (LA), carotenoids, and chlorophylls. Therefore, an eight-week feeding experiment was performed to evaluate the effects of dietary Klebsormidium sp. on the growth performance, antioxidant and anti-inflammatory status, metabolism, and mid-intestine morphology of Litopenaeus vannamei. Two isonitrogenous and isolipid diets supplemented with and without 5% Klebsormidium sp. were prepared. Results showed that L. vannamei fed with Klebsormidium sp. had better growth performance and feed utilization by optimizing mid-intestine morphology and improving the carbohydrate metabolism. In addition, Klebsormidium sp. also enhanced the antioxidant capacity of L. vannamei by downregulating antioxidant parameters (hepatopancreas T-SOD, hepatopancreas GSH-PX, hemolymph T-SOD, hemolymph MDA) and RNA expression levels of antioxidant genes (gsh-px and cat). Furthermore, the supplementations of dietary Klebsormidium sp. significantly improved hepatopancreas health by downregulating RNA expression levels of pro-inflammatory related genes (relish and rho). Therefore, a dose of 5% Klebsormidium sp. is recommended for the daily diet of L. vannamei to improve the growth performance, antioxidant and anti-inflammatory status, metabolism, and mid-intestine morphology of shrimp.

Transcriptomic and Metabolomic Response to High Light in the Charophyte Alga Klebsormidium nitens

The characterization of the molecular mechanisms, such as high light irradiance resistance, that allowed plant terrestralization is a cornerstone in evolutionary studies since the conquest of land by plants played a pivotal role in life evolution on Earth. Viridiplantae or the green lineage is divided into two clades, Chlorophyta and Streptophyta, that in turn splits into Embryophyta or land plants and Charophyta. Charophyta are used in evolutionary studies on plant terrestralization since they are generally accepted as the extant algal species most closely related to current land plants. In this study, we have chosen the facultative terrestrial early charophyte alga Klebsormidium nitens to perform an integrative transcriptomic and metabolomic analysis under high light in order to unveil key mechanisms involved in the early steps of plants terrestralization. We found a fast chloroplast retrograde signaling possibly mediated by reactive oxygen species and the inositol polyphosphate 1-phosphatase (SAL1) and 3'-phosphoadenosine-5'-phosphate (PAP) pathways inducing gene expression and accumulation of specific metabolites. Systems used by both Chlorophyta and Embryophyta were activated such as the xanthophyll cycle with an accumulation of zeaxanthin and protein folding and repair mechanisms constituted by NADPH-dependent thioredoxin reductases, thioredoxin-disulfide reductases, and peroxiredoxins. Similarly, cyclic electron flow, specifically the pathway dependent on proton gradient regulation 5, was strongly activated under high light. We detected a simultaneous co-activation of the non-photochemical quenching mechanisms based on LHC-like stress related (LHCSR) protein and the photosystem II subunit S that are specific to Chlorophyta and Embryophyta, respectively. Exclusive Embryophyta systems for the synthesis, sensing, and response to the phytohormone auxin were also activated under high light in K. nitens leading to an increase in auxin content with the concomitant accumulation of amino acids such as tryptophan, histidine, and phenylalanine.

Growth and Biochemical Composition Characteristics of Arthrospira platensis Induced by Simultaneous Nitrogen Deficiency and Seawater-Supplemented Medium in an Outdoor Raceway Pond in Winter

Arthrospira platensis, a well-known cyanobacterium, is widely applied not only in human and animal nutrition but also in cosmetics for its high amounts of active products. The biochemical composition plays a key role in the application performance of the Arthrospira biomass. The present study aimed to evaluate the growth and biochemical composition characteristics of A. platensis, cultured with a nitrogen-free and seawater-supplemented medium in an outdoor raceway pond in winter. The results showed that the biomass yield could achieve 222.42 g m⁻², and the carbohydrate content increased by 247% at the end of the culture period (26 d), compared with that of the starter culture. The daily and annual areal productivities were 3.96 g m⁻² d⁻¹ and 14.44 ton ha⁻¹ yr⁻¹ for biomass and 2.88 g m⁻² d⁻¹ and 10.53 ton ha⁻¹ yr⁻¹ for carbohydrates, respectively. On the contrary, a profound reduction was observed in protein, lipid, and pigment contents. Glucose, the main monosaccharide in the A. platensis biomass, increased from 77.81% to 93.75% of total monosaccharides. Based on these results, large-scale production of carbohydrate-rich A. platensis biomass was achieved via a low-cost culture, involving simultaneous nitrogen deficiency and supplementary seawater in winter.

Effect of the compound bacterial agent on microbial community of the aerobic compost of food waste

In our study, we used 16SrRNA and ITS to investigate the microbial community composition and the effect of compound bacterial agent on the microbial community composition in the aerobic composting process of food waste (FW). At the bacterial level, the main phyla of Group A (compost naturally) were Proteobacteria and Firmicutes, and the main species were Pseudomonas_sp._GR7, Bacillus licheniformis and Pediococcus acidilactici. The main phyla of Group B (compost with compound bacterial agent) were Proteobacteria, Firmicutes and Streptophyta, and the main species were Klebsiella pneumoniae, Cronobacter sakazakii, Macrococcus caseolyticus, Enterococcus faecalis, Citrobacter freundii and Bacillus velezensis. It is worth noting that M. caseolyticus may be able to improve the effect of odour which is an important sensory index during aerobic composting. At the fungal level, the main phylum of both Groups A and B was Ascomycota, and the main species of Group A were Paecilomyces variotii, Byssochlamys spectabilis and Aspergillus fumigatus. The main species of Group B were Ogataea polymorpha and Millerozyma farinosa. Finally, the degradation rate of Group B was 81% that was about 15% higher than that of Group A, indicating that the compound bacterial agent could effectively improve the degradation rate and the composting process, while the low abundance of the compound bacterial agent in the composting process might be due to the small initial addition or the inhibition of other bacteria or fungi in the composting process.