A Strategy for the Sequential Recovery of Biomacromolecules from Red Macroalgae Porphyra umbilicalis Kützing

Red seaweed biorefinery: The influence of sequential extractions on the functional properties of extracted agars and porphyrans

Red seaweeds are exploited for their hydrocolloids, but other fractions are usually overlooked. In a novel approach, this study aimed to evaluate cold-water (CWE), ethanolic (EE), and alkaline (SE) extractions, alone and in sequence, to simultaneously: i) decrease the hydrocolloid extraction waste (valorizing bioactive side-streams and/or increasing extraction yield); and ii) increase the hydrocolloids' texturizing properties. It is the first time these extractions' synergetic and/or antagonistic effects will be accessed. For Porphyra dioica, a combination of CWE and EE was optimal: a positive influence on the melting temperature (increasing 5 °C to 74 °C) and sulphate content (a 3-fold reduction to 5 %) was observed, compared to a direct porphyran extraction. The same was observed for Gracilaria vermiculophyla, recovering two additional bioactive fractions without impacting the hydrocolloid's extraction (agar with 220 g/cm2 gelling strength and 14 % yield was obtained). The sequential use of CWE, EE, and SE was the most beneficial in Gelidium corneum processing: it enhanced agar's texturizing capacity (reaching 1150 g/cm2, a 1.5-fold increase when compared to a direct extraction), without affecting its 22 % yield or over 88 % purity. Ultimately, these findings clarified the effects of cascading biorefinery approaches from red seaweeds and their pertinence.

Catalytic hydrolysis of agar using magnetic nanoparticles: optimization and characterization

BACKGROUND

Agar is used as a gelling agent that possesses a variety of biological properties; it consists of the polysaccharides agarose and porphyrin. In addition, the monomeric sugars generated after agar hydrolysis can be functionalized for use in biorefineries and biofuel production. The main objective of this study was to develop a sustainable agar hydrolysis process for bioethanol production using nanotechnology. Peroxidase-mimicking Fe3O4-MNPs were applied for agar degradation to generate agar hydrolysate-soluble fractions amenable to Saccharomyces cerevisiae and Escherichia coli during fermentation.

RESULTS

Fe3O4-MNP-treated (Fe3O4-MNPs, 1 g/L) agar exhibited 0.903 g/L of reducing sugar, which was 21-fold higher than that of the control (without Fe3O4-MNP-treated). Approximately 0.0181% and 0.0042% of ethanol from 1% of agar was achieved using Saccharomyces cerevisiae and Escherichia coli, respectively, after process optimization. Furthermore, different analytical techniques (FTIR, SEM, TEM, EDS, XRD, and TGA) were applied to validate the efficiency of Fe3O4-MNPs in agar degradation.

CONCLUSIONS

To the best of our knowledge, Fe3O4-MNP-treated agar degradation for bioethanol production through process optimization is a simpler, easier, and novel method for commercialization.

The utility of algae as sources of high value nutritional ingredients, particularly for alternative/complementary proteins to improve human health

As the global population continues to grow, the demand for dietary protein is rapidly increasing, necessitating the exploration of sustainable and nutritious protein sources. Algae has emerged as a promising food source due to their high value ingredients such as proteins, as well as for their environmental sustainability and abundance. However, knowledge gaps surrounding dietary recommendations and food applications restrict algae's utilization as a viable protein source. This review aims to address these gaps by assessing the suitability of both microalgae and macroalgae as alternative/complementary protein sources and exploring their potential applications in food products. The first section examines the potential suitability of algae as a major food source by analyzing the composition and bioavailability of key components in algal biomass, including proteins, lipids, dietary fiber, and micronutrients. Secondly, the biological effects of algae, particularly their impact on metabolic health are investigated with an emphasis on available clinical evidence. While evidence reveals protective effects of algae on glucose and lipid homeostasis as well as anti-inflammatory properties, further research is required to understand the longer-term impact of consuming algal protein, protein isolates, and concentrates on metabolic health, including protein metabolism. The review then explores the potential of algal proteins in food applications, including ways to overcome their sensory limitations, such as their dark pigmentation, taste, and odor, in order to improve consumer acceptance. To maximize algae's potential as a valuable protein source in the food sector, future research should prioritize the production of more acceptable algal biomass and explore new advances in food sciences and technology for improved consumer acceptance. Overall, this paper supports the potential utility of algae as a sustainable and healthy ingredient source for widespread use in future food production.

Potential of Red, Green and Brown Seaweeds as Substrates for Solid State Fermentation to Increase Their Nutritional Value and to Produce Enzymes

Seaweeds are valuable feedstocks with the potential to be used as ingredients in aquafeeds. However, their use are still limited, given their recalcitrant polysaccharide structure. To break this structure, a biotechnological approach such as solid-state fermentation (SSF) by filamentous fungi can be used, which simultaneously increases the nutritional value of the biomass. However, SSF has hardly been studied in seaweeds; thus, in this study, five different seaweeds (Gracilaria sp., Porphyra dioica, Codium tomentosum, Ulva rigida, and Alaria esculenta) were used as substrates in SSF with Aspergillus ibericus MUM 03.49 and A. niger CECT 2915. Firstly, the seaweeds were fully characterized, and, then, changes in the crude protein and carbohydrate contents were assessed in the fermented biomass, as well as any carbohydrases production. The SSF of U. rigida with both fungi resulted in the maximum xylanase and β-glucosidase activities. The maximum cellulase activity was achieved using Gracilaria sp. and U. rigida in the SSF with A. niger. The protein content increased in C. tomentosum after SSF with A. ibericus and in U. rigida after SSF with both fungi. Moreover, U. rigida's carbohydrate content decreased by 54% and 62% after SSF with A. ibericus and A. niger, respectively. Seaweed bioprocessing using SSF is a sustainable and cost-effective strategy that simultaneously produces high-value enzymes and nutritionally enhanced seaweeds to be included in aquafeeds.

Comparative Gene Expression and Physiological Analyses Reveal Molecular Mechanisms in Wound-Induced Spore Formation in the Edible Seaweed Nori

Genetic reprogramming of differentiated cells is studied broadly in multicellular Viridiplantae as an adaptation to herbivory or damage; however, mechanisms underlying cell development and redifferentiation are largely unknown in red algae, their nearest multicellular relatives. Here we investgate cell reprogramming in the widely cultivated, edible seaweed Neopyropia yezoesis ("nori"), where vegetative cells in wounded blades differentiate and release as large numbers of asexual spores. Based upon physiological changes and transcriptomic dynamics after wound stress in N. yezoensis and its congener Neoporphyra haitanensis, another cultivar that does not differentiate spores after wounding, we propose a three-phase model of wound-induced spore development in N. yezoensis. In Phase I, propagation of ROS by RBOH and SOD elicites systematic transduction of the wound signal, while Ca²⁺ dependent signaling induces cell reprogramming. In Phase II, a TOR signaling pathway and regulation of cyclin and CDK genes result in cell divisions that spread inward from the wound edge. Once sporangia form, Phase III involves expression of proteins required for spore maturation and cell wall softening. Our analyses not only provide the first model for core molecular processes controlling cellular reprogramming in rhodophytes, but also have practical implications for achieving greater control over seeding in commercial nori farming.

Hydrogel-Forming Algae Polysaccharides: From Seaweed to Biomedical Applications

With the increasing growth of the algae industry and the development of algae biorefinery, there is a growing need for high-value applications of algae-extracted biopolymers. The utilization of such biopolymers in the biomedical field can be considered as one of the most attractive applications but is challenging to implement. Historically, polysaccharides extracted from seaweed have been used for a long time in biomedical research, for example, agarose gels for electrophoresis and bacterial culture. To overcome the current challenges in polysaccharides and help further the development of high-added-value applications, an overview of the entire polysaccharide journey from seaweed to biomedical applications is needed. This encompasses algae culture, extraction, chemistry, characterization, processing, and an understanding of the interactions of soft matter with living organisms. In this review, we present algae polysaccharides that intrinsically form hydrogels: alginate, carrageenan, ulvan, starch, agarose, porphyran, and (nano)cellulose and classify these by their gelation mechanisms. The focus of this review further lays on the culture and extraction strategies to obtain pure polysaccharides, their structure-properties relationships, the current advances in chemical backbone modifications, and how these modifications can be used to tune the polysaccharide properties. The available techniques to characterize each organization scale of a polysaccharide hydrogel are presented, and the impact on their interactions with biological systems is discussed. Finally, a perspective of the anticipated development of the whole field and how the further utilization of hydrogel-forming polysaccharides extracted from algae can revolutionize the current algae industry are suggested.