Nutritional optimization of Arthrospira platensis for starch and Total carbohydrates production

Antiglycating Effects of Spirulina platensis Aqueous Extract on Glucose-Induced Glycation of Bovine Serum Albumin

Glucose, the predominant carbohydrate in the human body, initiates nonenzymatic reactions in hyperglycemia, potentially leading to adverse biochemical interactions. This study investigates the interaction between glucose and Bovine Serum Albumin (BSA), along with the protective effects of Spirulina platensis PCC 7345 aqueous extract. Phycobiliproteins (phycocyanin, phycoerythrin, and allophycocyanin) in the extract were quantified using spectrophotometry. The extract's anti-glycation potential was assessed by analyzing its effects on albumin glycation, fluorescent advanced glycation end products (AGEs), thiol group oxidation, and β-amyloid structure generation. Additionally, its antidiabetic potential was evaluated by measuring α-amylase and α-glucosidase enzyme inhibition. Results indicate that the Spirulina extract significantly mitigated ketoamine levels, fluorescence, and protein-carbonyl production induced by glucose, demonstrating a 67.81 % suppression of AGE formation after 28 days. Moreover, it effectively inhibited amyloid formation in BSA cross-linkages. These findings suggest the potential of S. platensis as an anti-glycation and antidiabetic agent, supporting its consideration for dietary inclusion to manage diabetes and associated complications.

Microalgae biomass as an alternative source of biocompounds: New insights and future perspectives of extraction methodologies

Microalgae have characteristics that make them unique and full of potential. Their capacity to generate interesting bioactive molecules can add value to various industrial applications. However, most of these valuable compounds are intracellular, which makes their extraction a major bottleneck. Conventional extraction methodologies have some drawbacks, such as low eco-friendly character, high costs and energy demand, long treatment times, low selectivity and reduced extraction yields, as well as degradation of extracted compounds. The gaps found for these methods demonstrate that emergent approaches, such as ohmic heating, pulsed electric fields, ionic liquids, deep eutectic solvents, or high-pressure processing, show potential to overcome the current drawbacks in the release and extraction of added-value compounds from microalgae. These new processing techniques can potentially extract a variety of compounds, making the process more profitable and applicable to large scales. This review provides an overview of the most important and promising factors to consider in the extraction methodologies applied to microalgae. Additionally, it delivers broad knowledge of the present impact of these methods on biomass and its compounds, raising the possibility of applying them in an integrated manner within a biorefinery concept.

Recent Advances in Marine Microalgae Production: Highlighting Human Health Products from Microalgae in View of the Coronavirus Pandemic (COVID-19)

Blue biotechnology can greatly help solve some of the most serious social problems due to its wide biodiversity, which includes marine environments. Microalgae are important resources for human needs as an alternative to terrestrial plants because of their rich biodiversity, rapid growth, and product contributions in many fields. The production scheme for microalgae biomass mainly consists of two processes: (I) the Build-Up process and (II) the Pull-Down process. The Build-Up process consists of (1) the super strain concept and (2) cultivation aspects. The Pull-Down process includes (1) harvesting and (2) drying algal biomass. In some cases, such as the manufacture of algal products, the (3) extraction of bioactive compounds is included. Microalgae have a wide range of commercial applications, such as in aquaculture, biofertilizer, bioenergy, pharmaceuticals, and functional foods, which have several industrial and academic applications around the world. The efficiency and success of biomedical products derived from microalgal biomass or its metabolites mainly depend on the technologies used in the cultivation, harvesting, drying, and extraction of microalgae bioactive molecules. The current review focuses on recent advanced technologies that enhance microalgae biomass within microalgae production schemes. Moreover, the current work highlights marine drugs and human health products derived from microalgae that can improve human immunity and reduce viral activities, especially COVID-19.

The Hypoxia-Associated Localization of Chemotaxis Protein CheZ in Azorhizorbium caulinodans

Spatial organization of chemotactic proteins is important for cooperative response to external stimuli. However, factors affecting the localization dynamics of chemotaxis proteins are less studied. According to some reports, the polar localization of chemotaxis system I is induced by hypoxia and starvation in Vibrio cholerae. However, in V. cholerae, the chemotaxis system I is not involved in flagellum-mediated chemotaxis, and it may play other alternative cellular functions. In this study, we found that the polar localization of CheZ, a phosphatase regulating chemotactic movement in Azorhizobium caulinodans ORS571, can also be affected by hypoxia and cellular energy-status. The conserved phosphatase active site D165 and the C-terminus of CheZ are essential for the energy-related localization, indicating a cross link between hypoxia-related localization changes and phosphatase activity of CheZ. Furthermore, three of five Aer-like chemoreceptors containing PAS domains participate in the cellular localization of CheZ. In contrast to carbon starvation, free-living nitrogen fixation can alleviate the role of nitrogen limitation and hypoxia on polar localization of CheZ. These results showed that the localization changes induced by hypoxia might be a strategy for bacteria to adapt to complex environment.

Microalgae as Contributors to Produce Biopolymers

Biopolymers are very favorable materials produced by living organisms, with interesting properties such as biodegradability, renewability, and biocompatibility. Biopolymers have been recently considered to compete with fossil-based polymeric materials, which rase several environmental concerns. Biobased plastics are receiving growing interest for many applications including electronics, medical devices, food packaging, and energy. Biopolymers can be produced from biological sources such as plants, animals, agricultural wastes, and microbes. Studies suggest that microalgae and cyanobacteria are two of the promising sources of polyhydroxyalkanoates (PHAs), cellulose, carbohydrates (particularly starch), and proteins, as the major components of microalgae (and of certain cyanobacteria) for producing bioplastics. This review aims to summarize the potential of microalgal PHAs, polysaccharides, and proteins for bioplastic production. The findings of this review give insight into current knowledge and future direction in microalgal-based bioplastic production considering a circular economy approach. The current review is divided into three main topics, namely (i) the analysis of the main types and properties of bioplastic monomers, blends, and composites; (ii) the cultivation process to optimize the microalgae growth and accumulation of important biobased compounds to produce bioplastics; and (iii) a critical analysis of the future perspectives on the field.

Application of an in situ CO2-bicarbonate system under nitrogen depletion to improve photosynthetic biomass and starch production and regulate amylose accumulation in a marine green microalga Tetraselmis subcordiformis

BACKGROUND

Microalgal starch is regarded as a promising alternative to crop-based starch for biorefinery such as the production of biofuels and bio-based chemicals. The single or separate use of inorganic carbon source, e.g., CO₂ and NaHCO₃, caused aberrant pH, which restricts the biomass and starch production. The present study applied an in situ CO₂-NaHCO₃ system to regulate photosynthetic biomass and starch production along with starch quality in a marine green microalga Tetraselmis subcordiformis under nitrogen-depletion (-N) and nitrogen-limitation (±N) conditions.

RESULTS

The CO₂ (2%)-NaHCO₃ (1 g L^-1) system stabilized the pH at 7.7 in the -N cultivation, under which the optimal biomass and starch accumulation were achieved. The biomass and starch productivity under -N were improved by 2.1-fold and 1.7-fold, respectively, with 1 g L^-1 NaHCO₃ addition compared with the one without NaHCO₃ addition. NaHCO₃ addition alleviated the high-dCO₂ inhibition caused by the single CO₂ aeration, and provided sufficient effective carbon source HCO₃ ^- for the maintenance of adequate photosynthetic efficiency and increase in photoprotection to facilitate the biomass and starch production. The amylose content was also increased by 44% under this CO₂-bicarbonate system compared to the single use of CO₂. The highest starch productivity of 0.73 g L^-1 day^-1 under -N cultivation and highest starch concentration of 4.14 g L^-1 under ±N cultivation were both achieved with the addition of 1 g L^-1 NaHCO₃. These levels were comparable to or exceeded the current achievements reported in studies. The addition of 5 g L^-1 NaHCO₃ under ±N cultivation led to a production of high-amylose starch (59.3% of total starch), which could be used as a source of functional food.

CONCLUSIONS

The in situ CO₂-NaHCO₃ system significantly improved the biomass and starch production in T. subcordiformis. It could also regulate the starch quality with varied relative amylose content under different cultivation modes for diverse downstream applications that could promote the economic feasibility of microalgal starch-based biofuel production. Adoption of this system in T. subcordiformis would facilitate the CO₂ mitigation couple with its starch-based biorefinery.