Algal Research-Biomass Biofuels and Bioproducts最新文献

Cyanobacteria are a group of photosynthetic bacteria and a rich secondary metabolites source. The Bank of Algae and Cyanobacteria of the Azores (BACA) culture collection holds a significant number of strains, including many novel genera and species. 56 strains from freshwater, brackish, and thermal habitats were selected, and grown under standard conditions. Biomass was extracted with methanol, and cytotoxicity was assessed on two carcinoma cell lines, HepG2 and HCT116. The reduction of lipids was tested in zebrafish larvae, and in a steatosis model with fatty acid overloaded human liver cells. The cyanobacterial metabolome was analyzed by HR-ESI-LC-MS/MS and compared using CompareMS2. High similarities were observed in strains of the same genus when isolated from similar habitats, clustering in concordance to the taxonomical order, while no relation could be observed between strains from different genera originated from the same habitat. The extracts of Cyanobium sp. BACA0019, Pseudocalidococcus azoricus BACA0433 and Pegethrix atlantica BACA0077 reduced neutral lipids >40 % in zebrafish at 25 μg/mL, while from Symphyonema sp. BACA0090 and Aliinostoc sp. BACA0355 induced mortality. Lipid reduction in the steatosis model was observed in many strains, with significant results varying from 50 % to 100 %. Several strains reduced cell viability with the strongest effects from Scytonematopsis sp. BACA0005 (HepG2, 59.8 % and HCT116, 68.1 %), Aliinostoc sp. BACA0035 (HepG2, 43.3 %, and HCT116, 59.4 %) and Aliinostoc sp. BACA0355 (HepG2, 46.2 %, and HCT116, 75.5 %). The feature-based molecular networking identified several cluster of mass peaks related to the observed bioactivities. Chlorophyll derivatives and glycerolipids from Cyanobium sp. BACA0019, Pseudocalidococcus azoricus BACA0433 and Pegethrix atlantica BACA0077 were correlated with the reduction of lipids in zebrafish larvae, while several oligopeptides and fatty amides of Symphyonema sp. BACA0090 and Aliinostoc sp. BACA0355 with toxicity. Many clusters associated to the bioactivities remained unidentified, which may represent novel compounds, highlighting the chemodiversity of the BACA culture collection.

Mutations are the origin of genetic diversity and are fundamental parameters needed to understand the molecular evolution of species. Estimations of mutation rates have been conducted for many diverse taxa, although rates in several major eukaryotic lineages remain unexplored. Here, the first estimation is reported of the spontaneous mutation rate for the multicellular eukaryote red alga, Pyropia yezoensis, which exhibits a complex life cycle. An estimated mutation rate of 2.97 × 10⁻⁸ (95 % CI: 2.16 × 10⁻⁸–3.99 × 10⁻⁸) per site per generation was generated for the primary life cycle, the sexual cycle, which is the highest sexual mutation rate among published sexual plants. Combined with tetrad analysis, meiosis I was identified as the primary period responsible for the high mutation rate during the complex life cycle of P. yezoensis. This result provides direct evidence for the “meiosis is mutagenic” hypothesis for multicellular organisms. The accurate estimate of the mutation rate of P. yezoensis also informs several immediate applications. Based on the above estimate, the effective population size (N_e) of P. yezoensis was estimated at about 19,000, with extensive haploid phases and asexual reproduction through monospores possibly leading to linked selection that may reduce the genome-wide genetic diversity of P. yezoensis and consequently influence N_e estimation. Lastly, P. yezoensis was estimated to have diverged from P. haitanensis about 4.2 Ma, representing a more recent date than estimates from fossil-calibrated phylogenies. These findings provide valuable new information for understanding the evolution of red algae, in addition to the underlying mechanism of mutations.

Brining as a cost-effective stabilising method to preserve the quality of fresh Ulva fenestrata was studied. The brines contained from 0 to 25 % (w/w) of sodium chloride or from 0 to 50 % sucrose and were combined with seaweed at a ratio of 1: 10 (w/v) prior to storage at 4 °C for up to 3 months. During this storage, the water activity of U. fenestrata was reduced from 0.94 to ≤0.89 with ≥15 % salt brines, which kept the microbial load <7 log (CFU/g) for 78 days. Among the sucrose brines, 50 % provided microbial shelf life <7 log (CFU/g) for 48 days. Further, 25 % salt or 50 % sucrose brines effectively retained the greenness (a*) of the U. fenestrata blades (< −20 a*-value for 80 days), while the tensile strength was only retained with 25 % salt brine (>3 Newton for 80 days). There was a time-dependent loss of crude proteins and fatty acids during storage, especially for 50 % sugar brined seaweed, where 58 % and 28 %, respectively, were lost after 20 days. Nutrients were best preserved in the 5 % salt-brine. Overall, the results indicate that brining with 25 % salt or 50 % sugar yields microbial stability and maintained colour of U. fenestrata for at least 48 days, with the former even exceeding 78 days at 4 °C, however, at a cost of nutritional value.

Marine microalgae are a promising innovation platform for carbon capture and utilization (CCU) biotechnologies to mitigate industrial greenhouse gas emissions. However, industrial-scale cultivation of algal mono-cultures is challenging and often unscalable. Non-axenic microalgae in large semi-open photobioreactors lead to the co-cultivation of diverse microbial communities. There is limited knowledge about the “bioreactor ecology” involving microalgae interacting with the microbiome and its subsequent impact on process stability and productivity. In this study, we describe the semi-continuous industrial mass cultivation of the cold-adapted marine diatom, Porosira glacialis UiT201, by investigating the prokaryotic and microeukaryotic (phytoplankton and heterotrophic protist) communities. Data were collected in two consecutive time series experiments, representing the initiation and operation of an industrial-scale CCU photobioreactor (300,000 L). The first experiment experienced a culture “crash” of the focal strain after 39 days, while the second culture remained stable and “healthy” for 60 days. The results highlight that this mass cultivation system represents a unique industrial marine microbial ecosystem. The succession of the prokaryotic community was primarily driven by species replacement, indicating turnover due to selective bioreactor conditions and/or biological interactions. Nonetheless, the bioreactor consistently harbors a recurring and abundant core microbiome, suggesting that the closely associated bacterial community is influenced by microalgae-specific properties and can endure a dynamic and variable environment. The observed culture collapse of P. glacialis coincided with changes in the core microbiome structure and different environmental growth conditions compared to the stable and “healthy” experiment. These findings imply that cohabiting microbial taxa within industrial microalgae cultivation likely play a critical role in stabilizing the conversion of industrial CO₂ into marine biomass, and changes in community structure serve as an indicator of process stability.

Arthrospira, commonly known as Spirulina in the commercial sector, is the most produced algae globally. A significant challenge in Arthrospira mass cultivation is zooplankton contamination, which might result in an annual loss of up to 30 % in biomass productivity if the zooplanktonic predation is not managed. This study, based on comprehensive field tests conducted in 1000 m² raceway ponds, demonstrates the feasibility of using sodium dodecyl benzene sulfonate (SDBS) as a pesticide for managing zooplanktonic predators in Arthrospira mass cultivation. Under compensatory SDBS application, planktonic predators such as rotifers and ciliates are completely eliminated. This involves an initial application of SDBS at 15 mg L⁻¹ followed by an additional enhancement of 5 mg L⁻¹ after 24 h. Early detection of the contamination and apply the SDBS pesticide as soon as possible by a compensatory manner is beneficial for a better management of the contaminations. The findings provide a novel approach for managing zooplanktonic predations and ensuring efficient and sustainable production of Arthrospira.

Algae respond rapidly with a respiratory oxidative burst during and after exposure to numerous environmental stresses. However, NADPH oxidase (Nox) homologs related to the generation of reactive oxygen species by algae are still poorly understood. In the present study, we identified 46 Nox homologs in eight red algae species; these Noxs possessed key functional domains similar to plant respiratory burst oxidase homologs but most of them were clustered into an independent clade in evolution. Furthermore, the cis-acting regulatory elements, transcription profiles, transcription factors co-expression correlation and differential expression of Pyropia haitanensis nox genes (Phnoxs) were detected. Results revealed that abundant elements involved in phytohormone responsiveness, abiotic stress induction, light regulation and transcription factor binding were harbored at the promoter region of Phnoxs. And they possessed differential transcript profiles during alternating heteromorphic generations. Phnox5C and 2C were the main genes expressed in free-living conchocelis and gametophyte, respectively, and their expression might be regulated by different transcription factors; an implication of their importance in nori growth and carpospore development. In addition, Phnox2C, 4 and 5A were significantly up-regulated after flg22 or oligoagar exposure, indicating they may provide resistance to pathogens. Conversely, Phnox2A, 2C, 4 and 5A responded positively to mechanical damage or drought stress. The findings presented in this study could be valuable for further elucidating the functions and regulatory mechanisms of NADPH oxidases during the development and adaptation of red algae to diverse stresses.

Tribonema minus, a eukaryotic filamentous yellow-green alga, is widely regarded as an optimal candidate for the production of biofuels and high-value chemicals such as palmitoleic acid and eicosapentaenoic acid. To achieve artificial regulation of the biosynthetic pathways for target compounds in T. minus, it is crucial to establish a stable multi-gene genetic expression system. Genetic engineering provides an effective approach for regulating the expression of multiple genes. A crucial breakthrough in this context involves expanding the effective genetic tools, which enables the integrated use of promoters, terminators, resistance markers and reporter genes to express the endogenous or heterologous gene-of-interest. To this end, we have devised tools suitable for multi-gene expression in T. minus. These tools include promoters (Ptubulin, Phsp70A and Phsp90A), F2A peptide, resistance marker genes (nptII, aadA and ble) and an enhanced green fluorescent protein reporter gene (eGFP). The genetic elements incorporated into the tools have demonstrated efficacy in T. minus. The experimental findings indicate that the endogenous promoters identified in T. minus exhibit transcriptional activity, and are capable of driving enhanced green fluorescent protein gene (eGFP) expression and could result in the production of corresponding proteins that can be easily detected through fluorescence microscopy. The F2A peptide functions properly in T. minus, with its activity remaining unaffected by the location when the gene sequences preceding and following the F2A peptide are relatively short (<1 kbp). The precise cleavage of enhanced green fluorescent protein (eGFP) has been confirmed through immunoblotting experiments, which can be readily detected using fluorescence microscopy. The utilization of the F2A peptide not only decreases the number of promoters required but also mitigates gene silencing.

Variations in nutrient compositions, especially amino acid (AA) profiles, among microalgal species may enable a superior feeding outcome from a combined than singular supplementation in poultry diets. Therefore, a feeding trial was conducted to compare the effects of three strains of microalgal biomass supplemented alone or in combination to replace 5 % (starter) and 10 % (grower) soybean meal (on weight-to-weight basis) on growth performance, protein metabolism, and meat quality of broiler chickens. Day-old Cornish Cross male chicks (total = 180) were divided into 5 groups (6 cages/treatment, 6 birds/cage) and fed a corn-soybean meal basal diet (BD), BD + H117 (Chlorella sp., H117), BD + C985 (Tetraselmis sp., C985), BD + Nannochloropsis oceanica (NO), and BD + H117 + C985 + NO (Combination). Feeding any of the microalgae diets did not alter growth performance nor meat quality including texture, pH, color, and water holding capacity of breast and thigh meats. However, the breast weight percentages were decreased (P < 0.05) by feeding the C985, NO, and Combination diets. Compared with the BD, the 4 microalgal diets led to higher (P < 0.05) plasma uric acid and protein concentrations at weeks 3 and (or) 6. The mRNA levels of MAFbx, MURF1, FOXO1, and calpastatin in the breast and thigh muscles were altered by the microalgal diets but not those of genes associated with other quality traits. In conclusion, replacing 5 % or 10 % soybean meal with three sources of microalgae in broiler diets decreased breast weights percentage but not absolute weight. Feeding chickens with the combination of three microalgae did not restore the breast loss and induced different expressions of genes related to muscle hypertrophy or atrophy.

Microalgae are recognized as a valuable source of a panoply of compounds. In addition to the extensively investigated lipid fraction comprising polyunsaturated fatty acids (PUFA), microalgae biomass also encompasses other compounds with potentially relevant biological activities. This work innovatively repurposes the defatted biomass (DB) of Nannochloropsis oculata, highlighting its potential value beyond the lipid fraction. By subjecting the DB to enzymatic hydrolysis, we explored an underutilized resource, potentially reducing waste and promoting sustainable bioprocessing. The resulting soluble fraction was chemically characterized and a comprehensive assessment of its chemical and biological activities was performed to ascertain its potential applications. Those included antioxidant, anti-hypertensive, and antidiabetic capacities, as well as potential metabolic inhibition, anti-inflammatory, and antimicrobial activities. The chemical characterization revealed the presence of several low molecular weight peptides (<1.2 kDa), as well as polysaccharides. The DB exhibited a relevant antioxidant capacity of 3.15 μmol_{Trolox equivalent(TE)}/mg_{freeze-dried biomass(FDB)} and an IC₅₀ of 77.3 ± 0.3 μg_protein/mL concerning angiotensin-I converting enzyme inhibitory activity, while α-glucosidase activity was inhibited by 19.4 %. Biological activities revealed no relevant inhibition of metabolic activity, an immunosuppression potential and anti-inflammatory activity (decreased expression of all pro-inflammatory cytokines in lipopolysaccharide (LPS)-induced inflammation) was also observed. Moreover, significant antimicrobial activity was observed, particularly against Gram-positive bacteria. These results underscored the potential of the DB to be utilized within a biorefinery concept, thereby transforming it into a resource (co-product) rather than considering it as waste. This study is groundbreaking due to its integrative approach, being the first to report the potential bioactivities of non-lipid extracts from N. oculata cultivated under modulated stress conditions.

Alexandrium causes serious food safety and human death due to paralytic shellfish toxins (PSTs) production. The associated bacteria can affect PSTs production of Alexandrium. However, the influencing mechanism is still unclear. Here we firstly screened functional associated bacteria for affecting PSTs production of Alexandrium catenella in Yangtze Estuary and further studied their influence on physiological process and molecular regulation of A. catenella. Thirteen bacteria strains for affecting PSTs production of A. catenella were selected. The A. catenella strains co-cultured with different functional associated bacteria all produced more PSTs than axenic strain with antibiotic treatment. Compared with axenic A. catenella, the non-axenic A. catenella produced more algal cells, soluble sugar, soluble protein and neutral lipid. By RNA-seq, it was found that non-axenic A. catenella produced more upregulated functional genes than axenic A. catenella. The biosynthesis of cofactors and spliceosome were the dominant different pathways between axenic and non-axenic A. catenella strains. The sxtA expression was closely related with Arginine and proline metabolism, Arginine biosynthesis, Fatty acid biosynthesis, TCA cycle and Glutathione metabolism, which were all downregulated in axenic A. catenella. Meantime, the non-axenic A. catenella under nitrogen deprivation produced less PSTs and functional genes than non-axenic strain under common culture condition, indicating the nitrogen significance for PSTs production. The detailed signal molecular released by associated bacteria for regulating PSTs of A. catenella needs to be further studied.