Algal Research-Biomass Biofuels and Bioproducts最新文献

N-glycosylation is a major post-translational modification of proteins that has a crucial influence on cell targeting, activity, and half-life. This process starts in the endoplasmic reticulum where an oligosaccharide precursor is added to the newly synthesized protein and continues in the Golgi apparatus where the N-linked carbohydrate sequences are processed. Importantly, the most approved recombinant pharmaceutical proteins (so-called biologics) are glycoproteins mainly currently produced in mammalian cells which is a lengthy, costly, and complex process. Today, several microalgae such as the diatom Phaeodactylum tricornutum, and the green microalgae Chlamydomonas reinhardtii, Chlorella vulgaris, and Dunaliella salina are considered as efficient and eco-friendly alternative platforms for the production of biologics. However, unlike for C. reinhardtii, C. vulgaris, and P. tricornutum, there is to date no data reported regarding the protein N-glycosylation pathway in D. salina. Here, we first investigated the protein N-glycosylation in this green microalga by MALDI-TOF mass spectrometry. These analyses showed that proteins from D. salina are N-glycosylated with Man₅GlcNAc₂ oligomannoside. Using genome mining approaches, we then identified genes encoding proteins involved in the N-glycosylation pathways in D. salina. Genetic similarities and phylogenetic relationships of the putative sequences with homologues from C. reinhardtii, P. tricornutum, and humans were investigated. These data revealed that in D. salina the biosynthesis of nucleotide sugars and N-glycan biosynthesis share mainly similarities with the GnT I-independent pathway of C. reinhardtii that gives rise to the synthesis of a non-canonical oligomannoside Man₅GlcNAc₂. Although an α(1,3)-fucosyltransferase is identified in the D. salina genome, impairment of the cytosolic GDP-Fuc biosynthesis prevents the Golgi fucosylation of N-glycans. Taken together, these data demonstrated that proteins from D. salina are homogeneously N-glycosylated with a non-canonical Man₅GlcNAc₂.

C-phycocyanin (C-PC) is a highly valuable bioproduct from the cyanobacterium Arthrospira platensis. A crucial factor affecting growth and C-PC production yield is nitrogen nutrients. In this work, an ODE-based dynamic model was constructed to simulate the effect of ammonium concentrations in a batch system on cyanobacterial growth and C-PC production. The model included dynamic regulation of the ammonium transporter and key enzymes involved in the nitrogen assimilation pathway. The prediction of C-PC production, cyanobacterial growth, and remaining ammonium concentration over 24 h strongly correlated with experimental data. Furthermore, the model was able to capture the response of genes involved in ammonium assimilation and C-PC production, as well as the primary metabolites. The dynamic interplay among ammonium, glutamine, and glutamate levels reflects the complexity of nitrogen metabolism in regulating the transcription of genes involved in ammonium uptake, assimilation, and C-PC synthesis and degradation, thus highlighting the cellular response to nitrogen stress. These findings provide a foundation for understanding these biological processes and offer a potential tool for further exploring the complex relationship between nitrogen availability and C-PC accumulation in A. platensis C1 using ammonium as a nitrogen source.

Neurotoxin β-N-methylamino-L-alanine (BMAA) has been implicated as a major inducer of human neurodegenerative diseases. In recent years, marine diatoms were verified to produce BMAA-containing proteins. It will be an important cue to elucidate the subcellular distribution of BMAA in marine diatoms for disclosing its biosynthesis pathway. In this study, three species of Thalassiosira (T. andamanica, T. allenii and T. minima) were used to investigate the subcellular distribution of BMAA in organelles. Results showed that the crushing efficiency of diatoms was species-specific and increased with the rise of ultrasonic intensity of 22, 50 and 100 W (pulse = 0.2 s/s, 4 min), of which T. andamanica and T. allenii obtained the lowest and highest crushing efficiency, respectively. Interestingly, although T. allenii and T. minima were more efficiently crushed at 50 W and 100 W power (pulse = 0.2 s/s), their organelles were largely fragmented, which was verified by cytochrome c oxidase (CCO) enzyme analysis and transmission electron microscopy (TEM) observation. Their organelles were not fragmented only at 22 W. However, the crushing efficiency of T. andamanica was more reliable, and its organelles were essentially intact and only damaged at 100 W. Analysis of the BMAA-containing proteins showed that these proteins exclusively distribute in the Golgi and endoplasmic reticulum (ER) organelles. The nearly intact membranes of nucleus, mitochondria, Golgi and ER organelles testified that the absence of BMAA in other organelles was not caused by damage of nucleus or mitochondria. Results demonstrated that the BMAA-containing proteins were produced and accumulated in the ER and Golgi of diatoms.

Cancer and antimicrobial resistance are pressing global health concerns, with cancer ranking as a foremost reason of death across the world, estimated to be about 10 million in 2020, while antimicrobial resistance (AMR) poses a significant threat, with projected deaths attributed to AMR set to exceed 10 million by 2050. Recent research has highlighted Actinomyces, Bacteroidetes, Proteobacteria, and Cyanobacteria as promising sources of therapeutic compounds. Among cyanobacteria, the genus Leptolyngbya has garnered relatively less attention. Leptolyngbya is a polyphyletic in nature and widely distributed across various ecosystems. Although over 140 species have been identified within this genus, its systematic position has only recently been clarified. Leptolyngbya's diverse metabolite spectrum, including compounds with antioxidant, antimicrobial, and antiproliferative properties, as discussed in this review, makes it a valuable candidate for drug discovery. However, challenges in laboratory cultivation have hindered the identification of novel metabolites from Leptolyngbya, which would have been otherwise discovered. Hence, this article focuses on the antiproliferative and antimicrobial activities of the diverse genus Leptolyngbya, as well as the cutting-edge technologies that have the potential to expand the untapped metabolite spectrum of the genus.

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.