Algal Research-Biomass Biofuels and Bioproducts最新文献

Algae has long been studied as a source of fuel, but till date its commercialization does not seem feasible. The only way forward is developing an algal biorefinery that can generate revenues from recovering multiple products via different routes. Integration of wastewater bioremediation using algae and a biomass processing technique like hydrothermal liquefaction (HTL) to valorize the biomass shows potential of developing a sustainable biorefinery. In the current study, algal biomass cultivated in municipal wastewater was processed using HTL to produce 43 % biocrude and multiple bioproducts of high value. Efforts were made to reduce the biocrude's nitrogen content to 1.2 % (of TS) and oxygen to 22.3 % (of TS) using ZSM-5, produce methyl esters (33–53 %) using alcoholic solvents (methanol or butanol) and increase hydrocarbons (68 %) in the biocrude using CO₂ as the reaction gas. On the other hand, two bioactives: minoxidil-18.96 ± 0.24 mg kg⁻¹ (dried algal biomass basis) and ethosuximide-41.07 ± 0.42 mg kg⁻¹ (dried algal biomass basis) were synthesized in the aqueous fraction. Further, the same aqueous fraction which was also rich in calcium and phosphorus was hydrothermally mineralized to produce hydroxyapatite (8.5 %, dry biomass basis), a bone mineral. The results are encouraging to adopt HTL as a process to valorize algal biomass and extract multiple high value products. Using hydrothermal upgradation and mineralization strategies for the HTL biocrude and aqueous fraction, a sustainable biorefinery can be developed.

Algae polysaccharides were discovered to act as pathogen-associated molecular patterns (PAMPs) to trigger immune responses, while bioactivities of oligosaccharides have not been thoroughly explored. Ulva oligosaccharides from Ulva prolifera were obtained using PL25 family ulvan lyase and evaluated for cell viability and phagocytic activity. Ulva oligosaccharides with 542 Da (OUP), consisting of tetrasaccharide (∆UA-RhaS-Xyl-RhaS) and disaccharides (∆UA-RhaS), exhibited the most pronounced phagocytic activities. Besides, OUP could effectively stimulate the expressions of proinflammatory cytokines and chemokines like TNF-α, IL-1β, IL-6, IFN-γ and CXCL1 in primary macrophages and subsequently promote the proliferation and activation of T and B lymphocytes in vitro. Transcriptome analysis also gave rise to the systemic proinflammatory responses triggered by OUP in macrophages, such as activation of multiple PRRs-related signaling pathways and downstream JAK-STAT and NF-κB signaling. Furthermore, in an in vivo mouse OVA immunization model, OUP upregulated the specific anti-OVA IgG antibody production in vivo, pointing to its immunoadjuvant capacity. OUP increases cell proliferation and secretion of IL-4 and IFN-γ of splenocytes in response to OVA stimulation ex vivo, thereby enhancing both Th1 and Th2 immune responses. Collectively, all this data suggests that OUP could function as the immune stimulator to enhance host immune response to infections.

Shifts in phytoplankton biodiversity drive frequent community successions within aquatic ecosystems. While significant progress has been made in understanding the factors influencing phytoplankton growth under controlled conditions, the processes driving phytoplankton succession in natural waters remain poorly understood. To address this gap, we conducted high-frequency monitoring of the phytoplankton community in the Jiangdong River Reservoir (Southeast China) from 2021 to 2022. High-frequency data captured 17 complete cycles of phytoplankton growth and decline. Our analysis showed that cryptophytes, though not the dominant group, played a key role in shaping the temporal dynamics of phytoplankton community structure and abundance. The relative abundance of cryptophytes consistently mirrored fluctuations in total chlorophyll-a concentrations. Rainfall-induced low-light conditions enhanced the competitive advantage of cryptophytes. Throughout each cycle of phytoplankton changes, cryptophytes leveraged this short-term advantage to proliferate by utilizing available ammonia nitrogen, ascending from the fourth to the second most abundant group. However, as ammonia nitrogen levels declined to 0.1 mg/L, cryptophyte populations began to decline. These new findings highlight the critical role of cryptophytes in driving phytoplankton succession patterns.

Some natural carotenoids remain unexplored in terms of their function because they occur only in trace amounts, or their stereochemistry is unclear. It is expected that scientists will discover new physiological activities that have a positive impact on human heath by analysis of such carotenoids. The purpose of this study was to analyze the carotenoids synthesized by the novel aerial microalga Coelastrella rubescens KGU–H009, and the dynamics of their accumulation. Cultivation experiments were conducted for 7 days at 25 °C, combining different light conditions with the presence or absence of nitrate ions. Short-term (2-h) cultivation was also performed, and tests were conducted with the addition of the inhibitor of photosynthesis 3-(3,4-dichlorophenyl)-1, 1-dimethylurea (DCMU). Strain KGU-H009 exhibited its highest carotenoid content (34.5 mg g⁻¹) in the presence of nitrogen sources and strong light. Upon nitrogen source depletion, the content of zeaxanthin and β-carotene decreased, while the content of astaxanthin and adonixanthin increased. Strain KGU-H009 exhibited reversible control of the xanthophyll cycle to adapt to changes in light intensity, but the xanthophyll cycle was inhibited by the addition of DCMU. Strain KGU-H009 demonstrated the ability to synthesize carotenoids involved in both light harvesting and photoprotection, suggesting its adaptability to environmental change.

This study studied the effects of white light (WL), blue light (BL), and yellow-green light (YGL) on astaxanthin production in mixotrophically grown Chromochloris zofingiensis. The biomass yield achieved under BL was higher than that obtained under WL and YGL, respectively. Remarkably, compared with WL and YGL, the RuBisCO activity under BL was reduced, suggesting that the light wavelength could influence the RuBisCO activity. The results showed that BL was more suitable for astaxanthin accumulation than WL and YGL. When C. zofingiensis was grown under BL, the total yields of astaxanthin reached 0.2844 g·L⁻¹ in 12 days, of which the biomass yield was 204.5 g·L⁻¹ and astaxanthin content was 0.139 % of DW. The metabolomic study revealed that the central carbon metabolism and astaxanthin biosynthesis were enhanced, supporting fast cell growth and high astaxanthin contents under BL. Moreover, BL could enhance astaxanthin production by increasing the PSY, LCYb, CHYb, and BKT gene expression. This study provides effective strategies to facilitate astaxanthin production in C. zofingiensis.

The cultivation of Ulva lags behind that of red and brown seaweeds despite its high growth rate and richness in nutrients. This study aimed to investigate the biochemical changes that occur during the transition of Ulva ohnoi from vegetative to reproductive (determination and differentiation) phases. Changes in proximate content, pigments, antioxidant activities, hormones, metabolites, and minerals were analyzed during the phase transition. Through the vegetative to determination phase, lipid decreased from 0.85 to 0.61 %, while chlorophyll a increased from 184.23 to the 244.89 μg g⁻¹. Catalase activity increased from 1079 to 7017 units mg⁻¹ protein, while indole acetic acid raised from 0.004 to 0.027 μg g⁻¹ during the transition from the vegetative to the differentiation phase. Among minerals, carbon (35.08 %), sulphur (0.32 %), phosphorus (4.53 mg 100 g⁻¹), and calcium (6.20 mg 100 g⁻¹) increased in the differentiation phase compared to that in the preceding phase. It is essential to understand these biochemical changes as this might help in both cultivation and natural resource management.

Microalgae-derived biostimulants are increasingly used as viable tools to improve growth, yield of crops, and reduce agricultural environmental footprint. However, microalgae isolated from aquatic environments are the main strains used in the production of biostimulants. This study aims to evaluate the biostimulant effect of a terrestrial Chlorella vulgaris strain isolated from arid soil on germination and growth of wheat (Triticum aestivum, var. Achtar). Different concentrations 0.2 %, 0.5 %, 25 % and 50 % (v/v) of four C. vulgaris treatments (aqueous extract, filtered culture, crude culture and sonified culture) were investigated by measuring several biometric parameters to assess wheat germination and growth performance. All C. vulgaris treatments significantly enhanced wheat germination and growth with concentration dependent effect. The crude culture and filtrate at 25 % were the most effective compared to untreated plants. They significantly improved wheat germination index by 16.86 %, germination rate coefficient by 7.87 %, germination energy by 20.40 % as well as growth parameters such as root length (62.82 % and 52.84 %), stem length (71.36 % and 59.19 %), and root (662.5 % and 391.67 %) and stem dry biomass (675 % and 370.83 %), respectively. Principal Component Analysis (PCA) revealed that crude culture and filtrate at the lowest doses of 0.5 and 25 % were closely correlated to enhanced wheat root and shoot length and dry weight. The plant nutrients, mineral elements, chlorophyll a, total proteins and carbohydrates contents were positively correlated with enhanced shoot length and dry weight. The soil physicochemical properties were significantly increased under all C. vulgaris treatments at higher dose (50 %) whereas plants N and P contents enhancement was correlated to the soil nutrients increase. Thus, the results highlighted the potential of soil microalgae as an eco-friendly biostimulant for promoting sustainable agriculture.

The present study investigates the cyanobacterial diversity of Tatapani hot spring, Chhattisgarh, India, using a polyphasic approach, their pigment system, biofuel properties and ability to bioremediate emerging pollutant triclosan. While the microscopic analyses of the natural samples reflected high cyanobacterial diversity with all morpho-forms, physicochemical studies revealed temperature being the major factor affecting the cyanobacterial distribution in the hot spring. Among the 22 collected cyanobacterial samples, 14 were grown successfully under laboratory conditions and 10 of them showed optimum growth at 45 °C. However, four strains displayed preference for lower temperature (27 °C) for optimum growth. The polyphasic characterization of 14 strains revealed that all the thermophiles belonged to the genus Mastigocladus whereas the strains Sytonema sp. TPJ-3, Calothrix sp. TPB-2, Westiellopsis sp. TPR-29 and Desikacharya sp. TPB-4 constituted the group of mesophiles. Calothrix sp. TPB-2 was identified as a novel genus (Neocalothrix thermalis) based on distinct morphology and phylogenetic position with unique ITS folding pattern. Additionally, our study disclosed the production of comparatively higher amounts of pigments and medium chain length fatty acids (C16 to C18) by the thermophilic strains, which indicated their potential to be used as feedstocks for pigments and biofuel production respectively. Although the triclosan bioremediation study reflected considerable triclosan removal efficiencies of all the strains, most impressive results were observed in case of Westiellopsis sp. TPR-29 (93.08 %) and Mastigocladus sp. TA-8 (91.92 %). Moreover, the in-silico study-based revelation of high triclosan binding ability of cyanobacterial laccase (−5.8 and − 5.4 kcal/mol) and catechol 2,3-dioxygenase (−5.9 and − 6.0 kcal/mol) suggested the probable triclosan degrading potential of Westiellopsis and Mastigocladus. Conclusively, the Tatapani hot spring represents a unique environment with the dominance of true-branched heterocytous thermophilic cyanobacteria that have enormous potential to remove triclosan and produce high amounts of pigments and medium chain length fatty acids.

Chlorella vulgaris photoacclimation was monitored over eight instantaneous light intensity changes. The intensities ranged between $35\mathrm{\mu mol\; Photo}{n}_{\mathrm{PAR}}.m^{-2}.s^{-1}$ and $600\mathrm{\mu molPhoto}{n}_{\mathrm{PAR}}.m^{-2}.s^{-1}$. Cultures were grown in ultra-thin flat panel photobioreactors under continuous light and maintained in low cell density to ensure homogeneous light availability. Photoacclimation was evaluated through spectral quantification of pigments and fluorometric assays. The former gave access to a proxy of chlorophyll and carotenoid content, the latter to the Photosystem-II cross-section (${\sigma }_{\mathrm{PSII}}$) and qualification of the photosynthetic machinery (via $\mathrm{OJIP}$ assays). Both the acclimated steady-state values of pigment content and the dynamic of their evolutions after sudden light intensity change were monitored. The characteristic times of the transitions were estimated based on a first-order assumption. Results consistently showed that antenna size adjustment of Chlorella vulgaris was primarily dictated by the light availability, both regarding the acclimated steady-state values and the acclimation dynamics. An energetic limitation was highlighted by the acclimation dynamics at low light. The characteristic time of transition was estimated to be $16.6\pm 2.17h$ for the transition to the lowest light intensity ($35\mathrm{\mu mol\; Photo}{n}_{\mathrm{PAR}}.m^{-2}.s^{-1}$) and $3.55\pm 1.01h$ for intensities higher than the maximal intensity of photolimitation ($120\mathrm{\mu mol\; Photo}{n}_{\mathrm{PAR}}.m^{-2}.s^{-1}$). No hysteresis effect was observed as light intensities were shifted once and reverted to their original values. These results extend the literature regarding photoacclimation dynamics of antenna size and photosynthetic apparatus. They are well-suited to calibrate photoacclimation models and can provide valuable insight into the strategies to implement for culture scale-up, fed-batch, and semi-continuous processes.