Algal Research-Biomass Biofuels and Bioproducts最新文献

The interplay between the host and microbiome has emerged as a central issue in biological science. This concept considers both host and microbiome sides to investigate their physiological and metabolic mechanisms, often referred to as a holobiont. Macroalgae, which can provide tremendous habitats to associated microorganisms in coastlines by constituting the marine forest, are promising targets to explore the interaction. Undaria pinnatifida is one of the edible brown macroalgae that is intensively cultured in Northeast Asia. Despite its ecological and economical importance, the microbiome of its phycosphere is largely unknown. In this study, we explored the microbial communities from 41 whole-genome resequencing data collected from South Korea (KR), New Zealand (NZ), and France (FR). We investigated the microbiome profiles and microbial ecological network to identify ecological and functional central taxa. We demonstrated that the microbiome profiles of KR cultivars are more similar to those of overseas introduced populations (i.e., NZ, and FR) than to those of the KR natural populations. We also identified two groups of central genera of the algal species' microbiome, the algal polysaccharide depolymerizing group (e.g., Lacinutrix and Winogradskiella) and the algal growth-promoting group (e.g., Sulfitobacter). This study supports the idea that the microbiome can be secured from unmapped reads of the host sequencing data. Furthermore, our data provide the first study on the U. pinnatifida microbiome, which probably will be used to develop new aquaculture strategies for this important seaweed.

The co-pyrolysis of biomass wastes is of great importance for the integration of waste management and renewable energy sources, and the achievement of sustainable development goals. In this context, this study aimed to understand the reaction mechanisms and their behavior by examining the co-pyrolysis reactions of de-oiled microalgae and wood sawdust wastes. In this scope, the co-pyrolytic behavior of wood sawdust – de-oiled microalgae blends was determined by the thermogravimetric method, and co-pyrolysis kinetics and thermodynamics were calculated using model-free methods. In addition, biochar was produced from these blends under the conditions of 600 °C temperature and 20 °C min⁻¹ heating rate, and the characterization of biochars was performed. According to the obtained results, it was observed that the degradation time of de-oiled microalgae was longer than that of wood sawdust, depending on the complexity of its structure. The main decomposition of wood sawdust occurred in a single step within the temperature range of approximately 200–400 °C, whereas the main decomposition of de-oiled microalgae occurred in multiple steps within the temperature range of approximately 200–550 °C. The calculated pyrolysis activation energy values for the biomasses ranged from approximately 149 to 180 kJ mol⁻¹, while for the blends, these values ranged from approximately 159 to 203 kJ mol⁻¹. Additionally, the higher HHV values of the biochars produced from the blends (approximately 10 MJ kg⁻¹ higher than the others) increased their potential as a fuel. Based on these results, biochars produced via co-pyrolysis can be considered as a suitable option to be used as a fuel in terms of energy efficiency.

In the present investigation, fucoidan isolated from Nizamuddinia zanardinii was hydrolysed using 0.01 N HCl at boiling temperature for 10, 20, 40 and 60 min. Native and hydrolysed fucoidans contained a close chemical compositions, most importantly constituted of sulfates and uronic acids as well as fucose, galactose and mannose. Hydrolysis and cross-flow ultrafiltration produced fucoidan hydrolysates having different weight average molecular weights. The FH20 fucoidan was the most potent polysaccharide hydrolysate to stimulate NO-release from RAW264.7 macrophage cells. After cross-flow ultrafiltration of FH20, 100 < kDa fucoidan, polysaccharide with high branching degree consisting mainly of (1 → 2)-Fucp, (1 → 2,3)-Fucp, (1 → 3)-Galp, (1 → 2,3)-Galp, (1 → 2)-Manp and (1 → 3)-Manp residues, exerted the highest stimulation effect on RAW264.7 macrophage cells, secreting considerable NO, TNF-α, IL-1β, IL-6 and IL-12 proinflammatory mediators. Also, 100 < kDa fucoidan activated NK-92 cells to release TNF-α, INF-γ, granzyme-B, perforin, NKG2D and FasL. Both RAW264.7 and NK-92 cells were activated through NF-κB and MAPKs signalling pathways and the degree of stimulation capacity in fucoidan from N. zanardinii was in close correlation with the molecular weight.

Oleaginous diatoms, including the marine model species Phaeodactylum tricornutum, have been identified as promising sources of compounds with a biotechnological interest including triacylglycerol and the soluble polysaccharide chrysolaminarin. These two molecules are accumulated in cells under nutrient starvation conditions, however, their consumption after nutrient replenishment lack a precise characterization. In this study, two ecotypes of P. tricornutum (Pt1 and Pt4) have been subjected to a nitrate starvation followed by a resupply to monitor their response through biochemical assays and gene expression quantification. We highlighted that both ecotypes experienced a two-step response to nitrogen resupply, with a rapid initial consumption of stored soluble carbohydrates probably allowing the restart of photosynthesis and protein synthesis, followed by a consumption of neutral lipids fueling cell division. Some genes were particularly upregulated after resupply, especially those encoding the lipases Phatr3_EG02408 and Phatr3_EG00720 and the exoglucosidase Phatr3_J43302, suggesting their role in degradation processes. Additionally, ecotype Pt4 recovered faster from stress than ecotype Pt1, possibly due to differences in specific gene regulations. Overall, these findings provide potential targets for understanding lipid and carbohydrate degradation, and for creating high-lipid producing strains.

The potential of selenium-containing polysaccharides as organic selenium nutritional supplements has attracted considerable interest; however, they also encounter obstacles, including the presence of impurities and a low selenium binding efficiency. In this study, a novel method combining Q-Sepharose Fast-Flow (QFF) column chromatography with the HNO₃–Na₂SeO₃ method was proposed. Through the application of this methodology, the selenium binding efficiency of polysaccharides was enhanced by a factor of 3.41. The selenium binding capacities of rhamnose and glucose were the highest among the monosaccharides, reaching 770.7 mg/L and 955.3 mg/L, respectively. Spirulina polysaccharide-3 (SPS-3) was selected for further investigation because of its elevated total rhamnose and glucose contents and optimal selenium binding efficiency. Employing common assays, a comparative analysis of selenium-containing Spirulina polysaccharide-3 (SeCSPS) and SPS-3 is presented. Upon selenium binding, the surface morphology of the monosaccharides changed, whereas the main chain structure remained unaltered. The antihyperglycemic activity of SeCSPS was enhanced by selenium binding. Furthermore, both SeCSPS and SPS-3 can be degraded by the simulated digestive system. In conclusion, SeCSPS can be employed as an organic selenium supplement in food or nutraceuticals while also resulting in a high selenium content. The findings of this study will provide a viable avenue for the high-value utilization of Spirulina, which will help resolve the selenium deficiency issue faced by populations with low selenium intake globally.

Polyhydroxyalkanoates (PHA) are biopolymers synthesized by a wide range of microbes and they have been considered as substitutes for the petroleum-based plastics. The only way to select microalgae for PHA synthesis is to assess their diversity, occurrence, and environmental factors in various environments. Occurrence, habitat diversity, and environmental tolerance are assessed for selecting the microalgae for PHA production. In this study, microalgal and cyanobacterial diversity is analyzed along with its physicochemical parameters of water samples from 10 freshwater habitats of Visakhapatnam, Andhra Pradesh, India. The whole 132 species from 55 microalgal genera have been identified. The diversity index revealed the dominancy of Chlorophyceae (Green algae) members preceding the Cyanophyceae (Cyanobacteria) and Bacillariophyceae (Diatoms). Physicochemical parameter of water indicated the presence of calcium and chloride in increased concentration. Nitrite and sulphate significantly influence the microalgal population dynamics with distinct pond, stream, lake, waterfalls and stagnant water habitats. Furthermore, the influence of nitrogen and phosphorous availability in protein, lipid and accumulation of PHA during the cultivation of axenic cyanobacterial isolates of Visakhapatnam including Oscillatoria acuta, Nostoc calcicola and Spirulina fusiformis, are visualized using nile red dye and estimated. Modification of cyanobacterial growth media composition leads to the degradation of proteins, and accumulation of lipids and PHAs. Oscillatoria acuta and Nostoc calcicola unable accumulate PHA granules in a culture medium formulated with limited nitrogen, phosphorous and combination of both. Remarkably, Spirulina fusiformis as a unique species accumulates 8.2 % PHA in nitrogen limited zarrouk media. Nevertheless, no traces of PHA granules are observed in other nutrient limited and standard culture media (BG-11⁺, BG-11⁻ and Zarrouk). Therefore, S. fusiformis possess the tendency for the production of higher concentration of PHA.

The study presents a spray drying process for Euglena gracilis. Concentrate obtained by a disc centrifuge was used as the starting material. The process was established and scaled up using pilot and production-scale spray drying towers. Optimal conditions for the pilot scale included an inlet temperature of 200 °C, an outlet temperature of 85 °C, and a solid mass fraction of E. gracilis mud of 12 %. Key parameters influencing E. gracilis powder physicochemical indexes were identified by correlation analysis as drying time for droplets (T_drying), which can be adjusted by the outlet air temperature, the Peclet number for mass (Pe_mass), and heat (Pe_heat), and the evaporation rate ($\frac{d_w}{d_t}$), all of which can be adjusted by the outlet temperature. The process was successfully scaled up by optimizing the outlet temperature, achieving a productivity of 36.63 kg·h⁻¹ and a yield of 98.35 %. This work offers a commercially viable method for large-scale E. gracilis powder production.

In this study, the physiological responses and kinetic parameters of Botryococcus braunii were analyzed during a highly irradiated fed-batch culture in a cylindrical photobioreactor. This work includes a model of photon distribution throughout the bioreactor, coupled with an analysis of photosynthetic performance to simulate the level of photosaturation, photolimitation, or photoinhibition during cell growth culture. Under this simulation, the kinetic and physiological behavior was evaluated during four cycles of fed-batch culture. Physiological responses showed cellular photoacclimation to high irradiance conditions, increasing the Electron Transport Rate ($\mathrm{ETR}$) values 2.5 times from cycle 1 to cycle 4, while photoprotection mechanisms such as quantum yield $\left(Y_{\mathrm{II}}\right)$ and non-photochemical quenching $\left(\mathrm{NPQ}\right)$ remained efficient. The total pigment content was low compared to other studies, and a gradual decrease in Chl a, Chl b, and carotenoids was evident between each fed-batch cycle (a 25 % reduction from cycle 1 to cycle 4). Kinetics showed a gradual increase in productivity, growth rates, and nutrient consumption between cycles. The maximum biomass concentration as dry weight (4.86 ± 0.26gL⁻¹) was obtained in cycle 4, which also showed the highest values of productivity (0.45gL⁻¹d⁻¹), specific growth rate (0.134 d⁻¹) and consumption rate (NO₃, PO₄). The results correlate the engineering approach to the physiological characteristics of the species, indicating that it is possible to establish an efficient fed-batch system for microalgae production.

Owing to their diverse applications, TiO₂-nanoparticles have been extensively discharged into the aquatic environment, posing serious threats to aquatic life and human health. Meanwhile, the aquatic organisms such as cyanobacteria affect the mobility and fate of the nanoparticles, in turn, these aquatic organisms also may be influenced by the nanoparticles, and which further elicits more hazard to ecosystem. In this study, the different concentration of TiO₂ nanoparticles were added into the algal solution to observe the status of TiO₂ nanoparticles and assess their influences, especially for photocatalytic toxicity on algal growth. The results demonstrated that algal cells and extracellular polymeric substances (EPS) simultaneously affected the TiO₂ aggregation and settling in algae culture. In addition, TiO₂ NPs inhibited the growth of algal cells through the multiple effects on the light adsorption, photosynthetic activity, oxidative stress and lipid peroxidation. Particularly, the reactive oxygen species generated by photoactive TiO₂ NPs caused the changes of EPS and microcystin-LR (MC-LR) release, and these extracellular matters were crucial intermediate to the state of TiO₂ NPs and algal cells growth. This study will not only be significant for understanding TiO₂ behavior in the real aquatic environment but also be helpful for exploring the effects of TiO₂ nanoparticles on cyanobacteria, especially for the released extracellular matters.

Chlorella lipids are rich in essential fatty acids and have potential for development in food and healthcare products. This study established a novel enzyme-assisted biphasic extraction to obtain functional lipids from Chlorella sp. MBFJNU-17 biomass, and evaluated the anti-inflammatory function of the extracted lipids. The obtained results showed that the enzyme-assisted biphasic extraction mediated with pectinase and organic solvents (n-hexane and ethanol) achieved 17.3 % Chlorella cell wall disruption and 268.30 mg/g lipid extraction rate. After the optimization of this process, the n-hexane phase had 83.20 % neutral lipids (NLs), the ethanol phase contained 94.02 % polar lipids (53.65 % glycolipids (GLs) and 40.37 % phospholipids (PLs)), manifesting that the established biphasic lipid extraction exhibited the attracting feature to separate the NLs and polar lipids after lipids extraction. In term of the anti-inflammatory, the Chlorella polar lipids were found to perform superior anti-inflammatory effect with lower levels of inflammatory factors TNF-α and IL-6 than those of NLs. Compared to the lipids in the n-hexane and ethanol phases, three individual lipids (NL, GLs and PLs) performed poorer anti-inflammatory effects, indicating that the synergistic action could be effectively improved by the combination of three lipids. Taken together, the developed enzyme-assisted biphasic extraction method for Chlorella sp. MBFJNU-17 lipids was the potential lipid extraction process to concurrently extract and separate anti-inflammatory lipids. The study offered essential and scientific details to exploit high-value Chlorella lipids for nutritional and healthy bioproducts.