Biological Carbon Recovery from Sugar Refinery Washing Water into Microalgal DHA: Medium Optimization and Stress Induction

Cultivation of Chlorella sp. HS2 using wastewater from soy sauce factory

Incorporation of wastewater from industrial sectors into the design of microalgal biorefineries has significant potential for advancing the practical application of this emerging industry. This study tested various food industrial wastewaters to assess their suitability for microalgal cultivation. Among these wastewaters, defective soy sauce (DSS) and soy sauce wastewater (SWW) were chosen but DSS exhibited the highest nutrient content with 13,500 ppm total nitrogen and 3051 ppm total phosphorus. After diluting DSS by a factor of 50, small-scale cultivation of microalgae was conducted to optimize culture conditions. SWW exhibited optimal growth at 25-30 °C and 300-500 μE m-2 s-1, while DSS showed optimal growth at 30-35 °C. Based on a 100-mL lab-scale and 3-L outdoor cultivation with an extended cultivation period, DSS outperformed SWW, exhibiting higher final biomass productivity. Additionally, nutrient-concentrated nature of DSS is advantageous for transportation at an industrial scale, leading us to select it as the most promising feedstock for microalgal cultivation. With further optimization, DSS has the potential to serve as an effective microalgal cultivation feedstock for large-scale biomass production.

Straw mulch improves soil carbon and nitrogen cycle by mediating microbial community structure and function in the maize field

This study was conducted to investigate the capability of the microbial community characteristics and soil variables to promote carbon and nitrogen cycles in maize fields under straw mulch. We covered the surface soil of the maize field with different amounts of wheat straw (0 kg/ha, 2,250 kg/ha, and 4,500 kg/ha) and used 16S rRNA and ITS sequencing, Biology ECO-plate, traditional enzymology, TOC analyzer, and HPLC to measure bacterial and fungal community composition and functions, characteristics of microbial carbon source metabolism, carbon and nitrogen fraction, enzyme activity, and organic acid content in the maize rhizosphere and non-rhizosphere. The results indicated that short-term straw mulch insignificantly affected the alpha diversity of bacterial and fungal communities whereas significantly influenced their beta diversity. The results of functional prediction revealed that straw mulch considerably boosted the relative abundances of bacteria belonging to chemoheterotrophy, aerobic chemoheterotrophy, ureolysis, and nitrogen fixation and inhibited fermentation and nitrate reduction in maize rhizosphere soil. These processes primarily drove the C and N cycles in soil. Straw mulch also improved fungal saprotrophs by raising the proportion of Chaetomiaceae and Chaetosphaeriaceae. The Biology ECO-plate results illustrated that straw mulch weakened the metabolism capacity of microbial labile carbon resources. As a result, the labile C and N fractions were raised under straw mulch. Our results also showed that straw mulch primarily regulated the microbial community structure in rhizosphere soil by significantly decreasing Firmicutes and Ascomycota relative abundance while increasing Basidiomycota. The fungal community structure is more than bacterial for affecting soil microbial biomass carbon, readily oxidizable organic carbon, dissolved organic carbon, available nitrogen, ammonium, and nitrate directly and indirectly through malic acid content and cellulase, protease, and amylase activity. Overall, our findings imply that straw mulch might influence the bacterial and fungal community structures, thereby boosting the production of labile C and N components and accelerating the C and N cycle in maize fields.

An auxin-like supermolecule to simultaneously enhance growth and cumulative eicosapentaenoic acid production in Phaeodactylum tricornutum

Phaeodactylum tricornutum, a model alga, is well known for its ability to accumulate intracellular omega-3 eicosapentaenoic acid (EPA). However, P.tricornutum cells need to have a higher EPA content if they are to be used for industrial applications. In this study, an auxin-like supermolecule (SM) was synthesised and used for the cultivation of P. tricornutum. Results show that the addition of 1 ppm of SM significantly increased the P. tricornutum cell density and boosted the P. tricornutum biomass. The experimental group treated with 5 ppm of SM, had an EPA content of 31.7%, which was a 2.09-fold increase over the EPA content in the untreated group. Overall, our results demonstrated that SM can significantly improve the microalgal growth and EPA accumulation in P. tricornutum, providing a feasible strategy to achieve efficient and cost-effective EPA production.