A Coculture of Photoautotrophs and Hydrolytic Heterotrophs Enables Efficient Upcycling of Starch from Wastewater toward Biomass-Derived Products: Synergistic Interactions Impacting Metabolism of the Consortium

Abstract

Even with particular interest in sustainable development, due to the limited types of bioavailable carbon sources that could support heterotrophic/mixotrophic growth, microalgae-derived products still suffer from inconsistent yield and high costs. This study demonstrates a successful cocultivation of the photoautotroph Chlorella vulgaris with a hydrolytic-enzyme-abundant heterotroph, Saccharomycopsis fibuligera , enabling efficient starch upcycling from water/wastewater toward enhancing microalgae-dominant biomass and lipid production. The enzymatic activities of S. fibuligera contributed to the hydrolysis of starch into glucose, generating a 7-fold higher biomass through mixotrophic/heterotrophic growth of C. vulgaris . Further, scanning transmission electron microscopy (STEM) and quantitative analysis suggested a significantly induced accumulation of lipids in C. vulgaris . Results of meta-transcriptomics revealed the critical regulatory role of illumination in interaction shifting. Gene expression for glycolysis and lipid biosynthesis of C. vulgaris were highly activated during dark periods. Meanwhile, during illumination periods, genes coding for glucoamylase and the sulfur-related activities in S. fibuligera were significantly upregulated, leading to induced starch hydrolysis and potential increased competition for sulfur utilization, respectively. This study indicates that hydrolytic organisms could collaborate to make starch bioavailable for nonhydrolytic microalgae, thus broadening the substrate spectrum and making starch a novel biotechnological feedstock for microalgae-derived products, e.g., biofuels or single-cell protein.

Aerobic Denitrification Promoting by Actinomycetes Coculture: Investigating Performance, Carbon Source Metabolic Characteristic, and Raw Water Restoration

“…Previous studies indicated that the central carbon metabolism (including glycolysis, TCA cycles, and pentose phosphate pathway) was the main carbon metabolic pathway of the Streptomyces genus. , In a cocultured strains (Chlorella vulgaris and Saccharomycopsis fibuligera) consortium, the expressions of most genes encoding the conversion from glucose to pyruvate of Chlorella vulgaris (glycolysis pathway) were significantly up-regulated, indicating a highly stimulated consumption of glucose by the Chlorella vulgaris . The stronger carbon source metabolism performance (especially carbohydrate) of the strains coculture in this study indicated that the glycolysis pathway was significantly enhanced.…”

“…Moreover, the potential quorum sensing and syntrophic pathway between the two strains drove specific pollutant removal. Therefore, the cross-feeding, quorum sensing, and syntrophic pathway might be the cooperation mechanism for two strains of actinomycetes coculture. ,− …”