Characterization of the de-oiled yeast biomass for plausible value mapping in a biorefinery perspective

Anaerobic conversion of de-oiled yeast biomass fractionation waste to biomethane and biohydrogen for resource efficiency in biorefineries

High-value intracellular bio-compounds are extracted from microbial biomass through cell fractionation processes, which generate discharge streams. These discharges are rich in organic carbon and nitrogen that are derived from the soluble and insoluble protein and carbohydrate polymers. The present study investigated the anaerobic conversion of such a tertiary waste stream generated during the production of glucan-chitin complex through fractionation of de-oiled yeast biomass (a type of spent microbial biomass, which is the solid leftover residue of yeast lipid production process). Fed-batch anaerobic processes of methanogenesis and acidogenesis were investigated for the generated discharge streams. An average COD removal of 47 % with 294 and 323.51 mg VFA/g COD, with a maximum yield of 133.61 mL CH4/g COD and 53.45 mL H2/g COD in methanogenic and acidogenic fermentation was achieved. Considering CH4 production and COD removal, methanogenesis performed better, while in terms of VFA production and subsequent COD removal, acidogenesis was suitable. The investigation indicated the relevance of anaerobic processes for the conversion of de-oiled biomass fractionation discharge streams and suggested a route for integrating aerobic downstream waste to anaerobic fermentation systems, subsequently eliminating a greywater footprint of 5233.04 g/L and opening a prospect for an industrial symbiosis system. The findings highlighted the potential of these systems in process integration for fermentation-based process chains to achieve circularity and resource efficiency in production.

Sustainable lipid production by oleaginous yeasts: Current outlook and challenges

Yeast lipid has gained prominence as a sustainable energy source and so various oleaginous yeasts are being investigated to create efficient lipogenic platforms. This review aims to assess the various biotechnological strategies for enhanced production of yeast lipids via agro-waste processing and media engineering including multiomic analyses, genetic engineering, random mutagenesis, and laboratory adaptive evolution. The review also emphasizes the role of cutting-edge omics technologies in pinpointing differentially expressed genes and enriched networks crucial for designing advanced metabolic engineering strategies for prominent oleaginous yeast species. The review addresses the challenges and future prospects of a viable lipid production industry that is possible through advancements in current technologies, strain improvement, media optimization and techno-economic and life cycle analyses at lab, pilot and industrial scales. This review comprehensively provides deep insights for enhancement of yeast lipid biosynthesis to reach industrially benchmarked standard of a lipid production platform.