Agricultural biomass (residue) will play an important part in our future energy mix after converted to the liquid fuel. Due to the low density and distributed nature of agricultural biomass, a robust small-scale conversion process with low capital investment and operating costs is urgently needed. The fungal accumulation of bio-lipids shows greater potential for lignocelluloses utilization and possible recent commercialization. Our research group at UMN is systematically developing a platform technology to convert agricultural residue to the microbial lipid via innovated fungal fermentations, with the following preliminary conclusions. 1) We have found two fungal strains from soybean grains with the lipid content reaching more than a third of the dry cell biomass even when growing on a low C/N medium; 2) We have found the key operational conditions to induce the fungal pelletization through changing the cultivation conditions, a much better approach than current available methods such as providing CaCO3 powder as nuclei. Self-aggregated pellets/granules can greatly improve the cell cultivation performance and simplify the separation and extraction from the fermentation broth. 3) We are also studying the solid state fermentation (SSF) with several oleaginous model strains on soybean hulls. These fungal species can accumulate high lipid content for the entire solid state fermentation biomass composites. Major fatty acid components produced during the SSF are primarily C16 (12% of total lipid), C18:1 (16%), C18:2 and C18:3 (26), similar as microalgae and vegetable lipids.
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