Recent energy crisis triggers significant attentions on microbial synthesis of bio-lipids, the raw material for the biodiesel production. Microbial oil accumulation with filamentous fungi has great potentials because filamentous fungi can form pellets during the cell growth (Fig 1) and this cell pelletization can effectively improve the fermentation performance and facilitate the cell harvest. We have found the key operational conditions to induce the fungal pelletization by precisely controlling the cell growth at different growth phase. This study focused on effects of various cultural conditions on cell growth, lipid accumulation and fatty acid composition in pelletized fermentation of Mucor circinelloides. Influences of different carbon and nitrogen sources, C/N ratio, carbon concentration, growth temperature and age of spores were investigated. It was revealed that glucose and xylose can both serve as the carbon sources for the cell growth, and the spores aged at 6 to 10 days were more suitable for lipid accumulation. It was also observed that with the increase of C/N ratio, the lipid content of dry cell biomass generally increased while the amount of biomass decreased. Similar to other oleaginous species, significant lipid accumulation of pelletized Mucor circinelloides occurred under stressed conditions, such as high C/N ratio and high temperature.
Figure
1. pellets of Mucor circinelloides
