MICROBIAL LIPID PRODUCTION BY OLEAGINOUS FUNGUS MORTIERELLA ISABELLINA THROUGH MORPHOLOGY ENGINEERING

Difeng Gao

The oleaginous fungus Mortierella isabellina, is a promising feedstock for lipid-based biofuel production as it can accumulate a considerable amount of lipids. Simultaneous saccharification and fermentation (SSF) of cellulosic materials allows low usage of enzymes, simplified process and enhanced productivity. The feasibility of SSF process was investigated for lipid production with M. isabellina. Operational parameters including solid and enzyme loadings were optimized. The additions of Avicel and cellulases were found to have significant effects on the morphological forms of M. isabellina. This study suggested SSF could be a potential process for lipid production from cellulosic materials by M. isabellina. The specific productivities of filamentous fungi in submerged fermentation are often correlated with morphological forms. However, the relationship between morphological development and lipid accumulation is not well known. Therefore, distinct morphological forms of M. isabellina developed by additions of different concentrations of magnesium silicate microparticles were investigated to illustrate the relationships between lipid accumulation and morphology. Different morphological forms led to different levels of lipid accumulation as well as different spatial patterns of lipid distribution within pellets/mycelial aggregates. Significant higher lipid content (0.75 g lipid per g cell biomass) and lipid yield (0.18 g lipid per g glucose consumed) were achieved in free dispersed mycelia than in pellets. However, the lack of efficient and economic technologies to control macromorphology impedes improvement in lipid production. Thus, a biochar supplement strategy was developed, which could customize the macromorphology of M. isabellina, and substantially increase the lipid production. Biochars of two different sizes led to distinct macromorphologies with substantially increased lipid accumulation. Fine biochars led to a biochar-core shell structure of the pellets, while medium biochars significantly reduced the pellet size. Results suggested that biochars altered macromorphology by interfering with spore-spore and spore-hypha aggregations. The mode of action of interference was proposed to be the electrostatic repulsion between biochars and spores/hyphae. These results provide insights into understanding the links between morphological development and lipid accumulation, and developing novel approaches for bioprocess of lipid-based biofuel production.

MICROBIAL LIPID PRODUCTION BY OLEAGINOUS FUNGUS MORTIERELLA ISABELLINA THROUGH MORPHOLOGY ENGINEERING

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