Microbial lipid production from SPORL-Pretreated Douglas fir by Mortierella isabellina

Microbial lipids are promising feedstock for biodiesel and hydrocarbon fuels production in the future. Lignocellulosic biomass has been identified as an inexpensive and renewable raw material for microbial lipids production by oleaginous microorganisms. In this study, we evaluated the SPORL (sulfite) pretreatment of Douglas-fir as a substrate for the production of intracellular microbial lipids by Mortierella isabellina NRRL 1757. Both the SPORL pretreated Douglas fir (solid substrate) and pretreatment spent liquor were used either separately or jointly for lipid production. The lipids were produced in a batch fermentation using different strategies viz. separate hydrolysis and fermentation, quasi-simultaneous saccharification and fermentation (Q-SSF), and whole slurry (solid substrate and spent liquor) saccharification and fermentation. The maximum lipid yield (0.21 g/g of sugars) was obtained with Q-SSF from the solid substrate. Nutrient supplementation was not necessary for lipid production form SPORL-pretreated Douglas fir. For the spent SPORL pretreatment liquor, detoxification with lime was required to remove the inhibitors and improved the fermentation for lipid production. The lipid produced had a similar fatty acid compositional profile to those of vegetable oil, suggesting that it could have the potential as a feedstock for biodiesel production.