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

The solid substrate and spent liquor obtained after SPORL pretreatment of Douglas fir residues were evaluated as substrates for the production of intracellular microbial lipid by Mortierella isabellina NRRL 1757. The production of lipid was investigated 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 sugar) was obtained with Q-SSF of the solid substrate. Nutrient supplementation was not necessary for lipid production from SPORL-pretreated Douglas fir. Detoxification of SPORL spent liquor with lime did 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 potential as a substrate for biodiesel production.