Microbial lipid production from pretreated and hydrolyzed corn fiber.

With its high content of carbohydrates and low percentage of lignin, corn fiber represents a renewable feedstock that can be processed to produce biofuels. Through a combination of pretreatment by lime and enzymatic hydrolysis, total reducing sugars of 700 mg/g corn fiber were released. This amount is equivalent to 92.7% of theoretically available sugars in corn fiber. The resulting hydrolysate itself did not support any growth of Cryptococcus curvatus. But with addition of minerals, C. curvatus grew to a cell density of 6.6 g/L in 6 days. Using the adapted cells, rapid sugar consumption and cell growth were observed. This study demonstrated that it is feasible to produce microbial lipids from corn fiber through pretreatment, enzymatic hydrolysis, and fermentation. In addition, C. curvatus is an excellent candidate for this application since it can utilize all major sugars, glucose, xylose, and arabinose with yield of cells and lipids as 0.55 and 0.27 g/g sugars, respectively.