Optimizing lime pretreatment of rice straw for biolipid production using oleaginous microorganisms

This work focuses on the lime pretreatment of rice straw, agricultural waste in northeast Vietnam, for microbial lipid (bio-lipid) production. A response surface methodology approach was performed to optimize parameters for the pretreatment process. These parameters are the concentration of Ca(OH)₂, hydrolysis temperature, and maintained time; the effect is considered bio-lipid production yield. The lipid yield was estimated through consolidated bioprocessing of the pretreated rice straw as a substrate and using the fungus strain (Aspergillus oryzae 32) and the yeast strain (Lipomyces starkeyi 22). As a result, the optimal pretreatment conditions for maximum lipid yield were obtained at Ca(OH)₂ concentration of 12 g/L and hydrolysis temperature of 110 °C within 60 min. The accumulated lipid in fermentation using these oleaginous microorganisms was 8.5g/100g oven-dry weight of rice straw (10.9g/100g for pretreated rice straw). The biolipid consisted of 42.6% saturated, 21.1% monounsaturated (MUFA), and 35.1% polyunsaturated (PUFA) fatty acids.