Lipid production from lignocellulosic biomass: Efficient strategies for pretreatment-induced inhibitors
Jungeun Lee1, Yadhu N. Guragain1, Krishna P.Bastola1, Praveen V.Vadlani1,2
Bioprocessing and Renewable Energy Laboratory, Department of Grains Science and Industry1, Department of Chemical Engineering2, Kansas State University, Manhattan, Kansas, USA
Oleaginous yeast containing triacylglycerides can be effectively produced from lignocellulosic biomass. For utilization of lignocellulosic biomass, pretreatment methods are employed to obtain sugars via effective depolymerization. However, since harsher methods are employed during pretreatment, toxic compounds are generated during monomer sugar production. This study focuses on innovative strategies to alleviate toxic compounds, which improve lipid production within oleaginous yeast. Initially, absorption was adopted to remove toxic compounds from monomer sugar solution. Activated charcoal and resins were tested to remove toxic compounds from sorghum hydrolysates. Activated charcoal efficiently removed hydrophobic compounds such as hydroxymethylfurfural (HMF) and furfural. However, acetic acid was not removed, and 3% of sugar loss was detected. Whereas, resin mixture (7:3 ratio of cation and anion exchangers) removed all types of inhibitors without sugar loss. This result showed that detoxification column with resin mixture was an efficient method for detoxifying hydrolysates, and it is anticipated that this method will improve lipid production during fermentation. Other approach to handle toxic compounds was selection of robust oleaginous yeast for lipid production. In our study, three types of oleaginous yeast (Trichosporon oleaginous, Lipomyces starkeyi and Cryptococcus albidus) with high tolerance to toxic compounds were evaluated using sorghum hydrolysates. T. oleaginosus accumulated about 40% of lipids, and produced total 6.2g/L of lipids at 120h fermentation. L. starkeyi and C.albidus accumulated about 40% of lipids, and produced total 4g/L of lipids. Our experiments confirmed that T. oleaginosus is the appropriate microbial system for effective production of lipids from sorghum hydrolysates.