Advantages of ozone and soaking aqueous ammonia pretreatment for microbial lipid production as advanced biofuel feedstock from agricultural residues

The use of existing agricultural residues as a feedstock to be converted to sugars and lignin offers an opportunity for the development of drop-in fuels and chemicals. The ozone and soaking aqueous ammonia pretreatment process offers a unique dual benefit through a low temperature and pressure process that removes a majority of the lignin present in biomass into pretreatment ammonia effluent. This allows the production of a hydrolysable biomass with a low lignin content. The current study demonstrates the positive effects of a clean pretreated biomass with minimal lignin content on its ability to be used in SSF for fermentation in to lipids by Cryptococcus curvatus. Fermentation kinetics demonstrate that as much as 21% (w/w) of available sugars can be converted into lipid for further processing into long-chain fuels. The minimal presence of lignin in fermentation broth improves yield and also shows promise to ease the separation of lipid after fermentation is complete. The results show that the separation of lignin during pretreatment provides significant benefits for sugar production and utilization in a biorefinery.