Microbial Oil Production by Oleaginous Fungi and Yeasts Using the Hydrolysate From the Dilute Sulfuric Acid Pretreatment of Wheat Straw

Microbial oil production by oleaginous fungi and yeasts using the hydrolysate from the dilute sulfuric acid pretreatment of wheat straw

Xiaochen Yu, Jijiao Zeng, Yubin Zheng and Shulin Chen

Department of Biological Systems Engineering, Washington State University, Pullman, WA 99164-6120

Abstract

Taking into account the fundamental problems around the world: hunger, the lack of energy and the deterioration of the environment, biodiesel production from lignocellulosic biomass has increasingly attracted much attention, since it decreases the potential to spark conflicts between food and energy issues by using non-starch, non-food biomass, and additionally it emits less green house gas to the environment than conventional fossil fuels. Generally lignocellulosic biomass is firstly hydrolyzed either chemically or biologically to fermentable sugars derived from cellulose and hemicellulose, which will be then converted to single cell oil by oleaginous microorganisms, as the feedstock for biodiesel production. Our work comprehensively explores the use of the hydrolysate from the dilute sulfuric acid pretreatment of wheat straw for microbial oil production. In this study, we investigated the performance of the oleaginous yeast and fungi on both detoxified and non-detoxified hydrolysate. The results showed that all the strains could use the hydrolysate to produce lipids and detoxification of the hydrolysate was not necessary for optimal cell growth and lipid production by the fungus and yeast strains. Among all the tested strains, the yeast Cryptococcus curvatus and the fungus Mortierella isabellina achieved 34% and 50% lipid content respectively on the non-detoxified hydrolysate with up to 20% lipid yield. The overall mass balance shown in Fig.1 indicated that lipid yield using the hydrolysate from dilute sulfuric acid pretreatment of wheat straw was 4.7 g lipids/ 100 g initial dry biomass. Our finding is quite significant as (1) it elucidates the feasibility of microbial oil production from lignocellulosic materials and suggests an alternative strategy for biodiesel production, (2) it provides the possibilities for the further scale-up and demonstration, which will accelerate the development of biodiesel production towards the commercialization, (3) it simplifies the hydrolysate fermentation process and could probably reduce the cost since the detoxification step is not required.

Fig. 1. The overall mass balance of converting lignocellulosic biomass into lipids