Ethanol Production from Wheat Straw Hydrolysate by Issatchenkia Orientalis Isolated from Waste Cooking Oil

The interest in using non-conventional yeasts to produce value-added compounds from low cost substrates, such as lignocellulosic materials, has increased in recent years. Setting out to discover novel microbial strains that can be used in biorefineries, an <i>Issatchenkia orientalis</i> strain was isolated from waste cooking oil (WCO) and its capability to produce ethanol from wheat straw hydrolysate (WSHL) was analyzed. As with previously isolated <i>I. orientalis</i> strains, WCO-<i>isolated I. orientalis</i> KJ27-7 is thermotolerant. It grows well at elevated temperatures up to 42 °C. Furthermore, spot drop tests showed that it is tolerant to various chemical fermentation inhibitors that are derived from the pre-treatment of lignocellulosic materials. <i>I. orientalis</i> KJ27-7 is particularly tolerant to acetic acid (up to 75 mM) and tolerates 10 mM formic acid, 5 mM furfural and 10 mM hydroxymethylfurfural. Important for biotechnological cellulosic ethanol production, <i>I. orientalis</i> KJ27-7 grows well on plates containing up to 10% ethanol and media containing up to 90% WSHL. As observed in shake flask fermentations, the specific ethanol productivity correlates with WSHL concentrations. In 90% WSHL media, <i>I. orientalis</i> KJ27-7 produced 10.3 g L^-1 ethanol within 24 h. This corresponds to a product yield of 0.50 g g^-1 glucose (97% of the theoretical maximum) and a volumetric productivity of 0.43 g L^-1 h^-1. Therefore, <i>I. orientalis</i> KJ27-7 is an efficient producer of lignocellulosic ethanol from WSHL.