Conversion of Corn Stalk to Ethanol by One-Step Process using an Alcohol Dehydrogenase Mutant of Phanerochaete chrysosporium

The potential of Phanerochaete chrysosporium in ethanol fermentation was evaluated. During the initial submerged cultivation, 1.76 g/L ethanol was obtained using glucose as substrate. After mutation, the ethanol concentration of an alcohol dehydrogenase (ADH) mutant reached 5.02 g/L. Both base transition and nine-base frame shift mutation occurred in the ADH gene of the mutant, changing the secondary and tertiary structures of ADH, as well as increasing the ADH activity during cultivation. Moreover, P. chrysosporium converted corn stalk to ethanol by a one-step process. After statistical optimizations, 0.26 g/g center dot substrate of ethanol yield was obtained on day 10. During the fermentation, the maximum lignin peroxidase, Mn-dependent peroxidase, and cellulase activities were 29.0 U/L, 256.5 U/L, and 40 U/mL, respectively, thus explaining why the fungus directly ferments corn stalk to ethanol. This study is the first report of the conversion of corn stalk without pretreatment to ethanol using a white-rot fungus.