Production of acetic acid from wheat bran by catalysis of an acetoxylan esterase

In this study, a gene encoding for acetylxylan esterase was cloned and expressed in E. coli. A single uniform band with molecular weight of 31.2 kDa was observed in SDS-PAGE electrophoresis. Served as the substrate, p-nitrophenol butyrate was employed to detect the recombinant enzyme activity. It exhibited activity at a wide temperature range (30-100 degrees C) and pH (5.0-9.0) with the optimal temperature of 70 degrees C and pH 8.0. Acetylxylan esterase showed two substrates' specificities with the highest Vmax of 177.2 U/mg and Km of 20.98 mM against p-nitrophenol butyrate. Meanwhile, the Vmax of p-nitrophenol acetate was 137.0 U/mg and Km 12.16 mM. The acetic acid yield of 0.39 g/g was obtained (70 degrees C and pH 8.0) from wheat bran pretreated using amylase and papain. This study showed the highest yield up to date and developed a promising strategy for acetic acid production using wheat bran.