Simultaneous production of food additives ferulic acid and xylose from wheat bran by bifunctional enzyme catalysis

High-value food additives including ferulic acid and xylose production from biomass conversion was a reliable strategy. In this study, a putative bifunctional xylanase/feruloyl esterase was detected in Sphingobacterium soilsilvae Em02 which rapidly showed cellulose degradation. For further grasping its function, the gene cloning and expression of this bifunctional enzyme were performed using an exogenous host Escherichia coli. The bifunctional enzyme with molecular mass of 44 kDa was obtained from cytoplasmic components. The enzyme activity of xylanase was detected using xylan. Meanwhile, feruloyl esterase activity was analyzed with 4-nitrophenyl trans-ferulate. The optimum activity of xylanase and feruloyl esterase were exhibited at 60 °C and pH 7. Furthermore, the bifunctional enzyme exhibited activity using the substrate de-starched wheat bran. A maximum of 6.1 mg/g of ferulic acid and 148 mg/g of xylose could be obtained from de-starched wheat bran. The bifunctional enzyme has application prospects in food industry.