Canola meal and tomato pomace as novel substrates for production of thermostable Bacillus subtilis T4b xylanase with unique properties

Abstract

In this study, the Bacillus subtilis T4b xylanase was characterized in terms of optimal catalytic activity and production culture medium based on agro-industrial by-products using response surface methodology (RSM). The xylan concentration, pH, and temperature were statistically optimized to achieve the highest xylanase activity. The most suitable combination of variables for higher xylanase activity (412 U/mL) was 7.07%, 6.26, and 48.96 °C for substrate concentration, pH, and temperature, respectively. The stability of partially purified xylanase was highlighted at a pH range of 5.0–10.0 and a temperature of 40 °C for 48 h. A significant improvement in xylanase activity was found by adding NaCl (up to 50 mM) and 5% ethanol to the substrate. A molecular mass of 35.0 kDa was demonstrated for partially purified xylanase on SDS-polyacrylamide gel. An economical culture medium based on novel substrates including canola meal and tomato pomace screened among different agro-industrial by-products to replace the high-cost ingredients in the defined enzyme production medium. To maximize the enzyme’s yield in the newly developed culture medium, statistical optimization of final selected ingredient concentrations was done using RSM. An optimized medium resulted in more than threefold higher xylanase production. It could be concluded that the B. subtilis T4b xylanase is an interesting option to develop the bioconversion of valuable by-products such as tomato pomace to high value-added products via suitable enzymatic hydrolysis.