Investigation of culture conditions for recombinant xylanase a production and its enzymatic hydrolysis of agricultural wastes

Abstract

Xylanase A of Aspergillus niger dsm 1957 was successfully expressed in strain Pichia pastoris GS115/pXlnA in YP medium induced by methanol. Molecular weight of the recombinant xylanase A was 35 kDa, that was consistent with the theoretical calculation and the enzyme activity in the culture was 7310 U/mL. Maximal xylanase activity (11180 U/mL) was gained after culturing the recombinant yeast for 120 hours in the present of 1% methanol. Among of seven media (BMMY, MMY, MM, YPM, YPTM, YPTCM, and YP) utilized for the yeast culture, the highest activity of the produced recombinant xylanase A (21620 U/mL) was reached in BMMY medium, while the lowest activity (1410 U/mL) was found in YPTCM medium. At the appropriate conditions, the recombinant xylanase A activity was 2.96 folds higher than that expressed in normal conditions. The conditions for recombinant xylanase A enzymatic hydrolysis of several agricultural wastes were also investigated. The results showed that in appropriate conditions (40^oC, 24 hours, substrate concentration of 40 mg), the highest amount of reducing sugars produced from cob, rice bran and soybean meal substrates were 0.617 ± 0.002 μmol/mL, 0.663 ± 0.002 μmol/mL, and 0.814 ± 0.003 μmol/mL, respectively. Overall, with these distinctive properties, the recombinant xylanase A may initially become a potential candidate for various industrial applications.