Isolation of Bacterial Strain with Xylanase and Xylose/Glucose Isomerase (GI) Activity and Whole Cell Immobilization for Improved Enzyme Production

Abstract

The optimization of fermentation parameters for higher yield of bacterial enzymes have significant contribution to the industries. The qualitative enzymatic assay of strain HK2 in xyan agar and xylose agar plates showed a zone of clearance which indicated that the strain has potential to produce xylanase and xylose/glucose isomerase (GI) respectively. The strain produced highest xylanase activity of 23.09 ± 0.009 U/ml when grown in beechwood xylan and yeast extract in a ratio of 3:2 (w/w) at 37 °C and pH 7 for 96 h. Similarly, the strain preferred 35 to 40 °C temperature and 8 to 9 pH for efficient GI production. The GI activity was 3.3 folds higher than control when 1.5% xylose and 1:3 (w/w) ratio of peptone and yeast extract were used in the culture medium. SDS-PAGE of crude enzyme revealed that the molecular weight of xylanase and GI were about 55 kDa and 63 kDa respectively. The strain HK2 was identified as the Serratia marcescens by 16S rRNA gene sequencing. The strain has an ability to utilize low cost agricultural residue and the whole cell immobilization of strain improved the enzyme production which can further minimize the cost of down streaming processing. Thus, S. marcescens HK2 could be a promising candidate for foods and biofuels industries.