Biocatalytic potential of an alkalophilic and thermophilic dextranase as a remedial measure for dextran removal during sugar manufacture

The present study is focused on dextranase from Streptomyces sp. NK458 with potential to remove dextran formed during sugar manufacture. The dextranase had molecular weight of 130 kDa and hydrolyzed 15–25 and 410 kDa dextran. Dextranase production was optimized using statistical designs and the enzyme was purified 1.8-fold with 55.5% recovery. It displayed maximum activity at pH 9.0 and 60 °C and was stable over a wide range of pH from 5.0 to 10.0. The km and Vmax values were 3.05 mM and 17.97 mmol/ml/h, respectively. Ten units of dextranase could reduce dextran content by 67% in 24 h and 56% in 72 h from sugarcane juice of cane variety CoS 86032. The enzyme was stable up to 3 days at 30 °C beyond which its activity decreased and dextran removal could be retained by supplementation of 5 U of dextranase. These properties make it a promising biocatalyst for sugar industry.

► Dextranase from Streptomyces sp. NK458 has a molecular mass of 130 kDa.
► It has optimum activity at pH 9.0 and 60°C and is stable in wide pH and temperature range.
► Dextranase activity is not inhibited by metal ions reported to occur in sugarcane juice.
► It degrades pullulan formed due to contamination of sugarcane juice with Aureobasidium pullulans.
► Ten units of dextranase reduces dextran content in sugarcane juice by 67% in 24 h.