Cold-tolerant endoglucanase producing ability of Mrakia robertii A2-3 isolated from cryoconites, Hamtha glacier, Himalaya

Abstract

A psychrotolerant yeast strain Mrakia robertii A2-3 isolated from cryoconites of Hamtah glacier, Himalaya, India was investigated for the production of cold-tolerant endoglucanase. Optimum endoglucanase production was found at 15°C with an initial pH of 5.5, and potent inducers were 1% wt/vol of xylose and KNO₃ and 0.1% wt/vol of NaCl. Under optimum conditions, the enzyme production was 1.81-fold higher than the unoptimized conditions. Crude enzyme was partially purified by ammonium sulfate precipitation followed by dialysis. The enzyme was purified to 2.53-fold and the yield was 6.03% with specific activity of 17.38 U/mg and molecular weight ~57 kDa. The K_m and V_max values of the partially purified enzyme were found to be 1.57 mg/ml and 142.85 U/mg, respectively. The characterization study revealed that the best temperature was 15°C for activity and stability. Furthermore, the enzyme showed the highest activity at pH 11.0 and was stable at pH 6.0. Fe²⁺ , Mn²⁺ _, Na²⁺ , Cu²⁺ , Co²⁺ , Ca²⁺ proved to be activators of endoglucanase. Ethylenediamine tetraacetic acid showed very low effect on the enzyme activity whereas it was active with Tween-80 and sodium deoxycholate. The present study successfully produced a cold-active endoglucanase with novel properties making it promising as a biocatalyst for industrial processes.

Keywords: Himalaya; cellulase; cryoconites; endoglucanase; extracellular enzyme.