초록
<P><B>Abstract</B></P><P>A psychrotolerant yeast strain <I>Mrakia robertii</I> 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 KNO<SUB>3</SUB> 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 <I>K</I><SUB>m</SUB> and <I>V</I><SUB>max</SUB> 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. Fe<SUP>2+</SUP>, Mn<SUP>2+</SUP><SUB>,</SUB> Na<SUP>2+</SUP>, Cu<SUP>2+</SUP>, Co<SUP>2+</SUP>, Ca<SUP>2+</SUP> 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.</P>