Biochemical characterization of cellulases from the psychrotolerant yeast Rhodotorula mucilaginosa BPT1 and assessment of their potential application in 2G bioethanol

Abstract

Cellulases from the yeast Rhodotorula mucilaginosa were partially purified applying ammonium sulfate fractionantion. The enzyme activities recovered in 60 % precipitate exhibited a SDS-PAGE molecular mass of 26 kD. The FPase activity was 0.76 IU mg-1 showing three peaks at 4oC, 30oC and 50oC. The optimum pH was pH 9.0 with more than 75% residual activity between pH 5.0 and pH 11.0. It was metal sensitive; Ca2+ ion inhibiting by 40%, Cu2+ and Na+ by nearly 99% and Mn2+, Mg2+ and Pb2+ by 88%, 80% and 52% respectively. CMCase activity was 9.13 IU mg-1 exhibiting 100% activity at 20oC, with residual activity of more than 70% between 4oC, and 60oC. It showed optimum pH 5.0, and metal sensitivity with Ca2+ causing 70% inhibitions and Zn2+, Mn2+ and Mg2+ showing almost 99% inhibition. The cellobiase activity was 5538 IU mg-1 exhibiting 100% activity at 4oC, 30oC, 50oC and 60oC. It showed more than 98% of activities between pH 5.0 and pH 11.0. It showed activation in presence of Ca2+ and Pb2+ by 40% and 42% respectively and inhibition in presence of Na+ and Zn2+by nearly 70%. It showed glucose tolerance upto 3%.The enzyme was highly active on microcrystalline cellulose and salicin.Among tested monosaccharides, minimum inhibition was caused by cellobiose (77.9 %) and maximum by maltose (56.6 %). The enzyme showedsaccharification of wheat straw by 20.92 %, rice straw by 20.7 %, Ailanthus excelsa wood by 8.1 %, and saw dust by 8.01 %. newline