Abstract
POTENTIALITIES of twenty four fungal isolates were investigated for their ability to produce L-asparaginase using modified Czapek's Dox medium. Fusarium solani AUMC 8615 was selected as the most potent fungal strain for the enzyme production under solid state fermentation (SSF) using agro-industrial residues. Wheat bran supported maximum enzyme production followed by rice bran and corn cob. The optimum conditions for maximum production of L-asparaginase under SSF occurred on the fifth day of incubation at 30 degrees C, pH 8.0, 60% of initial moisture content and supplementation with 0.2% (wlv) glucose and 0.5% (wlv) ammonium sulphate. L-asparaginase was purified to homogeneity by ammonium sulphate precipitation, gel filtration and ion exchange chromatography giving 299.58 purification fold. SDS-PAGE showed that the purified enzyme consists of two subunits of molecular weights 70 and 80 kDa, respectively. The enzyme was efficiently immobilized by covalent binding with activated charcoal giving an immobilization yield of 80.40%. Optimum pH values were 9.0 and 8.0 for free and immobilized enzyme, respectively. While, Optimum reaction temperatures were 37 degrees C and 45 degrees C for free and immobilized enzyme, respectively. After incubation for 2 hr at 37 degrees C, the relative activity of free enzyme decreases to 35% whereas for the immobilized enzyme decreased only to 57% at 45 degrees C.