Purification and immobilisation of inulinase from Aspergillus candidus for producing fructose
1999
Kochhar, A. | Gupta, A.K. | Kaura, Ainna
A high-inulinase-producing strain of Aspergillus candidus (10 units cm(-3) of medium) for producing fructose from inulin has been identified. The extracellular inulinase from this fungi was purified 56-fold by ammonium sulphate fractionation, DEAE cellulose and Sephadex G-150 column chromatography. Invertase to inulinase ration of 1.8 in culture filtrate was reduced to 0.14 in the purified preparation. The pH an temperature optima were 5.5 and 45 degrees C, respectively. The molecular weight of inulinase was determined as 54 +/- 4 kDa. K(m) of inulinase with inulin as a substrate was 3.8 mmole dm(-3). The purified preparation produced only fructose as the product of inulin, indicating that inulinase has primarily exo-inulinase activity. Inulinase was immobilised on chitin and casein using glutaraldehyde as a linking agent and on cellulose using FeCl(3)-HCl as a metal chelation agent. Maximum immobilisation of 45.8% was achieved on cellulose. All three immobilised preparations had a higher temperature optima of 55 degrees C. The inulinases immobilised on cellulose and casein were stable at pH 5-7. The cellulose-immobilised preparation was more stable than the other two preparations after heating for 1 h at 55 degrees C.
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