Production, thermal stability and immobilisation of inulinase from Fmarium oxysporum

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Abstract
Fusarium oxysporum produced maximum extracellular inulinase after 9 days of its growth at 25°C on a medium (pH 5.5) containing 3% fructan and 0.2% sodium nitrate. The level of this enzyme decreased on the addition of either glucose, fructose, galactose or sucrose to F. oxysporum already growing on a fructan‐containing medium. A significant increase in invertase production which resulted in an increase of the invertase/inulinase (S/I) ratio, was observed on addition of inulin to this fungus growing on other carbon sources. Glycerol (10%) gave better protection to inulinase against thermal denaturation at 50°C compared to ethylene glycol and sorbitol. Inulinase immobilised in polyacrylamide gel retained 45% of its original activity. The immobilised enzyme showed a higher optimum temperature (45°C) compared to free enzyme (37°C). The immobilised enzyme after storage at 25°C for 96 h showed 58% activity. Thermal stability of entrapped inulinase increased in the presence of inulin.