Porcine pancreas lipase was immobilized by entrapment in Gellasan beads, a polyionic hydrogel obtained by
complexation between gellan gum and chitosan. The activity of free and immobilized lipase was assayed in aqueous and
organic solvents using p-NPP as the substrate. The comparison of activities of free and immobilized lipase in aqueous and
organic media resulted in higher activity in the aqueous media. Amongst the organic solvents, non-polar solvents like
cyclohexane, carbon tetrachloride and n-heptane gave higher activity than polar solvents. Similarly, the amount of added
water upto 100 μl in the organic medium of cyclohexane increased the reaction rate of the immobilized than free. The
immobilized enzyme exhibited a shift towards alkaline pH for its optimal activity. The apparent optimum temperature for the
immobilized enzyme was 8-100C higher than that for the free enzyme, stabilizing the immobilized enzyme against heat
treatment and thereby improving its thermal stability. The optimum loading obtained was 500 mg lipase/g of the support.
The immobilizate showed a decent operational stability retaining almost 50% activity in aqueous medium and 40% activity
in organic medium after four reuses. The storage stability was remarkable too since, the enzyme retained 25% activity even
after three months at room temperature.
Key words: Gellasan; Lipase Assay; non-conventional media; protein loading; Enzyme stability
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