PJB-2018-1083
EXTRACTION AND CHARACTERIZATION OF A HYPERACTIVE PECTIN METHYLESTERASE FROM γ-IRRADIATED CITRUS LIMON (L.) PEELS
Sikander Ali
Abstract
In the present study, thermostable pectin methylesterase (TS-PME) was extracted and partially purified from γ-irradiated lemon (Citrus limon L.) peels irradiated at 150 krad. Under different conditions such as pH, temperature and cation concentration, the relative enzyme activity was measured. The enzyme exhibited maximum activity when extracted with 1 M Tris-base solution containing 0.8 M NaCl at pH 10, 50°C incubation temperature and 2.5 mM CaCl2 concentration. The enzyme showed thermostability till 70°C. The molecular weight of the enzyme was found to be 35 kDa. The partially purified enzyme was used for the clarification of freshly extracted apple juice under different parameters. The maximum apple juice clarification was observed with 5 U/ml TS-PME, 2.5 mM CaCl2, 15 min holding time and 20 % juice dilution. Scanning electron microscopy revealed the release of substrate after enzyme extraction. Texture analysis showed a marginal difference among the peels before and after enzyme extraction. The results in terms of maximum TS-PME activity with thermophilic behaviour are highly significant (HS, p≤0.05) indicating a viable bioprocessing strategy. It was further concluded that the extraction of enzyme from γ-irradiated is not only important for juice clarification but also bears the potential to be exploited in food industry.
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