Extracellular Thermostable Polygalacturonase from Bacillus sp. AD 1

[摘要] The production of polygalacturonase (PG ase) by a locally isolated aerobic bacterium, Bacillus sp. in submerged fermentation (SmF) was optimized. The effects of the fermentation parameters namely initial pH, temperature, cultivation time and nitrogen source on enzyme production were studied using both pure pectin and citrus wastes as the sole carbon source. Polygalacturonase from the strain was maximally secreted at 37°C, initial pH 7.0 with 0.15% (w/v) of pure pectin as sole carbon source. Among citrus wastes, 1% (w/v) orange peel and lemon peel gave the most promising results at pH 7 and 5 respectively. Tryptone was found to be the best nitrogen source for enzyme synthesis. Under optimized conditions, highest PG ase production was achieved at 24th hour, at mid stationary phase of growth of the strain. The enzyme was extremely thermostable and 75% of the activity was restored even after the exposure of the enzyme protein at 80°Cfor 90 minutes. The enzyme was 86% stable in a broad range of pH of 4 to 9. The PG ase activity was found to increase in presence of Mn2+ and also by addition of exogenous thiols like DTT, Cysteine, GSH indicating the presence of thiol groups at the active site.

[学科分类] 药理学