Production and partial purification and characterization of a thermo-alkali stable polygalacturonase from Bacillus sp MG-cp-2

Bacillus sp. MG-cp-2, isolated from the outer covering of seeds of Celastru s paniculatus, optimally produced an alkaline and thermostable polygalactur onase in minimal (47 U/ml) and enriched (98 U/ml) media, supplemented with 1% (w/v) citrus pectin in submerged fermentation. Various agro-byproducts, such as wheat bran, sunflower seed cake, rice bran, orange peel and guar gu m, significantly enhanced the polygalacturonase yield by 1.92-fold (188.8 U /ml), 1.47-fold (144 U/ml), 1.44-fold (140.8 U/ml), 1.43-fold (140.1 U/ml) and 1.42-fold (140 U/ml), respectively. In an immobilized cell system using polyurethane foam (PUF), the polygalacturonase yield was enhanced by 1.5-f old (147 U/ml). In SSF using wheat bran and decorticated ramie fibre as the prime solid substrates, polygalacturonase yields of 3200 U/g and 590 U/g d ry solid substrate, respectively, were obtained at substrate-to-moisture ra tio of 90%. The partially purified polygalacturonase was optimally active a t 60 degreesC at pH 10.0 with half-lives of 120, 118 and 20 min at 60, 70 a nd 80 degreesC, respectively. The enzyme was 100% stable at 50 degreesC for more than 12 h. Polygalacturonase was stable in a broad alkaline pH range 7.0-12.0 for more than 24 h at room temperature, retaining more than 80% of its activity. Surface-active detergents such as Tweens, Triton X-100 and S DS stimulated the polygalacturonase activity up to 41%, whereas metal ions, such as Ag+, Li+, Ca2+, Ba2+ and Ni2+ stimulated the polygalacturonase up to 28%, and Mn2+, iodoacetamide and iodoacetic acid completely inhibited th e enzyme activity. (C) 2000 Elsevier Science Ltd. All rights reserved.