Produção de poligalacturonase, pelo termofílico Bacillus sp. e algumas de suas propriedades

Abstract

Polygalacturonase production by thermophilic Bacillus sp strain SMIA-2 cultivated in liquid media containing citrus pectin as a carbon source reached the maximum activity at 30 hour with levels of 42 IU.mL-1. Among the various organic and inorganic nitrogen sources, ammonium sulphate was found to be the best for the enzyme secretion. An increase in the citrus pectin concentration in the medium of more than 0.5% did not enhance enzyme synthesis. The microorganism was capable of utilizing a wide range of carbon sources, but the activity of poligalacturonase varied depending on the carbon source. Apple's pectin was the best carbon source in the present study for polygalacturonase secretion (56 IU. mL-1) while fructose and maltose were not very effective. Rafinose and glucose inhibited the enzyme synthesis. Studies on the polygalacturonase characterization revealed that the optimum temperature of this enzyme was 70 ??C and that it maintained 62 and 58% of its activity when incubated at 40 ??C and 90 ??C for 2 hour, respectively. The optimum pH of the enzyme was found to be 7.0. The enzyme maintained 90% and 75% of its maximal activity when incubated at pH 8.0 and 8.5 for 24 hour at room temperature, respectively. The enzyme activity was enhanced in the presence of Mg2+and Zn2+. On the other hand, the activity was inhibited in the presence of Cs+2, Hg+2, Li+2 and Sr+2.