Optimization of cultural conditions for pectinase production by Streptomyces sp. and characterization of partially purified enzymes

Abstract

The cultural parameters of Streptomyces sp. for pectinase production were optimized using the Box-Behnken design. The maximum pectinase production was obtained after 58 hours at 35℃ and pH 7 upon submerged fermentation in yeast extract-containing media. The enzymes were partially purified with acetone precipitation and the analysis by SDS-PAGE and zymogram revealed that Streptomyces sp. produced two pectinases with molecular weights of about 25 and 75 kDa. The pectinase activity was detected in a wide range of temperatures (30℃ to 80℃) and pH (3 to 9) with maximum pectinase activities observed at 70℃ and pHs 5 and 9. The enzymes retained about 30 to 40% of their activities even after incubating the enzyme at different temperatures for 120 mins. The pectinase activities of Streptomyces sp. were enhanced in the media containing 1.5% pectin, 1% casein as a nitrogen source, 0.5 mM MgSO4, and 5 mM NaCl. Further, the addition of Tween-20, amino acids, and vitamins to the media also enhanced the pectinase activity. Moreover, the bacterium illustrated the ability to decolorize crystal violet dye efficiently. The decolorization rate ranged from 39.29 to 53.75% showing the highest bacterial decolorization in the media containing 2mg/mL crystal violet at 144 hours. Therefore, the bacterium has the potential in treating wastewater produced by industries like textile industries.