Bioconversion of Sago Starch to Bioplastic Poly-β-Hydroxybutyrate (PHB) by Local Strain Bacterial Bacillus megaterium PSA10

Nur Arfa Yanti* and Nurhayani

Abstract

The potential local strain Bacillus megaterium PSA10 in bioconversion sago starch to bioplastic, Poly-β- hydroxybutyrate (PHB) was investigated in this study. The bacterial strain was grown in fermenter using sago starch minimal media, furthermore was observed enzymatic activity, the products and its growth pattern. Amylase enzyme activity measurements performed using 3’5-dinitrosalicylic acid (DNS) and PHB synthase enzyme activity using Valentin and Steinbuchel methods. Reducing sugar and PHB levels were detected using spectrophotometric method and the biomass growth was measured by gravimetric method. The highest specific activity of the enzyme amylase and reducing sugar concentration were obtained at 18 hours of incubation, i.e. 170.72 U/mg protein and 14.08 g/L, respectively while the highest specific activity of PHB synthase enzyme and the PHB concentration were obtained at 36 hours of incubation i.e. 85.72 U/mg protein and 2.86 g/L, respectively. The growth maximum of B.megaterium PSA10 was obtained at 42 hours of incubation and the strain bacteria was able to accumulate PHB as much as 85.04% wt/wt of the cell dry weight at 36 hours of incubation. Therefore, B.megaterium PSA10 converts sago starch into bioplastic PHB via direct bioconversion