Agro-industrial residues and starch for growth and co-production of polyhydroxyalkanoate copolymer and α-amylase by Bacillus sp. CFR-67.

Abstract

Polyhydroxyalkanoates (PHA) and α-amylase (α-1,4 glucan-4-glucanohydrolase, E.C. 3.2.1.1) were co-produced by Bacillus sp. CFR-67 using unhydrolysed corn starch as a substrate. Bacterial growth and polymer production were enhanced with the supplementation of hydrolysates of wheat bran (WBH) or rice bran (RBH) individually or in combination (5–20 g L-1, based on weight of soluble substrates-SS). In batch cultivation, a mixture of WBH and RBH (1:1, 10 g L-1 of SS) along with ammonium acetate (1.75 g L-1) and corn starch (30 g L-1) produced maximum quantity of biomass (10 g L-1) and PHA (5.9 g L-1). The polymer thus produced was a copolymer of polyhydroxybutyrate-co-hydroxyvalerate of 95:5 to 90:10 mol%. Presence of WBH and corn starch (10–50 g L-1) in the medium enhanced fermentative yield of α-amylase (2–40 U mL-1 min-1). The enzyme was active in a wide range of pH (4–9) and temperature (40–60°C). This is the first report on simultaneous production of copolymer of bacterial PHA and α-amylase from unhydrolysed corn starch and agro-industrial residues as substrates.