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

ABSTRACT

Polyhydroxyalkanoates (PHA) and -amylase (-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 (11, 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 955 to 9010 mol%. Presence of WBH and corn starch (10-50 g L-1) in the medium enhanced fermentative yield of -amylase (2-40 U mL-1 min-1). The enzyme was active in a wide range of pH (4-9) and temperature (40-60ºC). This is the first report on simultaneous production of copolymer of bacterial PHA and -amylase from unhydrolysed corn starch and agro-industrial residues as substrates.