Bioconversion of glycerine pitch into a novel yellow-pigmented P(3HB-co-4HB) copolymer: synergistic effect of ammonium acetate and polymer characteristics.

Glycerine pitch waste generated from oleochemical industry was exploited as a carbon source for poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P(3HB-co-4HB)) copolymer production by a novel, yellow-pigmented bacterium Cupriavidus sp. USMAHM13 to improve the economics of microbial polyhydroxyalkanoate production and to establish a feasible waste management approach. Medium optimization using response surface methodology through shake-flask fermentation had led to the accumulation of P(3HB-co-51%4HB) copolymer using a combination of glycerine pitch (10 g/l), 1,4-butanediol (8.14 g/l), and ammonium acetate (2.39 g/l). P(3HB-co-4HB) copolymers with 4HB monomer compositions ranged from 3 to 40 mol% were obtained through batch fermentation in a bioreactor using different concentrations of ammonium acetate. The copolymers exhibited a wide range of material properties depending on the monomer composition and type of carbon sources. P(3HB-co-40%4HB) was a typical random copolymer, whereas other P(3HB-co-4HB) produced were blend copolymers. Carotenoid pigment which was produced simultaneously with the polymer production was found to have negligible effect on the mechanical and thermal properties of the P(3HB-co-4HB) copolymer films.