Production and recovery of poly-3-hydroxybutyrate [P(3HB)] of ultra-high molecular weight using fed-batch cultures of Azotobacter vinelandii OPNA strain

BACKGROUND: Poly-3-hydroxybutyrate P(3HB) is a bioplastic that is characterized for its biodegradability and biocompatibility and can be used in the biomedical field. The aim of this study was to evaluate the scaling-up process at pilot level, for the production and recovery of P(3HB) synthesized by Azotobacter vinelandii OPNA strain, based on the use of fed-batch fermentation coupled to a recovery method using nonhalogenated solvents (ethanol and acetone). RESULTS: In fed-batch cultivations at the 3-L scale, using yeast extract and sucrose of industrial grade with a carbon:nitrogen ratio of 14 and manipulating the agitation rate from 500 to 700 rpm to give a maximal biomass concentration of 33.8 ± 1.5 g L⁻¹, P(3HB) concentrations of 29 ± 4.5 g L⁻¹ were reached. By simulating the gassed volumetric power input observed in the 3-L bioreactors at the different agitation rates (500 and 700 rpm), a scaling-up to 30-L bioreactors was performed. At this scale, the P(3HB) concentration, and productivity were similar or even better than those values obtained at the smaller scale. The production process was coupled to a P(3HB) separation process, in which the polymer was precipitated with ethanol and washed with acetone, reaching a purity close to 95% and a yield of 85%. The P(3HB) obtained was of ultra-high molecular mass, with values of 5693 ± 615 kDa. CONCLUSION: In this study a successful scaling-up process for the production of P(3HB) of ultra-high molecular weight at pilot scale was developed.