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. © 2019 Society of Chemical Industry