Co-Production of Poly(3-hydroxybutyrate) and Gluconic Acid from Glucose by Halomonas elongata

Abstract

Polyhydroxyalkanoates (PHA) are biopolyesters regarded as an attractive alternative to petroleum-derived plastics. Nitrogen limitation and phosphate limitation in glucose cultivations were evaluated for poly(3-hydroxybutyrate) (P(3HB)) production by <i>Halomonas elongata</i> 1H9^T, a moderate halophilic strain. Co-production of P(3HB) and gluconic acid was observed in fed-batch glucose cultivations under nitrogen limiting conditions. A maximum P(3HB) accumulation of 53.0% (<i>w</i>/<i>w</i>) and a maximum co-production of 133 g/L of gluconic acid were attained. Fed-batch glucose cultivation under phosphate limiting conditions resulted in a P(3HB) accumulation of only 33.3% (<i>w</i>/<i>w</i>) and no gluconic acid production. As gluconic acid is a valuable organic acid with extensive applications in several industries, this work presents an interesting approach for the future development of an industrial process aiming at the co-production of an intracellular biopolymer, P(3HB), and a value-added extracellular product, gluconic acid.