Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) production in a system with external cell recycle and limited nitrogen feeding during the production phase

•Proposition of an alternative system to produce polyhydroxyalkanoates using substrate with moderate carbon concentration.•Sustaining a residual growth during production phase improves specific P(3HB-co-3HV) production rate.•The nitrogen supply, during production phase, changes the 3-hydroxyvalerate incorporation profile.

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (P(3HB-co-3HV)) is a biodegradable, biocompatible and thermoplastic biopolymer produced by microorganisms. Considering their high current production cost, the use of wastes and culture strategies designed to increase the process productivity has been studied. The aim of the present work was to evaluate the P(3HB-co-3HV) production from Cupriavidus necator in a repeated fed-batch system with external cell recycle, maintaining a controlled residual cell growth during the production phase by nitrogen feeding strategy. The glucose, at the feeding culture medium, simulated the carbon concentration usually found in agro-industrial wastes. Two cultures were performed: one conducted with nitrogen exhaustion and another with nitrogen feeding in limited concentrations, during the production phase. Propionic acid was added to allow 3HV production. In both cultures 73 % of P(3HB-co-3HV) was produced, but at the culture with nitrogen feeding, during the production phase, productivity reached 1.24 gP(3HB-co-3HV).L−1.h−1 and qP(3HB-co-3HV) remain at the maximum level (0.13 gP(3HB-co-3HV).gXr−1.h−1) during more time. The 3HV percentage was similar at the end of both cultures. It can be concluded that the system with external cell recycle and nitrogen feeding, during the production phase, is a good alternative to utilize agro-industrial wastes with moderate carbon concentration and to increase productivity of P(3HB-co-3HV).