High cell density strategy for poly(3-hydroxybutyrate) production by Cupriavidus necator

Abstract

Poly(3-hydroxybutyrate) (P(3HB)) is a carbon and intracellular storage source for different microorganisms and its production can achieve high productivities by means of high cell density cultures. The aim of this study was to propose a high cell density strategy for P(3HB) production by Cupriavidus necator. The exponential growth phase demands an accurate control of the oxygen transfer system in the bioreactor, due to maximum specific growth rate (μX1), and, consequently, a maximum specific oxygen uptake rate (QO2), in addition to significant residual biomass (Xr) growth in high cell density cultures. In this context, this work investigated the strategy for obtaining high cell density, with the inclusion of a linear growth phase for P(3HB) production by C. necator in a fed-batch culture. The linear growth phase was included between the exponential growth phase and the P(3HB) production phase as a strategy to reduce the specific growth rate (μX1) and specific oxygen uptake rate (QO2), with constant residual biomass growth rate (d(V.Xr)/dt = k = constant) and linear increase of biomass. Three strategies of culture were performed. The results showed that a high residual biomass concentration (30 gXr·L-1) can be reached by the inclusion of the linear growth strategy and specific growth rates (μX1) between 0.08 and 0.05 h-1, at the beginning of the production phase, are necessary to attain a high P(3HB) productivity. © 2011 The authors.