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 (µ Xr ), and, consequently, a maximum specific oxygen uptake rate (QO 2 ), 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 (µ Xr ) and specific oxygen uptake rate (QO 2 ), 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 g Xr .L -1 ) can be reached by the inclusion of the linear growth strategy and specific growth rates (μ Xr ) between 0.08 and 0.05 h -1 , at the beginning of the production phase, are necessary to attain a high P(3HB) productivity.

CAN VINASSE BE USED AS CARBON SOURCE FOR POLY(3-HYDROXYBUTYRATE) PRODUCTION BY Cupriavidus necator DSM 545?

“…The natural nitrogen concentration present in vinasse, when this culture started, was approximately 0.06 g.L -1 . This concentration indicated nitrogen limitation, according to Ienczak et al (2011) since the beginning of the culture and allowed PHB accumulation during all the course of the culture even with low carbon available, achieving a concentration around 35%. Since this cultivation ( Fig.…”

A Review on Established and Emerging Fermentation Schemes for Microbial Production of Polyhydroxyalkanoate (PHA) Biopolyesters

“…Here, one either resorts to periodic sampling and ex situ substrate analysis, or to modern online sensors enabling in situ substrate control; in the PHA case, such analytical online systems are described for the use of glucose or methanol as substrates. However, more advanced systems resort to the coupling of carbon source feeding to the actual concentration of dissolved oxygen in fermentation broth, or the CO2 level in the gas stream leaving the bioreactor; a lack of carbon source results in increased pO2 levels due to reduced metabolic activity, and decreased CO2 levels in exhaust gas due to decreased aerobic respiration [81,82].…”

POLY(3-HYDROXYBUTYRATE) PRODUCTION BY Cupriavidus necator SUPPLEMENTED WITH MINIEMULSIFIED SOYBEAN OIL

“…Evaluating the different moments when the supplement was added, the nitrogen concentration that promoted the highest lipase activity was 0.4 g.L -1 , considered to be the limiting concentration of this substrate in the medium, which promotes the beginning of the synthesis of P(3HB) (Ienczak et al, 2011), for both ways in which the oil was supplemented. From these results, to achieve better enzymatic activities of lipases, the moment at which the supplement should be added to the cultures is when the nitrogen concentration in the culture medium is 0.4 g.L -1 .…”