Abstract Studies have shown that the supplementation of vegetable oils, in poly(3-hydroxybutyrate) production, provides an increase in the process productivity, besides inducing lipase activity in the medium. The supplementation with miniemulsified oils could potentialize these results. In this work, the influence of supplementation of the medium with soybean oil, without treatment and miniemulsified, on polymerr production was evaluated. The best moment to supplement the medium and its influence on lipase activity were also analyzed. The results showed that the supplementation with miniemulsified soybean oil promoted an increase of 9.7% in polymer content and the productivity increased from 0.58 to 0.63 g.L-1.h-1, when compared with the culture without supplementation. The best time to add the supplement is in the beginning of the production phase. The lipase activity was higher for the culture supplemented with miniemulsified soybean oil, promoting the use of the oil.

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 (µXr), 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 (µXr) 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 (µXr) between 0.08 and 0.05 h-1, at the beginning of the production phase, are necessary to attain a high P(3HB) productivity.