Enhanced growth of Pichia pastoris under increased air pressure on different carbon sources

Abstract

Batch fermentations, in hyperbaric reactor, were performed to study the effect of increase total air pressure on the growth of Pichia pastoris CBS 2612 on different carbon sources and respective anti-oxidative cellular response. Pichia pastoris strain was grown in glucose, glycerol and methanol media under total air pressure from 1 bar to 5 bar. In all the experiments, the cultures reached maximum cell density at 5 bar of total air pressure. A 3-fold increase on specific growth rate was obtained at 5 bar on glycerol compared to the value at 1 bar. Biomass yield was also enhanced by air pressure rise, for all carbon sources. With 5 bar air pressure biomass yield (g cells/g carbon) was 0.97, 1.53 and 1.86 whereas at 1 bar was 0.67, 1.72 and 0.77, respectively in methanol, glucose and glycerol media. For all carbon sources tested, an increase of air pressure led to an enhance of malondialdehyde, a lipid peroxidation marker. It was also observed an induction of anti-oxidant enzymes, such as SOD, catalase and glutathione reductase, indicating that cells were able to respond to the oxidative stress caused by oxygen partial pressure increase.