Most fermentation studies are carried out under ambient pressure. Although pressurized fermentation has been widely applied in brewing industry to reduce the production of yeast ester and fusel alcohol for better flavor and aroma control, there is no systematic study of the effects of elevated pressure on bacterial growth, cell viability and productivity of C1 gas organisms such as C. necator H16. The BIV award was used to start research to investigate the effect of pressure on the growth of C. necator H16 during fermentation:
(a) under heterotrophic cultivation conditions
(b) under autotrophic cultivation conditions
A snapshot of the results are shown below, where increase in optical density (as a measure of bacterial growth) is plot as a function of time. The heterotrophic growth with Gluconate as the carbon is compared with autotrophic growth based on H2, CO2 and air feed, at 1, 3 and 4 bar. The improvement from 1 to 3bar is clear but further increase in pressure further did not continue the trend.
The reactor was equipped not only with HEL’s optical density probe but also with an FTIR from Bruker and an Aber probe to monitor viable cell density.
The objective is to continue this work in 2019 and develop the technology further.
The experiments were done at HEL’s laboratory in Borehamwood, using a BioXplorer 400 bioreactor system, with a 500 ml bioreactor, rated to 10 bar, under the direction of Dr Kang Lan Tee (supervised by Dr Tuck Seng Wong) of Sheffield University.