Effect of fluid dynamic conditions on 2,3‐butanediol production by Raoultella terrigena in SBTR: oxygen transfer and uptake rates

Abstract

BACKGROUND The fluid dynamic conditions play a key role in the development and scaling‐up of bioprocesses. In aerobic cultures, oxygen is an essential substrate for microbial growth, production and culture maintenance; an effective gas–liquid transfer must be achieved. Changes in fluid dynamics due to stirrer speed can affect the culture negatively, causing hydrodynamic stress (increasing shear stress) or oxidative stress (by an increase of available oxygen in the liquid phase). RESULTS Under oxygen‐limiting conditions, specific growth rate increases with stirrer speed, and several fermentation products were specifically released to the culture medium. 2,3‐butanediol production increased with stirrer speed, reaching a maximum at 400 rpm. When the agitation was increased over 550 rpm, the metabolic flux was mainly routed to increase the cell growth. Negative effects of fluid dynamic conditions on biomass production were observed at 1900 and 2000 rpm. Cellular response to shear stress conditions was also shown in the large increase of the broth viscosity over time. CONCLUSIONS Raoultella terrigena is able to adapt the carbon metabolic flux to the availability of oxygen, producing fermentation products, alcohols or directing microbial growth. Moreover, cells can withstand aggressive agitation conditions (up to 1600 rpm). © 2016 Society of Chemical Industry

Improved Raoultella planticola Strains for the Production of 2,3-Butanediol from Glycerol

“…The dissolved oxygen concentration was set at 5% in all cases because it has been reported that 2,3-BD production with Raoultella sp. strains is efficient under oxygen limiting conditions [18]. Statistical analysis of variability associated to each factor indicated that glycerol concentration, temperature and cobalt-salt concentration significantly influenced the objective functions.…”

“…By increasing oxygen supply, higher cell densities and higher production rates are obtained. However, too much aeration, exceeding the microbial oxygen demand, leads to biomass and carbon dioxide as products [18]. Therefore, fine-tuning of oxygen availability is required in order to optimize 2,3-BD production, so the oxygen saturation was controlled at 5%.…”

“…Concentration of organic acids such as succinic acid, lactic acid and acetic acid are very low or not detected under the conditions of the assays, particularly in bioreactor tests. Only acetoin and ethanol were detected by HPLC method (see Materials and Methods section), then considering metabolic pathways of 2,3-BD production from glycerol, the fermentation conditions were properly optimized [18,21]. The potential that lies in the improvement of biocatalysts and intensified fermentation methods, coupled with optimization procedures and making worthy fermentation systems, will enable the development of bioprocesses to achieve 2,3-BD production efficiently [29].…”

Behavior of several pseudomonas putida strains growth under different agitation and oxygen supply conditions

“…In a stirred tank bioreactor (STBR), the airflow rate and the agitation are the main variables affecting fluid dynamic conditions, and they have a decisive importance in the growth rate of cells and in product distribution, even in the controlling step of the overall bioprocess rate culture . Many studies have shown how the agitation and aeration rates influence the oxygen transfer rate but there are much less studies on the influence on cell growth and metabolites productivity …”

“…[3][4][5] Many studies have shown how the agitation and aeration rates influence the oxygen transfer rate but there are much less studies on the influence on cell growth and metabolites productivity. 4,[6][7][8] The biodesulfurization of fossil fuels has been widely studied, employing different biocatalysts to transform dibenzotiophene (DBT) into 2-hydroxybiphenil (2-HBP). 4,[9][10][11][12] This bioprocess has experienced a great impulse, since the 4S route had been discovered in Rhodococcus erythropolis IGTS68.…”