초록
<P><B>ABSTRACT</B></P><P>It is well established that metabolic pathways in the fermentation of organic waste are primarily controlled by dissolved H<SUB>2</SUB> concentrations, but there is no reported study that compares observed and predicted shifts in fermentation pathways induced by manipulating the dissolved H<SUB>2</SUB> concentration. A perfusion system is presented that was developed to control dissolved H<SUB>2</SUB> concentrations in the continuous fermentation of glucose by a culture highly enriched towards <I>Thermoanaerobacterium thermosaccharolyticum</I> (86 ± 9% relative abundance) from an originally diverse consortia in the leachate of a laboratory digester fed with municipal solid waste. Media from a 2.5 L CSTR was drawn through sintered steel membrane filters to retain biomass, allowing vigorous sparging in a separate chamber without cellular disruption. Through a combination of sparging and variations in glucose feeding rate from 0.8 to 0.2 g/L/d, a range of steady state fermentations were performed with dissolved H<SUB>2</SUB> concentrations as low as an equivalent equilibrated H<SUB>2</SUB> partial pressure of 3 kPa. Trends in product formation rates were simulated using a H<SUB>2</SUB> regulation partitioning model. The model correctly predicted the direction of products redistribution in response to H<SUB>2</SUB> concentration changes and the acetate and butyrate formation rates when H<SUB>2</SUB> concentrations were less than 6 kPa. However, the model over‐estimated acetate, ethanol and butanol productions at the expense of butyrate production at higher H<SUB>2</SUB> concentrations. The H<SUB>2</SUB> yield at the lowest dissolved H<SUB>2</SUB> concentration was 2.67 ± 0.08 mol H<SUB>2</SUB>/mol glucose, over 300% higher than the yield achieved in a CSTR operated without sparging. Biotechnol. Bioeng. 2015;112: 1177–1186. © 2014 Wiley Periodicals, Inc.</P>