ABSTRACT
Hydrogen was produced from steam-exploded corn stover by using a combination of the cellulolytic bacterium Clostridium cellulolyticum and non-cellulolytic hydrogen-producing bacteria. The highest hydrogen yield of the co-culture system with C. cellulolyticum and Citrobacter amalonaticus reached 51.9 L H2/kg total solid (TS). The metabolites from the co-culture system were significantly different from those of the mono-culture systems. Formate, which inhibits the growth of C. cellulolyticum, could be consumed by the hydrogen-evolving bacteria, and transformed into hydrogen. Glucose and xylose were released from corn stover via hydrolysis by C. cellulolyticum and were quickly utilized in dark fermentation with the co-cultured hydrogen-producing bacteria. Because the hydrolysis of corn stover by C. cellulolyticum was much slower than the utilization of glucose and xylose by the hydrogen-evolving bacteria, the sugar concentrations were always maintained at low levels, which favored a high hydrogen molar yield.
Subject(s)
Citrobacter/metabolism , Clostridium cellulolyticum/metabolism , Fermentation , Hydrogen/metabolism , Zea mays/metabolism , Biomass , Cellulose/metabolism , Citrobacter/cytology , Citrobacter/growth & development , Clostridium cellulolyticum/cytology , Clostridium cellulolyticum/growth & development , Coculture Techniques , Formates/metabolism , Glucose/metabolism , Hydrolysis , Steam , Xylose/metabolism , Zea mays/chemistryABSTRACT
Hydrolysis is usually the rate-limited step for methane production from lignocellulosic substrate. Two bioaugmentation strategies, using the cellulolytic anaerobic bacteria Clostridium cellulolyticum, were adopted to enhance the hydrolysis of wheat straw with the purpose of improving the biochemical methane potential (BMP). Namely, the 24-h-incubated seed (C24S) with cellobiose as carbon source and the 60-h-incubated seed (WS60S) with wheat straw as carbon source were respectively used as the bioaugmentation agents. As a result, the BMPs were respectively 342.5 and 326.3 ml g(-1) VS of wheat straw, with an increase of 13.0% and 7.6% comparing to the no-bioaugmentation BMP of 303.3 ml g(-1) VS. The result indicates that the anaerobic digestion efficiency can be improved by bioaugmentation, which therefore may be a promising method for improving methane production from lignocellulosic substrate.
