Biological hydrogen production from renewable lignocellulosic waste has attracted significant attention due to its advantages such as low energy input and high production rate and environmentally friendly. Clostridium thermocellum, a cellulose-degrading bacterium,has great potential for the direct production of hydrogen from lignocellulosic waste but it still has some weaknesses. So a combination of cellulose-hydrolyzing bacteria and highly efficient hydrogen-producing bacteria was needed to improve hydrogen production from cellulosic waste under thermophilic or mesophilic fermentation conditions.

Researchers with Institute of Process Engineering (IPE) developed a synergistic co-culture process to optimize the combination of cellulolytic and hydrogen-producing microbial strains, allow for the scale-up of the fermentation process and include low-cost pretreatment methods for the lignocellulosic waste.

Researchers carried out co-culture experiments in anaerobic bottles and in continuous stirred tank reactor (CSTR) respectively. In their work, raw cornstalk waste was used to test the co-culture performance of C. thermosaccharolyticum and C. thermocellum for hydrogen production. Results showed the hydrogen yield in the co-culture fermentation process reached 68.2 mL/g-cornstalk which was 94.1% higher than that in the mono-culture. The hydrogen fermentation process was successfully scaled-up from 125 mL anaerobic bottles to an 8 L continuous stirred tank reactor, and the hydrogenproduction from cornstalkwaste was significantly improved in the bioreactor system due to efficient mixing and mass transfer.

Hydrogen production in the co-culture of C. thermocellum and C. thermosaccharolyticum in a CSTR was analyzed. The hydrogen yield in the bioreactor reached 74.9 mL/g-cornstalk which was 9.8% higher than that in the 125 mL anaerobic bottle. To the best of our knowledge, this is the first report of successful hydrogenproduction from cornstalkwaste by thermophilicco-culture in a bioreactor system.

The study not only improves our understanding on the synergistic co-culture process but also aids in the development of a promising strategy for biohydrogen productionvia the direct microbial conversion of lignocellulosic waste. These results provide the basis for exploring the future process development of thermophilic hydrogen fermentation of cornstalk waste by cellulolytic anaerobes combined with high-yield biohydrogen producers.

The paper was published in International Journal of Hydrogen Energy.