Thermoanaerobacterium thermosaccharolyticum M18 Shows Potential for Hydrogen Gas Production via Consolidated Bioprocessing

Consolidated bioprocessing (CBP) of lignocellulosic biomass to produce hydrogen gas possesses great potential due to its lower cost and higher efficiency. The focus of many studies today is the utilization of certain thermophilic bacteria such as Clostridium thermocellum and Caldicellulosiruptor saccharolyticus in CBP-based hydrogen production. However, moderately thermophilic bacteria from the genus Thermoanaerobacterium have not been evaluated for its capability to be the sole microorganism to accomplish both cellulose degradation and hydrogen generation. 

Moderately thermophilic cellulolytic bacteria capable of producing hydrogen from lignocellulosic materials were screened. Three new strains were isolated, all from the genus Thermoanaerobacterium, growing at 60°C. All bacteria grew well on various plant polymers. One isolated bacterium, named Thermoanaerobacterium thermosaccharolyticum M18, showed high cellulolytic activity and a high yield of hydrogen gas. When the bacterium was grown in microcrystalline cellulose, its production rate reached a maximum of 2.05 mmol H²/L/hour. Corn cobs, corn stalks, and wheat straws without any pretreatment also supported the growth of strain M18 and yielded of 3.23 to 3.48 mmol H2/g of biomass at an average production rate of 0.13 mmol H²/L/hour.

The newly isolated strain T. thermosaccharolyticum M18 proved to be effective in degrading lignocellulose and producing large amounts of hydrogen. The extraordinary yield and specific rate of hydrogen for strain M18 obtained from lignocellulose make it more attractive in monoculture fermentation. T. thermosaccharolyticum M18 is thus a potential candidate for rapid conversion of lignocellulose to biohydrogen in just a single step.