Metabolic Division of Labor between Clostridium Thermocellum Dsm 1313 and Thermoanaerobacterium Thermosaccharolyticum Mj1 Enhanced Hydrogen Production from Lignocellulose

Abstract

Lignocellulose is a cheap, readily available, and abundant raw material for renewable energy. Hydrogen production from lignocellulose by anaerobic fermentation has been paid more attention in recent years. Microbial consortia play an important role in a variety of bioenergy and environmental applications. However, their interactions and underlying mechanisms are poorly understood. In this consortium, DSM 1313 was responsible for degrading lignocellulose by cellulosome, while the highly efficient hydrogen-producing bacterium MJ1 consumed the sugar produced by DSM 1313 to grow and produce more hydrogen. The results showed that the maximum hydrogen production of 115.88 mM was obtained at the inoculation ratio (OD600) of 2:1 (DSM 1313:MJ1) and hydrogen peroxide-acetic acid-sugarcane bagass (HPAC-SCB) concentration of 10 g/L, 70.84% higher than pure culture. Furthermore, MJ1 dominated in the co-culture system by using various sugars resulting from the biodegradation of hydrogen peroxide-acetic acid sugarcane bagasse, thereby relieving the inhibition of sugar on DSM 1313 and leading to more hydrogen production. In the co-culture system, the value of extracellular oxidation-reduction potential was lower and the ratio of NADH/NAD+ was higher than that of pure culture. Additionally, at the gene level, [NiFe]- hydrogenase and [FeFe]- hydrogenase related enzymes such as HypA, HypB, HydE, HydF, etc. were significantly up-regulated, leading to a two-fold increase in hydrogenase activity of co-culture compared with pure culture. This study shed light on the metabolic division of labor between DSM 1313 and MJ1 in co-culture and its underlying mechanism.

Keywords: Co-culture, Anaerobic fermentation, Transcriptome, Potential mechanism.