[Cellulose degradation and ethanol production of different Clostridium strain]

Cellulose degradation and ethanol production of two types of cellulosic materials with different concentration were evaluated in batch system of mono-cultures of cellulolytic ethanol producing strains (Clostridium thermocellum strain LQRI and Clostridium thermocellum strain VPI), and co-cultures of LQRI or VPI in combination with one of the non-cellulolytic ethanol producing strains (Thermoanaerobacter ethanolicus strains X514 or Thermoanaerobacter ethanolicus 39E). Results demonstrated that higher cellulose degradation abilities about 1.2 times were detected in LQRI mono-culture than in VPI mono-culture, while no significant difference of ethanol yields was found between the two mono-cultures. Abilities of cellulose degradation and ethanol production decreased significantly with the increasing of substrate cellulose concentration (1%, 2%, 5%). In the co-culture system, cellulose degradation abilities of LQRI were also significantly higher than VPI, the former is 1.28-1.58 times of the latter. Cellulose degradation rate of LQRI + Thermoanaerobacter and VPI + Thermoanaerobacter decreased gradually with the increasing of substrate cellulose concentration, while the absolute value of cellulose degradation was also affected by the partner Thermoanaerobacter strain. Additionally, the ethanol yields in the co-cultures of LQRI + Thermoanaerobacter were significantly higher than that in the co-cultures of VPI + Thermoanaerobacter with same Thermoanaerobaeter partner, the former is 1.27-1.77 times of the latter. However, ethanol yields in the co-cultures have not significantly declined with the increasing of substrate cellulose concentration.