Studies On Bio-Hydrogen And Ethanol Production From Sugarcane Bagasse Through Thermophilic Anaerobic Fermentation

Nowadays,growing demand on energy,fossil fuel exhaustion and increasing concerns about environmental pollution problems resulted from the use of fossil fuel become more serious,the development of alternative and renewable energy sources has become a key consideration in discussion of sustainable development.Biofuels such as biological hydrogen and ethanol are regarded as the most promising new energy in the 21 st century for its clean,efficient and renewable characteristics.Biofuels from aboundant lignocellulosic materials on earth have drawn attention of global countries.This study investigated hydrogen and ethanol production from sugarcane bagasse?SCB?by Clostridium thermocellum ATCC 27405 and Thermoanaerobacterium aotearoense SCUT27/?ldh from several aspects: 1)enhanced hydrogen and ethanol production from SCB by C.thermocellum and T.aotearoense supplemented with CaCO₃;2)effect of pH control strategies on hydrogen production from SCB by C.thermocellum;3)enhanced degradation of SCB by C.thermocellum and T.aotearoense supplemented with CaCO₃ and nonionic surfactant Triton X-100.Hydrogen production could be significantly enhanced by C.thermocellum supplemented with CaCO₃.Under the optimal CaCO₃ concentration of 20 mM,the hydrogen production reached 97.83±5.19 mmol/L from 2% pretreated SCB,a 116.72% increase over the control.Comparing with the mono-culture of C.thermocellum,hydrogen production could not be enhanced by the co-culture process of C.thermocellum and T.aotearoense supplemented with CaCO₃,but ethanol production could be significantly enhanced.Under the optimal fermentation condition,the ethanol production reached 10.60±0.81 mM from 2% pretreated SCB,a 192.82% increase over the control.The stimulatory effects of CaCO₃ on hydrogen and ethanol production are mainly attributed to the buffering capacity of carbonate.Hydrogen production could be significantly influenced by constant pH control and two-stage pH control strategies in 500 m L CSTR bioreactor.The optimal pH for hydrogen production by C.thermocellum is about 6.0.Hydrogen production rivalled with other metabolites in fermentation broth in C.thermocellum metabolism.Two-stage pH control strategy could not enhance hydrogen production significantly by C.thermocellum.The biodegradation of SCB could be enhanced significantly by the co-culture process of C.thermocellum and T.aotearoense supplemented with CaCO₃ and nonionic surfactant Triton X-100.Under the optimal fermentation condition,the concentration of reducing sugars reached 14.07±0.67 g/L.Nonionic surfactant Triton X-100 was toxic to C.thermocellum and T.aotearoense,and it could terminate the metabolism.But Triton X-100 could promote the enzymatic activities of CMCase,xylanase and ?-glucosidase,and contributed to the saccharification of SCB.This study,on one hand,provides a novel strategy to enhance hydrogen and ethanol production by thermophilic anaerobes from lignocellulosic materials in consolited bioprocessing.On the other hand,a new idea is put forward to enhance the biological saccharification of lignocellulosic materials.