期刊
BIOTECHNOLOGY AND BIOENGINEERING
卷 115, 期 7, 页码 1755-1763出版社
WILEY
DOI: 10.1002/bit.26590
关键词
biohydrogen; Clostridium thermocellum; consolidated bioprocessing (CBP); lignocellulose; thermophile; xylose
资金
- National Renewable Energy Laboratory (NREL) Laboratory Directed Research and Development (LDRD) Subtask [0627-1403]
- US Department of Energy (DOE) Energy Efficiency and Renewable Energy (EERE) Fuel Cell Technologies Office [DE-AC36-08-GO28308]
- DOE Bioenergy Technologies Office
Cellulose and hemicellulose are the most abundant components in plant biomass. A preferred Consolidated Bioprocessing (CBP) system is one which can directly convert both cellulose and hemicellulose into target products without adding the costly hydrolytic enzyme cocktail. In this work, the thermophilic, cellulolytic, and anaerobic bacterium, Clostridium thermocellum DSM 1313, was engineered to grow on xylose in addition to cellulose. Both xylA (encoding for xylose isomerase) and xylB (encoding for xylulokinase) genes from the thermophilic anaerobic bacterium Thermoanaerobacter ethanolicus were introduced to enable xylose utilization while still retaining its inherent ability to grow on 6-carbon substrates. Targeted integration of xylAB into C. thermocellum genome realized simultaneous fermentation of xylose with glucose, with cellobiose (glucose dimer), and with cellulose, respectively, without carbon catabolite repression. We also showed that the respective H-2 and ethanol production were twice as much when both xylose and cellulose were consumed simultaneously than when consuming cellulose alone. Moreover, the engineered xylose consumer can also utilize xylo-oligomers (with degree of polymerization of 2-7) in the presence of xylose. Isotopic tracer studies also revealed that the engineered xylose catabolism contributed to the production of ethanol from xylan which is a model hemicellulose in mixed sugar fermentation, demonstrating immense potential of this enhanced CBP strain in co-utilizing both cellulose and hemicellulose for the production of fuels and chemicals.
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