Engineering of a Cell Factory That Can Utilizing the Biomass for Biochemical Production

A single-cell factory that can degrading large molecular biomass and can use various components in biomass or waste material is the key for biochemical and biofuels production. We recently identified the catalytic domain of a cellulase (Cel-CD) from Bacillus sp. that can be secreted into the medium from recombinant E. coli in large quantities without its native signal peptide. This protein can degrading cellulose efficiently in the culture medium indicating a great potential. By subcellular location analysis, we proved that the secretion was a two-step process via the SecB-dependent pathway through the inner membrane. Both the Cel-CD and its N-terminal sequence can serve as carriers for efficient extracellular production of select target proteins with a concentration from 101 to 691 mg/L in flask cultivation. A recombinant E.coli that can directly utilize cellulose as sole carbon source by fusion Cel-CD with a b-glucosidase was constructed.

By knocking out the genes involved in the phosphotransfer cascade of the Phosphoenolpyruvate-dependent glucose-specific phosphotransferase system (PTS^Glc)^c in the host E.coli, the effect of each mutation on cell growth and substrate consumption in the presence of glucose was investigated. We found that the engineered strains have different capability for utilizing the mixture of glucose and xylose. Finally, we investigated the polyhydroxybutyrate (PHB) and succinate production using the different metabolic engineered mutants in the presence of both sugars with different ratios. The results suggested that this system has a potential application in lignocellulosic biomass degradation and biochemical biofuel production.