Simultaneous uptake of lignocellulose‐based monosaccharides by Escherichia coli

Abstract

Lignocellulosic waste is a naturally abundant biomass and is therefore an attractive material to use in second generation biorefineries. Microbial growth on the monosaccharides present in hydrolyzed lignocellulose is however associated with several obstacles whereof one is the lack of simultaneous uptake of the sugars. We have studied the aerobic growth of Escherichia coli on D-glucose, D-xylose, and L-arabinose and for simultaneous uptake to occur, both the carbon catabolite repression mechanism (CCR) and the AraC repression of xylose uptake and metabolism had to be removed. The strain AF1000 is a MC4100 derivative that is only able to assimilate arabinose after a considerable lag phase, which is unsuitable for commercial production. This strain was successfully adapted to growth on L-arabinose and this led to simultaneous uptake of arabinose and xylose in a diauxic growth mode following glucose consumption. In this strain, a deletion in the phosphoenolpyruvate:phosphotransferase system (PTS) for glucose uptake, the ptsG mutation, was introduced. The resulting strain, PPA652ara simultaneously consumed all three monosaccharides at a maximum specific growth rate of 0.59 h(-1) , 55% higher than for the ptsG mutant alone. Also, no residual sugar was present in the cultivation medium. The potential of PPA652ara is further acknowledged by the performance of AF1000 during fed-batch processing on a mixture of D-glucose, D-xylose, and L-arabinose. The conclusion is that without the removal of both layers of carbon uptake control, this process results in accumulation of pentoses and leads to a reduction of the specific growth rate by 30%.

Reciprocal Regulation ofl-Arabinose andd-Xylose Metabolism in Escherichia coli

“…Most of these efforts have focused on the coutilization of glucose and another sugar (36). Less effort has been directed toward the coutilization of nonglucose sugar (7,(37)(38)(39). In the context of this work, the work of Groff and coworkers (37) is notable.…”

Single-Cell Biorefinery

“…23 Catabolite repression allows bacteria to adapt quickly to a preferred carbon and energy source first. CCR is an important part of global control system of various bacteria and other microbes.…”

Enhancement of xylose utilization from corn stover by a recombinant Escherichia coli strain for ethanol production

“…Desai and Rao (2010) demonstrated that the sugar utilization in E. coli involves multiple layers of regulation, where cells will consume glucose first, then arabinose and finally xylose. The xylose uptake is directly inhibited by the AraC regulator (Desai and Rao, 2010;Jarmander et al, 2014). This indicates that the expression of xylose metabolic genes is repressed and only low levels of xylose transport will occur from the promiscuous pentose transporters in the presence of arabinose.…”