Kenji Abe
Ajinomoto Co. Inc., Japan
Title: Engineering of Escherichia coli to facilitate efficient utilization of isomaltose and panose in industrial glucose feedstock
Biography
Biography: Kenji Abe
Abstract
Fermentative production of useful compounds, such as alcohols, gases, pharmaceutical ingredients, and organic/amino acids, is conducted worldwide. Escherichia coli is one of the most useful bacterium for the production of valuable compounds, such as amino acids and organic acids, because E. coli cells grow quickly, convert substrates to products rapidly, and are genetically engineered readily. For example, L-lysine, which is used as a feed additive worldwide, is produced on the scale of approximately 1,500,000 metric tons per year.
On the other hand, in the industrial production of useful compounds by fermentation, glucose is one of the most frequently used carbon sources. Industrial glucose feedstock prepared by enzymatic digestion of starch typically contains significant amounts of disaccharides such as maltose and isomaltose, and trisaccharides such as maltotriose and panose. Maltose and maltosaccharides can be utilized in Escherichia coli fermentation using industrial glucose feedstock because there is an intrinsic assimilation pathway for these sugars. However, saccharides that contain α-1,6 bonds, such as isomaltose and panose, are still present after fermentation because there is no metabolic pathway for these sugars. To facilitate more efficient utilization of glucose feedstock, we introduced glvA, which encodes phospho-α-glucosidase, and glvC, which encodes a subunit of the phosphoenolpyruvate-dependent maltose phosphotransferase system (PTS) of Bacillus subtilis, into E. coli. The heterologous expression of glvA and glvC conferred upon the recombinant the ability to assimilate isomaltose and panose. The recombinant E. coli assimilated not only other disaccharides but also trisaccharides, including alcohol forms of these saccharides, such as isomaltitol. To the best of our knowledge, this is the first report to show the involvement of the microbial PTS in the assimilation of trisaccharides. Furthermore, we demonstrated that an L-lysine-producing E. coli harboring glvA and glvC converted isomaltose and panose to L-lysine efficiently. These findings are expected to be beneficial for industrial fermentation.
Figure 1. Schematic illustaration of GlvAC pathway for assimilation of isomaltose (iMal) and panose (Pan).