Whole cell biosynthesis of a functional oligosaccharide, 2′-fucosyllactose, using engineered Escherichia coli
1 Department of Food Science and Human Nutrition, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
2 Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
3 Department of Food Science and Technology, Chungbuk National University, Cheongju, 361-763, Korea
4 Department of Agricultural Biotechnology and Center for Agricultural Biomaterials, Seoul National University, Seoul, 151-921, Korea
Microbial Cell Factories 2012, 11:48 doi:10.1186/1475-2859-11-48Published: 30 April 2012
2'-Fucosyllactose (2-FL) is a functional oligosaccharide present in human milk which protects against the infection of enteric pathogens. Because 2-FL can be synthesized through the enzymatic fucosylation of lactose with guanosine 5′-diphosphate (GDP)-L-fucose by α-1,2-fucosyltransferase (FucT2), an 2-FL producing Escherichia coli can be constructed through overexpressing genes coding for endogenous GDP- L-fucose biosynthetic enzymes and heterologous fucosyltransferase.
The gene for FucT2 from Helicobacter pylori was introduced to the GDP- L-fucose producing recombinant E. coli BL21 star(DE3) strain. However, only small amount of 2-FL was produced in a batch fermentation because the E. coli BL21star(DE3) strain assimilated lactose instead of converting to 2-FL. As an alternative host, the E. coli JM109(DE3) strain which is incapable of assimilating lactose was chosen as a 2-FL producer. Whole cell biosynthesis of 2-FL from lactose was investigated in a series of batch fermentations using various concentrations of lactose. The results of batch fermentations showed that lactose was slowly assimilated by the engineered E. coli JM109(DE3) strain and 2-FL was synthesized without supplementation of another auxiliary sugar for cell growth. A maximum 2-FL concentration of 1.23 g/l was obtained from a batch fermentation with 14.5 g/l lactose. The experimentally obtained yield (g 2-FL/g lactose) corresponded to 20% of the theoretical maximum yield estimated by the elementary flux mode (EFM) analysis.
The experimental 2-FL yield in this study corresponded to about 20% of the theoretical maximum yield, which suggests further modifications via metabolic engineering of a host strain or optimization of fermentation processes might be carried out for improving 2-FL yield. Improvement of microbial production of 2-FL from lactose by engineered E. coli would increase the feasibility of utilizing 2-FL as a prebiotic in various foods.