Biosynthetic Routes for Producing Various Fucosyl-Oligosaccharides

L-Fucose is involved in human-gut microbiome interactions

L-Fucose is one of the key metabolites in human-gut microbiome interactions. It is continuously synthesized by humans in the form of fucosylated glycans and fucosyl-oligosaccharides and delivered into the gut throughout their lifetime. Gut microorganisms metabolize L-fucose and produce short-chain fatty acids, which are absorbed by epithelial cells and used as energy sources or signaling molecules. Recent studies have revealed that the carbon flux in L-fucose metabolism by gut microorganisms is distinct from that in other sugar metabolisms because of cofactor imbalance and low efficiencies in energy synthesis of L-fucose metabolism. The large amounts of short-chain fatty acids produced during microbial L-fucose metabolism are used by epithelial cells to recover most of the energy used up during L-fucose synthesis. In this review, we present a detailed overview of microbial L-fucose metabolism and a potential solution for disease treatment and prevention using genetically engineered probiotics that modulate fucose metabolism. Our review contributes to the understanding of human-gut microbiome interactions through L-fucose metabolism. KEY POINTS: • Fucose-metabolizing microorganisms produce large amounts of short-chain fatty acids • Fucose metabolism differs from other sugar metabolisms by cofactor imbalance • Modulating fucose metabolism is the key to control host-gut microbiome interactions.

Hyperglycemia alters N-glycans on colon cancer cells through increased production of activated monosaccharides

Diabetes Mellitus (DM) is both, correlated and a known risk factor for colorectal cancer (CRC). Besides favoring the incidence of CRC, DM also accelerates its progression, worsening its prognosis. Previously, hyperglycemia, the DM hallmark, has been shown to lead to aberrant glycosylation of CRC cells, heightening their malignancy both in vivo and in vitro. Here we use mass spectrometry to elucidate the composition and putative structures of N-glycans expressed by MC38 cultured in normoglycemic (LG) and hyperglycemic-like conditions (HG). N-glycans, 67, were identified in MC38 cells cultured in LG and HG. The cells grown in HG showed a greater abundance of N-glycans when compared to LNG cells, without changes in the proportion of sialylated, fucosylated and mannosylated N-glycans. Among the identified N-glycans, 16 were differentially expressed, mostly mannosylated and fucosylated, with a minority of them being sialylated. Metabolomics analysis indicates that the alterations observed in the N-glycosylation may be mostly due to increase of the activated monosaccharides pool, through an increased glucose entrance into the cells. The alterations found here corroborate data from the literature regarding the progression of CRC, advocating for development or repositioning of effective treatments against CRC in diabetic patients.

2'-Fucosyllactose production in engineered Escherichia coli with deletion of waaF and wcaJ and overexpression of FucT2

2'-Fucosyllactose (2'-FL), a major oligosaccharide of human breast milk, and is currently supplemented into infant formula. For the overproduction of 2'-FL via fucosylation of lactose, conventional approaches have focused on the episomal overexpression of de novo or salvage GDP-L-fucose biosynthetic pathway and α-1,2-fucosyltransferase (FucT2) through T7 RNA polymerase expression system in engineered E. coli. However, these approaches have drawbacks of metabolic burden, plasmid instability, and inclusion body formation. In this study, a deletion mutant of waaF coding for ADP-heptose:LPS heptosyltransferase II was employed for 2'-FL production. As the waaF deletion induces accumulation of colanic acid, additional deletion of wcaJ coding for UDP-glucose-1-phosphate transferase in the waaF deletion mutant resulted in enhanced accumulation of GDP-L-fucose. Besides, 2'-FL yields and titers were drastically improved when T7 promoter was replaced with Trc promoter for α-1,2 fucosyltransferase expressions in the waaF and wcaJ deleted strain. As a result, when FucT2 was expressed under Trc promoter in the E. coli JM109(DE3) ΔwaaFΔwcaJ, 14.7 g/L of 2'-FL was produced with a productivity of 0.31 g/L/h in a fed-batch fermentation. We envision that the deletion-based metabolic design and decreased promoter strength for fucosyltransferase expression can resolve the drawbacks of T7 RNA polymerase-based expression design for 2'-FL production in E. coli.

In Vitro Prebiotic and Anti-Colon Cancer Activities of Agar-Derived Sugars from Red Seaweeds

Numerous health benefits of diets containing red seaweeds or agar-derived sugar mixtures produced by enzymatic or acid hydrolysis of agar have been reported. However, among various agar-derived sugars, the key components that confer health-beneficial effects, such as prebiotic and anti-colon cancer activities, remain unclear. Here, we prepared various agar-derived sugars by multiple enzymatic reactions using an endo-type and an exo-type of β-agarase and a neoagarobiose hydrolase and tested their in vitro prebiotic and anti-colon cancer activities. Among various agar-derived sugars, agarotriose exhibited prebiotic activity that was verified based on the fermentability of agarotriose by probiotic bifidobacteria. Furthermore, we demonstrated the anti-colon cancer activity of 3,6-anhydro-l-galactose, which significantly inhibited the proliferation of human colon cancer cells and induced their apoptosis. Our results provide crucial information regarding the key compounds derived from red seaweeds that confer beneficial health effects, including prebiotic and anti-colon cancer activities, to the host.