Chemoenzymatic synthesis of sialylated lactuloses and their inhibitory effects on Staphylococcus aureus

Abstract

BackgroundSialylated glycoconjugates play important roles in physiological and pathological processes. However, available sialylated oligosaccharides source is limited which is a barrier to study their biological roles. This work reports an efficient approach to produce sialic acid-modified lactuloses and investigates their inhibitory effects on Staphylococcus aureus (S. aureus).MethodsA one-pot two-enzyme (OPTE) sialylation system was used to efficiently synthesize sialylated lactuloses. Silica gel flash chromatography column was employed to purify the sialylated products. The purity and identity of the product structures were confirmed with mass spectrometry (MS) and nuclear magnetic resonance (NMR). The inhibitory effect of sialylated lactuloses against S. aureus was evaluated by using microplate assay, fluorescence microscopy, DAPI (4',6-diamidino-2-phenylindole) fluorescence staining and protein leakage quantification.ResultsNeu5Ac-containing sialylated lactuloses with either α2,3- or α2,6-linkages were efficiently synthesized via an efficient OPTE sialylation system using α-2,3-sialyltransferase or α-2,6-sialyltransferase, respectively. Neu5Ac-α2,3-lactulose and Neu5Ac-α2,6-lactulose significantly inhibited the growth of S. aureus. Fluorescence microscopy and DAPI fluorescence staining indicated that the sialylated lactuloses might disrupt nucleic acid synthesis of S. aureus.ConclusionsNeu5Ac-containing sialylated lactuloses had higher antibacterial activity against S. aureus than non-sialylated lactulose. The inhibitory effect of Neu5Ac-α2,3-lactulose was superior to that of Neu5Ac-α2,6-lactulose. The sialylated lactuloses might inhibit S. aureus by causing cell membrane leakage and disrupting nucleic acid synthesis.

Safety of 3’‐sialyllactose (3’‐SL) sodium salt produced by derivative strains of Escherichia coli BL21 (DE3) as a Novel Food pursuant to Regulation (EU) 2015/2283

“…d ‐Lactose is the most abundant component of human milk (~ 7%) and its monomers d ‐glucose and d ‐galactose are normal constituents of human milk. Sialic acid is an endogenous human and ubiquitous nutritional monosaccharide (EFSA NDA Panel, 2017 ; Röhrig et al, 2017 ), while 3’‐sialyllactulose is derived from 3’‐SL by isomerisation of the terminal d ‐glucose moiety into d ‐fructose mainly under alkaline conditions during the production process (Zeng et al, 2018 ). N‐acetyl‐ d ‐glucosamine is also present in human milk as a building block for oligosaccharides (Garrido et al, 2012 ).…”

Changes in HMO Concentrations throughout Lactation: Influencing Factors, Health Effects and Opportunities

“…Although the role of oligosaccharides as the bifidogenic factor in human milk was identified in the 1930s [ 70 ] and the main HMO structures were reported in 1954 [ 86 ], it was only in the late 2010s that researchers were able to produce the first oligosaccharide structurally identical to those in human milk at a large scale [ 12 , 13 ]. Such progress has made available many individual HMOs, namely 2′-FL [ 87 ], LNT [ 88 ] and LNnT [ 89 ], 3-FL [ 90 ], 3′-SL, and 6′-SL [ 91 ].…”

Molecular Study of Vancomycin Resistance in Hospital Acquired Staphylococcus Infection

“…The mechanism of transmission of hospital acquired resistance strain could be by many ways from patients or health care worker as well as from the environmental surfaces, while the transmission of coagulase-negative staphylococci is not fully known but it's probably the same rout of transmission [20]. Also the duration of hospital stay and history of glycopeptides antibiotics and to some extent the causes of underlying diseases as renal failure appear to be significant risk factor in increasing the resistance [22].…”

“…Plates were incubated overnight at 35°C for any visible growth. Readings were taken according to NCCLS guidelines [17][18][19][20]…”