Lipase-Catalyzed Synthesis of Sucrose Monolaurate and Its Antibacterial Property and Mode of Action against Four Pathogenic Bacteria

Abstract

The aim of this work was to evaluate the antibacterial activities and mode of action of sucrose monolaurate (SML) with a desirable purity, synthesized by Lipozyme TL IM-mediated transesterification in the novel ionic liquid, against four pathogenic bacteria including L. monocytogenes, B. subtilis, S. aureus, and E. coli. The antibacterial activity was determined by minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and the time–kill assay. SML showed varying antibacterial activity against tested bacteria with MICs and MBCs of 2.5 and 20 mM for L. monocytogenes, 2.5 and 20 mM for B. subtilis, 10 and 40 mM for S. aureus, respectively. No dramatic inhibition was observed for E. coli at 80 mM SML. Mechanism of bacterial inactivation caused by SML was revealed through comprehensive factors including cell morphology, cellular lysis, membrane permeability, K+ leakage, zeta potential, intracellular enzyme, and DNA assay. Results demonstrated that bacterial inactivation against Gram-positive bacteria was primarily induced by the pronounced damage to the cell membrane integrity. SML may interact with cytoplasmic membrane to disturb the regulation system of peptidoglycan hydrolase activities to degrade the peptidoglycan layer and form a hole in the layer. Then, the inside cytoplasmic membrane was blown out due to turgor pressure and the cytoplasmic materials inside leaked out. Leakage of intracellular enzyme to the supernatants implied that the cell membrane permeability was compromised. Consequently, the release of K+ from the cytosol lead to the alterations of the zeta potential of cells, which would disturb the subcellular localization of some proteins, and thereby causing bacterial inactivation. Moreover, remarkable interaction with DNA was also observed. SML at sub-MIC inhibited biofilm formation by these bacteria.

Antilisterial Activity of Lactose Fatty Acid Esters in Milk

“…Moreover, physical changes occur at reduced temperatures; it is possible that the listerial cell wall and membranes become less malleable or interactive at lower temperatures thus less permeable to a carbohydrate ester. Recently Shao [11] investigated the antimicrobial activity of sucrose monolaurate against L. monocytogenes. They showed that the sucrose ester caused pronounced damage to the cell membrane integrity and may form a hole in the peptidoglycan layer.…”

“…Previous research [4] [8] [9] [10] [11] has documented the bactericidal/inhibitory activity of carbohydrate esters in growth media. Our lab was the first to enzymatically synthesize lactose esters [12] and shows the microbial inhibitory properties of lactose monolaurate (LML) [9].…”

Chemical Reactivity Descriptors and Molecular Docking Studies of Octyl 6-O-hexanoyl-β-D-glucopyranosides

“…Efforts are continuing to make and establish them as safe therapeutic drugs [3][4][5]. Many esters, known as sugar esters (SEs), are known for their multiple surfactants [6,7], and biological properties [8][9][10][11]. These are mainly used as nonionic type surfactants [6,7].…”

“…These are mainly used as nonionic type surfactants [6,7]. Different biological properties and applications are reported by many researchers [10,11]. The most common structural features of SEs are the combination of hydrophilic and hydrophobic parts [12,13].…”

“…Also, the combination of hydrophilicity and lipophilicity with reasonable molecular weight are responsible for their low stimulatory effects [15]. Most of them are colourless syrup and have no taste in general [10,11]. In addition, this hydrophilicity and lipophilicity ratio can be manipulated via changing their hydrophobic chains [16].…”