Search

Background: Fermentation is a traditional food-preserving technique. It is an effective process, widely used to enrich the nutrients diversity and bioactivity of the fermented foods since ancient times. This study aimed at investigating the effects of various fermentation starters on the physicochemical, antioxidant, antimicrobial, and antidiabetic properties of blueberry juices. The blueberry juices were fermented by natural fermentation (NFBJ), self-made starters fermentation (SFBJ), and commercial starters fermentation (CFBJ); fresh blueberry juice (BBJ) was processed without fermentation for comparison., Results: Probiotics-fermented blueberry juices (SFBJ and CFBJ) showed less total and reducing sugars, higher titratable acidity, and a wider variety and higher amounts of organic acids than non-fermented blueberry juice (BBJ) did. All the fermented blueberry juices (NFBJ, SFBJ, and CFBJ) showed significantly (P < 0.05) higher antioxidant potentials than that of BBJ measured by 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid, cupric-reducing antioxidant capacity, and ferric-reducing ability power assays. The SFBJ exhibited the highest antibacterial activities against Escherichia coli, Staphylococcus aureus, and Salmonella Typhimurium, with inhibition zone diameters of 38.84 ± 1.74 mm, 34.91 ± 1.53 mm, and 36.18 ± 3.16 mm respectively. Compared with BBJ, the α-glucosidase inhibitory activity of the SFBJ and CFBJ increased by two-to threefold. The α-amylase inhibitory activity of the SFBJ and CFBJ increased by 600%, whereas the spontaneous fermentation showed no improvement. The SFBJ and CFBJ promoted glucose consumption of HepG2 cell lines, indicating the promising potential for a higher glucose bio-utilization., Conclusions: The SFBJ and CFBJ showed remarkable improvements in the antioxidant, antimicrobial, and antidiabetic activities compared with non-fermented and spontaneous fermented juices, indicating their promising potentials as an antihyperglycemic agent. © 2021 Society of Chemical Industry., (© 2021 Society of Chemical Industry.)

Background: Sugar medium-chain fatty acid esters are a new type of biodegradable, non-toxic, non-irritant and non-ionic surfactant with proven antimicrobial activity. Various sugar medium-chain fatty monoesters were prepared enzymatically using Lipozyme TLIM in organic solvent. Properties such as surface tension, antimicrobial activity, and ability to foam, emulsify and stabilize emulsions at room temperature were evaluated to conduct systematic studies on the structure-function relationships of these compounds., Results: Results showed that all monoesters displayed good surface activity properties. In particular, sucrose monolaurate was the most excellent surfactant among 12 monoesters. Sugar monoesters containing C8 to C12 alkyl chains showed a broad spectrum of increasing antimicrobial activity. All tested monoesters were more effective against Staphylococcus aureus (Gram-positive bacterium) than Escherichia coli O157:H7 (Gram-negative bacterium). Methyl α-d-glycoside monoesters were the most effective, whereas raffinose monoesters possessed poor antimicrobial activity., Conclusions: Generally, the length of fatty acid chain (hydrophobic group) and sugar groups (hydrophilic group) for sugar medium-chain fatty acid monoesters both affected the surface properties and antimicrobial activities., (© 2014 Society of Chemical Industry.)

The objective of this research was to determine the effect of sugar or fatty acid in sugar ester compounds on the surface-active properties and antimicrobial activities of these compounds. Disaccharides of medium-chain fatty acid monoesters were synthesized through transesterifications by immobilized lipase (Lipozyme TLIM) to yield nine monoesters for subsequent study. Their antimicrobial activities were investigated using three pathogenic microorganisms: Staphylococcus aureus, Escherichia coli O157:H7 and Candida albicans. Their surface-active properties including air-water surface tension, critical micelle concentration, and foaming and emulsion power and stability were also studied. The results showed that all of the tested monoesters were more effective against Staphylococcus aureus (Gram-positive bacterium) than against Escherichia coli O157:H7 (Gram-negative bacterium). The results demonstrated that the carbon chain length was the most important factor influencing the surface properties, whereas degree of esterification and hydrophilic groups showed little effect.

The structure-activity relationship of a U-type antimicrobial microemulsion system containing glycerol monolaurate and ethanol at a 1∶1 mass ratio as oil phase and Tween 20 as surfactant were investigated along a water dilution line at a ratio of 80∶20 mass% surfactant/oil phase, based on a pseudo-ternary phase diagram. The differential scanning calorimetry results showed that in the region of up to 33% water, all water molecules are confined to the hydrophilic core of the reverse micelles, leading to the formation of w/o microemulsion. As the water content increases, the water gains mobility, and transforms into bicontinuous in the region of 33-39% water, and finally the microemulsion become o/w in the region of above 39% water. The microstructure characterization was confirmed by the dynamic light scattering measurements and freeze-fracture transmission electron microscope observation. The antimicrobial activity assay using kinetics of killing analysis demonstrated that the microemulsions in w/o regions exhibited relatively high antimicrobial activity against Escherichia coli and Staphylococcus aureus due to the antimicrobial oil phase as the continuous phase, while the antimicrobial activity started to decrease when the microemulsions entered the bicontinuous region, and decreased rapidly as the water content increased in the o/w region, as a result of the dilution of antimicrobial oil droplets in the aqueous continuous phase.

The characterization of a pharmaceutical microemulsion system with glycerol monolaurate as oil, ethanol as cosurfactant, Tween 40 as surfactant, sodium diacetate and water, and the antimicrobial activities against Escherichia coli, Staphylococcus aureus, Bacillus subtilis, Candida albicans, Aspergillus niger and Penicillium expansum have been studied. The influence of ethanol and sodium diacetate on oil solubilization capability was clearly reflected in the phase behavior of these systems. One microemulsion formulation was obtained and remained stable by physical stability studies. The antimicrobial assay using solid medium diffusion method showed that the prepared microemulsion was comparable to the commonly used antimicrobials as positive controls. The kinetics of killing experiments demonstrated that the microemulsion caused a complete loss of viability of bacterial cells (E. coli, S. aureus and B. subtilis) in 1 min, killed over 99% A. niger and P. expansum spores and 99.9% C. albicans cells rapidly within 2 min and resulted in a complete loss of fungal viability in 5 min. The fast killing kinetics of the microemulsion was in good agreement with the transmission electron microscopy observations, indicating the antimembrane activity of the microemulsion on bacterial and fungal cells due to the disruption and dysfunction of biological membranes and cell walls., (Copyright (c) 2010 Elsevier B.V. All rights reserved.)

Microemulsions are colloidal nanodispersions of oil and water stabilized by an interfacial film of surfactant molecules, typically in conjunction with a cosurfactant. There is a limited number of reports in the literature on microemulsion use for antimicrobial purposes. The physicochemical characterization of a food-grade fully dilutable microemulsion system with glycerol monolaurate (GML) as oil, organic acids as cosurfactant, Tween 80 as surfactant, and the antimicrobial activities against Escherichia coli and Staphylococcus aureus have been studied in this paper. The influence of organic acids on oil solubilization was clearly reflected in the phase behavior of these systems. Propionic acid demonstrated the greatest capability to improve the oil solubilization among the tested linear and nonlinear chain organic acids and contributed to the formation of U-type microemulsion systems. One microemulsion formulation with an average particle size of 8nm was selected, the composition is GML/propionic acid/Tween 80/water=3:9:8:12. The kinetics of killing experiments demonstrated that the undiluted microemulsion caused a complete loss of viability of E. coli or S. aureus cells in 1min and still had effective bactericidal effects even when diluted, more than 99% viable E. coli cells were killed within 15min and a complete loss of viability was achieved at 45min while more than 99% viable S. aureus cells were killed within 30min and a complete loss of viability was achieved at 60min in the presence of the 10-fold diluted microemulsion. The fast killing kinetics of the ten-fold serial dilutions of microemulsions were in good agreement with the mode of action studies, indicating that the interaction between the antimicrobial microemulsions and bacterial membranes significantly decreased the bacterial cell surface hydrophobicity and induced the quick release of 260nm absorbing materials. This work suggests the potential use of food-grade fully dilutable microemulsions for antimicrobial purposes in beverages or seafood products.

The purpose of this study was to improve the depression, enhance the bioavailability, hence strengthen the antimicrobial ability of poorly water-soluble glycerol monolaurate (GML) by loading it in microemulsion system. Microemulsions were prepared with GML as oil, tweens as surfactant, and medium-and-short chain alcohols at different ratio as cosurfactants. The effect of the ratio of surfactant to cosurfactant on the stability of microemulsion was tested. And the effect of the composition and ratio of cosurfactant and the effect of potassium sorbate dissolved in water at different concentration on the area of O/W microemulsion region in pseudo-ternary phase diagrams were also investigated. The results showed that the microemulsion is most stable when the ratio of surfactant to cosurfactant was 3:2, the suitable cosurfactant is pentanol to dodecane at 2:1, the area of O/W microemulsion region in pseudo-ternary phase diagram increased with increasing content of potassium sorbate. The conclusion of this study was that GML loaded in microemulsion had much higher anti-microbial activity than GML alone.

The DNA microarray was employed in this study to investigate the gene expression profiles of E scherichia coli treated by oil in water (o/w) microemulsion in order to better understand the antimicrobial mechanism of the microemulsion as a promising food-grade antimicrobial system. Among 5,440 open reading frames of E . coli, a total of 634 and 501 were highly induced and repressed, respectively. According to the annotation and analysis in the Gene Ontology ( GO) and Kyoto Encyclopedia of Genes and Genomes ( KEGG) databases, it was found that the differently expressed genes were mainly involved in the biosynthesis of cell wall components and membranes, phosphate-related metabolism and some other biosynthetic pathways, suggesting that the main antibacterial mechanisms of the o/w microemulsion were the attacks to the cell surface structure, especially the cell wall, and its influences on the metabolism of phosphate of the E . coli cells through phosphate absorption inhibition. Practical Applications In the panorama of the increasing need to search for novel strategies in order to prevent foodborne outbreaks, microemulsion systems have been of great interest to researchers for their broad antimicrobial properties. In our group, a series of food-grade or pharmaceutical microemulsion systems based on glycerol monolaurate have been established for antimicrobial applications. It was found that the prepared microemulsions possessed excellent broad-spectrum antimicrobial activities due to the disruption and dysfunction of biological membranes and cell walls, as suggested by the transmission electron microscopy observations and membrane permeability experiments. The antimicrobial mechanisms analysis of the microemulsion mediated by DNA microarray in this work will be of great importance in exploring the structure-activity relationship of the o/w microemulsion at molecular biological levels in future work, in order to provide a guideline in designing food-grade antimicrobial microemulsions. [ABSTRACT FROM AUTHOR]

The purpose of this study is to load glycerol monolaurate (GML) in a microemulsion system for the inactivation of Stenotrophomonas maltophilia. The influence of ethanol, propylene glycol (PG) and sodium benzoate (Na-Bz) on oil solubilization of GML microemulsions is clearly reflected in the phase behavior of these systems. One dilution-stable microemulsion formulation was determined and stable by the examination of the physical stability. Results showed that the microemulsion at 100 ppm, comparable to 3 mg/L ceftazidime, had much higher antimicrobial activities against S. maltophilia, with a major contribution of GML, and Na-Bz enhanced the antimicrobial activities as a hydrotrope. [ABSTRACT FROM AUTHOR]

Organogels have been prepared with corn oil as organic solvent and glycerol monolaurate (GML) as organogelator for antimicrobial purpose. The critical gelation concentration (CGC) was found to be 3% (w/w) by the inverted tube method. The physical properties of the organogels containing 3%, 10%, 20%, 30%, 40% GML were studied by light microscopy, differential scanning calorimetry, and rheological analysis. The results showed that with the increasing organogelator concentration, the gels had a more compact three-dimensional network as the GML molecules crystallized and grew into a stronger backbone network as the gel skeleton, leading to higher thermal stability, higher resistance to deformations and lower spreadability. The antimicrobial assay using zone of inhibition indicated that the prepared organogels possessed strong antimicrobial activities against Staphylococcus aureus and Escherichia coli . The successful development of GML-based organogels suggests the potential application as new gelled capsules or spreadable products for controlled drug delivery. [ABSTRACT FROM AUTHOR]