Biosynthesis of Neokestose Laurate Catalyzed by Candida antarctica Lipase B and Its Antimicrobial Activity against Food Pathogenic and Spoilage Bacteria

A lipid toolbox of sugar alcohol fatty acid monoesters for single-component lipid nanoparticles with temperature-controlled release

This study aimed to prepare single-component LNPs with sugar alcohol fatty acid monoesters for temperature-controlled release. In total, 20 kinds of lipids with a series of sugar alcohol head groups (ethylene glycol, glycerol, erythritol, xylitol and sorbitol) and fatty acyl tails (12:0, 14:0, 16:0 and 18:0) were synthesised via lipase-catalysed esterification. Their physicochemical properties and upper/lower critical solution temperature (LCST/USCT) were analysed. Two groups of mixed lipids, 78 % ethylene glycol lauric acid monoester + 22 % sorbitol stearic acid monoester (LNP-1) and 90 % ethylene glycol lauric acid monoester + 10 % xylitol myristic acid monoester (LNP-2), had LCST/USCT of approximately 37 °C, which formed empty LNPs using the emulsification-diffusion method. These two mixed lipids were prepared for LNPs loaded with curcumin, showing high encapsulation (>90 %), mean particle sizes of approximately 250 nm and low polydispersity index (≤0.2). These lipids have the potential for tailor-made LNPs achieving thermo-responsivity in delivering bioactive agents and drugs.

Recent advances in the enzymatic synthesis of lipophilic antioxidant and antimicrobial compounds

Due to the increase in the consumption of highly processed food in developed countries, as well as, a growing number of foodborne diseases, exploration of new food additives is an issue focusing on scientific attention and industrial interest. Functional compounds with lipophilic properties are remarkably desirable due to the high susceptibility to the deterioration of lipid-rich food products. This paper in a comprehensive manner provides the current knowledge about the enzymatic synthesis of lipophilic components that could act as multifunctional food additives. The main goal of enzymatic lipophilization of compounds intentionally added to food is to make these substances soluble in lipids and/or to obtain environmentally friendly surfactants. Moreover, lipase-catalyzed syntheses could result in changes in the antioxidant and antimicrobial activities of phenolic compounds, carbohydrates, amino acids (oligopeptides), and carboxylic acids. The review describes also the implementation of a new trend in green chemistry, where apart from simple and uncomplicated chemical compounds, the modifications of multi-compound mixtures, such as phenolic extracts or essential oils have been carried out.

Synthesis of lutein esters using a novel biocatalyst of Candida antarctica lipase B covalently immobilized on functionalized graphitic carbon nitride nanosheets

Lutein scavenges free radicals and inhibits vision damage caused by photo oxidation, while decomposing easily with light and heat. Its stability and bioavailability can be tremendously improved by lutein ester synthesis. However, green and efficient esterification preparation methods are urgently needed. In this study, which used functionalized graphitic carbon nitride nanosheets (g-C₃N₄-Ns) as the immobilized carrier, a novel biocatalyst was designed and prepared to accommodate Candida antarctica lipase B (CALB), considerably enhancing the performance. It was characterized by TEM, XRD, FTIR, XPS, TGA, and BET to demonstrate successful preparation and then applied to catalyze esterification between lutein and succinate anhydride in dimethyl formamide (DMF) solvent resulting in a conversion rate up to 92% at 50 °C in 60 h, 34% more than free CALB under the same conditions. We believe this is the highest esterification rate in lutein esters synthesis and it has great potential to facilitate eco-friendly and efficient preparation.

Synthesis of Amphiphilic Copolymers Containing Ciprofloxacin and Amine Groups and Their Antimicrobial Performances As Revealed by Confocal Laser-Scanning Microscopy and Atomic-Force Microscopy

Two series of amphiphilic antimicrobial copolymers containing ciprofloxacin (CPF) and amine functional groups have been synthesized via free-radical copolymerization. The chemical structures of the different amine groups and the copolymer compositions have been systematically varied to study how the structure of the copolymer exerts an influence on the antibacterial activity. The viability of Escherichia coli in the presence of antimicrobial copolymers was observed by confocal laser-scanning microscopy (CLSM). CLSM as well as atomic-force microscopy (AFM) were applied to visualize changes in morphology of bacteria treated with antimicrobial copolymers and elucidate the antimicrobial mechanism of the antimicrobial copolymers. Morphological changes of bacteria observed via AFM and CLSM demonstrated that the antibacterial mechanism was due to the disruption of the bacterial membrane. The destruction of the cell membrane was also confirmed by the leakage of intracellular components, which had a strong absorbance at 260 nm. The inhibitory process was monitored by UV absorption dynamically.