Amperometric Detection of Conformational Change of Proteins Using Immobilized-Liposome Sensor System

An immobilized liposome electrode (ILE)-based sensor was developed to quantify conformational changes of the proteins under various stress conditions. The ILE surface was characterized by using a tapping-mode atomic force microscopy (TM-AFM) to confirm surface immobilization of liposome. The uniform layer of liposome was formed on the electrode. The current deviations generated based on the status of the proteins under different stress were then measured. Bovine carbonic anhydrase (CAB) and lysozyme were tested with three different conditions: native, reduced and partially denatured. For both proteins, a linear dynamic range formed between denatured concentrations and output electric current signals was able to quantify conformational changes of the proteins. The pattern recognition (PARC) technique was integrated with ILE-based sensor to perform data analysis and provided an effective method to improve the prediction of protein structural changes. The ILE-based stress sensor showed potential of leveraging the amperometric technique to manifest activity of proteins based on various external conditions

Lipase-catalyzed production of pyridoxine monolaurate in solvent-free bioreactor system

This study demonstrated that solvent-free gas bubbling system enhanced production efficiency of pyridoxine monolaurate in the esterification catalyzed by immobilized Candida antarctica lipase B (Lipozyme 435). Volumetric productivity in solvent-free gas bubbling system (41.24 mmol/L/h) was 3.7 and 2.1-fold higher than those in conventional organic solvent system (11.10 mmol/L/h) and solvent-free system (19.86 mmol/L/h) using magnetic stirring, respectively. Among the three bioreactor systems, solvent-free gas bubbling system provided the best reusability of the lipase retaining 94.45 % of initial activity for six batch reactions. In the bioreactor system, 5-O-lauroyl-pyridoxine was regioselectively produced with maximum production of 371.17 mmol/L at 70 ? and 0.10 of substrate molar ratio ([pyridoxine]/[lauric acid]) for 9 h. Pyridoxine monolaurate exhibited interfacial activity at oil-water interfaces, suggesting it had emulsifying properties. Pyridoxine monolaurate is expected to be applied as a multi-functional emulsifier with nutritional values to replace both small molecule emulsifiers and pyridoxine hydrochloride in fortified beverages.N

Antimicrobial Characterization of Erythorbyl Laurate for Practical Applications in Food and Cosmetics

In this study, antimicrobial spectrum of erythorbyl laurate (EL) against bacteria and fungi, leading to food-borne and infectious skin diseases, was evaluated for its practical applications in food and cosmetics. Furthermore, the influences of environmental factors including pH, oxidative stress, and dispersion medium on antimicrobial activity of EL were investigated. The three Gram-positive bacteria and the three molds were susceptible to 3.0 mM EL, while the yeast was susceptible to 6.0 mM EL. It was demonstrated EL retained antibacterial activity against Staphylococcus aureus after being oxidized while the antibacterial activity against the three Gram-positive bacteria including S. aureus, Bacillus cereus, and Listeria monocytogenes was significantly enhanced as decrease of pH from 7.0 to 5.0. Moreover, EL exhibited bactericidal effects against both Gram-positive and Gram-negative bacteria in an oil-in-water emulsion. Treatment of 5.0 mM EL for 4 h reduced 5.29 ± 0.24, 6.01 ± 0.18, 5.95 ± 0.13, and 6.24 ± 0.30 log CFU/mL against S. aureus, L. monocytogenes, Pseudomonas aeruginosa, and Escherichia coli, respectively. In a multipassage resistance selection study, it was observed minimum inhibitory concentrations of EL against S. aureus were not increased over 20 passages, indicating EL might not develop drug resistance of bacteria. This study suggests EL has a potential to be applied as the multifunctional additive in food and cosmetics

Synergistic Inactivation of Bacteria Using a Combination of Erythorbyl Laurate and UV Type-A Light Treatment

This study evaluated the synergistic antimicrobial activity of erythorbyl laurate (EL) and UV type-A (UVA). To investigate the mode of synergism, changes in gene expression and bacterial inactivation activity were examined. Individual treatments with EL (10 mM) or UVA caused a 1.9- or 0.5-log CFU/ml reduction respectively, whereas EL/UVA co-treatment resulted in a 5.5-log CFU/ml reduction in Escherichia coli viable cell numbers. Similarly, treatment with either EL (2 mM) or UVA for 30 min resulted in a 2.8- or 0.1-log CFU/ml reduction in Listeria innocua, respectively, whereas combined treatment with both EL and UVA resulted in a 5.4-log CFU/ml reduction. Measurements of gene expression levels showed that EL and UVA treatment synergistically altered the gene expression of genes related to bacterial membrane synthesis/stress response. However, addition of 10-50-fold excess concentration of exogenous antioxidant compared to EL reduced the synergistic effect of EL and UVA by approximately 1 log. In summary, the results illustrate that synergistic combination of EL and UVA enhanced membrane damage independent of the oxidative stress damage induced by UVA and thus illustrate a novel photo-activated synergistic antimicrobial approach for the inactivation of both the Gram-positive and Gram-negative bacteria. Overall, this study illustrates mechanistic evaluation of a novel photochemical approach for food and environmental applications

Recent advances on erythorbyl fatty acid esters as multi-functional food emulsifiers

Over the past few decades, food scientists have investigated a wide range of emulsifiers to manufacture stable and safe emulsion-based food products. More recently, the development of emulsifiers with multi-functionality, which is the ability to have more than two functions, has been considered as a promising strategy for resolving rancidification and microbial contamination in emulsions. Erythorbyl fatty acid esters (EFEs) synthesized by enzymatic esterification of hydrophilic erythorbic acid and hydrophobic fatty acid have been proposed as multifunctional emulsifiers since they simultaneously exhibit amphiphilic, antioxidative, and antibacterial properties in both aqueous and emulsion systems. This review provides current knowledge about EFEs in terms of enzymatic synthesis and multi-functionality. All processes for synthesizing and identifying EFEs are discussed. Each functionality of EFEs and the proposed mechanism are described with analytical methodologies and experimental details. It would provide valuable insights into the development and application of a multi-functional emulsifier in food emulsion chemistry

Microfluidic Preparation of Liposomes Using Ethyl Acetate/n-Hexane Solvents as an Alternative to Chloroform

Although liposomes have been used as a nutrient delivery carrier in the pharmaceutical, cosmetic, and food industries, they still suffer from the critical issue caused by the use of halogenated solvents (e.g., chloroform), which may be harmful to humans. Nonhalogenated solvents have been screened as candidate substitutes for chloroform based on their physicochemical properties. However, none of the candidates examined to date could form stable inverted micelles when used alone. Here, to obtain physicochemical properties similar to chloroform, combined mixtures were prepared using various ratios of each candidate. Based on the results of random combination trials with numerous candidates, ethyl acetate: n-hexane = 4 : 1(v/v) was selected as the optimum ratio because it could form stable inverted micelles and a transparent liposome solution without phase separation. The ethyl acetate and n-hexane mixture are a potential substitute for chloroform, which may resolve concerns regarding the toxicity of residual halogenated solvents in lipid nanovesicles

Controlled rate slow freezing with lyoprotective agent to retain the integrity of lipid nanovesicles during lyophilization

We designed a novel lyophilization method using controlled rate slow freezing (CSF) with lyoprotective agent (LPA) to achieve intact lipid nanovesicles after lyophilization. During the freezing step, LPA prevented water supercooling, and the freezing rate was controlled by CSF. Regulating the freezing rate by various liquid media was a crucial determinant of membrane disruption, and isopropanol (freezing rate of 0.933 degrees C/min) was the optimal medium for the CSF system. Lyophilized lipid nanovesicle using both CSF and LPA retained 92.9% of the core material and had uniform size distributions (Z-average diameter = 133.4 nm, polydispersity index = 0.144), similar to intact vesicles (120.7 nm and 0.159, respectively), after rehydration. Only lyophilized lipid nanovesicle using both CSF and LPA showed no changes in membrane fluidity and polarity. This lyophilization method can be applied to improve storage stability of lipid nanocarriers encapsulating drugs while retaining their original activity.N

Amperometric Detection of Conformational Change of Proteins Using Immobilized-Liposome Sensor System

An immobilized liposome electrode (ILE)-based sensor was developed to quantify conformational changes of the proteins under various stress conditions. The ILE surface was characterized by using a tapping-mode atomic force microscopy (TM-AFM) to confirm surface immobilization of liposome. The uniform layer of liposome was formed on the electrode. The current deviations generated based on the status of the proteins under different stress were then measured. Bovine carbonic anhydrase (CAB) and lysozyme were tested with three different conditions: native, reduced and partially denatured. For both proteins, a linear dynamic range formed between denatured concentrations and output electric current signals was able to quantify conformational changes of the proteins. The pattern recognition (PARC) technique was integrated with ILE-based sensor to perform data analysis and provided an effective method to improve the prediction of protein structural changes. The ILE-based stress sensor showed potential of leveraging the amperometric technique to manifest activity of proteins based on various external conditions

An Overview of Nanotechnology in Food Science: Preparative Methods, Practical Applications, and Safety

As the researches to utilize nanotechnology in food science are advanced, applications of nanotechnology in various fields of the food industry have increased. Nanotechnology can be applied to the food industry for production, processing, storage, and quality control of foods. Nanomaterials, unlike conventional microscale materials, having novel characteristics can improve sensory quality of foods by imparting novel texture, color, and appearance. Nanotechnology has been used to design nanosensors for detection of harmful components in foods and a smart packaging system enabling to recognize food contamination very rapidly and sensitively. Nanoencapsulation is the most significant technology in food science, especially for bioactive compounds and flavors. Targeted delivery systems designed with nanoencapsulation can enhance bioavailability of bioactive compounds after oral administration. In addition, nanoencapsulation enables to control the release of flavors at the desired time and to protect the degradation of flavors during processing and storage. In this review, current applications of nanotechnology in food science including flavor control, enhancement of bioavailability of bioactive compounds, and detection of deleterious substances in foods are presented. Furthermore, this article overviews classification, preparative methods, and safety issues of nanomaterials for food science. This review will be of help to provide comprehensive information for newcomers utilizing nanotechnology to the food sector