Mixed-mode chromatographic performance using nicotinic acid-functionalized chito-oligosaccharide-bonded Ti/Si hybrid monolithic capillary columns.

This article describes the fabrication of porous nicotinic acid-functionalized chito-oligosaccharide-bonded titania/silica hybrid monoliths (TiO2/SiO2@ChO-N) through a co-gelation sol-gel process. A capillary monolith with a well-defined and homogeneous structure was obtained by controlling the hydrolysis speed of titanium alkoxides in a sol mixture by using glycerol and acetylacetone. As a result of the functionalization with chito-oligosaccharides (ChO)-modified nicotinic acid, the obtained stationary phase provides superior physiochemical properties, such as a cationic hydrophilic surface, porosity, and mechanical strength. Scanning electron microscope and attenuated total reflectance-infrared spectroscopy were used to characterize the functionalized monolithic columns. The produced capillary columns showed high chromatographic performance with acceptable selectivity for charged analytes as well as organic polar compounds such as nucleic bases, nucleosides, carbamate pesticides, and strobilurin fungicides. The obtained results also indicated that the functionalized ChO's amino, amide, hydroxyl, and pyridinium ring moieties served as hydrophilic electrostatic traps for charged substances, in addition to stroing π-π interaction with the carbamate pesticides and strobilurin fungicides analytes via hydrogen bonding.

A review of the modern principles and applications of solid-phase extraction techniques in chromatographic analysis.

Analytical processes involving sample preparation, separation, and quantifying analytes in complex mixtures are indispensable in modern-day analysis. Each step is crucial to enriching correct and informative results. Therefore, sample preparation is the critical factor that determines both the accuracy and the time consumption of a sample analysis process. Recently, several promising sample preparation approaches have been made available with environmentally friendly technologies with high performance. As a result of its many advantages, solid-phase extraction (SPE) is practiced in many different fields in addition to the traditional methods. The SPE is an alternative method to liquid-liquid extraction (LLE), which eliminates several disadvantages, including many organic solvents, a lengthy operation time and numerous steps, potential sources of error, and high costs. SPE advanced sorbent technology reorients with various functions depending on the structure of extraction sorbents, including reversed-phase, normal-phase, cation exchange, anion exchange, and mixed-mode. In addition, the commercial SPE systems are disposable. Still, with the continual developments, the restricted access materials (RAM) and molecular imprinted polymers (MIP) are fabricated to be active reusable extraction cartridges. This review will discuss all the theoretical and practical principles of the SPE techniques, focusing on packing materials, different forms, and performing factors in recent and future advances. The information about novel methodological and instrumental solutions in relation to different variants of SPE techniques, solid-phase microextraction (SPME), in-tube solid-phase microextraction (IT-SPME), and magnetic solid-phase extraction (MSPE) is presented. The integration of SPE with analytical chromatographic techniques such as LC and GC is also indicated. Furthermore, the applications of these techniques are discussed in detail along with their advantages in analyzing pharmaceuticals, biological samples, natural compounds, pesticides, and environmental pollutants, as well as foods and beverages.

Cell factory for γ-aminobutyric acid (GABA) production using Bifidobacterium adolescentis.

BACKGROUND: Bifidobacteria are gram-positive, probiotic, and generally regarded as safe bacteria. Techniques such as transformation, gene knockout, and heterologous gene expression have been established for Bifidobacterium, indicating that this bacterium can be used as a cell factory platform. However, there are limited previous reports in this field, likely because of factors such as the highly anaerobic nature of this bacterium. Bifidobacterium adolescentis is among the most oxygen-sensitive Bifidobacterium species. It shows strain-specific gamma-aminobutyric acid (GABA) production. GABA is a potent bioactive compound with numerous physiological and psychological functions. In this study, we investigated whether B. adolesentis could be used for mass production of GABA. RESULTS: The B. adolescentis 4-2 strain isolated from a healthy adult human produced approximately 14 mM GABA. It carried gadB and gadC, which encode glutamate decarboxylase and glutamate GABA antiporter, respectively. We constructed pKKT427::Pori-gadBC and pKKT427::Pgap-gadBC plasmids carrying gadBC driven by the original gadB (ori) and gap promoters, respectively. Recombinants of Bifidobacterium were then constructed. Two recombinants with high production abilities, monitored by two different promoters, were investigated. GABA production was improved by adjusting the fermentation parameters, including the substrate concentration, initial culture pH, and co-factor supplementation, using response surface methodology. The optimum initial cultivation pH varied when the promoter region was changed. The ori promoter was induced under acidic conditions (pH 5.2:4.4), whereas the constitutive gap promoter showed enhanced GABA production at pH 6.0. Fed-batch fermentation was used to validate the optimum fermentation parameters, in which approximately 415 mM GABA was produced. The conversion ratio of glutamate to GABA was 92-100%. CONCLUSION: We report high GABA production in recombinant B. adolescentis. This study provides a foundation for using Bifidobacterium as a cell factory platform for industrial production of GABA.

Development of a Solid-Phase Extraction (SPE) Cartridge Based on Chitosan-Metal Oxide Nanoparticles (Ch-MO NPs) for Extraction of Pesticides from Water and Determination by HPLC.

The present study aims to prepare two new types of chitosan-metal oxide nanoparticles (Ch-MO NPs), namely, chitosan-copper oxide nanoparticles (Ch-CuO NPs) and chitosan-zinc oxide nanoparticles (Ch-ZnO NPs), using sol-gel precipitation mechanism, and test them new as adsorbent materials for extraction and clean-up of different pesticides from water. The design of core-shell was implemented by metal oxide core with chitosan as a hard shell after crosslinking mechanism by glutaraldehyde and then epichlorohydrin. The characterizations of the prepared nanoparticles were investigated using Fourier transform infrared spectrometry (FT-IR), zeta potential, scanning electron microscopy (SEM), transmission electron microscope (TEM), and X-ray diffraction (XRD). FT-IR confirmed the interaction between chitosan, metal oxide, and crosslinking mechanism. SEM and TEM explained that the nanoparticles have a spherical morphology and nanosize of 93.74 and 97.95 nm for Ch-CuO NPs and Ch-ZnO NPs, respectively. Factorial experimental design was applied to study the effect of pH, concentration of pesticide, agitation time, and temperature on the efficiency of adsorption of pesticides from water samples. The results indicated that optimum conditions were pH of 7, temperature of 25°C, and agitation time of 25 min. The SPE cartridges were then packed with Ch-MO NPs, and seven pesticides of abamectin, diazinon, fenamiphos, imidacloprid, lambda-cyhalothrin, methomyl, and thiophanate-methyl were extracted from water samples and determined by HPLC. The extraction efficiency of Ch-ZnO NPs was higher than Ch-CuO NPs, but both removed a larger amount of most of tested pesticides than the standard ODS cartridge (C18). The results showed that this method achieves rapid and simple extraction in small quantities of adsorbents (Ch-MO NPs) and solvents. In addition, the method is highly sensitive to pesticides and has a high recovery rate.

The Antibacterial Activity of Chitosan Products Blended with Monoterpenes and Their Biofilms against Plant Pathogenic Bacteria.

This study focuses on the biological activities of eleven chitosan products with a viscosity-average molecular weight ranging from 22 to 846 kDa in combination with the most active monoterpenes (geraniol and thymol), out of 10 tested, against four plant pathogenic bacteria, Agrobacterium tumefaciens, Erwinia carotovora, Corynebacterium fascians, and Pseudomonas solanacearum. The antibacterial activity was evaluated in vitro by the agar dilution technique as a minimum inhibitory concentration (MIC) that was found to be dependent on the type of the microorganism tested. The most active product of chitosan was used for biofilm production enriched with geraniol and thymol (0.1 and 0.5%) and the films were also evaluated against the tested bacteria. The biological bioactivities summarized here may provide novel insights into the functions of chitosan and some monoterpenes and potentially allow their use for food protection from microbial attack.