Effects of Liquid Hot Water Pretreatment on Enzymatic Hydrolysis and Physicochemical Changes of Corncobs

Liquid hot water (LHW) pretreatment is an efficient chemical-free strategy for enhancing enzymatic digestibility of lignocellulosic biomass for conversion to fuels and chemicals in biorefinery. In this study, effects of LHW on removals of hemicelluloses and lignin from corncobs were studied under varying reaction conditions. LHW pretreatment at 160 °C for 10 min promoted the highest levels of hemicellulose solubilization into the liquid phase, resulting into the maximized pentose yield of 58.8% in the liquid and more than 60% removal of lignin from the solid, with 73.1% glucose recovery from enzymatic hydrolysis of the pretreated biomass using 10 FPU/g Celluclast?. This led to the maximal glucose and pentose recoveries of 81.9 and 71.2%, respectively, when combining sugars from the liquid phase from LHW and hydrolysis of the solid. Scanning electron microscopy revealed disruption of the intact biomass structure allowing increasing enzyme’s accessibility to the cellulose microfibers which showed higher crystallinity index compared to the native biomass as shown by x-ray diffraction with a marked increase in surface area as revealed by BET measurement. The work provides an insight into effects of LHW on modification of physicochemical properties of corncobs and an efficient approach for its processing in biorefinery industry.     

Betulinic Acid Modulates the Expression of HSPA and Activates Apoptosis in Two Cell Lines of Human Colorectal Cancer

Betulinic acid (BA) is a pentacyclic triterpene usually isolated from botanical sources. Numerous studies have reported the inhibitory effect of BA against human colorectal cancer cells (CRC). However, its effect on the expression of the molecular chaperone HSPA is unclear. The aim of this research is to investigate the anti-cancer activities of BA purified from Piper retrofractum and study its effect on the expression of HSPA in colorectal cancer HCT116 and SW480 cells. The viability of both cancer cells was reduced after they were treated with an increasing dosage of BA. Flow cytometry assay revealed that levels of cell apoptosis significantly increased after incubation with BA in both cancer cells. Pro-apoptotic markers including Bax, cleaved-caspase-3 and cleaved-caspase-9 were increased while anti-apoptotic marker Bcl-2 was decreased after BA treatment. Western blot also showed that the expression of HSPA fluctuated upon BA treatment, whereby HSPA was increased at lower BA concentrations while at higher BA concentrations HSPA expression was decreased. Preliminary molecular docking assay showed that BA can bind to the nucleotide binding domain of the HSP70 at its ADP-bound state of the HSP70. Although further research is needed to comprehend the BA-HSPA interaction, our findings indicate that BA can be considered as potential candidate for the development of new treatment for colorectal cancer.     

Influence of extraction methodologies on the analysis of five major volatile aromatic compounds of citronella grass (Cymbopogon nardus) and lemongrass (Cymbopogon citratus) grown in Thailand

This paper deals with the systematic comparison of extraction of major volatile aromatic compounds (VACs) of citronella grass and lemongrass by classical microhydrodistillation (MHD), as well as modern accelerated solvent extraction (ASE). Sixteen VACs were identified by GC/MS. GC-flame ionization detection was used for the quantification of five VACs (citronellal, citronellol, geraniol, citral, and eugenol) to compare the extraction efficiency of the two different methods. Linear range, LOD, and LOQ were calculated for the five VACs. Intraday and interday precisions for the analysis of VACs were determined for each sample. The extraction recovery, as calculated by a spiking experiment with known standards of VACs, by ASE and MHD ranged from 64.9 to 91.2% and 74.3 to 95.2%, respectively. The extraction efficiency of the VACs was compared for three solvents of varying polarities (hexane, dichloromethane, and methanol), seven different temperatures (ranging from 40 to 160 degrees C, with a gradual increment of 20 degrees C), five time periods (from 1 to 10 min), and three cycles (1, 2, and 3 repeated extractions). Optimum extraction yields of VACs were obtained when extractions were carried out for 7 min with dichloromethane and two extraction cycles at 120 degrees C. The results showed that the ASE technique is more efficient than MHD, as it results in improved yields and significant reduction in extraction time with automated extraction capabilities.     

Ion Chromatographic Analysis of Monosaccharides and Disaccharides in Raw Sugar

A simple and effective method using ion chromatography was developed for the simultaneous determination of five monosaccharides (arabinose, glucose, fructose, xylose, and ribose) and two disaccharides (sucrose and lactose) in raw sugar samples. The separation was performed on a CarboPac PA 10 column using the gradient elution of sodium hydroxide and water as the mobile phase. Monosaccharides and disaccharides were detected by an integrated pulsed amperometric detection (IPAD) using gold working electrode. Acid hydrolysis was used for sample preparation before the analysis of glucose and fructose. All the studied sugars showed good linear ranges within 0.5–100 µg mL⁻¹ with the correlation coefficients higher than 0.997. The limits of detection were all less than 0.5 µg mL⁻¹. The RSDs of the method were less than 10 %. The recoveries of the sugars that spiked in raw sugar samples ranged from 96.1 to 102.4 %. The method was successfully applied for the analysis of sugars in raw sugar samples. Sucrose is the major constituent found in the samples at 97 %.

     

Ultra-trace determination of Pb(II) and Cd(II) in drinking water and alcoholic beverages using homogeneous liquid-liquid extraction followed by flame atomic absorption spectrometry

The determination of Pb(II) and Cd(II) in different sample matrices, including drinking water, distilled spirits and fruit wine, was carried out by flame atomic absorption spectrometry (FAAS) after pre-concentration using homogeneous liquid-liquid extraction (HLLE). First, the HLLE method was optimised with lead diethyldithiocarbamate (Pb-DDTC) complex which was extracted with a perfluorooctanoate anion (PFOA^?) dissolved in lithium hydroxide under acidic conditions. The optimum extraction conditions, using 0.01 M DDTC, 0.05 M PFOA^?, 3 M HCl and 1 mL of 30 vol. % acetone, were obtained. The Pb-DDTC complex in the nitric acid digest of the samples (50–150 mL) was extracted quantitatively into a drop of 100 μL of sediment phase. The sediment phase dissolved in 1 vol. % HNO₃ with at least 3–5 mL of the final volume was then determined by FAAS, affording a pre-concentration factor of 10–50. Hence, the HLLE method afforded an increase in both sensitivity and selectivity for the metal determination by conventional FAAS, resulting in ultra-trace level detection of Pb(II) in all samples analysed (drinking water, 9.2–23 ng mL^?1; distilled spirits, 23–50 ng mL^?1; fruit wine, 24–53 ng mL^?1). In addition, the proposed method could successfully be applied to Cd(II) determination in these samples.     

Reversed Phase Chromatographic Analysis of 13 Amino Acids in Honey Samples

A simple method using reversed phase high-performance liquid chromatography (RP-HPLC) was developed for the simultaneous analysis of 13 amino acids. Amino acids were pre-column derivatized with 9-fluorenylmethyl chloroformate (FMOC-Cl) before analysis by RP-HPLC. Experimental parameters affecting the derivatization and chromatographic separation were investigated. Amino acids were derivatized with FMOC-Cl under alkaline condition in 0.1 mol/L borate buffer pH 10.0 at room temperature. The FMOC-amino acid derivatives were separated on an Atlantis C18 column under the gradient elution of 0.05 % trifluoroacetic acid and acetonitrile and UV detection at 265 nm. Linear ranges were 0.2–100.0 μg/mL with the correlation coefficients greater than 0.992. Limits of detection and limits of quantitation were in the range of 0.05–2.0 and 0.2–5.0 µg/L, respectively. The intra-day precision (n = 3) of retention time was less than 1 %, while for the peak area was less than 4 %. The inter-day precision (n = 3 × 3) of retention time was less than 2 % and the peak area was less than 8 %. This method was applied in honey samples and the results showed that proline is the major amino acids in honey samples.

     

Core–shell SiO2‐coated Fe3O4 with a surface molecularly imprinted polymer coating of folic acid and its applicable magnetic solid‐phase extraction prior to determination of folates in tomatoes

A novel core–shell magnetic surface molecularly imprinted polymer with folic acid as a template was successfully synthesized by the sol–gel method. To generate Lewis acid sites in the silica matrix for the interaction of the metal coordinate with the template, 3‐aminopropyltriethoxysilane was used as a functional monomer, tetraethyl orthosilicate as a cross‐linker, and aluminum ions as a dopant. The magnetite encapsulated by the silica shell plays an important role as a magnetic‐coated polymer. The synthesized product was characterized by powder X‐ray diffraction, scanning electron microscopy, transmission electron microscopy, and FTIR and UV/Vis spectroscopy. The powder X‐ray diffraction patterns, FTIR and UV/Vis spectra confirmed the characteristics of the as‐prepared silica coated magnetite and folic acid molecularly imprinted polymer. It was successfully applied for magnetic solid‐phase extraction prior to the determination of folates in tomato samples using high‐performance liquid chromatography with photodiode array detection. The detection limit of the proposed method was 1.67 μg/L, and results were satisfactory, with a relative standard deviation of < 3.94%.