Aiquan Jiao

Simultaneous saccharification and fermentation of broken rice: an enzymatic extrusion liquefaction pretreatment for Chinese rice wine production

Broken rice, pretreated by enzymatic extrusion liquefaction, was used to produce Chinese rice wine by simultaneous saccharification and fermentation (SSF) process in this study. The study compared the novel process and traditional process for Chinese rice wine fermentation utilizing broken rice and head rice, respectively. With the optimum extrusion parameters (barrel temperature, 98xa0°C; moisture content, 42xa0% and amylase concentration, 1xa0‰), 18xa0% (v/v at 20xa0°C) alcoholic degree, 37.66xa0% fermentation recovery and 93.63xa0% fermentation efficiency were achieved, indicating enzymatic extrusion-processed rice wine from broken rice exhibited much higher fermentation rate and efficiency than traditional-processed rice wine from head rice during SSF. The starch molecule distribution data indicated that the alcoholic degree was related to the oligosaccharides’ formation during enzymatic extrusion. Sum of amino acid (AA) in the extrusion-processed wine was 53.7xa0% higher than that in the traditional one. These results suggest that the enzymatic extrusion pretreatment for broken rice is a feasible and alternative process in the fermentation of Chinese rice wine.

Porous starch extracted from Chinese rice wine vinasse: characterization and adsorption properties.

Chinese rice wine vinasse (the fermentation residue after removal of the crude wine or beer) contains 20-30% residual native starch. These starches are partly hydrolyzed by amylase and glucoamylase during rice wine fermentation, indicating that it is a potential source of porous starch, which is a value-added material. In the present study, morphological, short-range order, crystalline, and thermal studies were determined to characterize the structural and chemical properties of vinasse starch. The results showed that vinasse starch granule had a rough and porous shape and was much more ordered than native starch. Vinasse starch also could tolerate a higher temperature than native starch. The water and oil adsorptive capacities of vinasse starch were 1.89 and 4.14 times higher than that of native rice starch. These results suggest that vinasse is an effective and economical source of porous starch for using as adsorbent.

Impact of α-amylase combined with hydrochloric acid hydrolysis on structure and digestion of waxy rice starch

The structure and in vitro digestibility of native waxy rice starch by the combined hydrolysis of α-amylase and hydrochloric acid were investigated in this study. The combined hydrolysis technique generated higher hydrolysis rate and extent than the enzymatic hydrolysis. The granular appearance and chromatograph profile demonstrated that α-amylase and hydrochloric acid exhibited different patterns of hydrolysis. The rise in the ratio of absorbance 1047/1022cm(-1), the melting temperature range (Tc-To), and the melting enthalpy (ΔH) were observed during the combined hydrolysis. These results suggest that α-amylase simultaneously cleaves the amorphous and crystalline regions, whereas the amorphous regions of starch granules are preferentially hydrolyzed during the acid hydrolysis. Furthermore, the combined hydrolysis increased rapidly digestible starch (RDS) while decreased slowly digestible starch (SDS) and resistant starch (RS), indicating that the hydrolysis mode affected the digestion property of native waxy rice starch.

Isolation of cycloamylose by iodine affinity capillary electrophoresis

In contrast to α-, β- and γ-cyclodextrins, little information is available on the isolation and separation of cycloamylose (CA) with degree of polymerization (DP) larger than 22. The objective of the current study was to develop a new iodine affinity capillary electrophoresis (CE) for separation of CA with DP of 22-42, which was based on the formation of CA-iodine inclusion complexes, CA with twisted conformations made complicated mobility behaviors on CE instead of merely size dependent. The influences of iodide/iodine ratio, iodine concentration, pH, ion strength of running phosphate buffer, voltage, and temperature on the peak resolution and electrophoretic mobility were further investigated. Our results suggest that iodine affinity capillary electrophoresis provides a versatile and selective tool for the isolation and analysis of CA with DP from 22 to 42.

Cyclodextrin-derived chalcogenides as glutathione peroxidase mimics and their protection of mitochondria against oxidative damage

A series of novel glutathione peroxidase (GPx) mimics based on organochalcogen cyclodextrin (CD) dimer were synthesized. Their GPx-like antioxidant activities were studied using hydrogen peroxide H2O2, tert-butylhydroperoxide (BHP), and cumene hydroperoxide (CHP) as substrates and glutathione as thiol co-substrate. The results showed that 6A,6B-ditelluronic acid-A,6B′-tellurium bridged γ-cyclodextrin (6-diTe-γ-CD) had the highest peroxidase activity, which was ~670-fold higher than ebselen, a well-known GPx mimic. Reduction of lipophilic CHP often proceeded much faster than reduction of the more hydrophilic H2O2 or BHP, which cannot bind into the hydrophobic interior of the CD. The biological activities were also evaluated for their capacity to protect mitochondria against ferrous sulfate/ascorbate-induced oxidative damage. 6-diTe-γ-CD was the best inhibitor which significantly suppressed ferrous sulfate/ascorbate-induced cytotoxicity as determined by swelling of mitochondria, lipid peroxidation and cytochrome c oxidase activity. Our data suggests that 6-diTe-γ-CD has potential pharmaceutical application in the treatment of ROS-mediated diseases.

A study on the potential interaction between cyclodextrin and lipoxygenase

To get a more complete view on the lipoxygenase (LOX) catalysis in presence of cyclodextrin, the investigation into the interaction between cyclodextrins (CDs) and LOX was carried out. Effects of cyclodextrins on the activity and structure of LOX were explored in this work. It is confirmed that inhibition effect induced by complexation of CDs and LOX plays a leading role in inhibition factors of LOX catalysis in presence of CDs. Inhibition of β-cyclodextrin on LOX depended on concentration and tended to be intensified with the increase of β-CD. The enhancement of intrinsic fluorescence of LOX induced by β-CD was detected, which was probably due to the formation of complexes between aromatic amino acid residues of LOX and β-CD. The results of circular dichroism assay indicated that β-CD altered the secondary structure and microenvironment of LOX which was responsible for inhibition of enzyme catalysis.

Organotellurium-bridged cyclodextrin dimers as artificial glutathione peroxidase models

To elucidate the importance of the goodness of fit in complexes between substrates and glutathione peroxidise (GPX) mimics, we examined the decomposition of a variety of structurally distinct hydroperoxides at the expense of glutathione (GSH) catalyzed by 2,2′-ditellurobis(2-deoxy-γ-cyclodextrin) (2-Te-γ-CD), and by the corresponding derivatives of β-cyclodextrin (β-CD) and α-cyclodextrin. The good fit of the cumene group into the γ-CD binding cavity reflected the result of well-defined reaction geometry, leading to the most excellent peroxidase activity with high substrate specificity. Furthermore, the catalytic constant and the combination with the best binding also exhibited the highest regioselectivity in the substrate decomposition. Saturation kinetics were observed and the catalytic reaction agreed with a ping-pong mechanism, in analogy with natural GPX, and might exert its thiol peroxidase activity via tellurol, tellurenic acid, and tellurosulfide. The stoichiometry of the inclusion complex was determined to be of 2:1 host-to-guest. The value of stability constant Kc for (2-Te-γ-CD)2/GSH at room temperature was calculated to be 3.815xa0×xa0104xa0M−2, which suggested that 2-Te-γ-CD had a moderate ability to bind GSH. Importantly, the proposed mode of the (2-TeCD)2/GSH complex was the possible important noncovalent interactions between enzymes and substrates in influencing catalysis and binding.

Study on the intermediate ions formed by glutathione peroxidase mimic 2,2'-ditellurobis(2-deoxy-β-cyclodextrin) by electrospray ionization mass spectrometry.

RATIONALEn2,2-Ditellurobis(2-deoxy-β-cyclodextrin) (2-TeCD) is one of the most well-known glutathione peroxidase (GPx) mimics. However, because the critical reaction intermediates had not previously been isolated or directly detected due to its short lifetime, the catalytic mechanism of 2-TeCD is not very clear and further experiments are needed to characterize each of the intermediates in the catalytic cycle.nnnMETHODSnUsing electrospray ionization mass (and tandem) spectrometry (ESI-MS and ESI-MS/MS) experiments, the decomposition of hydrogen peroxide at the expense of glutathione (GSH) catalyzed by 2-TeCD was monitored on-line.nnnRESULTSnThe key intermediates were successfully intercepted and structurally characterized for the first time by coupling a microreactor on-line to the ESI ion source, which permitted the fast screening of intermediates directly from solution.nnnCONCLUSIONSnThe catalytic mechanism of 2-TeCD catalysis has been elaborated based on mass spectrometric data and exerted its peroxidase activity via tellurol, tellurenic acid, and tellurosulfide, in analogy with natural GPX.