Self-adhesive PMIA membranes with chitosan porous beads immobilized pullulanase for efficient biological aging of beer.

A novel pulluanase@chitosan porous beads/Poly (m-phthaloyl-m-phenylenediamine) (PULL@CPB/PMIA) membrane with good separation and biocatalysis properties was prepared by a self-adhesive method by introducing an immobilized enzyme (PULL@CPB) onto the PMIA membrane. The combination of PULL@CPB and PMIA could increase the one-step refining of protoplasmic beer as well as the ability of biocatalysis to lower the alcohol-to-ester ratio. The experimental results showed that the addition of PULL@CPB and the increase in the ratio of EtOH/water in the coagulation bath both increased the load of pullulanase on the membrane surface, while excessive addition decreased the activity of pullulanase. Under the amount of PULL@CPB is 0.5 g·L-1 and the ratio of EtOH/water is 60%, the relative activity of pullulanase in PULL@CPB modified PMIA membrane was the highest, which was 91.7% of the initial activity. The interception rates of protein and macromolecular ß-glucan were 92.2% and 87.3%, respectively, under the condition of beer flux (162.3 L·m-2·h-1). At the same time, the PULL@CPB/PMIA membrane has strong antibacterial performance and thus plays a role in extending the shelf life of beer. Compared with free pullulanase, the thermal stability, pH stability, organic solvent stability, and storing stability of immobilized pullulanase were significantly improved. The effects of PULL@CPB dosage and operating temperature on biocatalysis efficiency were discussed. The immobilized pullulanase activity on the membrane remained at 70.8% after 10 continuous uses. Therefore, the PMIA membrane is an excellent carrier of pullulanase, so its bioactive membrane has a wide range of prospects in food, medicine, and other fields.

An in-depth mechanistic study of the p-hydroxyphenylglycine synthetic process using in situ ATR-IR spectroscopy.

In this study, an in situ ATR-IR technique was used as a powerful tool to gain insight into the synthetic process of p-hydroxyphenylglycine (p-HPG) by the sulfamic acid-glyoxylic acid-phenol method. Combined with other chemical and instrumental analysis technologies, the reaction sequence and key intermediates of this one-pot reaction were determined, and two concomitant reaction paths have been put forward for the first time. The possible reaction mechanism has been suggested, and the reaction efficiency of each path is discussed in detail. Through the optimization of the experimental parameters, an approximately 40% increase in the final product yield was achieved compared with previous reports. We believe that this study will without a doubt trigger research interest in understanding the industrial production process of important chemicals and pharmaceuticals and as a result will promote the sustainable development and application of novel, efficient chemical reaction routes.

Olfactory impact of guaiacol, ortho-vanillin, 5-methyl, and 5-formyl-vanillin as byproducts in synthetic vanillin.

To better control the quality of synthetic vanillin obtained by using the guaiacol synthesis method, the olfactory impacts of byproducts on the aroma of the synthetic vanillin samples were evaluated and their optimum concentration ranges were determined. Four byproducts (guaiacol, ortho-vanillin, 5-methyl-vanillin, and 5-formyl-vanillin) were identified by gas chromatography-mass spectrometry (GC-MS) and quantified by gas chromatography-flame ionization detection (GC-FID) in the synthetic vanillin samples with different degrees of purity. The aroma intensities (AIs) of the four byproducts obtained by gas chromatography-olfactometry (GC-O) were: guaiacol (AI: 3.5-4.0, smoke), ortho-vanillin (AI: 1.6-2.5, almond), 5-methyl-vanillin (AI: 2.5-3.3, aldehyde), and 5-formyl-vanillin (AI: 3.2-3.8, green). The aroma perceptual interactions of the four byproducts and the vanillin in the synthetic vanillin samples were determined by S-curve analysis. Guaiacol and 5-methyl-vanillin showed synergistic effects by Feller's additive model. Combined with the results of an addition experiment, when the contents of guaiacol, ortho-vanillin, 5-methyl-vanillin, and 5-formyl-vanillin were within 50, 10, 400, and 1,000 mg/kg respectively, the byproducts had no effects on the aroma quality of the synthetic vanillin samples. PRACTICAL APPLICATION: Synthetic vanillin is one of the most commonly used food additives. Currently, the purity of synthetic vanillin can reach 99.9%, but trace byproducts are still present. Continuing to improve the purity of synthetic vanillin will significantly increase its production costs. Therefore, it is necessary to determine whether the presence of these byproducts affects the aroma quality of the synthetic vanillin samples or not. If they have a negative effect on its aroma, it will be important to reduce their content. If they have no influence or positive role, there is no need to control the content of these byproducts to very low levels. This study determined the content of the byproducts produced during the synthesis of vanillin by guaiacol glyoxylic acid method, judged the perceptual interaction between the byproducts and the vanillin in the synthetic vanillin samples, and determined the optimum range within which the byproducts had no effects on the aroma quality. This study provides a theoretical basis for improving the aroma quality of synthetic vanillin while controlling the production costs.

[Characteristics of organic carbon forms in the sediment of Wuliangsuhai and Daihai Lakes].

The characteristics and differences of organic carbon forms in the sediments of the Wuliangsuhai and the Daihai Lakes with different eutrophication types were discussed in the present study. The results showed that the range of total organic carbon content (TOC) in Wuliangsuhai Lake was 4.50-22.83 g x kg(-1) with the average of 11.80 g x kg(-1). The range of heavy-fraction organic carbon content was 3.38-21.67 g x kg(-1) with the average of 10.76 g x kg(-1). The range of light-fraction organic carbon content was 0.46-1.80 g x kg(-1) with the average of 1.04 g x kg(-1); The range of ROC content was 0.62-3.64 g x kg(-1) with the average of 2.11 g x kg(-1), while the range of total organic carbon content in Daihai lake was 6.84-23.46 g x kg(-1) with the average of 14.94 g x kg(-1). The range of heavy-fraction organic carbon content was 5.27-22.23 g x kg(-1) with the average of 13.89 g x kg(-1). The range of light-fraction organic carbon content was 0.76-1.57 g x kg(-1). The range of ROC content was 1.54-7.08 g x kg(-1) with the average of 3.62 g x kg(-1). The results indicated that the heavy-fraction organic carbon was the major component of the organic carbon and plays an important role in the accumulation of organic carbon in the sediments of two Lakes. The content of light-fraction organic carbon was similar in the sediments of two lakes, whereas, the contents of total organic carbon and heavy-fraction organic carbon in the sediment of Wuliangsuhai Lake were less than those in the sediment of Daihai Lake, and the value of LFOC/TOC in the Wuliangsuhai Lake was larger than that in the Daihai Lake. The humin was the dominant component of the sediment humus, followed by fulvic acid in the two lakes. The values of HM/HS in the sediments of Wuliangsuhai lake range from 43.06% to 77.25% with the average of 62.15% and values of HM/HS in the sediments of Dahai lake range from 49.23% to 73.85% with the average of 65.30%. The tightly combined humus was the dominant form in the sediment humus of two lakes, and the followed was loosely combined humus. As a whole, the carbon storage of two lakes were all relatively stable, but the values of PQ, LFOC/TOC, the ratio of loosely to tightly combined humus and HA/FA revealed that, in the sediment of Wuliangsuhai, the humification degree of organic matter was lower than that of Daihai, while the activity of humus was higher than that of Daihai, thus the carbon storage is less stable than that of Daihai.

[Examination of silicate limitation of primary production by diatoms phytoplankton in the Daihai Lake].

The Daihai Lake (40 degrees 29'27"-40 degrees 37'6"N, 112 degrees 33'31"-112 degrees 46'40"E) is a typical inland lake in a semiarid region in Inner Mongolia, China. Based on the geochemistry character of biogenic silica (BSi) in the water-sediments system of the Daihai Lake, the theory of silicate limitation of Primary Production by Diatoms phytoplankton in the Daihai Lake are discussed in this work by interpreting the information of the BSi concentrations, horizontal and vertical distributions and the response relation between BSi and past environmental conditions. It is found that the concentration of Si is very low in overlying water while very high in the sediments. The spatial distribution patters of SiO3(2-) and BSi suggest the Si source of the lake. The geochemistry information of BSi is well archived in the lake sediment profiles, and the geochemistry information of BSi well responses to the past environmental conditions of the Daihai drainage basin. The ratios between Si, and C, N, P in the water-sediment system and the response relation between BSi and past environmental conditions indicate the main reasons for the theory of silicate limitation of Primary Production by Diatoms phytoplankton. Furthermore, the dominant factor for silicate limitation of Primary Production by Diatoms phytoplankton is different in different periods.

Study of structural and electronic origin of ambergris odor of some compounds.

The correlation between structural, stereochemical as well as electronic features and ambergris odor of some tricyclic ethers is established based on quantum chemical calculation method. A definite structural fragment (a "new ambergris triangle") with certain electronic properties determining the origin of the odor is revealed. The influence of HOMO-LUMO energy gaps and total energies of some ambergris compounds on their odor intensity is investigated.