超高压对酶活的影响

综述了酶在超高压条件下的作用机理及动力学研究进展,并对各类酶在超高压条件下的灭活情况作了归纳,展望了超高压在酶灭活发展中的应用。     

酶制剂和活性干酵母在大曲酱香型酒中的应用

提出将酶制剂和活性干酵母同时应用于大曲酱香型优质白酒生产。试验表明酒酷酒精含量随着酶制剂、干酵母的加入量的增多而增大,且达到最高酒精份的时间逐步缩短,出酒率最高可增产71.7％;在不影响大曲酱香型酒质量的前提下,酶制剂和活性干酵母的最佳加入排次宜从四排开始,并选取适当加入量,大曲用量减少10％～15％之间时可提高发酵活力,加速糖转化为酒的过程,缩短发酵期。实例计算证明,采用该工艺可明显提高经济效益。     

Levels of glutathione and related enzymes in yellowtail fish muscle subjected to ice storage in a modified atmosphere

We investigated the effects of ice storage in a modified atmosphere on levels of glutathione (GSH) and its related enzyme activities, the metmyoglobin to total myoglobin ratio (metMb%), and the K value (a freshness index) of yellowtail fish muscle. GSH in ordinary muscle (fast skeletal muscle) as well as in dark muscle (slow skeletal muscle) stored in air decreased. GSH in those muscles was almost unchanged during storage when packaged with an oxygen absorber or with an oxygen absorber-CO(2) generator. Glutathione disulfide in each type of packaging remained at low concentrations during storage. The GSH peroxidase activities of ordinary muscle and of dark muscle after 7 d of storage in air were lower than when packaged with the oxygen absorber or with the oxygen absorber-CO(2) generator. The GSH reductase (GR) activities of ordinary muscle at the 4th and 7th day of storage when packaged with the oxygen absorber showed a tendency to be lower than when stored in air. The GR activity of dark muscle in each type of packaging method was unchanged during storage. The packaging method did not influence the K values of either the ordinary muscle or the dark muscle during storage. The metMb% of dark muscle when packaged with the oxygen absorber was lower than in the other types of packaging during storage. Therefore, packaging with the oxygen absorber is an effective method to prevent the loss of GSH in fish meat as well as to reduce the discoloration during storage. PRACTICAL APPLICATION: This study examined whether modified atmosphere packaging preserves the level of GSH, which is unstable to oxidative stress, in fish muscle. The use of an oxygen absorber for packaging can allow us to take in a sufficient amount of the bioactive compound from fish meat after storage as well as fresh fish.     

酶制剂在啤酒品质改良中的应用

啤酒的澄清度、色度、风味、稳定性、持泡性是衡量其品质的重要因素，介绍了几种改良啤酒品质的酶制剂。     

亚麻/棉混纺织物的生物酶前处理

根据亚麻、棉纤维的含杂情况，选择果胶酶、木聚糖酶、纤维素酶和漆酶等四种酶制剂进行前处理试验。以处理后织物的白度、润湿性、布面麻皮和织物强力损失为主要指标，与传统高温强碱亚麻／棉织物前处理效果进行比较，确立了亚麻／棉织物生物酶前处理汽蒸工艺为酶退浆→酶精练→漂前处理→氧漂→氧漂。     

Recrystallization in Sugar/Stabilizer Solutions as Affected by Molecular Structure

The influence that a range of polysaccharides (galactomannans) had on ice recrystallization was determined. The concentration dependence of the recrystallization inhibition occurring with locust bean and guar gums was determined. The degree of galactose substitution in a range of enzyme modified guars was dominant in the effect of a galactomannan to inhibit recrystallization. The fine structure of the substituents were less important. Where the galactose content of comparable polysaccharides was similar the fine structure became dominant. The influence of sugar size on recrystallization was also investigated. Increasing molecular weight resulted in reduced recrystallization rates. The observed rates appeared to follow Williams -Landell-Ferry kinetics.     

高产溶纤酶菌株的选育

以枯草芽孢杆菌 YL-P2、YL-F2作为出发菌株,分别采用紫外线诱变、硫酸二乙酯诱变以及紫外线和硫酸二乙酯复合诱变,以脱脂牛奶平板法为初筛方法结合纤维蛋白平板复筛的方法选育出溶纤酶活力高的菌株, 获得了高产溶纤酶菌株 UV-8。UV-8溶纤酶活力达到2 314 IU/mL,与出发菌株相比,酶活力提高了2倍。结果表明,经多次传代后菌株 UV-8的溶纤酶酶活达到稳定,具有很好的潜在开发前景。     

酶法生产小麦麦胚油操作单元研究

用于提取麦胚油的麦胚最适宜颗粒为40目。麦胚用微波90s稳定可以获得满意结果。采用少孢根霉发酵液,最适宜料液比为1∶4,最适宜酶法提取工艺条件为在pH5.5、60℃时,催化水解6h。酶解出油率最高达到73%。     

酶解牛乳铁蛋白制备乳铁素 B的酶解条件研究

乳铁素B是牛乳铁蛋白经胃蛋白酶酶解后所得到的最重要的抗菌肽，乳铁蛋白酶解生成乳铁素后抗菌活性大大增强。通过正交试验确立了牛乳铁蛋白酶解制备乳铁素B的最佳条件，指出在底物质量浓度为50g／L，酶与底物质量浓度比为1：30(质量比)，酶解时间为60min时所得的乳铁素质量浓度及活性较好。     

Kinetic behaviour and stability of Escherichia coli ATCC27257 alkaline phosphatase immobilised in soil humates

Alkaline phosphatase (EC 3.1.3.1) extracted from Escherichia coli ATCC27257 was immobilised by co‐flocculation with soil humates in the presence of Ca²⁺. The effects of time, temperature, pH and concentration of enzyme and support on immobilisation were studied. Between 58 and 92% of the added phosphatase was strongly bound to the humates, depending on the conditions of immobilisation used. Some characteristics of the humate–phosphatase complexes and of the free enzyme were compared. The enzymatic complexes showed values of K_m (2.22 mM ) and activation energy (33.4 kJ mol^?1) similar to those of the free enzyme (2.00 mM and 27.6 kJ mol^?1). The pH/activity profiles revealed no change in terms of shape or optimum pH (10.5) upon immobilisation of alkaline phosphatase. However, the immobilised enzyme showed maximal activity in the range of 80–100 °C, while the free enzyme had its highest activity at 60 °C. The thermal stability of alkaline phosphatase was enhanced by complexation to the soil humates. © 2003 Society of Chemical Industry