磁性复合粒子固定化葡萄糖氧化酶的制备

采用化学共沉淀法,制备了Fe3O4粒子,并将带正电荷的PDDA吸附在其表面,形成PDDA-Fe3O4磁性复合体。为提高葡萄糖氧化酶的稳定性和重复利用率,以自制的PDDA-Fe3O4磁性复合体为载体,通过静电引力来固定葡萄糖氧化酶。研究结果表明,PDDA-Fe3O4磁性载体表面的Zeta电位为47.6mV,载体平均粒径为275d.nm。葡萄糖氧化酶固定化最佳条件为：温度15℃,pH=6,酶与载体质量比为15mg/g。固定化酶的热稳定性、pH稳定性及重复使用性能都有很大的提高。     

葡萄糖氧化酶活性变化的分析

利用黑曲霉发酵法生产葡萄糖酸钠,起主要作用的酶是葡萄糖氧化酶.发酵中葡萄糖氧化酶活性高低对降糖速率的快慢、葡萄糖酸钠产率高低都起到了关键作用,所以对葡萄糖氧化酶活性变化趋势的研究越发重要.该文将葡萄糖氧化酶存放于不同温度下,随时间延长观察酶活性的变化趋势,从而总结规律,在适当温度下利用合理的检测方法,准确测定酶活性,进而调整生产工艺,利用最优生产工艺增加产品质量和产量.     

含环氧基固定化葡萄糖氧化酶共聚载体的催化性能研究

环氧基团可以在温和条件下与酶分子的氨基发生共价结合使其固定于载体表面。选用含有活性环氧基团的甲基丙烯酸缩水甘油酯(GMA)为单体,N,N′-亚甲基双丙烯酰胺(MBAA)为交联剂,聚乙烯吡咯烷酮(PVP)为稳定剂,2,2′-偶氮二异丁腈(AIBN)为引发剂,乙醇水溶液为分散介质,并加入Fe3O4磁流体,通过反相悬浮聚合成功合成了大孔Ferrofluid-GMA-MBAA共聚物载体(FGM)。通过调节磁流体和交联剂用量,可调节载体比表面积,孔径以及溶胀性能。将葡萄糖氧化酶(GOD)偶联于GMA含量20%,磁流体含量4%,交联剂含量40%的共聚物载体4FGM (40),制成固定化葡萄糖氧化酶,其表观酶活高达546.23±2.33 U/g。讨论了固定化葡萄糖氧化酶的酶学性质,在最适条件(55 ℃,pH 8.0)下,固定化酶的表观酶活回收率为90.45%;连续使用15次活性仍接近初始值的60%;固定化酶在4 ℃保存30 d,活性保持不变。     

Covalent attachment of lactase to low-density polyethylene films

ABSTRACT:  Polymer films to which bioactive compounds such as enzymes are covalently attached offer potential for in-package processing of food. β-galactosidase (lactase) was covalently attached to surface-functionalized low-density polyethylene films. A two-step wet chemical functionalization introduced 15.7 nmol/cm² primary amines to the film surface. Contact angle, dye assays, X-ray photoelectron spectroscopy, and appropriate protein assays were used to characterize changes in film surface chemistry after each step in the process of attachment. Glutaraldehyde was used to covalently attach lactase to the surface at a density of 6.0 μg protein per cm² via reductive amination. The bond between the covalently attached lactase and the functionalized polyethylene withstood heat treatment in the presence of an ionic denaturant with 74% enzyme retention, suggesting that migration of the enzyme into the food product would be unlikely. The resulting polyethylene had an enzyme activity of 0.020 lactase units (LU)/cm² (approximately 4500 LU/g). These data suggest that enzymes that may have applications in foods can be covalently attached to inert polymer surfaces, retain significant activity, and thus have potential as a nonmigratory active packaging materials.     

两种葡萄糖氧化酶活力测定方法的比较

对比研究了连续分光光度法和滴定法测定葡萄糖氧化酶活力的适用范围、换算关系,并探讨了在实际应用中的可行性。研究结果表明,对于连续分光光度法和滴定法,酶活力分别在0.044～0.351U·mL-1和1.125～5.321U·mL-1时线性关系较好;对于连续分光光度法,在此范围内可以用两点法代替标准方法进行测定;相同的样品采用滴定法测定的结果要高于连续分光光度法,两种方法测定数值的换算关系为:滴定法测定值=（连续分光光度法测定值+0.1454）×1.2868+0.3793。鉴于分光光度法在大量样品分析时更加方便,又对连续分光光度法测定发酵液酶活进行了初步研究。      

葡萄糖氧化酶的生产及应用

葡萄糖氧化酶能够利用氧气将葡萄糖氧化成葡萄糖酸而有效去除氧,因而被广泛用作抗氧化剂、葡萄糖酸、尿糖试纸和生物传感器的生产。综述了葡萄糖氧化酶作为生物去氧剂的作用机理、生产工艺条件以及在食品、医药等行业的广泛应用。     

产葡萄糖氧化酶黑曲霉紫外诱变及产酶条件的研究

目的提高黑曲霉中葡萄糖氧化酶的产量。方法紫外诱变法选出产酶优势菌株,优化碳源、氮源、碳酸钙、发酵时间等条件。结果黑曲霉发酵液酶活达到6.5 U/mL,比初始酶活提高5倍;单因素条件试验表明,最适碳源是蔗糖,最适氮源是蛋白胨和NaNO₃,发酵周期为48 h,培养温度是30℃,液体培养基的初始pH值为6.0产酶效果最好。结论紫外诱变后,葡萄糖氧化酶的活力有明显提高。     

葡萄糖氧化酶等天然保鲜剂对树莓保鲜效果的研究

以树莓果实为试材,采后分别以4种天然保鲜剂（0.1%葡萄糖氧化酶+0.1%葡萄糖、0.05%溶菌酶、0.1%葡萄糖氧化酶+0.1%葡萄糖+0.1%壳聚糖涂膜液、0.05%溶菌酶+0.1%壳聚糖涂膜液）处理,以蒸馏水处理为对照,用聚乙烯保鲜膜包装后于4℃下贮藏,定期取样测定腐烂率、失重率、可溶性固形物含量、褐变度和硬度等生理生化指标的变化。结果表明:经0.1%葡萄糖氧化酶+0.1%葡萄糖+0.1%壳聚糖涂膜液复合保鲜剂处理后的树莓果实综合保鲜效果最佳,在贮藏12d后,果实腐烂率为13.26%,失重率为10.57%,可溶性固形物含量为10.8%,抑制褐变、保持硬度和可滴定酸含量的效果优于其他处理组,且与对照组差异显著（p<0.05）。      

葡萄糖氧化酶简介及其应用

葡萄糖氧化酶是用黑曲霉等发酵制得的一种需氧脱氢酶,对人体无毒、副作用,具有去除葡萄糖、脱氧、杀菌等功能,已广泛应用于食品、饲料、医药等行业中。该文从葡萄糖氧化酶的作用机理、酶学性质、分离纯化、固定化、基因工程和应用等方面对其进行了简单介绍。     

产葡萄糖氧化酶黑曲霉紫外诱变及产酶条件的研究

目的提高黑曲霉中葡萄糖氧化酶的产量。方法紫外诱变法选出产酶优势菌株,优化碳源、氮源、碳酸钙、发酵时间等条件。结果黑曲霉发酵液酶活达到6．5U／mL,比初始酶活提高5倍;单因素条件试验表明,最适碳源是蔗糖,最适氮源是蛋白胨和NaNO3,发酵周期为48h,培养温度是30℃,液体培养基的初始pH值为6．0产酶效果最好。结论紫外诱变后,葡萄糖氧化酶的活力有明显提高。     

固定化葡萄糖异构酶活化条件对其酶活的影响

固定化葡萄糖异构酶在使用前需先进行活化,从而使酶发挥其最佳催化功效。本文从糖液浓度、温度、pH、活化时间和金属离子五个方面研究了活化条件对GENSWEETTMIGI-SA固定化葡萄糖异构酶酶活的影响。该酶的最适活化条件为:葡萄糖液浓度60%、温度55℃、pH7.5、时间4h。经此条件活化之后,其酶活达815U/g,与常规活化条件相比,酶活提高了40%以上。固定化葡萄糖异构酶活化时不宜加入Mg2+、Co2+、Mn2+和Zn2+。      

葡萄糖/葡萄糖氧化酶抗菌纸及抗菌性研究

葡萄糖氧化酶是氧化葡萄糖的专一催化酶,具有脱氧、杀菌的功能。通过定性和定量抗菌实验方法研究了葡萄糖/葡萄糖氧化酶体系在以淀粉作为载体和不混合淀粉时施涂于纸张表面的抗菌效果。定性抗菌实验表明,葡萄糖/葡萄糖氧化酶抗菌纸具有良好的抗菌效果。而定量检测结果表明,pH等于5.5时,35℃反应10min,不添加淀粉时,葡萄糖氧化酶最小的抑菌浓度约为70U/m2,葡萄糖足量时,酶用量越高,抗菌率越好;添加0.7g/m2淀粉后,最小抑菌浓度提高到约650U/m2。淀粉对葡萄糖/葡萄糖氧化酶体系的抗菌效果有较大影响,主要原因是淀粉能够促进细菌的繁殖。     

葡萄糖氧化酶和谷氨酰胺转胺酶在面制品中应用

该文综述葡萄糖氧化酶和谷氨酰胺转胺酶的特性、作用机理,及其对面团流变学特性和面制品品质影响。     

Short communication: Effect of active food packaging materials on fluid milk quality and shelf life

Active packaging, in which active agents are embedded into or on the surface of food packaging materials, can enhance the nutritive value, economics, and stability of food, as well as enable in-package processing. In one embodiment of active food packaging, lactase was covalently immobilized onto packaging films for in-package lactose hydrolysis. In prior work, lactase was covalently bound to low-density polyethylene using polyethyleneimine and glutaraldehyde cross-linkers to form the packaging film. Because of the potential contaminants of proteases, lipases, and spoilage organisms in typical enzyme preparations, the goal of the current work was to determine the effect of immobilized-lactase active packaging technology on unanticipated side effects, such as shortened shelf-life and reduced product quality. Results suggested no evidence of lipase or protease activity on the active packaging films, indicating that such active packaging films could enable in-package lactose hydrolysis without adversely affecting product quality in terms of dairy protein or lipid stability. Storage stability studies indicated that lactase did not migrate from the film over a 49-d period, and that dry storage resulted in 13.41% retained activity, whereas wet storage conditions enabled retention of 62.52% activity. Results of a standard plate count indicated that the film modification reagents introduced minor microbial contamination; however, the microbial population remained under the 20,000 cfu/mL limit through the manufacturer’s suggested 14-d storage period for all film samples. This suggests that commercially produced immobilized lactase active packaging should use purified cross-linkers and enzymes. Characterization of unanticipated effects of active packaging on food quality reported here is important in demonstrating the commercial potential of such technologies.     

葡萄糖氧化酶的发酵生产与发酵工艺的研究

葡萄糖氧化酶是酶应用技术领域中一种非常重要的酶,作为国家允许使用的酶制剂之一,它在食品、医药、饲料等行业中得到了广泛应用。该文简要介绍了葡萄糖氧化酶及两种菌种的葡萄糖氧化酶的发酵生产,对发酵工艺的影响进行了探讨,并展望了其在食品工业上的应用前景。     

产胞外葡萄糖氧化酶菌株的筛选、鉴定及酶学性质初步研究

乳酸脱氢酶（LDH）是乳酸生成途径中的关键酶,敲除乳酸脱氢酶基因,理论上可以减少甚至消除乳酸的产生,提高2,3-丁二醇的产量和得率。该研究采用体外拼接方式构建乳酸脱氢酶基因的同源线性片段ldhL-Cmr-ldhR,将其电转化至Klebisella oxytoca HD79中,通过Red同源重组技术筛选敲除成功的重组菌株,经聚合酶链式反应（PCR）、荧光定量-聚合酶链式反应（FQ-PCR）及2,3-丁二醇产量检测验证。结果表明,重组菌株2,3-丁二醇产量为40.20 g/L、转化率为0.38 g/g和生产强度为0.48 g/（L·h）,相比供试菌株分别提高了26.8%、11.8%和45.5%;而乳酸产量则由4.83 g/L下降至2.45 g/L,相比供试菌株降低了49.3%。该实验为后续进一步提高2,3-丁二醇的产量和扩大菌株选择范围奠定基础。     

Processing optimization of probiotic yogurt containing glucose oxidase using response surface methodology

Exposure to oxygen may induce a lack of functionality of probiotic dairy foods because the anaerobic metabolism of probiotic bacteria compromises during storage the maintenance of their viability to provide benefits to consumer health. Glucose oxidase can constitute a potential alternative to increase the survival of probiotic bacteria in yogurt because it consumes the oxygen permeating to the inside of the pot during storage, thus making it possible to avoid the use of chemical additives. This research aimed to optimize the processing of probiotic yogurt supplemented with glucose oxidase using response surface methodology and to determine the levels of glucose and glucose oxidase that minimize the concentration of dissolved oxygen and maximize the Bifidobacterium longum count by the desirability function. Response surface methodology mathematical models adequately described the process, with adjusted determination coefficients of 83% for the oxygen and 94% for the B. longum. Linear and quadratic effects of the glucose oxidase were reported for the oxygen model, whereas for the B. longum count model an influence of the glucose oxidase at the linear level was observed followed by the quadratic influence of glucose and quadratic effect of glucose oxidase. The desirability function indicated that 62.32 ppm of glucose oxidase and 4.35 ppm of glucose was the best combination of these components for optimization of probiotic yogurt processing. An additional validation experiment was performed and results showed acceptable error between the predicted and experimental results.     

Browning,polyphenol oxidase activity and headspace gas composition during storage of minimally processed pears using modified atmosphere packaging

Modified atmosphere packaging was used to prevent browning of minimally processed Conference pears, thus extending their shelf‐life. Colour changes as well as PPO activity were strongly influenced by the package headspace gas composition, which was determined by the packaging conditions. The initial colour of minimally processed pears was preserved for several weeks under cold storage in plastic pouches of very low O₂ permeability and an initial atmosphere of 100% N₂. A fractional conversion kinetic model fitted the experimental browning data with high accuracy. Colour degradation (ΔE*) of minimally processed pears occurred exponentially (k_ΔE = 0.019–0.077 day^?1) owing to changes in lightness (k_L = 0.021–0.07 day^?1). In contrast, PPO exhibited a linear increase in activity which could be related to the availability of O₂ in the package headspace. © 2002 Society of Chemical Industry     

Effect of dimorphic regulation on heterologous glucose oxidase production by Mucor circinelloides

The production of Aspergillus niger glucose oxidase (GOX) and native amylase by the recombinant M. circinelloides KFA199 strain under conditions of dimorphic growth was investigated. The recombinant KFA199 strain was compared to its parental ATCC 1216b strain and a wild‐type CBS 232.29 strain under similar morphology‐controlled conditions. Cultivation in Vogel's medium supplemented with ergosterol/Tween‐80 and sparged with nitrogen gas was most suitable for yeast‐like biomass production under anaerobic conditions. Anaerobic growth was characterized by high levels of ethanol formation and linear growth rates of 0.24–0.05/h, indicating metabolic stress. Subsequent to anaerobic growth, cultures were shifted to aerobic conditions to induce aerobic mycelial growth. GOX produced by the recombinant KFA199 after the shift to aerobic conditions was poorly secreted and accumulated intracellularly to 0.56 U/ml_culture. Amylase production by the KFA199, ATCC12b and CBS 232.29 strains was determined during growth on starch after the shift to aerobic culture. Growth‐associated amylase production by the ATCC 1216b (0.63 U/ml_culture) and wild‐type CBS 232.29 (0.33 U/ml_culture) strains was substantially higher than by the recombinant KFA199 strain (0.07 U/ml_culture), which may be related to the leucine auxotrophy of the transformation host, or genetic changes induced during transformation of the KFA199 strain. Copyright © 2010 John Wiley & Sons, Ltd.     

葡萄糖氧化酶复合改良剂对面粉烘焙品质改良效果的验证实验

用添加葡萄糖氧化酶复合改良剂的小麦粉进行馒头、面条及面包的烘焙实验。通过评价面制品的蒸煮或烘焙品质, 研究复合改良剂对食用品质和加工性能的影响。实验的结论验证了文献[8]中葡萄糖氧化酶复合改良剂对面团流变学特性的影响,进而验证了品质较低的面粉经葡萄糖氧化酶复合改良剂改良后,可显著改善其烘焙品质,适宜制作馒头、面条及面包。本文旨在为安全、天然、健康的葡萄糖氧化酶复合改良剂的推广使用提供必要的理论指导。