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。     

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.     

Naringinase Immobilization in Packaging Films for Reducing Naringin Concentration in Grapefruit Juice

Naringin, a bitter compound in citrus, may be converted to a nonbitter form by enzymic hydrolysis. Our objective was to determine the feasibility of immobilizing naringinase in a food contact approved packaging film. Naringinase from Penicillium sp. was immobilized in cellulose acetate films with up to 23% efficiency at 7°C. Kinetic studies showed that the free enzyme had an optimum pH=3.5 and the immobilized enzyme pH=4.0. Activation energy decreased upon immobilization (from 14.2 to 11.0 Kcal/mol), thus providing an increased catalytic efficiency for immobilized naringinase. The Michaelis constant for immobilized naringinase (K_m=2.1 mM) was lower than for free enzyme (K_mm=3.6 mM). Keeping films under dry storage for 1 mo at room temperature did not cause decreased enzyme activity. A film area/volume ratio (cm²/mL of 10° Brix grapefruit juice) of 7.2 hydrolyzed 60% of the naringin in 15 days at 7°C.     

奶制品葡萄糖含量的酶法分析

本文介绍了利用葡萄糖氧化酶测定奶制品中葡萄糖含量的方法,并讨论了测量条件。该方法灵敏准确,操作简便,测定范围0－150mg/L,用于实际样品的测定,结果满意。     

纳米花固定化葡萄糖异构酶的制备及性能分析

该研究采用共沉淀法制备了葡萄糖异构酶（Glucose Isomerase,GI）纳米花,对固定化条件进行了优化,同时对纳米花固定化酶的形态特征以及酶学性质进行了探究。结果表明,40 μL酶液中加入9 mL、pH值7.4的PBS缓冲液后与30 μL CuSO4混合,在35 ℃条件下静置反应18 h,制得的纳米花固定化葡萄糖异构酶（Glucose Isomerase @ Nano flowers,GI@NFs）的酶活回收率高达183.06%。SEM表征结果显示GI@NFs有完整的纳米花结构,傅里叶红外光谱显示GI@NFs具有酶和PO43-的特征吸收,X-射线衍射结果进一步证明其载体为Cu3(PO4)2。酶学性质研究发现,GI@NFs的最适反应温度为60 ℃,比自由酶的提高了10 ℃;最适反应pH值为8,比游离酶的最适pH更高;GI@NFs的温度稳定性和pH稳定性均比自由酶的明显提高;固定化酶被循环使用8次,其酶活力仍保持最初活力的60.32%。实验结果表明,纳米花结构提高了葡萄糖异构酶的酶活,表现出较好的循环性能和稳定性,具有一定的应用价值。     

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。     

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。     

磁性生物活性玻璃共固定葡萄糖氧化酶-过氧化氢酶的研究

生物活性玻璃具有良好的生物相容性和生物活性,利用其进行酶的固定化是一种新的实验理念。本文对生物活性玻璃进行改性,加入一定量乙二醇利用溶胶-凝胶的方法制备了表面具一定磁性的磁性生物活性玻璃微球,并利用该微球对葡萄糖氧化酶和过氧化氢酶进行固定。实验表明,同时固定两种酶比单独固定效果更为显著。之后将GOD-CAT以一定的比例分别在传统水相和有机相二恶烷中进行共固定化,比较水相共固定化酶和有机相共固定化酶的酶比活力和酶学性质,找到了最佳的固定介质。实验表明,戊二醛浓度为0.4%,加酶活力比GOD:CAT为1:2,二恶烷含水量1.5%时,GOD的表观酶活回收率达到90.25%;而传统水相中,GOD的表观酶活回收率最大仅为72.18%。连续使用10次后,有机相固定化酶活为初始值的67.30%,而传统水相中酶活仅为初始值的44.33%。     

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.     

酶型时间-温度指示剂在食品包装中的应用及研究进展

酶型时间温度指示剂(TTI)具有性能稳定、成本低廉、易于控制等优点,在监测供应链中易腐食品的质量变化起着重要作用。本文对酶型TTI的最新研究进行综述,基于脂肪酶、淀粉酶、虫漆酶、脲酶、酪氨酸酶和其他酶,论述了液态酶型TTI的制备原理、优缺点及其在食品包装中的应用现状和存在的问题;基于脂肪酶、淀粉酶和酪氨酸酶,阐述了固定化酶技术在固态酶型TTI中的应用,以及使用新型载体材料对固态酶型TTI进行改进的方法。本文旨在为酶型TTI在食品包装中的应用提供理论基础和实验参考。     

黑曲霉1504产葡萄糖氧化酶的酶学特性及对馒头品质的改良

对来源于菌株黑曲霉1504的葡萄糖氧化酶(GOD)进行分离纯化,研究其酶学性质,并将其应用于面粉及馒头品质改良。GOD经PEG20000浓缩、硫酸铵分级沉淀、DEAE-SFF离子交换层析和Sephacryl S-200凝胶过滤层析,得到电泳单条带,纯化倍数为51.13,酶活回收率为27.07%,用凝胶过滤层析测得酶的分子质量为150.2 ku;纯酶的最适反应pH值为6.1,30℃时pH值稳定范围是4.5～8.0,最适反应温度40℃,50℃时处理4 h保留75%以上的酶活力。各种金属离子中,Pb²⁺对酶促反应的促进作用最强,Ag^+对酶促反应的抑制作用最强。利用双倒数作图法求得此GOD的K_m为36.7 mmol/L,V_max为20.83μmol/(L·s);考察GOD对馒头品质的影响:当加酶量为2.5 mg/kg时,馒头比容增加13.7%,延展率提高6.5%,同时馒头硬度明显下降,仅为对照组的41.1%。     

Partial purification and characterisation of banana [Musa (AAA Group) 'Gros Michel'] polyphenol oxidase

Polyphenol oxidase (PPO) from pulp of banana [Musa (AAA Group) 'Gros Michel'] was extracted and precipitated with 80% saturated ammonium sulphate followed by conventional column chromatography on Sephacryl S-200 HR and fast protein liquid chromatography on Mono Q column. The lyophilised PPO obtained from Sephacryl S-200 HR column was used for characterisation and inhibition studies. The partially purified PPO obtained from the Mono Q column exhibited at least three isoenzymes. The banana PPO had optimum pH for activity at 7 and it was stable around the same pH. Only 48% of initial enzyme activity was lost after heating at 70 °C for 30 min. The enzyme was completely inhibited by 2 m m sodium metabisulphite, 2 m m l -cysteine, 4 m m ascorbic acid, and 100 m m 4-hexylresorcinol. The K _m and V _max of banana PPO for dopamine were 2.08 m m and 0.124 m m  min⁻¹ respectively.     

黑曲霉Z-25产葡萄糖氧化酶胞外酶发酵培养基优化研究

以黑曲霉Z-25(Aspergillus niger Z-25)作为葡萄糖氧化酶胞外酶生产菌株,研究提高胞外酶活力的环境因素.通过单因素试验,确定了主要影响葡萄精氧化酶合成的四个因素,采用四因素三水平L9(34)正交试验,确定了产葡萄糖氧化酶胞外酶的优化发酵条件:葡萄糖添加量为10%、(NH4)2SO4添加量为0.5%、月示蛋白胨添加量为1.5%、吐温80添加量为3%.在优化条件下,葡萄糖氧化酶的活力是优化前的242%.     

壳聚糖凝胶固定葡萄糖氧化酶制备酶电极的工艺

以壳聚糖作为固定GOD载体 ,研究了壳聚糖溶液的粘度 ,交联剂戊二醛的浓度、用量以及铂丝在酶膜母液中浸涂时间等对葡萄糖传感性能的影响。在优化固定化条件的基础上 ,建立了通过调整固定化条件来适应载体溶液粘度变化的工艺 ,制备出性能基本一致的酶电极     

产葡萄糖氧化酶菌株的筛选及发酵培养基的优化

从土壤中筛选出了一株产葡萄糖氧化酶较高的菌株,利用响应面法对该菌株的产酶培养基进行优化以提高产酶量。响应面法优化的发酵培养基组成为：葡萄糖109.41g/L、复合氮源(m(月示蛋白胨):m((NH₄)₂SO₄)=3:1)37.36g/L、吐温-80 37.15g/L、KH₂PO₄ 2g/L、 MgSO₄·7H₂O 0.7g/L 和KCl 0.5g/L。采用该优化培养基所得葡萄糖氧化酶的活力为1.54U/mL,较优化前提高了31.6%。     

滁菊多酚氧化酶和过氧化物酶热钝化动力学研究

为深入研究热处理对滁菊中酶的钝化效果,以滁菊多酚氧化酶(polyphenol oxidase,PPO)和过氧化物酶(peroxidase,POD)为研究对象,探讨热处理过程中滁菊PPO和POD的热稳定性和热钝化动力学.结果表明:滁菊PPO的最适反应温度为30℃,滁菊POD的最适反应温度为45℃,随着热处理时间的延长,滁...