高压蒸汽提取啤酒废酵母还原型谷胱甘肽的工艺优化

为了得到高压蒸汽提取废酵母中还原型谷胱甘肽的最佳工艺条件,利用Box-Behnken的中心组合设计及响应面法（RSM）探讨了表压、提取时间、液料比和提取次数四因素的优化组合。通过建立二次回归模型,确定其最佳提取工艺条件为:表压1.1MPa,提取时间15min,液料比10∶1,提取次数1次,在此条件下得率最大为4.63mg/g。结果表明高压蒸汽提取技术是提高啤酒废酵母还原型谷胱甘肽得率的有效途径之一。      

硒元素对生理机能的调节作用及富硒功能性食品的开发

综述了近年来功能性微量元素硒在生物学以及人体健康领域研究的新进展,涉及酶活性的调节,控制癌变和高血脂,以及抗癌的性别选择性和对神经系统及心理的影响,并对当前应用在功能食品和医用保健品方面典型的硒复合产品开发作了介绍.     

我国大豆种皮过氧化物酶的酶活性及热稳定性研究

经检测的186个我国大豆品种，种皮过氧化物酶（SBP）含量最高达1720U／g，最低为0，平均活性为285．8U／g。根据SBP含量高低，大豆可分为高酶活与低酶活二大类型，分类临界值为100U，高酶活类约占1／3。北方大豆平均酶活性明显高于南方大豆。大豆种皮主要含一种过氧化物酶同工酶，不同品种间分子量相同。SBP热稳定性优异，经70℃（pH5．0）处理24h，45份高酶活品种中有20份剩余酶活超过50％的。种皮在2—6℃贮藏10个月剩余酶活为25．5％-45．27％，种子在室温下贮藏10个月则为8．0％-24．1％。     

大豆过氧化物酶纯化及酶学特性研究

大豆过氧化物酶与辣根过氧化物酶类似,是一种含有血红素的Ⅲ类过氧化物酶.我们从大豆加工副产物大豆皮中,采用精简的三步法提取和纯化大豆过氧化物酶,得到Rz值大于2.0的纯酶.三个纯化步骤分别是硫酸铵分级沉淀、丙酮分级沉淀和DEAE Sepharose离子交换层析.同时分析了温度、pH和常见化合物对酶促反应的影响,考查了酶的热稳定性、酸碱稳定性.结果表明,大豆过氧化物酶的温度和pH适用范围很宽,热稳定性、酸碱稳定性很高,并且在含有较高浓度有机溶剂的反应体系中的保持很好的酶活力.有这么优越的酶学特性,又有廉价的大豆皮来源,所以大豆过氧化物酶的产业化和应用前景将非常乐观.     

一株哈慈木霉生产木质素酶的培养条件研究

对一株哈慈木霉液态发酵生产木质素过氧化物酶的培养条件进行了优化研究。结果表明,0.6g/L淀粉、7.5g/L酵母浸粉为产酶适宜碳氮源;0.066g/LCaCl2·2H2O,4.0g/LKH2PO4,0.244g/LMgSO4以及40mL/L微量元素液为较优无机盐配方;添加2mmol/L藜芦醇和1.5g/L Tween80可获得较高酶产量;摇瓶装液量50mL/250mL,摇床转速220r/min为较优培养条件。上述结果说明菌的产酶特性极大程度受其培养条件的影响。通过系统的优化,使酶产量提高2.6倍,发酵所需时间缩短了4d,极大降低了酶的生产成本。     

Purification and characterisation of a novel antioxidant protein molecule from Phyllanthus niruri

The herb Phyllanthus niruri is known to possess antioxidant activity, but the nature of the responsible active principle(s) is not well defined. The present study reports the purification and characterisation of a 35 kDa antioxidant protein molecule from this herb using a bioassay in which oxidative stress was introduced in hepatocytes with the help of a suitable free radical inducer, tertiary butyl hydroperoxide (TBHP), and the prevention of that stress was monitored using the protein fraction(s) obtained at each step of the purification. Partial amino acid sequence of this protein revealed its unique structural features. The purified protein possesses potent radical-scavenging activity, enhances intracellular antioxidant power and protects the TBHP-induced alterations of the cytoprotective and antioxidant molecules, as well as other parameters used in this particular study. Combining, data suggest that the antioxidant activity of Phyllanthus niruri is at least partly due to this unique protein molecule.     

Kinetic Properties of (+)-Catechin Oxidation by a Basic Peroxidase Isoenzyme from Strawberries

The ability of a partially-heat stable strawberry (Fragaria × ananassa) peroxidase to oxidize (+)-catechin was studied and its oxidation followed the accepted model for peroxidase oxidations. Compound I (CoI) and compound II (CoII) were the main intermediates in the catalytic cycle. The reactivity of strawberry peroxidase with H₂O₂ [K₁= 2.63 μM^-1 s^-1] and with (+)-catechin [k₃= 0.57 μM^-1 s^-1] suggested that (+)-catechin is an excellent o-diphenol for CoII reduction. The strong cooperativity of this peroxidase isoenzyme indicates its great efficacy in oxidation of (+)-catechin at low H₂O₂ concentrations.     

Peroxidase Stability and Reactivation after Heat Treatment and Manothermosonication

The effect of several factors on the resistance of horseradish peroxidase (POX) to heat and manotbermosonication (MTS), the simultaneous application of heat and ultrasonic waves under pressure, has been studied. Reactivation after heat or MTS followed very similar patterns. Both heat and MTS inactivation of POX had a similar pH dependence. Addition of sucrose or glycerol to the treatment buffer resulted in more inactivation of POX by heat. MTS reversed these effects, especially after addition of glycerol. Addition of KC1 had a slightly protective effect against both heat and MTS treatments whereas addition of glucose increased the inactivation of POX by heat and MTS. Higher concentrations of POX were less sensitive to MTS. Both heat and MTS inactivation of POX appeared to result from a common mechanism.     

Ozone Storage Effects on Anthocyanin Content and Fungal Growth in Blackberries

Ozone exposure was assessed for storage of thornless blackberries which are prone to fungal decay. Blackberries were harvested and stored for 12 days at 2°C in 0.0, 0.1, and 0.3 ppm ozone. Berries were evaluated for fungal decay, anthocyanins, color and peroxidase (POD) activity. Ozone storage suppressed fungal development for 12 days, while 20% of control fruits showed decay. The main mold was Botrytis cinerea. Ozone storage did not cause observable injury or defects. By 12 days, anthocyanin content of juice was similar to initial levels for all treatments. Surface color was better retained in 0.1 and 0.3 ppm-stored berries by 5 days and in 0.3 ppm berries by 12 days, by hue angle values. POD was greater in controls and 0.1 ppm samples, and was lowest in 0.3 ppm fruits by 12 days. Ozone storage resulted in market quality extension.     

An optical flow injection analysis system for measurement of glucose in tomato

An optical flow injection analysis (FIA) system for glucose measurement in tomato was constructed by using a glucose oxidase (GOD) immobilized reactor and a photodiode sensor, a peristaltic pump and a personal computer. The GOD reactor was crammed with strip-shaped of a GOD immobilized membrane to an acrylic pipe. The GOD was immobilized on polytetrafluoroethylene membrane by crosslinking with glutaraldehyde. Hydrogen peroxide generated by the GOD reaction oxidized luminol to produce chemiluminescence in the presence of horseradish peroxide. The chemiluminescence was detected by using the photodiode. The glucose measurement system was calibrated with standard glucose solutions. The calibration range of the system for glucose was 2.0–100.0 mmol L⁻¹. Measurement time for every sample was within 3 min. Glucose concentrations of a fresh and processed tomato samples measured with this glucose measurement system could be evaluated rapidly and non-laboriously.