食品专业英语第八课译文整理

Lesson 8 Microbial Enzymes

Most industrial enzymes are produced by microorganisms, the largest group being photolytic enzymes from bacteria (59%) followed by carbohydrases (20%).大多数工业用酶类是由微生物生产的，最多的是光解酶，从细菌中来的有 59%，其次是糖酶，占 20%。 Animal enzymes include rennets (for cheese making) and pancreatic protease and lipases; the proteases are used primarily in leather processing.动物性酶（来源于动物的酶）包括胃和胰腺的蛋白酶与脂酶（来源于胃的用于奶酪的制作）；蛋白酶主要用在皮革制品中。 Among the plant enzymes, papain is the largest single industrial product. 所有植物性酶中，木瓜蛋白酶产量是最大的。Industrial enzymes are usually mixtures of different enzymes. Commercial products are standardized with diluents. 工业类用酶通常是不同酶的混合物；商业产品是稀释后的标准制品。

Enzymes of fungi and bacteria have a wide variety of industrial applications, including alcoholic beverages, food, detergents, and pharmaceuticals. 真菌和细菌酶类具有广泛的工业应用价值，包括酒精饮料、食品、清洁剂和医药品的工业生产方面。 Table 8-1 lists some of these enzymes, along with their microbial origins and selected uses. 表格 8-1

In the production of alcoholic beverages, microbial amylase may be used instead of the enzymes from barley malt to prepare grains for fermentation.在生产的酒精饮料，微生物淀粉酶可用于代替大麦麦芽酶准备谷物发酵。Protease can also chillproof beer by degrading the proteins that cause cloudiness in such beverages upon refrigeration.蛋白酶类也能通过降解那些在饮料冷藏中引起浑浊的蛋白质来冷却检验啤酒。

α-Amylases, together with β-amylases, are present in malt.α-淀粉酶与β-淀粉酶都存在于麦芽中。However, the industrial enzymes are produced from pancreas or from cultures of microorganisms. 然而，工业用的该酶却是从胰腺和微生物中生产出来的。The various types of α-amylases differ from each other not only in specificity, but also in optimal pH range and stability to heat. α-淀粉酶有很多种，每种各不同，不仅在转移性，而且在优化的pH范围和热稳定方面也不同。

α-Amylases from bacteria are available in either liquid or powder form. 从细菌中来的α-淀粉酶不论是液体还是粉末状的都是有价值的。 These preparations contain varying amounts of other enzymes such as proteinases and β-glucanases.这些制备产品含有酶的单位不同，诸如蛋白酶和β-葡聚糖酶。Enzymes concentrates, standardized with sodium chlorides or starch, are marketed as powders with activities of 20 000 to 30 000 SKB/g (pH 5.0). 市场上粉末状的用氯化钠或淀粉标准化的浓缩酶单位活性在 20 000 to 30 000 SKB/g（pH 5.0）。Liquid preparations containing 3 000 to 12 000 SKB/g are stabilized with sodium chloride or glycerol.含有3 000 to 12 000 SKB/g 的液体制剂添加了氯化钠或甘油而稳定。α-Amylases from Bacillus amyloliquefaciens (分解淀粉芽孢杆菌) has an especially high activity of 50 000 SKB per gram of protein.分解淀粉芽孢杆菌得到的α-淀粉酶有50 000 SKB/g蛋白质的高活性。

Bacterial α-amylases are divided into standard amylases and heat-stable amylases, depending on their stability to heat.根据热稳定性，细菌α-淀粉酶分为标准淀粉酶和热稳定淀粉酶两类。 Standard bacterial α-amylases from Bacillus subtilis ( 枯草芽孢杆菌) or B. amyloliquefaciens requires temperatures of 70-85 for optimal activity. 标准淀粉酶由枯草芽孢杆菌或分解淀粉芽孢杆菌制备而来，其需要在 70-85 度时能保持最高活性。 Heat-stable bacterial α-amylases from, e. g., B. licheniformis (地衣芽孢杆菌), has a temperature optimum between 90 and 105.地衣芽孢杆菌的热稳定α-淀粉酶，最适温度条件是 90-105 度。 However, this optimal depends on the pH, the concentration of calcium ions, and the substrate concentration. 但是，其最佳条件取决于pH值，钙离子浓度和底物浓度。 A typical reaction is carried out on a 30% starch suspension at pH 7.0 and 103-105 for 7-11 min in the presence of 70mg/l of calcium. 典型的最佳反应条件：30%淀粉悬液，pH7.0，用 70mg/l 的钙 103-105 度保持

7-11 分钟。The enzyme is inactivated by lowering the pH 3.5-4.5 and the temperature to 80-90 for a period of 5-30min.在低于 pH3.5-4.5 时和温

度 80-90 时，5-30 分钟内酶失去活性。

Bacterial α-amylases are generally stabilized with calcium ions; some types are also activated by sodium chloride. 细菌α-淀粉酶一般情况对钙离子稳定，氯化钠也使有些类型具有活性。 Indeed, amylases freed from calcium by electrodialysis or complex formation are inactive.实际上，用过电渗析或络合物存在是，使淀粉酶没有钙离子，其活性也就失去了。 Heavy metals such as copper, iron, or mercury inhibit enzyme activity.重金属，例如铜、铁或汞也一直酶活性。 The breakdown of starch yield dextrins. 淀粉断裂可产生糊精。For instance, hydrolysis of potato starch by standard bacterial α-amylases gives the following dextrin spectrum: 例如，用标准的细菌α-淀粉酶来水解土豆淀粉得到糊精谱，分为下列： G1 (glucose) 5% G1 (葡萄糖) 5%, G2 (maltose) 7% G2 (麦芽糖) 7%, G3 (maltotriose)，G3 (麦芽三糖), G4 (maltotetraose) 4% G4 (麦芽四糖) 4%, G5 (maltopentaose) 16% G5 (麦芽五糖) 16%, G6 (maltohexaose) 22%,G6 (麦芽六糖) 22%， higher dextrins 33%.更高糊精 33%。α-Amylases from fungi are obtained from Aspergillus niger (黑曲霉) or A.oryzae (米曲霉).黑曲霉或米曲霉中可以获得α-淀粉酶。其与细菌淀粉酶相比，对热更敏感，在糊化前就失活了。They are less resistant to heat than bacterial α-amylases and are inactivated before starch gelatinizes. This is important in the making of bread and biscuits. The following dextrin spectrum is typical of the action of fungal α-amylases: G1 8%, G3 32%, G4 18%, G5 9%, G6 4%, higher dextrins 17%.

β-Amylases, present in grain, soybeans, and sweet potatoes, attacks amylase chains, effecting successive removal of maltose units from the nonreducing ends. 谷物、大豆和红薯种的β-淀粉酶可以水解直链淀粉，从非还原端连续水解下麦芽糖单元。 In the case of amylopectin, this process stops two to three glucose residues from the α-1,6-branching points (the designation β-amylase refer to the cleaved maltose which has an anomeric carbon atom in the β-configuration). 对于支链淀粉，此过程在从α-1,6-分枝点起 2 至 3 个葡萄糖残基就停止水解。（β-淀粉酶则更易于切割麦芽糖，因为麦芽糖具有一个β-结构的异头碳原子。） The optimal temperature is 55 at the pH 5.1-5.5. β-Amylase is used in alcohol production and in breweries as a replacement for malt. Obtained in quantity from barley, it is used to saccharify starch in the production of maltose syrup.

Proteases and lipases are used in cleaning animal hides, a necessary step in leather production.皮革生产时，用蛋白酶和脂酶来清洁动物的皮，这是生产的必要的步骤。 Proteases are also used commercially for meat tenderizing, as they are capable of breaking down some of the tough meat protein. 商业上，蛋白酶因能使强韧肉蛋白分解，也作为嫩肉精来用。

One commercial application of microbial enzymes has been the removal of stains from clothing. 商业用微生物酶的一种用法是，可消除衣物的污渍。

Many substances that stain clothes either are made of lipids, proteins, or starches or are held in a fabric by these types of compounds.这些沾染衣物的物质，或是由脂、蛋白质或淀粉组成的，或是被这些化合物固定于织物中。Certain enzymes, under suitable conditions, can decompose stains or the cementing substances associated with them, thereby helping to clean the soiled fabric. 某些酶在适宜条件下，能分解污渍或粘合污渍，从而有助于清洁污染的织物。 Needless to say, stains can be caused by a large variety of substances, and appropriate enzymes may not be available, or, if available, may not be incorporated into detergent or presoak compounds used in laundering. Thus, it is not surprising that all stains are not removed by commercial products.不必说，污渍可由很多物质引起的，并且适宜的酶可能没有活性，或者，即使有活性，在洗烫时也可能与清洁剂或预浸复合物的成分不能合成一体。 Moreover, such enzyme-containing products have been associated with the development of allergies.

Microbial enzymes are obtained by process carried out either in shallow pans for optium aeration by diffusion or in tanks where aeration is produced by bubbling air through the growth medium. 在通过扩散得到良好通气条件的浅锅里，或利用气泡流过培养基来通风的罐子里进行培养可以获得微生物酶。Usually rich organic wastes from dairy or canning plants are used as the growth medium. 通常，从奶制品或罐头厂得到富氧废弃物作为微生物的生长培养基。 When microbial growth is judged to be complete on the basis of an analysis for the desired enzyme, the microorganisms are removed by filtration, leaving the culture filtrate, which can be processed for the desired enzyme.当通过分析目的酶，说明微生物的生长已经完成时，过滤除去微生物体，得到的滤液，可以加工得到需要的酶。