黄原胶中淀粉酶活性的检测

目的 基于淀粉遇碘变蓝的基本原理建立黄原胶中淀粉酶活性的检测方法 ,防止蚝油生产时使用黄原胶而引入淀粉酶导致产品变质,降低生产企业的经济损失。方法 以5份问题黄原胶为研究对象,通过建立的新方法检测黄原胶和由其生产的蚝油的淀粉酶活性和粘稠度,依据颜色变化和粘稠度变化判断是否含有淀粉酶。结果 通过检测发现,5份问题样品均含有淀粉酶,经高温处理后,其中2个样品,淀粉酶活力衰减或被破坏,另外3个样品其淀粉酶活力仍存在;黄原胶经加工成蚝油后,仅有1个样品检出淀粉酶,其他4个样未检出淀粉酶,但其中2个样品经60 ℃恒温保持10 d后,粘稠度降低,其可能与样品中淀粉酶活力大小、含量多少及加工工艺中添加辅料的影响有关。结论 建立了黄原胶中淀粉酶的快速检测方法,方法简单易操作,适合生产企业对黄原胶原料的初步检验,但其在蚝油产品中的作用机理还有待进一步深入研究。     

Enzymatic hydrolysis combined with high‐pressure homogenisation for the preparation of polysaccharide‐based nanoparticles from the by‐product of Flammulina velutipes

In this study, protease, α‐amylase and 5‰ β‐glucanase enzymolysis in combination with high‐pressure homogenisation were used for the preparation of polysaccharide‐based nanoparticles from Flammulina velutipes stipes, respectively, named FNP‐1, FNP‐2 and FNP‐3, and the nanoparticles were subsequently characterised. The FNP size distribution ranged from 50 nm to 300 nm, among which FNP‐2 and FNP‐3 were smaller than FNP‐1, based on the SEM images. GC‐MS results showed that these particles were mainly composed of glucose and glucosamine. The FNP dispersions at 1 wt% behaved as non‐Newtonian, shear‐thinning fluids, and the FNP‐3 dispersion presented superior viscoelasticity. With an increasing degree of enzymolysis, the thermal stability of the FNPs decreased. In addition, these particles presented various cation‐exchange properties. Therefore, the Flammulina velutipes polysaccharide‐based nanoparticles obtained from this study can be potentially used as a promising functional food ingredient in the food industry.     

诱导激活剂对不同曲霉菌株淀粉酶组分的激活作用

以活性电泳比较了不同酱油生产菌株的淀粉酶组分,研究了激活酿造时淀粉酶组分表达及活性的变化.结果表明,不同菌株淀粉酶组分数量各不相同,其中黑曲霉沪酿3350、黑曲霉3.324、米曲霉3.362和米曲霉HL均含有4个淀粉酶组分,而米曲霉3.042和米曲霉3042KG含有3个淀粉酶组分,米曲霉ZH含有2个淀粉酶组分.经诱导激活剂作用后,所有菌株的淀粉酶总活力提高,5株米曲霉的激活作用明显,米曲霉3.042的淀粉酶总活力提高15.55％.     

A154C/G155C双点突变对嗜热耐酸淀粉酶酶活性及热稳定性的影响

利用重叠延伸法对嗜热球菌Thermococcus sp.的高温酸性α-淀粉酶基因BD5088进行体外A154C/G155C双点定点突变,通过原核表达载体pET30a构建表达载体pET-BD5088C2,在大肠杆菌BL21(DE3)中表达,酶学性质分析表明,突变淀粉酶拓宽了反应pH值范围,尤其是酸性条件下提高更为显著。BD5088淀粉酶在100℃条件下酶活力半衰期约为22min,而突变酶酶活力半衰期40min,突变酶酶活力比BD5088淀粉酶提高近1倍。加热60min时,突变酶酶活力仍可维持原活力的40%,而BD5088淀粉酶只能维持20%左右。说明其热稳定性得到有效的提高。另外,突变酶在中温和90℃条件下酶活力有所提高,65℃时酶活力提高将近1倍。结果表明,BD5088淀粉酶的154、155位残基的突变为Cys对维持其热稳定性起到重要的作用,并且对其酶学性质有较大的影响,可能参与了二硫键的形成。     

金鳟消化器官淀粉酶和蛋白酶活性的初步研究

本试验研究了不同pH值对金鳟肝脏、胃、幽门盲囊、前肠、中肠及后肠中淀粉酶、蛋白酶的活性影响。结果表明:金鳟中肠淀粉酶活性最强,幽门盲囊活性最弱,所测定消化器官的淀粉酶活性强弱顺序为:中肠前肠肝脏后肠胃幽门盲囊。中肠、前肠、肝脏、后肠、胃和幽门盲囊最适pH值分别为6.8,8.0,7.6,8.0,6.8和7.6;胃蛋白酶活性最强,中肠蛋白酶活性则最弱,所测定消化器官蛋白酶活性强弱顺序为:胃幽门盲囊肝脏前肠后肠中肠。胃、幽门盲囊、肝脏、前肠、后肠和中肠最适pH值分别为2.2,7.6,7.6,7.6,8.0和8.0。     

甜酒曲华根霉淀粉酶菌株产酶条件的研究

对经紫外线诱变选育的甜酒曲华根霉高产淀粉酶菌株进行产酶条件研究,通过单因素试验和正交试验得该菌株的最佳产酶条件为∶培养基中麸皮豆粕比3∶2,加水量80%,初始pH值为5.0,培养时间36h,培养温度32℃.选取最佳产酶条件培养此菌株,测得其淀粉酶活力为58.831U,比优化前提高了60.96%.该研究对实现甜酒酿造工艺现代化、产业化具有一定的意义.     

酶法提取花生粕不溶性膳食纤维的研究

以花生粕为原料,采取酶法提取花生粕中的不溶性膳食纤维,探讨α-淀粉酶、木瓜蛋白酶最佳酶解条件。结果表明:α-淀粉酶的最佳酶解条件为温度60℃,时间30 min,pH4.0,酶量2%;木瓜蛋白酶的最佳酶解条件为温度80℃,时间2 h,pH7.0,酶量11%,花生粕不溶性膳食纤维的提取率达到37.72%。     

淀粉酶添加量对大米凝胶特性的影响

以大米为材料制作凝胶,研究了淀粉酶对大米凝胶特性的影响。结果表明,淀粉酶添加到大米凝胶中可以在一定程度上起到延缓凝胶老化的作用,使凝胶的抗断条能力增强。淀粉酶抗老化的最佳用量为0.01%。     

Evaluation of heterologous α‐amylase production in two expression platforms dedicated for Yarrowia lipolytica: commercial Po1g–pYLSC (php4d) and custom‐made A18–pYLTEF (pTEF)

In view of the constantly increasing demand for cost‐effective, low‐energy and environmentally friendly industrial processes and household care products, enzyme production occupies an essential place in the field of biotechnology. Along with increasing demand for industrial and household care enzymes, the demand for heterologous expression platforms has also increased. Apart from the conventional hosts, e.g. Escherichia coli, Saccharomyces cerevisiae and Pichia pastoris, routinely used in heterologous protein expression, the non‐conventional ones have become more and more exploited in this field. Among the available yeast host systems, Yarrowia lipolytica appears to be an attractive alternative. The aim of this study was to compare efficiency of two Yarrowia‐based expression platforms, commercial Po1g–pYLSC and custom‐made A18‐pYLTEF, in expression of an insect‐derived, raw‐starch‐digesting α‐amylase, to select the ‘champion’ system for further studies on this valuable enzyme. Both expression platforms were compared with respect to copy number of the integrated expression cassette/transformed genome, and the recombinant strains performance (Po1g–pYLSC‐derived 4.29 strain, and A18‐pYLTEF‐derived B9 strain) during batch bioreactor cultures. Our results demonstrate that the average number of integration events into the recipient's genome was comparable for both expression systems under investigation, but with varying distribution of the multicopy integrants; and the number of the recombinant gene copies was highly correlated with the acquired amylolytic activity of the strains. Due to severe susceptibility of the recombinant AMY1 polypeptide to native proteases of the custom‐made expression system, the final yield of the enzyme was substantially lower when compared to the commercial Po1g–pYLSC (reaching a maximum level of 142.84 AU/l). Copyright © 2015 John Wiley & Sons, Ltd.