枯草芽孢杆菌淀粉酶高产菌株的复合诱变研究

该研究以实验室保存的枯草芽孢杆菌为出发菌株,利用紫外和硫酸二乙酯（DES）复合诱变的方法,从大量突变菌株中获取可高效发酵生产淀粉酶的菌株。又通过连续传代实验,确定了该突变菌株突变性状能稳定遗传。结果表明,菌株D-2具有较高的的淀粉酶活力,其淀粉酶活力可达N6．599U／mL,较出发菌株提高到4倍。并在连续培养5代后,仍具有较好的遗传稳定性。该文探讨了一种高效的发酵生产淀粉酶菌株的选育方法,为下一步菌种生长条件优化打下了基础。     

Characterization of an α‐amylase from sorghum (Sorghum bicolor) obtained under optimized conditions

Sorghum malt α‐amylase can compete with bacterial α‐amylase in industrial applications, if sufficiently stable and produced in a large enough quantity. Conditions for maximal α‐amylase production in sorghum malt and the physico‐chemical properties of the α‐amylase so produced are reported in this study. Sorghum grains were steeped in buffers with varying pH (4.0–8.0) for 24 h, at room temperature, and germinated for another 48 h to obtain the green malt. The buffer that induced the highest quantity of α‐amylase was chosen as the optimal pH and served as the medium for further steeping experiments conducted at different temperatures (10, 20, 30, 40, 50 and 60°C). The α‐amylase activity in the extract was determined in order to obtain the optimum temperature for α‐amylase induction at this particular pH. For the purpose of comparison, the α‐amylase produced at the optimum pH and temperature was purified to apparent homogeneity by a combination of ion‐exchange and size‐exclusion chromatography, and further characterized. Eight‐fold higher α‐amylase activity was induced in pH 6.5 buffer at 20°C compared with water, the traditional steeping medium. The K_m and V_max were estimated to be 1.092 ± 0.05 mg mL^?1 and 3516 ± 1.981 units min^?1, respectively. The activation energy of the purified amylase for starch hydrolysis was 6.2 kcal K^?1 mol^?1. Chlorides of calcium and manganese served as good activators, whereas CuSO₄ inhibited the enzyme with a 42% loss in activity at 312 mm salt concentration. Copyright © 2012 The Institute of Brewing & Distilling     

Evidence for the improvement of thermostability of the maltogenic α‐amylase of Aspergillus niger by negative pressure

Thermostability of the enzymes is influenced by the different parameters and pressure also influences the biological activity of the enzymes. Recently reported maltogenic α‐amylase from Aspergillus niger acts optimally on starch at 40°C and it was unstable above 40°C at atmospheric pressure. Calcium could stabilize the maltogenic α‐amylase activity up to 50°C at atmospheric pressure. But, at negative pressure (−200 mbar) enzyme was stable at temperatures higher than 50°C either in the presence or absence of the substrate, starch making it adoptable for starch processing. Enzyme showed higher affinity to the starch at negative pressure compared to the atmospheric pressure and change in the surface roughness of the enzyme is almost similar to the native state at 70°C and negative pressure. These results suggest that thermolabile enzymes can be used at negative pressures for industrial applications.     

生物酶在超薄型服装革基布上的应用

选用高温淀粉酶退浆和酸性纤维素酶后整理,优选出最佳退浆工艺和后整理工艺,分析了高温淀粉酶和酸性纤维素酶对人棉织物的作用机理及温度、pH值、活化剂等因素对生物酶活性的影响。实验结果表明经生物酶处理后的人棉织物,具有柔滑、悬垂"天丝"般的特殊效果,大大提高了其服用性能和附加值,满足消费者需求。     

高直链玉米淀粉的糊化特性研究

目的研究水浴加热、微波加热和高压加热方法对高直链玉米淀粉糊化性能的影响,为高直链淀粉的进一步开发和应用提供理论基础。方法以高直链玉米淀粉为原料,在过量水分存在条件下,分别采用水浴加热、微波加热和高压加热制备高直链玉米淀粉糊,分别研究不同温度和微波功率下,高直链玉米淀粉糊碘兰值和酶解力随糊化时间增加的变化规律。结果水浴加热、微波加热和高压加热糊化过程中高直链玉米淀粉的碘兰值和酶解力均随时间的延长呈上升趋势,微波加热高直链玉米淀粉糊的碘兰值和酶解力低于高压加热但高于水浴加热,微波加热淀粉的糊化速度大于水浴加热和高压加热。结论高压加热淀粉糊化效果好,淀粉的糊化程度高,是使高直链淀粉完全糊化的较好方法。     

钙处理对发芽糙米中淀粉酶活力的影响

研究了Ca2 + 处理对发芽糙米中淀粉酶活力的影响。结果表明 ,在 (2 1± 0 5 )℃发芽温度下 ,0～ 15mmol/LCa2 + 浓度范围内 ,低浓度的Ca2 + 能提高发芽糙米中淀粉酶活力 ,最佳浓度为 0 5mmol/L ,超过此浓度则产生抑制作用。在不同的发芽时间里 ,糙米中淀粉酶活力都表现出这一变化趋势 ;淀粉含量随淀粉酶活力升高而降低 ;低浓度Ca2 + 有提早发芽糙米还原糖含量高峰出现的作用。     

生料酿酒用微生物的分离与筛选

研究了生料酿酒用微生物的分离与筛选，从4种洒曲中分离得到了7株糖化菌和4株酵母菌，以各菌株胞外糖化酶对糊化淀粉、生淀粉的糖化能力以及生淀粉对糖化酶的吸附率为参数对各菌株的酶活进行了实验，同时对酵母的发酵能力进行了比较实验。结果表明：根霉1号，根霉2号和黑曲霉1号具有较强的生淀粉水解能力，它们对糊化淀粉的酶活力分别为458．02U／g、321．93U／g和358．51U／g；对生淀粉的酶活力分别为240．5U／g，207．6U／g和11218．5U／g：生淀粉对它们的吸附率为49．95％、68．71％和46．37％；对酵母的酒精度发酵实验表明酵母2号和酵母4号具有较强的发酵产酒精能力。     

Risk factors associated with elevated serum pancreatic amylase levels during hemodialysis

Elevated levels of serum pancreatic enzymes are frequently observed in hemodialysis (HD) patients. The complex hemodynamic, biochemical, and physiological alterations in uremia were speculated to cause excessive release of pancreatic enzymes beyond decreased renal clearance. However, hemodynamic factors are seldom explored in this aspect. We performed the study to evaluate the association between intradialytic hemodynamic change and elevated serum pancreatic amylase (SPA). Eighty‐three prevalent HD patients without any clinical evidence of acute pancreatitis underwent pre‐HD and post‐HD blood sampling for serum pancreatic enzyme levels. Demographic, biochemical, and hematological data were collected from patient record review. Hemodialysis information including intradialytic blood pressure changes and ultrafiltration (UF) amount were collected and averaged for 1 month before the blood sampling day. Patients with elevated SPA during the HD session had greater mean systolic blood pressure and mean arterial pressure reduction, greater UF volume, greater pre‐HD blood urea nitrogen and serum creatinine, higher serum phosphorus, lower pre‐HD serum total CO₂, and lower left ventricle ejection fraction (LVEF). Using multivariate linear and logistic regression analysis, the independent predictors of elevated SPA were determined to be mean arterial pressure reduction during HD, mean UF amount, pre‐HD serum total CO₂, and LVEF. Greater blood pressure reduction during HD, greater UF volume, lower pre‐HD serum total CO₂, and lower LVEF were significantly associated with elevated SPA during HD. This suggests that hemodynamic factors contribute to elevated serum pancreatic enzymes in HD patients.     

淀粉酶和半纤维素酶改性二次纤维的对比分析

单独利用半纤维素酶或把半纤维素酶和淀粉酶按照一定配比混合处理二次纤维,研究其对纸料滤水速度、纸张强度性能的影响.随着半纤维素酶用量的增加,滤水速度、抗张指数和环压指数都逐渐下降,但是挺度的增加要优于两种酶混合使用.在α-淀粉酶用量一定(201U/g浆)时,加入不同用量的半纤维素酶可提高浆料的滤水速度、纸张的抗张指数和环压指数.     

Milk production and nutrient digestibility by dairy cows when fed exogenous amylase with coarsely ground dry corn

The digestibility of starch provided by coarsely ground corn is often low, which reduces the digestible energy (DE) concentration of the diet. We hypothesized that adding exogenous amylase to diets based on coarsely ground dent corn would increase dietary DE resulting in greater milk production. Total-tract nutrient digestibility was measured in a partially replicated Latin square experiment (6 cows and 4 periods) with a 2 × 2 factorial arrangement of treatments. Diets had 26 or 31% starch with or without exogenous amylase (amylase was added to the concentrate mixes at the feed mill). In the low and high starch diets, coarsely ground dry corn (mean particle size = 1.42 mm) provided 43 and 62% of total dietary starch (corn silage provided most of the remaining starch). No treatment interactions were observed. High starch diets had greater dry matter (DM), organic matter, and energy digestibility than low starch diets, and diets with amylase had greater neutral detergent fiber digestibility than diets without amylase. Digestibility of starch averaged 88% and was not affected by treatment. A long-term (98-d) lactation study with 48 Holstein cows (74 d in milk) was conducted using 3 of the diets (low starch diets with and without amylase and the high starch diet without amylase). Addition of amylase to a diet with 26% starch did not affect intake, milk yield, milk composition, body weight, or body condition. Cows fed the diet with 31% starch had greater DM and DE intakes; yields of milk, fat, and protein; and feed efficiency than those fed diets with 26% starch. Milk composition was not affected by starch concentration. Adding exogenous amylase to a lower starch diet did not make the diet nutritionally equivalent to a higher starch diet.