芝麻蛋白酶水解条件的研究

对芝麻蛋白的酶水解工艺进行了初步研究,结果为:①通过比较,选用木瓜蛋白酶为酶解芝麻蛋白制备功能性短肽的专用酶,其工艺参数为:底物质量浓度9.0 g/L,酶添加量20.0%,pH值6.5,温度50℃,时间6 h,在此工艺下得到的酶解产物的抗氧化活性最高,对邻苯三酚自氧化的抑制率为35.6%;②酶解前的热处理可以提高酶水解的效果,最佳的热处理条件是将蛋白溶液在90℃下加热10 min。     

杀线虫细菌W3胞外体壁降解蛋白酶的纯化及部分特性

[目的]为筛选和开发高效新型生物杀线虫剂提供依据。[方法]以土壤中筛选的1株具有明显杀线虫活性的细菌菌株W3为供试菌种,对其进行发酵培养,采用硫酸铵沉淀、疏水层析、阴离子柱层析等方法从发酵液中分离W3菌株的杀线虫活性成分,并对各活性成分的杀线虫活性进行测定。[结果]W3菌株粗蛋白处理线虫4h后,虫体活动异常,部分虫体静止不动,处理36h后大部分虫体不活动,部分虫体体壁断裂现象,最终所有线虫被完全消解;从发酵液中纯化出1种能降解线虫体壁的胞外蛋白酶,该酶的分子量约为45KDa,其作用的最佳pH值为7～8,最佳温度为45℃。[结论]W3菌株胞外蛋白酶具有明显的杀线虫活性和线虫体壁降解活性。     

菜籽粕蛋白肽制备工艺条件优化

试验改进了菜籽粕蛋白的酶解工艺,并对改进后的工艺条件进行了优化。采用2709碱性蛋白酶水解菜籽粕蛋白,分别考察了pH值、酶用量、酶解时间、温度、底物浓度对蛋白回收率的影响规律,在此基础上,利用响应面分析法对菜籽粕蛋白的酶解条件进行了优化。结果表明,2709碱性蛋白酶水解菜籽粕蛋白的较优条件为pH11.5、温度50℃、底物浓度4%、水解时间173min、酶用量5778U·g-1,此时蛋白回收率可达87.18%。     

一株产碱性蛋白酶的酵母菌发酵条件优化

对一株产碱性蛋白酶假丝酵母菌(Candidasp.N9211)的发酵条件进行了优化,研究各种碳源、氮源及无机盐对产酶的影响,应用正交试验优化发酵培养基组成。结果表明:最佳培养基组成为酵母膏20g/L,蛋白胨15g/L,干酪素20g/L,硫酸亚铁0.01g/L。优化后蛋白酶活性提高了27倍(由1.55U/mL提高到41.85U/mL)。摇瓶培养的最佳条件为:初始pH值10.0,接种量1%,发酵温度35℃,最佳培养时间为15h。     

海洋细菌L_1-9菌株产蛋白酶发酵条件的优化

海洋细菌L1-9是一株对多种植物病原真菌有强抑制作用并能产生蛋白酶、纤维素酶等细胞壁降解酶的优良菌株.采用比色法对该菌株产生蛋白酶的最适培养基和发酵条件进行了研究.结果表明,该菌株产蛋白酶的最佳培养基为豆饼粉2.00%、麸皮3.00%、玉米粉4.00%、Na2HPO4·12H2O 0.40%、KH2PO4 0.03%、CaCl2 0.10%、NaCO3·10H2O 0.10%;最适发酵条件为500mL三角瓶装液量70mL,接种量5%,培养基起始pH值6.0或9.0,转速190 r·min-1,温度25℃,发酵时间42h.     

超声波对尼罗罗非鱼幼鱼生长的影响

选择尼罗罗非鱼Tilapia nilotica幼鱼(平均体重为1.95 g±0.60 g)为试验对象,用3种不同强度的超声波对其进行辐射刺激,共设3个试验组和1个对照组。经过60 d的超声波辐射养殖,结果表明:各组间体重存在极显著性差异(P<0.01),其中每天受频率为23 kHz、声源声强为200 mW/cm2的连续超声波辐射刺激5 min的试验组鱼,其体重最高,比对照组鱼体重增长约7.58%;但每天受频率为23 kHz、声源声强为600 mW/cm2的连续超声波辐射刺激5 min的鱼体,其体重反而比对照组体重减少约5.80%。各试验组尼罗罗非鱼体重与胃蛋白酶活性之间没有明显关系。当环境声强为1.58~1.60 mW/cm2时,对尼罗罗非鱼幼鱼生长比较有利。     

酶法水解牦牛血制备蛋白多肽粉的技术研究

摘 要：[目的][方法]利用中性蛋白酶将牦牛血红蛋白水解,探讨各因素对中性蛋白酶水解牦牛血红蛋白的影响以及水解度的关系,并对酶解液进行了活性炭脱色效果的研究。通过单因素和正交试验（L16(45)）,[结果]确定了中性蛋白酶水解血红蛋白的适宜条件为 pH 7.0,温度 45℃,酶底物浓度比 4000 U/g 蛋白质液,底物浓度 5%,酶解时间 7 h。通过正交试验,确定酶解液的最佳脱色工艺条件为活性炭用量 4%,脱色温度 75℃,pH 5.0,脱色时间 60 min。     

三氯生与镉单一及复合污染对土壤呼吸和酶活性的影响

为了解典型药品和个人护理品(PPCPs)——三氯生与镉复合污染的生态效应,采用室内培养实验和联合毒性预测模型,首次评价了三氯生与镉单一及复合污染对土壤呼吸及参与土壤碳氮循环的相关酶活性的生态毒性。结果表明:三氯生与镉单一及复合污染对土壤呼吸呈现激活—抑制—激活的生态效应;刺激了蛋白酶活性,激活率先降低后升高,56 d时达到最大。整个实验期间均抑制了蔗糖酶活性,镉(10.0 mg kg-1)单一污染培养14 d抑制率达到最大值(81%),三氯生单一胁迫呈现负的剂量效应关系,两者复合污染无显著的剂量效应关系。联合效应评价模型预测表明,相比三氯生或镉单一污染,两者的复合胁迫对土壤呼吸呈现随时间变化的拮抗—协同—加和效应,对土壤蛋白酶呈现协同—加和—协同的联合效应,而对土壤蔗糖酶活性则主要为协同效应。     

Exogenous protease supplementation of poultry by‐product meal‐based diets for broilers: Effects on growth,carcass characteristics and nutrient digestibility

An experiment was conducted to investigate the effects of three levels (0%, 3% and 6%) of poultry by‐product meal (PBM) with or without protease on broiler growth, carcass characteristics and nutrient digestibility from 1 to 35 days. Two hundred and forty birds (n = 240) were fed equi‐caloric and equi‐nitrogenous (ME 2850 kcal/kg; CP 20%) diets throughout the experiment. The enzyme supplementation increased feed intake (p < .01) and body weight gain (p < .01), but feed:gain remained unaffected (p > .05) from 1 to 21 days. Increasing level of PBM decreased feed intake (p < .05), but body weight gain was improved (p < .05) at 3% PBM level during 1 to 21 days. The feed:gain was improved (p < .05) in birds fed diets containing 3% PBM. The feed:gain was also improved in birds fed diets containing 3% PBM from 1 to 35 days. However, feed intake and body weight gain in birds fed diets containing PBM remained unaffected. An interaction (p < .01) on feed intake between enzyme and PBM was noticed during 1 to 21 days. However, no interaction was recorded for body weight gain and feed:gain. The per cent carcass yield improved (p < .01) in birds fed diets supplemented with enzyme. The per cent breast meat yield was depressed (p < .005) in birds fed diets containing PBM. Apparent metabolizable energy (p < .001), nitrogen retention (p < .01), apparent metabolizable energy corrected for nitrogen (p < .001), and apparent digestibility coefficient for nitrogen (p < .01) improved in birds fed diets containing enzyme; however, a reverse was noticed in those fed diets containing only PBM. In conclusion, inclusion of 3% PBM along with supplementation of exogenous protease improved performance and nutrient digestibility in broilers.     

Involvement of a vascular hypersensitive response in quantitative resistance to Ralstonia solanacearum on tomato rootstock cultivar LS‐89

Ralstonia solanacearum causes bacterial wilt disease in Solanaceae spp. Expression of the Phytophthora inhibitor protease 1 (PIP1) gene, which encodes a papain‐like extracellular cysteine protease, is induced in R. solanacearum‐inoculated stem tissues of quantitatively resistant tomato cultivar LS‐89, but not in susceptible cultivar Ponderosa. Phytophthora inhibitor protease 1 is closely related to Rcr3, which is required for the Cf‐2‐mediated hypersensitive response (HR) to the leaf mould fungus Cladosporium fulvum and manifestation of HR cell death. However, up‐regulation of PIP1 in R. solanacearum‐inoculated LS‐89 stems was not accompanied by visible HR cell death. Nevertheless, upon electron microscopic examination of inoculated stem tissues of resistant cultivar LS‐89, several aggregated materials associated with HR cell death were observed in xylem parenchyma and pith cells surrounding xylem vessels. In addition, the accumulation of electron‐dense substances was observed within the xylem vessel lumen of inoculated stems. Moreover, when the leaves of LS‐89 or Ponderosa were infiltrated with 10⁶ cells mL^?1 R. solanacearum, cell death appeared in LS‐89 at 18 and 24 h after infiltration. The proliferation of bacteria in the infiltrated leaf tissues of LS‐89 was suppressed to approximately 10–30% of that in Ponderosa, and expression of the defence‐related gene PR‐2 and HR marker gene hsr203J was induced in the infiltrated tissues. These results indicated that the response of LS‐89 is a true HR, and induction of vascular HR in xylem parenchyma and pith cells surrounding xylem vessels seems to be associated with quantitative resistance of LS‐89 to R. solanacearum.