新乡市豆芽中亚硝酸盐含量的测定

采用分光光度法对新乡市市售豆芽中亚硝酸盐的含量进行了随机采样检测。结果表明,在亚硝酸盐的量为0～12.5ug/50ml水溶液时与吸光度有良好的线性关系,其线性回归方程为A=0.016x＋0.003（r=0.9990）,该方法简便、快捷、灵敏、实用,可作为食品中亚硝酸盐含量的测定方法,利用此方法测定的样品中亚硝酸盐含量均未超过相关标准。     

隧道管棚支护技术方案优化

依托大石包隧道进口段工程项目,以管棚支护技术为研究对象,选择外插角、拱顶加固范围、环向间距和拱顶加固距离为影响隧道稳定性的主要评价指标,借助ABAQUS 数值软件进行正交试验,采用CRITIC 法求解客观权重,结合G1 法所求的主观权重在引入博弈论后进行权重组合优化,并基于改进TOPSIS 法加权后探讨了在多因素同时改变的管棚支护工况下各评价指标的变化情况。 最后对各工况结果进行分析,确定最优方案,将最优方案与实测数据进行对比,验证了该方法的可行性,可为类似隧道工程提供参考。     

酸雨对不同农作物种子萌发的影响

实验采用不同pH的模拟酸雨,研究其对玉米和绿豆种子萌发的影响.结果表明:pH=2.0时,玉米和绿豆均不发芽;pH=2.5时,只有异状发芽;pH≥3.0时,二者的发芽率,发芽势、发芽指数、活力指数、贮藏物质的的消耗率与运转率均随pH值的上升而增大;异状发芽率、芽长和根长的抑制指数则随pH值的增大而降低;酸雨胁迫下,绿豆各项指标的变幅都小于玉米的结果,表明绿豆抗酸雨胁迫的能力比玉米强.     

设施无公害菜豆平衡施肥技术方案

通过对菜豆营养成分及其植物营养特性的分析,结合近年来菜豆施肥试验结果,提出了设施无公害菜豆平衡施肥技术方案.     

不同酸性条件下豆渣对Cd(Ⅱ)的吸附研究

研究了不同酸性条件下豆渣对水中Cd(II)的吸附特征.结果表明:(1)在强酸(pH=2.0)、中等酸性(pH=4.0)和弱酸(pH=6.0)条件下时豆渣对Cd(II)的最大吸附率分别为55.4%、99.2%和79.4%,中等酸性条件下豆渣对水中Cd(II)的吸附率最大.(2)豆渣对Cd(II)的吸附过程遵循F方程;而L方程对弱酸条件下的吸附过程拟合较好(R2>0.99).在中等酸性和弱酸条件下,豆渣吸附Cd(II)是向有利于吸附的方向进行的,而在强酸条件下则不利于吸附.     

基于虚拟样机技术的电子提花机开发研究

采用虚拟样机仿真分析软件ADAMS建立了电子提花机动力学仿真模型和设计开发了梭口数据计算方法,采用参数化分析功能中的试验设计,可一次自动完成全部梭口等有关数据的计算,大大提高了设计开发的效率和灵活性。     

Enzymatic preparation of manno-oligosaccharides from locust bean gum and palm kernel cake,and investigations into its prebiotic activity

BackgroundManno-oligosaccharides (MOS) is known as a kind of prebiotics. Mannanase plays a key role for the degradation of mannan to produce MOS. In this study, the mannanases of glycoside hydrolase (GH) families 5 Man5HJ14 and GH26 ManAJB13 were employed to prepare MOS from locust bean gum (LBG) and palm kernel cake (PKC). The prebiotic activity and utilization of MOS were assessed in vitro using the probiotic Lactobacillus plantarum strain.ResultsGalactomannan from LBG was converted to MOS ranging in size from mannose up to mannoheptose by Man5HJ14 and ManAJB13. Mannoheptose was got from the hydrolysates produced by Man5HJ14, which mannohexaose was obtained from LBG hydrolyzed by ManAJB13. However, the same components of MOS ranging in size from mannose up to mannotetrose were observed between PKC hydrolyzed by the mannanases mentioned above. MOS stability was not affected by high-temperature and high-pressure condition at their natural pH. Based on in vitro growth study, all MOS from LBG and PKC was effective in promoting the growth of L. plantarum CICC 24202, with the strain preferring to use mannose to mannotriose, rather than above mannotetrose.ConclusionsThe effect of mannanases and mannan difference on MOS composition was studied. All of MOS hydrolysates showed the stability in adversity condition and prebiotic activity of L. plantarum, which would have potential application in the biotechnological applications.How to cite: Zhang R, Li X-Y, Cen X-L, et al. Enzymatic preparation of manno-oligosaccharides from locust bean gum and palm kernel cake, and investigations into its prebiotic activity. Electron J Biotechnol 2021;49. https://doi.org/10.1016/j.ejbt.2020.11.001     

棚室生态条件恶化表现及防治对策

棚室处于相对封闭的环境，多年连作，土壤满负荷生产，加之人为管理不当等因素，使棚室生态条件逐步恶化。本对其恶化表现及原因做了较全面分析，并提出了防治恶化的技术对策，以期促进棚室高效生产的可持续发展。     

隧道长大管棚预支护施工放样技术 --横断面投影法

长大管棚超前支护是隧道施工穿越软弱破碎围岩的一种加固方法,根据长大管棚的施工放样实例,介绍横断面投影法放样的具体计算方法及操作要点。     

Pb~(2+)对蚕豆幼苗生长的影响

采用沙培法,研究了不同浓度(0mg/L,10mg/L,30mg/L,50mg/L,80mg/l)的乙酸铅对蚕豆幼苗生理指标的影响.结果表明,一定浓度的乙酸铅对蚕豆幼苗的生长具有促进作用,浓度为10mg/L的乙酸铅是蚕豆幼苗生长的最适浓度,与对照相比较,该浓度使得蚕豆幼苗的叶绿素含量增加了,保护酶系统中过氧化物酶(POD)活性升高了,但随着浓度的增大,膜相对透性、Pro含量、膜脂过氧化产物丙二醛(MDA)含量升高了,说明高浓度破坏了细胞膜的完整性,增加了膜的透性.