UPLC-IDMS法测定配方奶粉中的生物素含量

建立一种超高效液相色谱-同位素稀释质谱法测定配方奶粉中生物素含量的方法。样品中加入生物素-D2作为同位素内标,经水超声提取后,以含体积分数0.1%甲酸的10 mmol/L乙酸铵溶液和乙腈作为流动相进行梯度洗脱,采用电喷雾正离子模式、多反应监测方式进行定性定量分析。结果表明：生物素在1～50 ng/mL范围内线性关系良好,线性范围内对已知生物素含量样品3 个标准添加水平的平均回收率为89.6%～93.1%,相对标准偏差为1.71%～4.33%。方法检出限为0.6 μg/100 g,定量限为1.5 μg/100 g,该方法具有灵敏度高、重复性好、分析时间短等优点,可以满足配方奶粉中生物素含量的测定要求。     

柠檬酸钠和生物素对白色链霉菌发酵产ε-聚赖氨酸的影响

本文研究了不同生长期在培养基中添加柠檬酸钠和生物素对白色链霉菌生长及产ε-PL的影响,结果表明添加不同浓度柠檬酸钠对菌体生长的影响不明显,但对白色链霉菌ε-PL合成有正向促进作用。0 h添加2 g/L的柠檬酸钠可获得最大的ε-PL产量0.92g/L。随着柠檬酸钠浓度的增加,ε-PL产量先增加后降低。在0 h添加2 g/L柠檬酸钠并在36 h添加300μg/L生物素,发酵72 h后菌体干重和ε-PL产量分别达到了7.86 g/L和1.10 g/L,是空白对照组的1.30倍和1.93倍,说明外源添加柠檬酸钠和生物素对白色链霉菌发酵生产ε-PL有促进作用。     

初始生物素含量波动时谷氨酸发酵关键酶系的酶活变化模式

谷氨酸发酵培养基中的生物素初始含量会随玉米浆来源、批次的不同出现波动,进而影响谷氨酸发酵性能和稳定性。本文研究分析了谷氨酸发酵中,初始生物素含量正常/不当,特别是初始含量不当、采取补救措施条件下的丙酮酸、异柠檬酸和α-酮戊二酸代谢节点处关键酶的活性变化。生物素匮乏时,催化主代谢途径的关键酶活性均被弱化,特别是α-酮戊二酸脱氢酶完全失活,能量代谢主要靠乙醛酸循环维持。当发现生物素匮乏并补加生物素后,中心代谢途径关键酶--丙酮酸脱氢酶的活性恢复到正常水平,TCA重新成为主要供能途径。生物素过量时,丙酮酸羧化酶和谷氨酸脱氢酶活性基本不变,而其他关键酶均被激活。当发现生物素过量并添加吐温40后,丙酮酸脱氢酶和异柠檬酸脱氢酶依旧保持很高活性,而α-酮戊二酸脱氢酶和异柠檬酸裂解酶的活性则下降到正常水平。采用上述补救措施可以挽救因初始生物素匮乏或过量所引起的错误发酵,终酸浓度均可恢复到对照（生物素亚适量）水平（75～80 g·L^-1）。另外,对生物素初始含量和吐温添加进行复合式调控,终酸浓度可进一步提高,达到87 g·L^-1,比对照提高8.8%。     

牛乳中氨苄青霉素残留的受体分析法测定

建立基于受体识别技术检测牛乳青霉素类抗生素残留的新方法。通过生物技术制备与青霉素类抗生素具有高度亲和力的受体蛋白质,进而以其为识别元件开发间接竞争氨苄青霉素残留检测方法。青霉素受体包被质量浓度5μg/mL,生物素化氨苄青霉素质量浓度500ng/mL 条件下,对其残留量进行测定,检出限为2μg/kg,有较好的精密度及回收率。在样品中残留的青霉素种类已知的前题下(以氨苄青霉素为例),本方法可以作为定量筛选方法。     

特殊医学用途婴儿配方食品中生物素含量的测定

本研究建立了超高效液相色谱-串联质谱法测定特殊医学用途婴儿配方食品中生物素含量的分析方法.样品经0.2 mol/L磷酸121℃水解30 min提取,并通过生物素免疫亲和柱净化后,采用Acquity UPLC BEH C18(100 mm×2.1 mm,1.7μm)色谱柱进行分离,以乙腈-0.1％甲酸溶液为流动相进行梯度...     

有机氮源对谷氨酸棒杆菌发酵L-缬氨酸的影响

以L-缬氨酸生产菌谷氨酸棒杆菌XV0505为供试菌株,研究有机氮源对L-缬氨酸发酵的影响,确定了玉米浆代替豆饼水解液作为有机氮源的发酵工艺,降低了发酵成本;考察不同玉米浆浓度对谷氨酸棒杆菌XV0505发酵生产L-缬氨酸过程中生物量、耗糖速率、L-缬氨酸产量、副产物积累及氨消耗等方面影响,确定了玉米浆的适宜添加浓度;考察了玉米浆与生物素不同配比对L-缬氨酸分批发酵过程的影响,确定了最适生物素添加浓度。与原工艺相比,新工艺的菌体生物量及产酸提高了13.2%和18.5%。     

The impact of parity and duration of biotin supplementation on white line disease lameness in dairy cattle

A field study was conducted to examine effects of oral biotin supplementation for up to 18 mo on risks of lameness in dairy cows. The study included a total of 900 cattle from five dairy farms in Gloucestershire, southwest U.K., in a within-herd randomized control trial. The data from this trial were used in this paper to investigate the impact of parity and duration of supplementation with oral biotin at 20 mg/d on white line disease (WLD) lameness. Analysis of the data indicated that WLD increased with increasing parity independent of biotin supplementation from approximately two cases per 100 cow years in primiparous cows to 15.5 cases per 100 cow years in all multiparous cows, but up to 47.7 cases per 100 cow years for cows in parities > or = 5. Supplementation with biotin reduced WLD lameness by 45% in multiparous cows down to 8.5 cases per 100 cow years, whereas the effect of biotin supplementation in primiparous cows was not significant. Although numerical reductions in WLD lameness were observed for shorter periods of supplementation, a supplementation length of at least 6 mo was required to significantly reduce the risk of WLD lameness in multiparous cows. The effect of biotin supplementation in reducing lameness has potential impact for both animal welfare and farm economics.     

Effect of Pre‐Filtration on Selective Isolation of Tat Protein by Affinity Membrane Separation: Analysis of Flux,Separation Efficiency,and Processing Time

Abstract

The isolation and purification of Tat protein from bacterial lysate using avidin‐biotin interaction in microfiltration membranes have been reported in the literature. To increase the efficacy of the technique, improvements in flux, Tat separation efficiency, and processing time are essential. In the current research work a pre‐filtration step was introduced to remove unwanted high molecular weight proteins and other impurities from feed prior to affinity membrane separation. Significant enhancement in flux and separation efficiency of Tat was observed. Processing time was also reduced significantly. For example, with UF pretreatment step the total Tat recovery was around four times higher (with processing time 25% lower) than that observed with the untreated feed. The quality of purified Tat was analyzed by SDS‐PAGE, Western Blot, and biotin analysis. Flux behavior in affinity separation was described by model equations.     

Effect of biotin on milk performance of dairy cattle: a meta-analysis

A meta-analysis of the effect of biotin on production outcomes of dairy cattle was conducted following a literature review. A total of 11 studies from 9 papers, with information on the milk production and composition data from a total number of 238 cows were extracted and analyzed using meta-analysis software in Stata. Estimated size of effect of biotin was calculated for dry matter intake (DMI), milk production, and composition. Heterogeneity was not significant for all of the parameters (the highest I² = 12%). Therefore, fixed effects models were used for analysis. With the addition of biotin to lactating dairy cattle, DMI and milk production increased by 0.87 and 1.66 kg/d. No significant effect on percentage of milk fat and milk protein was observed. Additionally, Begg's test indicated no evidence of substantial publication bias for all variables. The influence analysis shows that the removal of any study did not change the direction or significance of the point estimates. It can be concluded that the use of biotin supplements increases DMI and milk yield in lactating dairy cows.