Lactose uptake rate measurements by C-labelled lactose reveals promotional activity of porous cellulose in whey fermentation by kefir yeast

Lactose uptake rate by kefir yeast, immobilized on tubular cellulose and gluten pellets during fermentation of lactose and whey, was monitored using ¹⁴C-labelled lactose. Results illustrated that, in all cases, lactose uptake rate was strongly correlated with fermentation rate and the fermentation’s kinetic parameters were improved by kefir yeast entrapped in tubular cellulose. As a result, twofold faster fermentations were achieved in comparison with kefir yeast immobilized on gluten. This is probably due to cluster and hydrogen bonds formation between cellulose and inhibitors, such as Ca⁺⁺ and generated lactic acid, by which they leave the liquid medium. The findings, regarding the promotional effect of cellulose, seem promising for application in industrial whey fermentations.     

改进水合工艺 提高重灰白度

在固相水合法生产重质纯碱工艺中，在水合水内加入一定量的添加剂，可抑制一水碱中Fe份对重灰白度的影响，从而提高重灰白度的目的。     

EFFECT OF IMPELLER SPEED AND VISCOSITY ON WHEY LACTOSE HYDROLYSIS AND β-GALACTOSIDASE STABILITY

In the present work, the effects of impeller speed and viscosity on the enzymatic hydrolysis of whey lactose and enzyme inactivation were studied. The experiments were carried out in 250 mL of 25 mM phosphate buffer solution containing 50 g/L whey lactose by using a commercial β-galactosidase produced from Kluyveromyces marxianus in a batch reactor system. The degree of lactose hydrolysis (%) and residual enzyme activity (%) was investigated versus impeller speeds from 100 to 600 rpm and viscosities from 1.005 to 13.43 cp for 30 minutes of processing time. The mathematical models depending on these process parameters were derived using the experimental data of residual lactose concentration and residual β-galactosidase activity. The predicted models have been confirmed with the experimental results.     

亚磷酸氢钙的结构特性分析

本文采用热分析和x衍射方法研究了亚磷酸氢钙的结构特性,获得了亚磷酸氢钙结晶水合物的热分解特性和有关热分析数据;获得了亚磷酸氢钙结晶水合物的x衍射图谱和有关衍射数据;分析了它们与结构及其变化的关系。研究结果可供亚磷酸氢钙生产、产品鉴定和应用的参考。     

D-塔格糖的生理活性及生物合成研究进展

D-塔格糖是一种重要的稀有己酮糖,其甜度是蔗糖的92%,热量只有蔗糖的三分之一;D-塔格糖分别于2001年和2014年被美国食品药品监督管理局和我国卫生和计划生育委员会批准为食品新原料。D-塔格糖具有降低血糖、减少肥胖、改善肠道菌群、抗龋齿、抗氧化等功能。D-塔格糖作为一种理想功能性甜味剂,具有广泛的应用价值,然而塔格糖的生产成本以及产量一直是限制塔格糖发展和应用的重要原因。D-塔格糖的合成方法主要有化学合成法和生物转化法。化学合成法生产D-塔格糖虽然是一种经济有效的方法,但是在生产过程中需要高温高压的条件,并且容易生成山梨糖、甘露糖等杂糖,不利于分离纯化。为了克服这些缺点,生物转化法生产D-塔格糖得到了广泛的关注和研究,因此,系统阐述了以不同底物,如己糖(半乳糖醇、D-半乳糖和D-果糖)、乳糖、多糖(麦芽糊精和淀粉)转化成D-塔格糖的研究进展和优缺点,并对其未来研究趋势进行了展望,以期为D-塔格糖的研发与生产提供借鉴。     

一水合硫酸氢钠的催化酯化作用

研究了以一水合硫酸氢钠催化合成乙酸正丁酯的最佳反应条件,在相同反应条件下,利用一水合硫酸氢钠催化合成了乙酸和丙酸的８种酯,其收率在８５．９％～９６．２％之间。     

以丙尔金为主盐的高纯度可焊性镀金工艺

以清洁环保的丙尔金[即一水合柠檬酸一钾二(丙二腈合金(I))]代替有毒氰化亚金钾为主盐,用市售的可焊性镀金工艺配方及规范,生产高纯度(99.99%)的金镀层。所得镀金层呈浅柠檬黄色、无色斑,比亚硫酸盐纯金层更均匀、致密,金线键合强度经高低温循环试验后稳定,与载体焊接牢固、无空穴,满足美国军标MIL-STD-883H–2010中方法2011.8──键合强度测试规范的性能要求。镀金液性能与亚硫酸盐纯金镀液相近。镀金液使用3年多后,不论是在加热状态或是长期放置都很稳定。     

重组大肠杆菌高密度发酵中乳糖诱导表达hBLyS

研究了乳糖代替异丙基硫代半乳糖苷(IPTG)诱导大肠杆菌表达重组人B淋巴细胞刺激因子(hBLyS). 结果表明,乳糖不仅能够作为诱导剂诱导外源蛋白的合成,而且能作为碳源促进菌体的生长. 通过对诱导条件进行优化,乳糖诱导外源蛋白的表达量约占菌体总蛋白的14.3%,达到IPTG的诱导水平(26%)的55%. 在5 L发酵罐中hBLyS的表达量达到16%,同时生物量OD600=62.     

Ultrasound-enhanced lactose hydrolysis in milk fermentation with Lactobacillus bulgaricus

The effects of ultrasonic irradiation during milk fermentation have been investigated in terms of the cell viability, β-galactosidase activity, the pH value of the culture medium, the degree of lactose hydrolysis and glucose content. The results showed that the ultrasonic irradiation caused the intracellular β-galactosidase to be released from the lactic acid bacteria cells. The released β-galactosidase showed a higher lactose hydrolysis activity than that in the cells. The β-galactosidase that was released to the medium has been more effectively used in pH-controlled fermentation. The results also showed that the continuous sonication caused the cell viability to decrease, but the viable cell count was again increased with static incubation after sonication. High degrees of lactose hydrolysis and high cell viabilities were obtained with the combination of pH-controlled sonicated fermentation and static incubation.