The Effect of Ozone Gas-Liquid Contacting Conditions in a Static Mixer on Microorganism Reduction

The effect of gas-liquid contacting conditions in a static mixer on ozone transfer efficiency and reduction of Bacillus subtilis spores was studied in an experimental ozone contactor. An empirical mathematical model was developed that related the transfer efficiency in the experimental system to the superficial liquid velocity in the mixer, the gas-liquid flow rate ratio and the height of the down-stream bubble column. Spore reduction was determined primarily by the dissolved ozone concentration-time (C_avgt_m) product in the reactive flow segment and was independent of the gas-liquid contacting conditions in the static mixer. In an integrated ozone contacting system, the static mixer should be designed to maximize ozone mass transfer while the reactive flow segment should be designed for efficient microorganism reduction.     

Surface-active properties of antifungal lipopeptides produced byBacillus subtilis

The interfacial behavior of antifungal lipopetides of the iturinic group was studied in comparison with that of surfactin, an anionic lipopeptide. All these lipopeptides were isolated from various strains ofBacillus subtilis; each strain produced surfactin and one antifungal compound. The iturinic compounds differ from surfactin by their lower surfactant properties. The critical micelle concentration (CMC) values were dependent on the nature of the peptide moiety in the iturinic compounds. The highest values were observed for anionic antibiotics. The arrangement of lipopeptides at the air-water interface was largely dependent on the size of the lipid moiety; surfactin, which has a C₁₄ or C₁₅ β-hydroxy fatty acid, iturins A, C, and bacillomycins D, L, which have a C₁₄ or C₁₅ β-amino fatty acid, occupied a smaller area than mycosubtilin and bacillomycin F, which have a C₁₆ or C₁₇ β-amino fatty acid. These data can be related to bioactivity of these lipopeptides.     

Crystal structure of the high-alkaline serine protease PB92 from Bacillus alcalophilus

The crystal structure of a serine protease from the alkalophilicstrain Bacillus alcalophilus PB92 has been determined by X-raydiffraction at 1.75 Â resolution. The structure has beensolved by molecular replacement using the atomic model of subtilisinCarlsberg. The model of the PB92 protease has been refined toan R-factor of 14.0% and contains 1882 protein atoms, two calciumions and 188 water molecules. The overall folding of the polypeptide chain closely resembles that of the subtilisins. Furthermore,almost all of the secondary structure elements found in subtilisinCarlsberg are also present in the PB92 protease. The major differencesbetween the two structures are located around the deletion regions(residues 37 and 158–161 in subtilisin Carlsberg) andin two loops which are known to be the most variable parts ofsubtilisin structures. Flexibility of one of these loops (residues126–130 in the PB92 protease) is believed to account forthe inducedfit mechanism of substrate binding.     

聚氨酯泡沫固定化重组枯草杆菌三段培养生产青霉素酰化酶

引　言青霉素G酰化酶 (penicillinGacylase ,EC3 5 1 11,PGA)是 β 内酰胺类抗生素工业中的关键酶之一 .目前主要采用大肠杆菌和巨大芽孢杆菌进行工业化生产 ,但由于产酶水平较低、变温发酵和需要苯乙酸诱导等缺点 ,国内外研究者尝试采用各种基因重组技术 ,以期大幅度提高产酶     

聚乙二醇800催化合成对硝基茴香醚的研究

以聚乙二醇800作为相转移催化剂合成对硝基茴香醚。研究了原料配比、反应时间、催化剂用量等对反应的影响。结果表明，甲醇用量为20mL，对硝基氯苯与氢氧化钠物质的量比为1：2．5，催化剂用量为1g，反应时间为3h，产物收率最高。     

Seawater Ozonation of Bacillus subtilis Spores: Implications for the Use of Ozone in Ballast Water Treatment

The potential of ozone for disinfection of ships’ ballast water was investigated using Bacillus subtilis spores as an indicator. The effects of pH, presence of iron, and bacterial strain on disinfection efficacy in seawater, under simulated ballast conditions, were investigated. Ozone dosages of 9 mg/L (pH 7) and 14 mg/L (pH 8.2) and 24 h contact achieved a 4-log inactivation with the various oxidant residuals formed. Iron surface at a ratio to water of 9 m²/m³ impaired the oxidant residuals and the disinfection of spores. Different strains of B. subtilis resulted in different CT values. Ozone does not seem to be a good choice for the control of spore-forming organisms in ballast water, but may be suitable for the control of other species.     

醋糟酶解液的制备及其发酵生产枯草芽孢杆菌TS-02

采用水热处理技术对醋糟进行预处理,优化了醋糟的纤维素酶酶解条件,制得葡萄糖浓度27.00 g/L的醋糟酶解液. 以醋糟酶解液为基础培养基替代培养基中的葡萄糖,发酵生产枯草芽孢杆菌TS-02活菌制剂. 结果表明,在醋糟酶解液培养基中摇瓶发酵44 h时活菌数活菌数最高达4.64×1010个/mL, 7 L发酵罐中发酵周期为22 h,活菌数达6.16×1010个/mL,芽孢率达80%以上.     

苏云金杆菌生长的结构动力学模型

考察了苏云金杆菌(Bt)的间歇及流加培养.根据对Bt间歇发酵实验现象的分析和讨论,提出了一个基于Williams分室模型的四组分结构模型,并从实验数据确定了各组分的初值.该模型能较好地拟合Bt间歇发酵实验数据.从间歇发酵获得的模型参数推算出流加培养曲线与实验值也基本吻合.     

基于变活化能模型的T800/环氧树脂预浸料固化反应动力学研究

为了深入了解某新型高温固化T800/环氧树脂预浸料的固化行为,借助差示扫描量热仪(DSC),采用非等温DSC法研究了T800/环氧树脂预浸料的固化反应过程。基于唯象模型,系统研究了该预浸料的固化反应特征温度及固化动力学参数,确定该预浸料中环氧树脂的固化反应动力学模型为自催化模型。采用等转化率法,分析了预浸料中环氧树脂的反应活化能随固化度的变化情况,结果表明在整个固化反应过程中,树脂固化反应活化能变化较大,传统模型法基于全固化过程活化能不变的假设无法准确描述该固化反应。采用变活化能自催化模型,利用粒子群全局优化算法,得到了T800/环氧树脂预浸料的固化动力学方程,结果表明该模型能较好地描述实验现象,可为进一步研究该预浸料的热力学性能及其成型过程中的质量控制提供理论基础。