The effects of water pollution on the immersion corrosion of mild and low alloy steels

The short-term immersion corrosion of mild and low alloy steels in seawaters is known to be proportional to the concentration of dissolved oxygen (DO) in the bulk water. Longer-term corrosion is a function of the activity of sulphate-reducing bacteria and is influenced by the concentration of nutrients in the bulk water. These influences are examined in more detail for the corrosion of steels in the brackish waters of the River Thames and for several immersion corrosion sites on the Eastern Australian seaboard and in the North Sea. The published data sources were supplemented with plausible assumptions about environmental conditions. New interpretations of the data are provided based on the previously published model for immersion corrosion. For waters with negligible salinity and sulphate levels early corrosion loss was shown to depend on the dissolved oxygen content of the waters, and later corrosion loss was a direct function of nitrogenous nutrient (pollution) levels. This also applies to longer-term corrosion.     

Analysis of microbial adaptation at enzyme level for enhancing biodegradation rate of BTX

Catechol was found to be a common intermediate in the degradation of benzene and toluene byAlcaligenes xyhsoxidans Y234, and the ring cleavage of the catechol mediated by catechol 1,2-dioxygenase was a rate-determining step. Since benzene induced higher level of catechol 1,2-dioxygenase than toluene, the cells pre-adapted to benzene showed higher degradation rate of benzene and toluene. The degradation rate ofm-xylene was also increased significantly when benzene-adapted cells were inoculated.m-Xylene was metabolized via 3-methyl catechol which was effectively cleaved by catechol 1,2-dioxygenase.     

化妆品微生物挑战试验

本文参照美国化妆品、盥洗用品和香精协会（CTFA）推荐的防腐体系效能评价方法，研究了不同产品在相同防腐条件下，微生物挑战试验结果的差异性。     

BOD微生物传感器和快速BOD测定仪的研制

报导了一种用皮状丝孢酵母组成的ＢＯＤ微生物传感器和流通式微机化愉速ＢＯＤ测定仪。本法的响应时间为（３～７）ｍｉｎ，测定范围为（１０～６０）ｍｇ／Ｌ，线性方程ΔＩ＝０．４２＋１．６４Ｃ，相关系数γ＝０．０９７。对４０ｍｇ／ＬＢＯＤ标样平行测定８次的相对标准偏差ＲＤ＝３．７１％，加标回收率为９４．１％～１０４．７％     

Analysis of effect of nicotine on microbial community structure in sediment using PCR-DGGE fingerprinting

Solid or liquid waste containing a high concentration of nicotine can pollute sediment in rivers and lakes, and may destroy the ecological balance if it is directly discharged into the environment without any treatment. In this study, the polymerase chain reaction(PCR) and denaturing gradient gel electrophoresis(DGGE) method was used to analyze the variation of the microbial community structure in the control and nicotinecontaminated sediment samples with nicotine concentration and time of exposure. The results demonstrated that the growth of some bacterial species in the nicotine-contaminated sediment samples was inhibited during the exposure. Some bacteria decreased in species diversity and in quantity with the increase of nicotine concentration or time of exposure, while other bacteria were enriched under the effect of nicotine, and their DGGE bands changed from undertones to deep colors. The microbial community structure, however, showed a wide variation in the nicotinecontaminated sediment samples, especially in the sediment samples treated with high-concentration nicotine. The Jaccard index was only 35.1%between the initial sediment sample and the sediment sample with a nicotine concentration of 0.030 mg/g after 28 d of exposure. Diversity indices showed that the contaminated groups had a similar trend over time. The diversity indices of contaminated groups all decreased in the first7 d after exposure, then increased until day 42. It has been found that nicotine decreased the diversity of the microbial community in the sediment.     

Konjac flour improved textural and water retention properties of transglutaminase-mediated,heat-induced porcine myofibrillar protein gel: Effect of salt level and transglutaminase incubation

Functional properties of heat-induced gels prepared from microbial transglutaminase (TG)-treated porcine myofibrillar protein (MP) containing sodium caseinate with or without konjac flour (KF) under various salt concentrations (0.1, 0.3 and 0.6 M NaCl) were evaluated. The mixed MP gels with KF exhibited improved cooking yields at all salt concentrations. TG treatment greatly enhanced gel strength and elasticity (storage modulus, G′) at 0.6 M NaCl, but not at lower salt concentrations. The combination of KF and TG improved the gel strength at 0.1 and 0.3 M NaCl and G′ at all salt concentrations, when compared with non-TG controls. Incubation of MP suspensions (sols) with TG promoted the disappearance of myosin heavy chain and the production of polymers. The TG-treated MP mixed gels had a compact structure, compared to those without TG, and the KF incorporation modified the gel matrix and increased its water-holding capacity. Results from differential scanning calorimetry suggested possible interactions of MP with KF, which may explain the changes in the microstructure of the heat-induced gels.     

Effect of non-meat proteins on hydration and textural properties of pork meat gels enhanced with microbial transglutaminase

The combined effect of incorporation of four non-muscle proteins, NMP (blood plasma, BP; sodium caseinate, SC; soy protein isolate, SPI; gelatin, G) at 2 g/100 g levels on hydration and textural characteristics of pork gels processed without or with 0.6 g/100 g microbial transglutaminase preparation (MTG) was investigated. Addition of SC and BP most favourably affected hydration properties and thermal stability, yielding lower cooking loss and expressible moisture for pork gels. Interactions between NMP and MTG were observed. Improvement of gel strength by addition of transglutaminase was observed for treatments containing SC and BP but not G nor soy isolate. Of the four proteins tested SC was found to be a superior substrate for MTG in enhancing textural properties of a gelled meat system. None of the tested ingredients was able to yield gel cohesiveness equivalent to the control containing 8% muscle proteins. Results of this study indicate a potential for using MTG to improve or modify the functional and textural properties of investigated food proteins (SC and BP in particular) in comminuted meat products.     

微生物转谷氨酰胺酶(MTGase)的蛋白质底物催化特性及其催化机理研究 (I)MTGase催化单底物蛋白质的聚合特性

采用SDS-PAGE结合凝胶成像技术比较了MTGase在还原状态下对酪蛋白酸钠(SC)、牛血清蛋白(BSA)、大豆球蛋白(glycinin)和β-伴豆球蛋白(β-conglycinin)、β-乳球蛋白(β-LG)和α-乳白蛋白(α-LA)等单底物蛋白的聚合效率。结果表明MTGase较易催化SC和BSA聚合,其次为大豆球蛋白,而β-伴豆球蛋白、β-LG和α-LA最不易。根据MTGase催化不同单底物蛋白质的聚合速率的差异,对MTGase催化单底物蛋白质的聚合特性进行了探讨,指出:①底物蛋白的分子结构对MTGase催化活性的重要性;②蛋白质表面疏水度对MTGase催化活性的重要性;③对蛋白质进行一定的预处理可增强MTGase对蛋白质(特别是球蛋白)的催化活性。     

Diversity and functional characteristics of lactic acid bacteria from traditional kefir grains

Traditional kefir grains were collected from distinct parts of Turkey, and their microbial profile was determined. A wide bacterial biota was observed formed by distinct lactic acid bacteria (LAB) in which Lactococcus lactis strains appeared to be dominant. Yeast species were also identified in kefir grains. Significant levels of antifungal and antibacterial activities were monitored in kefir isolates. All tested LAB produced an exopolysaccharide (EPS) containing glucose and galactose, and some strains formed a fructan‐type EPS. Importantly, low levels of antibiotic resistance were observed among the kefir isolates.