Effects of chlorine and pH on efficacy of electrolyzed water for inactivating Escherichia coli O157:H7 and Listeria monocytogenes

The effects of chlorine and pH on the bactericidal activity of electrolyzed (EO) water were examined against Escherichia coli O157:H7 and Listeria monocytogenes. The residual chlorine concentration of EO water ranged from 0.1 to 5.0 mg/l, and the pH effect was examined at pH 3.0, 5.0, and 7.0. The bactericidal activity of EO water increased with residual chlorine concentration for both pathogens, and complete inactivation was achieved at residual chlorine levels equal to or higher than 1.0 mg/l. The results showed that both pathogens are very sensitive to chlorine, and residual chlorine level of EO water should be maintained at 1.0 mg/l or higher for practical applications. For each residual chlorine level, bactericidal activity of EO water increased with decreasing pH for both pathogens. However, with sufficient residual chlorine (greater than 2 mg/l), EO water can be applied in a pH range between 2.6 (original pH of EO water) and 7.0 while still achieving complete inactivation of E. coli O157:H7 and L. monocytogenes.     

Detection of Cryptosporidium and Giardia in molluscan shellfish by multiplexed nested-PCR

A multiplexed nested-PCR procedure (ABC-PCR) previously developed to detect Cryptosporidium spp. and Giardia duodenalis assemblages A and B in whole human faeces was applied to DNA extracted from filter-feeding molluscs. Species of Cryptosporidium and G. duodenalis were identified by restriction fragment analysis of the PCR products and by DNA sequencing. The extraction and ABC-PCR procedures were shown to be suitable for application to shellfish by amplification of specific target sequences using DNA from Cryptosporidium parvum genotype 2 and G. duodenalis assemblages A and B which were spiked into DNA extracted from mussels. Using 49 molluscan shellfish specimens (18 clam, 22 mussel and 9 oyster samples) from Spain, cryptosporidial oocysts were detected in 56% by immunofluorescence microscopy, and in 44% by ABC-PCR. For detection of Cryptosporidium, there was a significant association, but not total agreement, between the results of microscopy and PCR. G. duodenalis assemblage B was detected from one oyster sample by PCR. Amongst 38 specimens (20 mussel and 18 cockle samples) collected in the UK and tested by the ABC-PCR, G. duodenalis was not detected, and Cryptosporidium was detected in 11% of the samples. Overall, the 26 samples where Cryptosporidium was detected, C. hominis/C. parvum genotype 1 was detected in 1, C. parvum genotype 2 in 22, and the remaining three samples contained either sequences similar to C. parvum genotype 2 or heterogeneous mixtures of Cryptosporidium species. There was no significant association between the level of Escherichia coli detected by conventional microbiological methods and the presence of Cryptosporidium detected by ABC-PCR.     

Environmental remediation by an integrated microwave/UV illumination technique. 8. Fate of carboxylic acids, aldehydes, alkoxycarbonyl and phenolic substrates in a microwave radiation field in the presence of TiO2 particles under UV irradiation

Thermal and nonthermal effects originating when a system is subjected to a microwave radiation field in the TiO2-photocatalyzed transformation of model substances containing various functional groups (e.g., benzoic acid, phthalic acid, o-formylbenzoic acid, phthalaldehyde, succinic acid, dimethyl phthalate, diethyl phthalate, and phenol) have been examined under simultaneous irradiation by ultraviolet (UV) and microwave (MW) radiations. Characteristics of the microwave effects and the fate of each substrate during the microwave-assisted photocatalytic process were monitored by UV absorption spectroscopy, HPLC methods, total organic carbon assays, and identification of intermediates using electrospray mass spectral techniques. Microwave thermal and nonthermal effects were delineated by comparing results from MW-generated internal heat versus conventional external heating, and at constant ambient temperature under a microwave field. Factors involved in the nonthermal component of the microwave radiation were inferred for the initial adsorption of the substrate and its subsequent degradation occurring on the surface of TiO2 particles. Microwave effects bear on the mechanism through which a model substrate undergoes oxidative degradation. A characteristic feature of these effects was briefly examined by considering the behavior of polar (dipole moments) substrates in a microwave radiation field.     

Isolation of an acetyl-CoA synthetase gene (ZbACS2) from Zygosaccharomyces bailii

A gene homologous to Saccharomyces cerevisiae ACS genes, coding for acetyl-CoA synthetase, has been cloned from the yeast Zygosaccharomyces bailii ISA 1307, by using reverse genetic approaches. A probe obtained by PCR amplification from Z. bailii DNA, using primers derived from two conserved regions of yeast ACS proteins, RIGAIHSVVF (ScAcs1p; 210-219) and RVDDVVNVSG (ScAcs1p; 574-583), was used for screening a Z. bailii genomic library. Nine clones with partially overlapping inserts were isolated. The sequenced DNA fragment contains a complete ORF of 2027 bp (ZbACS2) and the deduced polypeptide shares significant homologies with the products of ACS2 genes from S. cerevisiae and Kluyveromyces lactis (81% and 82% identity and 84% and 89% similarity, respectively). Phylogenetic analysis shows that the sequence of Zbacs2 is more closely related to the sequences from Acs2 than to those from Acs1 proteins. Moreover, this analysis revealed that the gene duplication producing Acs1 and Acs2 proteins has occurred in the common ancestor of S. cerevisiae, K. lactis, Candida albicans, C. glabrata and Debaryomyces hansenii lineages. Additionally, the cloned gene allowed growth of S. cerevisiae Scacs2 null mutant, in medium containing glucose as the only carbon and energy source, indicating that it encodes a functional acetyl-CoA synthetase. Also, S. cerevisiae cells expressing ZbACS2 have a shorter lag time, in medium containing glucose (2%, w/v) plus acetic acid (0.1-0.35%, v/v). No differences in cell response to acetic acid stress were detected both by specific growth and death rates. The mode of regulation of ZbACS2 appears to be different from ScACS2 and KlACS2, being subject to repression by a glucose pulse in acetic acid-grown cells.     

Adsorption of arsenic from water using activated neutralized red mud

In this paper activated seawater-neutralized red mud, herein referred to as activated Bauxsol (AB), is used as a novel adsorbent for removing inorganic arsenic (As) from water. The adsorption of As onto AB is studied as a function of contact time, particle size, pH, initial As concentration, AB dosage, and temperature. Kinetic data indicate that the process pseudoequilibrates in 3 and 6 h for As(V) (arsenate) and As(III) (arsenite), respectively, and follows a pseudo-first-order rate expression. Within the range tested, the optimal pH for As(V) adsorption is 4.5, and close to 100% removal can be achieved irrespective of the initial As(V) concentration. Desorption of As(V) is greatest at pH 11.6 where a maximum of 40% can be achieved. In contrast, the optimum pH for As(III) removal is 8.5, and the removal efficiency changes with the initial As(III) concentration. The adsorption data fit the Langmuir isotherm and its linearized form well, with thermodynamic data indicating the spontaneous and endothermic nature of the process. The FITEQL (V.4) and PHREEQC (V.2) computer programs are used to predict As(V) adsorption at various pH values (based on diffuse double layer models). The modeling results fit the experimental results very well and indicate that surface complexation modeling is useful in describing the complex AB surface during the adsorption process. This study shows that As(III) needs to be oxidized to As(V) for a favorable removal using AB and that AB can be a very efficient unconventional adsorbent for removing As(V) from water.     

羟乙基二甲基丙烯酸酯与革接枝共聚的条件优选研究

曾有研究证明，羟乙基二甲基丙烯酸酯(HEMA)以溶于甲醇中的过氧化苯酰(BP)作为引发剂，可接枝共聚于铬鞣革上，也研究了多项参数，如单体浓度、引发剂及作用温度等。当接枝聚合在铬鞣革上的HEMA增加时，革的吸水性降低抗张及延伸率改善。未接枝的及已接枝革的红外光谱分析图上，可看到一对应于丙烯酸酯的羰基1735cm^-1的波段，而电子扫描显微图反映了已接枝共聚体的表面上气孔的减少。     

用氢氧化钠提取铬革屑中蛋白质与铬及在鞣制中的重复利用

本工作研究了用NaOH对铬革屑进行的碱性消解．证明最佳条件为：NaOH的浓度为0.5M左右，反应时间为15分钟。此法可从液相回收蛋白质．从固相(铬饼)回收铬盐。液相经“冻干”后(Lyophllisation即低温真空干燥)即可得到干蛋白质．含氮量很高．含铬量甚微。为能重复利用．铬需经化学处理作净化，提纯的铬转换为33％盐基度的硫酸铬。在牛皮及山羊皮上．进行鞣制试验．研究回收铬的鞣制性能。测定氧化铬含量及收缩温度特征．也研究了所得革的外观质量(铬的渗透情况．蓝湿革的颜色及紧实度)     

用微生物转谷氨酰胺酶对胶原蛋白水解产物的酶法改性——Ⅰ.改性作用对明胶物性影响的研究

在以前的研究报道中，我们曾利用戊二醛、乙二醛和酰亚胺分别对胶原蛋白水解产物改性，制得了不同凝胶强度的工业明胶和试验明胶。利用这些常规的改性方法可有效的改善明胶的机械性能．但是这些交联剂潜在着一定的毒性。转谷氨酰胺酶是一种能和多种蛋白质发生分子内或分子间的交联反应的交联剂，它可催化肽链上的谷氨酰胺残基的γ-羧酰胺基为乙酰基供体和氨基为受体之间的转谷氨酰胺反应。当赖氨酸上的ε-氨基作为酰基受体时就会发生ε-(γ-谷氨酰基)赖氨酸结合反应。现在一般利用发酵法提取这种酶．在市场上易购得．价格低廉．且具有环保性。我们用微生物转谷氨酰胺酶交联制得了各种不同特性的改性明胶。实验结果表明了随着酶浓度的增加．低冻力值明胶的凝胶强度可得到改善，而高冻力值明胶其凝胶强度却不受影响或略有降低。酶用量或浓度的增加，所有改性的明胶其熔点也相应的提高，有些甚至超过90℃。在室温或接近室温和60℃下．改性明胶其粘度随酶浓度的提高而增加。正如文献中所提到的那样，明胶的凝胶温度不仅取决于明胶品质而且也和酶作用浓度有关。这种微生物转谷氨酰胺酶将可能在制革过程以及其副产物的利用方面得到更广泛地应用。     

新型硅铝微粒的助留助滤性能

研究了自制硅铝微粒与阳离子淀粉(CS)、CPAM组成的微粒系统、湿部剪切力及其pH值对纸料助留助滤性能的影响。研究结果表明硅铝微粒是一种性能优异的微粒助留助滤剂，与阳离子淀粉-CPAM构成的微粒系统有更好的助留和助滤性能，有更强的抗剪切能力和更宽的pH值适应范围。