生物絮凝剂絮凝活性评价方法的探讨

对生物絮凝剂絮凝活性的评价方法进行了探讨。研究发现,在固定絮凝剂添加量的情况下仅仅比较絮凝率大小,从而对絮凝活性进行评价的方法是不科学的。絮凝剂絮凝活性应以絮凝率和絮凝剂最适添加量两个指标为其活性评价参数,在有较高絮凝率的情况下,絮凝剂添加量越少则絮凝活性越高。     

絮凝酵母吸附Cr(VI)的机理

絮凝酵母SPSC01为酿酒酵母Saccharomyces cerevisiae和粟酒裂殖酵母Schizosaccharomyces pombe的融合菌株,用其吸附水溶液中的重金属Cr(VI),可以大大降低生物吸附的固液分离成本。为了探讨SPSC01菌体絮凝蛋白对Cr(VI)还原吸附的影响,对SPSC01与其亲本菌株的吸附行为进行了比较。结果表明,SPSC01和其具有絮凝性状的亲本S.pombe的Cr(VI)去除速率基本同步,远优于无絮凝性状的亲本S.cerevisiae;达到吸附平衡时,S.pombe、SPSC01和S.cerevisiae对总Cr去除率分别达68.8%、48.6%和37.5%;从而证明了絮凝有利于Cr(VI)的还原、吸附,絮凝蛋白在Cr(VI)的还原吸附过程中起促进作用。通过化学屏蔽方法和傅立叶变换红外光谱(FTIR)分析,对SPSC01菌体表面吸附Cr(VI)的机理进行了研究,结果表明SPSC01菌体表面吸附Cr(VI)起主要作用的基团是氨基、羧基和酰胺基。     

两株微生物絮凝剂产生菌筛选与复合培养研究

目的:从土壤中筛选出微生物絮凝剂产生菌株进行复合优化培养得到高效絮凝剂。方法:采用平板划线法分离、纯化和筛选得到生长条件相互匹配的目的菌株,通过单因素和正交实验优化培养件,寻求絮凝活性最佳发酵条件。结果:发现菌株X-3和S-11菌株絮凝活性较高;复合菌株在牛肉膏-蛋白胨培养基中培养,初始pH为8,培养箱温度为35℃的条件下,培养时间72h,产生的分泌物对0.4g/L的高岭土悬浊液加3mg/L CaCl2助凝下絮凝率达到77.15%以上。结论:经鉴定X-3为德克斯氏菌属菌株,S-11为拜叶林克氏菌属菌株,匹配率为85%以上。     

Comparison of the frequency of diphtheria toxin and thioguanine resistance induced by a series of carcinogens to analyze their mutational specificities in diploid human fibroblasts

The mutagenic specificities of ethylnitrosourea (ENU), X-rays (+/-)7 beta,8 alpha-dihydroxy-9 alpha,10 alpha-epoxy-7, 8,9,10-tetrahydrobenzo[a]pyrene (BPDE), ICR-191, and N-acetoxy-2-acetylaminofluorene (N-AcO-AAF) were analyzed and compared in diploid human fibroblasts and Salmonella typhimurium. In the human fibroblasts, we compared the frequency of diphtheria toxin (DT)-resistant mutants, presumably induced in the gene coding for elongation factor-2, with the frequency of 6-thioguanine (TG) resistance induced by mutations in the gene coding for hypoxanthine(guanine)phosphoribosyltransferase (HPRT). Recovery of DT-resistant (DTr) cells requires that the mutant EF-2 retain the ability to carry on protein synthesis since the normal EF-2 will be inactivated by DT selection. Therefore, the DTr mutation cannot involve major changes in the gene. In contrast, cells can acquire TG resistance by any mechanism which eliminates HPRT activity, e.g., base substitution, frameshift, deletion, loss of chromosomes. Each agent was assessed by calculating the ratio of the slopes of the dose-response plots (induced variant frequency as a function of dose of the agent used) for the two markers (DTr/TGr variants.). In S. typhimurium we examined the reversion frequency in four histidine-requiring strains bearing forward mutations of the frameshift (TA1538, TA98) or missense (TA1535, TA100) type. ENU, which was predominantly a base substitution mutagen in the bacteria, gave a ratio of DTr to TGr variants of 1.5. As expected of an agent inducing gross chromosomal changes, X-rays induced no revertants in bacteria and in human cells gave a ratio of 0.1. ICR-191 which was predominantly a frameshift mutagen in bacteria gave a ratio of 0.15. In the set of bacterial strains containing the plasmid pKM101, BPDE reverted both frameshift and base substitution mutations. It did not cause reversions in the other set of strains. In human cells BPDE gave a response similar to ENU, i.e., a ratio of DTr/TGr variants of 1.5. As reported by others, N-AcO-AAF was predominantly a frameshift mutagen in bacteria. However, in the human cells it gave a ratio of DTr/TGr variants of 1.5, similar to ENU and BPDE. These results suggest that in human cells, BPDE and N-AcO-AAF, like ENU, yield predominantly base substitutions, while ICR-191 and X-rays largely produce mutations by mechanisms which result in more extensive alterations in the gene.