Influence of manufacturing variables on the characteristics and effectiveness of chitosan products. III. Coagulation of cheese whey solids

Ten chitosan products, prepared as described in part I of this study, were evaluated in jar tests that measured their effectiveness for coagulation of suspended solids and removing turbidity from cheese whey. A polynominal regression analysis was found to be useful for determining the optimal effectiveness of each chistosan preparation, and was expressed as the percent reduction on turbidity per unit concentration of chitosan added. The effectiveness of the chitosan products was found to be inversely related to their molecular-weight values. This situation was different from the findings described in part II of this study, in which the filterability of activated sludge was tested. Enzymatic deproteination yielded chitosan products that performed better than those produced by alkali deproteination. Demineralized products were also more effective than those that had not been demineralized. The preparations deacetylated under a nitrogen atmosphere were more effective than those deacetylated in air, but this was shown to be true only for the first 5 min of deacetylation. When deacetylated for 15 min, no differences were noted. In this study, differences in performance between the various products were largely due to the differing dosages required to achieve the maximum reduction in turbidity of cheese whey, while the maximum responses achieved by the various products tested were about the same. A commercial product, which was less effective as a sludge coagulating agent in part II of this study, was more effective for cheese whey coagulation and turbidity removal than the majority of the experimental chitosan preparations tested.     

CERKL的过表达在人类视网膜变性疾病中的作用及其临床意义

目的:研究基因CERKL过度表达与色素性视网膜炎的关系及其临床治疗意义。方法:应用RT-PCR分析、比较基因序列CERKL的转录产物的结构差异。利用序列CERKL过表达的转化与细胞溶解,获得不同的CERKL蛋白,检测其体外磷酸化酶活性。结果:CERKL转录得到四种转录子,两个较长的CERKLa、CERKLb,两个较短的CERKLc、CERKLd。四种转录蛋白在体外酶活性实验中均没有产生酶解产物C1P,在300μM H2O2氧化条件下,转录子CERKL能有效抑制细胞凋亡,其24 h相对PARP清除率明显低于12 h相对PARP清除率(P0.01)。但在400μM H2O2氧化条件下其未能表现出抑制细胞凋亡的作用。结论:色素性视网膜炎有可能是基因CERKL转录时其终止子因无义突变导致缺陷,进而发生选择性转录,并由CERKL较长变异体(CERKLa、CERKLb)的缺失或CERKL较短变异体(CERKLc、CERKLd)毒性引起的。     

Influence of manufacturing variables on the characteristics and effectiveness of chitosan products. II. Coagulation of activated sludge suspensions

Chitosan samples manufactured under different conditions were compared for effectiveness of coagulating an activated sludge suspension grown on vegetable canning wastes. Computer analysis of data from Buchner funnel filterability tests resulted in quadratic polynomial equations describing the response curves for volume of filtrate versus dosage, expressed as g/liter chitosan/100 g sludge suspended solids (SSS). The quotient of the filtrate volume and dosage at the inflection points of the equations obtained for 10 test samples and 1 commercial chitosan sample were compared to evaluate the response (effectiveness) per unit amount for each chitosan product. The product made by a standard procedure (deproteinated with 3% NaOH at 100°C for 1 hr, demineralized with 1N HCL at ambient temperature for 30 min, and deacetylated with 50% NaOH at 145–150°C under N₂ for 5 or 15 min) gave the best performance as a coagulating agent for this activated sludge system. Other products, including the commercial preparation, required higher dosages to achieve the same effectiveness. Products deacetylated in the presence of sir rather than nitrogen decreased waste treatment effectiveness, which approximated the trends of reduced viscosity and molecular-weight distribution. The products containing minerals were less effective than products from which minerals had been removed prior to deacetylation, but they were more effective than the enzyme treated sample and the commercial product. In general, although chitosan products obtained after 15 min deacetylation were more effective than those receiving 5 min deacetylation, effectiveness did not correlate linearly with viscosity and molecular-weight distribution trends. However, chitosan products deacetylated for 15 min did show that the higher-molecular-weight products (0.65–1.1 × 10⁶) were more effective coagulating agents for activated sludge than the manufactured product having the lowest molecular weight (0.47 × 10⁶) and the commercial reference sample (0.56 × 10⁶). Thus, higher values for molecular weight were predictive of greater effectiveness for coagulation of activated sludge suspensions.