起泡葡萄酒的酵母菌耐受性研究

为了研究起泡葡萄酒的酵母菌稳定性,进行山梨酸钾和游离二氧化硫不同浓度的梯度实验,以确定不同压力条件下酵母菌的安全耐受浓度。实验结果表明,0.20 MPa的低泡葡萄酒山梨酸钾使用浓度范围为100~150 mg/L、游离二氧化硫浓度为30~40 mg/L;0.40 MPa的高泡葡萄酒产品山梨酸钾使用浓度范围为50~100 mg/L、游离二氧化硫浓度为20~30 mg/L。     

地参酚类化合物对亚硝酸盐的清除作用

采用对氨基苯磺酸-盐酸萘乙二胺分光光度法,以亚硝酸盐清除率为指标,测定地参酚类化合物在体外模拟胃液条件下对亚硝酸盐的清除作用。并采用福林酚法测定地参游离酚和不溶性细胞壁结合酚的酚含量。同时,对地参酚含量与亚硝酸盐的清除作用进行了相关性分析。结果表明,反应时间和提取液浓度与清除效果均呈良好的对数曲线关系,相关系数均大于0.88;游离酚的IC50值范围为0.0839~0.2427 mg/m L,结合酚的IC50值范围为0.1189~0.3131 mg/m L,说明游离酚对亚硝酸盐的清除能力显著强于结合酚;游离酚的IT50值的范围为9.3452~22.2861 min,结合酚的IT50值的范围为0.1110~0.4613 min,表明结合酚对亚硝酸盐的清除速率显著的快于游离酚。酚含量与清除亚硝酸盐的作用具有显著的正相关性(p0.05)。与VC相比,当地参酚类化合物提取液浓度为10 mg/m L时,相当于1.5 mg/m L的VC对亚硝酸盐的清除作用,基本上都达到全部清除,说明地参酚类化合物对亚硝酸盐具有显著的清除作用。     

固定化木聚糖酶的比较研究

以海藻酸钠和壳聚糖两种载体对木聚糖酶进行固定化,研究游离酶和固定化酶的性质.结果表明,游离酶的Km=0.546mg/L,以海藻酸钠和壳聚糖为载体的固定化酶的Km分别为38mg/L和0.342mg/L.尽管以壳聚糖固定的酶的最适pH与游离酶相同(都为5.0),但前者的适宜pH范围明显变宽;而经海藻酸钠固定的酶,最适pH向酸性范围移动0.5个pH;两种载体固定的酶最适温度与游离酶相比,都从40℃提高到50℃.实验还表明,固定化酶提高了游离酶的贮藏稳定性.     

高浓度印染废水处理工程实例

采用酸析+UASB的组合工艺处理高浓度印染废水,工程运行结果表明:退浆水进水pH值10~13,COD_(Cr)≤25 000 mg/L,SS≤600 mg/L,碱减量水进水pH值10~13,COD_(Cr)≤25 000 mg/L,SS≤400 mg/L,处理后出水pH值6~9,COD_(Cr)≤2 500 mg/L,SS≤300 mg/L。该工程可有效降低高浓度废水的pH值调节费用,减少末端综合废水的处理成本和难度。     

定向固定化葡萄糖氧化酶及其酶学性质的研究

戊二醛将伴刀豆球蛋白(ConA)和载体壳聚糖膜交联,然后利用ConA 与葡萄糖氧化酶糖链的特异性结合作用,实现酶的定向固定化。定向固定化的最适条件为戊二醛浓度0.1%、ConA 浓度0.02mg/ml、葡萄糖氧化酶浓度0.08mg/ml。定向固定化葡萄糖氧化酶的最适pH4.0、最适温度57℃,米氏常数Km 为15.84mmol/L,与游离酶及非定向固定化葡萄糖氧化酶比较,定向固定化葡萄糖氧化酶的最适pH 值向酸性范围发生了偏移并有更宽的pH 值适用范围,最适温度提高,与底物的亲和力较大。     

全自动固相萃取-气相色谱-质谱法测定地表水中的7种氯酚类

建立了水中7种氯酚类的痕量检测方法。使用全自动固相萃取,全自动干燥定量浓缩系统,和乙酸酐衍生化气相色谱质谱联用法,对7种氯酚类的前处理条件进行优化。对萃取前溶液pH值范围,乙酸酐用量和润洗溶剂的选择对回收率的影响进行了讨论。结果表明在0.0002～0.0200mg/L范围内,7支标准工作曲线的线性相关系数范围0.9970～0.9999;方法检出限范围:0.06μg/L～0.13μg/L;平均加标回收率范围分别为94.7%～127%;变异系数均低于12.3%,表明该分析方法可以用于水中氯酚类的痕量分析。     

O_3及O_3+AC一体化工艺深度处理印染废水对比研究

本文以印染废水二沉池的出水为研究对象,采用臭氧、臭氧+活性炭等工艺对其进行深度处理研究。对比发现,经过单独臭氧处理后,COD值去除率不足30%,且色度较高,而加入活性炭后处理效果明显改善。对活性炭加入量、活性炭预处理程度、pH值以及废水在反应器中的总停留时间等因素进行研究,结果表明:初始COD值在300~400 mg/L、pH值7.5、色度500倍的二沉池出水,在不调节pH值的情况下,按照活性炭投加量5 g/L与臭氧同时加入,在臭氧预处理15 min(浓度约4 mg/L),总水力停留5 h后,出水COD值稳定在100 mg/L以内,色度低于100倍,满足印染废水排放标准的二级排放要求。     

电化学法测定壳聚糖粗制品中壳聚糖含量

在pH为5.0时,六次甲基四胺缓冲液中偶氮氯膦Ⅲ能与壳聚糖生成一种复合物,该复合物可使偶氮氯膦Ⅲ在-0.158V处的还原波峰电流降低。在选定的最佳条件下,用线扫极谱法测定了其峰电流的降低值与壳聚糖的浓度在2.5~30 mg/L的范围内呈线性关系,线性回归方程为Δip(nA)=-193.1+62.40CCTS(mg/L),相关系数0.997,检出限0.5 mg/L。由此建立了一种快速、简便测定壳聚糖的方法。     

基于氯胺T法的胶原酶活力测定

羟基脯氨酸是胶原蛋白的特征氨基酸,实验基于氯胺T法测定胶原酶水解胶原后水解液中羟基脯氨酸浓度,表征胶原酶活力。确定了基于氯胺T法的Ⅰ型胶原酶活力的最适反应条件:以10 mg不溶性胶原为底物,反应pH 7.4,0.05 mol/L Tris-HCl缓冲液中,最适反应温度40℃。氯胺T法最低检测值为羟脯氨酸2μg/m L,线性范围在2~7μg/m L。与茚三酮法比较,氯胺T法适合于较低浓度样品的测定,但茚三酮法比氯胺T法测定的浓度范围广;测定同一种胶原酶的活性,茚三酮法测定结果低于氯胺T法测定结果,这是因为胶原水解产生中羟脯氨基含量较高,而羟脯氨酸与茚三酮显色后在570 nm无吸收峰。     

异硫氰酸苯酯柱前衍生RP-HPLC法同时测定莲雾中15种游离氨基酸的含量

采用异硫氰酸苯酯(PITC)为柱前衍生化试剂,结合反相高效液相色谱法,建立了同时测定莲雾果实中15种游离氨基酸含量的方法。采用Atlantis T3柱为固定相,以0.1 mol/L乙酸钠缓冲液(pH6.5,含0.5%三乙胺)和乙腈-水(4:1)为流动相进行梯度洗脱,流速为1.0 mL/min,柱温35 ℃,紫外检测器波长254 nm。各氨基酸组分在2.0~500 mg/L范围内具有良好的线性关系,相关系数r均大于0.99,检出限为0.08~0.35 mg/L,定量限为0.35~1.25 mg/L,加标回收率为85.61%~106.68%,相对标准偏差RSD均小于5%。该方法使得15种氨基酸很好的分离,且准确度和精密度好,灵敏度和回收率高,适用于莲雾果实游离氨基酸含量的分析。     

Chlorinated wash water and pH regulators affect chlorine gas emission and disinfection by-products

In the washing operations of fruit and vegetables, the maintenance of an appropriate range of pH in the water when using chlorine is crucial to ensure the maximum concentration of hypochlorous acid (HOCl), the form of chlorine with the highest antimicrobial activity. In this study, the effect of two inorganic acids (phosphoric and sulfuric) and two organic acids (carbonic and citric) as pH regulators was evaluated. Chlorinated wash water was generated using sodium hypochlorite as a chlorine source. The results showed that the optimal pH range with >90% of chlorine as HOCl was between 5.0 and 6.0 for all pH regulators. Phosphoric acid and sulfuric acid provided a wider pH range (3.0–6.0) for the maximum HOCl concentration than citric acid and carbonic acid (4.5–6.0 and 5.0–6.0, respectively). When citric acid was used as a pH regulator, a reduction of available chlorine was observed at pH < 4.5, decreasing 50% the concentration at pH 4.0. The implication of citric acid on chlorine gas emission was studied by the changes in free chlorine, comparing citric and phosphoric acids at pH 3.5 and 5.0. These analyses confirmed the emission of gaseous chlorine as after 15 min free chlorine decreased at pH 3.5, while the level was maintained at pH 5.0. Further experiments were conducted to assess the effect of these pH regulators on the generation of disinfection by-products (DBPs), including chlorates, haloacetic acids (HAAs), and trihalomethanes (THMs). Chlorine (25 mg L⁻¹ free chlorine) and different pH regulators were added to adjust the pH to 5.5 in lettuce wash water. The pH regulators tested neither affected the antimicrobial activity measured as the total mesophilic aerobic bacteria (0.32 log cfu 100 mL⁻¹) nor the accumulation of chlorates (28 mg L⁻¹), as mean values reached. However, pH regulators significantly affected the formation of chlorine halogenated DBPs. Citric acid, as the pH regulator most widely used in some sectors of the food industry, promoted the highest accumulation of THMs (710 μg L⁻¹), although the lowest HAAs (618 mg L⁻¹) at the maximum content of organic matter (600–700 mg L⁻¹). Among the pH regulators, phosphoric acid was identified as the best pH regulator for chlorine-based sanitizers because of the wide range of pH to generate HOCl (as compared to carbonic acid), its inorganic nature avoiding THM formation (as compared to citric acid), and less corrosive action to industrial equipment (as compared to sulfuric acid).     

Resonance scattering effect of rhodamine dye association nanoparticles and its application to respective determination of trace ClO2 and Cl2

A new resonance scattering method, based on resonance scattering (RS) effect, for the respective determination of ClO2 and Cl2 in water samples was developed. In HCl-NaAc buffer solutions with the pH value of 1.42, chlorine dioxide, or chlorine, oxidizes I- to form 12, which then reacts with the excess I- to form I3-. The resulting 13- would combine, respectively, with four rhodamine(Rh) dyes, including rhodamine B (RhB), butyl rhodamine B (b-RhB), rhodamine 6G (RhG), and rhodamine S (RhS), to form association particles which exhibit a stronger resonance scattering (RS) effect at 420 nm. For four systems of RhB, bRhB, RhG, and RhS, chlorine dioxide was, respectively, determined in the concentration range of 0.0056 to approximately 0.787 mg/L, 0.0034 to approximately 0.396 mg/L, 0.0057 to approximately 0.795 mg/L, and 0.0052 to approximately 0.313 mg/L, with the detection limits of 0.0011 mg/L, 0.006 mg/L, 0.0054 mg/ L, and 0.0023 mg/L ClO2, respectively. At the same experimental conditions as those for the determination of ClO2, chlorine was, respectively, determined in the concentration range of 0.013 to approximately 0.784 mg/L, 0.0136 to approximately 0.522 mg/ L, 0.014 to approximately 0.81 mg/L, and 0.014 to approximately 0.42 mg/L, with the detection limits of 0.0016 mg/L, 0.0104 mg/L, 0.0079 mg/L, and 0.0037 mg/L Cl2, respectively. The total RS value originally from ClO2 and Cl2 was recorded in the buffer solution, while the RS value from ClO2 was obtained by using dimethyl sulfoxide to mask chlorine. Thus the RS value of chlorine was calculated by deducting the RS value of chlorine dioxide from the total RS value. The RhB RS method was chosen for the determination of ClO2 and Cl2 in drinking water, with advantages of high sensitivity, good selectivity, simplicity, rapidity, and convenience.     

电解水在黑小麦发芽中的应用研究

本研究用电解水生产黑小麦芽,探究电解水对黑小麦发芽及生长的影响,并考察了电解水处理对黑小麦芽基本营养成分的影响,以期为电解水用于黑小麦的发芽提供科学依据。试验结果表明,电解水均可以促进黑小麦种子的萌发,其中p H值为4.55,有效氯浓度20.14 mg/L的酸性电解水处理组黑小麦发芽率比自来水对照组提高15.29%。但电解水处理组会不同程度的抑制黑小麦芽胚轴和胚根的生长,与自来水p H值相近的酸性或碱性电解水的抑制作用相对较弱。经p H值4.36~4.91,有效氯浓度10~30 mg/L的酸性电解水处理的黑小麦芽脂肪含量比自来水对照组降低27.06%~36.93%,还原糖含量降低21.84%~56.58%,总糖含量降低13.68%~27.11%,而蛋白质含量与对照组间无显著差异。因此在黑小麦芽的生产过程中,适宜在种子浸泡阶段使用电解水,而在芽苗淋浇阶段使用自来水,这样既促进了种子的萌发,也不会对黑小麦芽的生长产生抑制作用。     

微酸性电解水对黄瓜的消毒效果及安全性评价

目的评价微酸性电解水对黄瓜的消毒效果及安全性能。方法以黄瓜为载体,以大肠杆菌及黄瓜表面的自然菌为指标菌,探究微酸性电解水的消毒效果,并通过一次性皮肤刺激试验及急性经口毒性试验,评价其安全性能。结果 1%大豆卵磷脂、1%硫代硫酸钠、3%吐温80的复配使用能有效中和有效氯浓度为50 mg/L、pH值为6.5的微酸性电解水;微酸性电解水对黄瓜表面的自然菌及添加的大肠杆菌的杀菌效果显著,30次消毒试验后的平均杀灭对数值分别达到2.18和3.08;微酸性电解水小鼠急性经口毒性评价属实际无毒级别,家兔皮肤刺激强度属无刺激。结论微酸性电解水对黄瓜表面的消毒效果显著,且安全、绿色、环保,是一种比较理想的食品消毒剂。     

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.     

Stability of cyanogen chloride in the presence of free chlorine and monochloramine

Cyanogen chloride (CNCl) is a disinfection byproduct found in chlorinated and chloraminated drinking water. Although there is an apparent greater association of CNCI with chloraminated water relative to chlorination systems, it was not clear whether these phenomenological observations are explained by differences in the stability or formation potentials of CNCI between the two disinfectants. In this study, the stability of CNCl was examined in the presence of free chlorine and monochloramine using membrane introduction mass spectrometry. CNCI decomposes relatively rapidly when free chlorine is present but is stable in the presence of monochloramine. The decomposition kinetics and observed reaction products are consistent with a hypochlorite-catalyzed hydrolysis mechanism, and the rate law is described by (d[CNCl]/dt) = - kOCl[CNCl][OCl-]. At 25 degrees C, pH 7, and a free chlorine residual of 0.5 mg/L as Cl2, the half-life of CNCl is approximately 60 min, suggesting significant decomposition is expected over disinfection time scales. Under some winter season temperature conditions, however, the decay half-life of CNCl can be longer than typical disinfection contact times. The results of this study demonstrate that the observed association of CNCl with chloramination systems can in part be explained by the differences in its stability with chlorine and chloramines.     

Roles of hydroxyl radicals in electrolyzed oxidizing water (EOW) for the inactivation of Escherichia coli

The food industry has recognized electrolyzed oxidizing water (EOW) as a promising alternative decontamination technique. However, there is not a consensus about the sanitizing mechanism of EOW. In this study, we evaluated the disinfection efficacy of different types of EOW on Escherichia coli. Based on the hypothesis of hydroxyl radicals existing in EOW, in the present study, the hydroxyl radicals existed in slightly acidic electrolyzed water (SAEW) and acidic electrolyzed water (AEW) diluted to different levels were detected quantitatively. An ultraviolet (UV) spectrophotometer was used to scan EOW with different pH values. Accounting for the results of UV scanning to EOW with different pH value and the disinfection efficacy of different types of EOW, it can be concluded that considering the lower chlorine concentration of EOW compared with traditional chlorine disinfectants, the existing form of chlorine compounds rather than the hydroxyl radicals played important role in the disinfection efficacy of EOW.     

Effect of chlorination on Microcystis aeruginosa cell integrity and subsequent microcystin release and degradation

The proliferation of cyanobacteria in drinking water sources is problematic for water authorities as they can interfere with water treatment processes. Studies have shown that oxidants such as chlorine can enhance the coagulation of cyanobacteria; however, chlorine can potentially lyse cyanobacterial cells, releasing toxic metabolites. Chlorine also has the potential to effectively degrade these toxins. This study evaluated the effect of chlorine on the cell integrity of toxic Microcystis aeruginosa in reservoir water using flow cytometry. In addition, the effect of chlorine on the subsequent release and degradation of microcystin toxins was systematically assessed. Cell lysis occurred at chlorine exposure values between 7 and 29 mg min/L, which is within the range of normal disinfection practices. Intracellular toxin was shown to be released from damaged cells at a rate three times faster than it was degraded by chlorine. The degradation of extracellular microcystin by chlorine was found to be dependent upon the pH, chlorine exposure, and the presence of cyanobacterial cells.     

二氧化氯在鲜蛋消毒保鲜中的应用研究

以新鲜鸡蛋为原料,研究二氧化氯对其进行处理后消毒保鲜的效果。经挑选、分级后,分别将鸡蛋置于浓度为30、40、50mg/L的ClO2溶液中,各浸泡5、10、15min,另取二氧化氯浓度为50mg/L浸泡10min的处理组置于密封袋中为密封袋组,未做任何处理的鸡蛋设为对照组。所有实验组均在室温条件下贮藏,分别在第10、20、30、40d测定鸡蛋的失重率、蛋黄系数、哈夫值、挥发性盐基氮等指标。结果表明,二氧化氯对鸡蛋蛋壳有很好的灭菌作用,对鸡蛋的保鲜效果不显著,消毒后置于密封袋中的鸡蛋保鲜效果较好。     

Formation of chloroform and other chlorinated byproducts by chlorination of triclosan-containing antibacterial products

Triclosan is a widely used antibacterial agent found in many personal hygiene products. Although it has previously been established that pure triclosan and free chlorine readily react, interactions between triclosan-containing consumer products and free chlorine have not previously been analyzed in great depth. Sixteen double-blinded solutions including both triclosan-containing (1.14-3.12 mg triclosan/g product) and triclosan-free products were contacted with free chlorine at pH 7. Products detected included (chlorophenoxy) phenols, 2,4-dichlorophenol, 2,4,6-trichlorophenol, and chloroform. The daughter product yields were found to be highly variable and were dependent on the antimicrobial product investigated, the free chlorine to triclosan ratio, and the temperature at which the study was conducted. Lowering the temperature from 40 to 30 degrees C resulted in a decreased average chloroform yield from 0.50 to 0.37 mol chloroform/mol triclosan consumed after 1 min of reaction time for an initial free chlorine concentration of 4.0 mg/L as Cl2. At 40 degrees C the average molar chloroform yields decreased to 0.29 and <0.1 when the initial free chlorine concentration was decreased to either 2.0 or 1.0 mg/L as Cl2, respectively. Field experiments, in which Atlanta, GA and Danville, VA tap waters were augmented with various soap products, exhibited results varying from the laboratory experiments in that different productyields were observed. These differences are attributed to the chlorine demand of constituents in the tap water. A simple exposure model suggests that exposure to chloroform can be significant under some conditions.