乳酸氧化酶转化乳酶产丙酮酸

从土壤样品中富集、筛选和纯化获得了3株能产生乳酸氧化酶的菌株，其中SM-10#菌株的产酶活力最高，经初步鉴定，该菌株属腐生葡萄球菌（Staphylococcus saprophyticus），对SM-10#菌株还进行了破壁条件的优化、生长曲线的分析和酶液稳定性研究，并初步探讨了其酶液的底物转化效率，4h最高转化率达到80%，该研究结果为将这种有价值的酶源推向生产打下基础。     

响应面法优化菌株Bacillus sp.W77酯酶发酵条件

为开发适应性好的工业用酶,从深圳福田红树林自然保护区土壤中分离纯化获得一株产耐高温嗜碱性酯酶的菌株,通过形态学和分子生物学初步鉴定该菌株为芽孢杆菌属(Bacillus sp.),命名为Bacillus sp.W77;对所产的粗酶液进行酶活测定,发现该菌产的酯酶的最适反应温度是50℃,最适pH为8.0,且在碱性条件下较稳定;采用响应面法(Response surface methodology)对土壤菌株Bacillus sp.W77的产酯酶条件进行了优化,酵母提取物6.67 g/L,磷酸氢二钾0.56 g/L,硫酸镁0.36 g/L时,此时预测的最大酯酶活力的D405 nm值为1.266,在最佳产酶条件下,优化后酯酶活力的D405 nm值由0.829提高到1.235,实际值达到理论预测值的97.5%.     

单宁酶产生菌的筛选和发酵条件研究

利用富集培养技术，从天然源分离得到具有较高单宁酶活性的黑曲酶Ｎｏ．１７株（ＡｓｐｅｒｇｉｌｕｓｎｉｇｅｒＮｏ．１７）．该菌株能把五倍子中的单宁酶法水解成没食子酸，在对Ｎｏ．１７株开展产酶条件和参数优化实验的基础上，进行了实验室酶法制备没食子酸试验，并获得产物浓度为１４．１ｇ／Ｌ的没食子酸，经大孔吸附树脂分离，最终净产率达到７０％．该样品经熔点测定、元素分析、ＴＬＣ、红外等理化方法分析检测，结果均与没食子酸标样一致     

具脂肪酶和酯酶活性酵母菌的选育和酶学性质初步研究

从济南市区得到的含油土壤中筛选得到一株酵母Ｓ９ 菌株,它可以同时产生较高酶活的脂肪酶和酯酶．对影响Ｓ９ 产脂肪酶和酯酶的各种因素进行了研究,确定２ ％ 的黄豆粉为最佳氮源,１ ％ 的可溶性淀粉为最佳碳源,最适的初始培养ｐＨ和温度分别为ｐＨ６ ．５ 和２８℃,另外不同的表面活性剂对产酶也有不同的影响．对Ｓ９脂肪酶和酯酶的各种酶学性质进行的研究表明,脂肪酶和酯酶的最适作用温度都为３０℃,最适作用ｐＨ 分别为７ ．０ 和８．０,两者都属于常温酶,在３０℃～４０ ℃范围内比较稳定,前者在中性偏碱的ｐＨ 环境中比较稳定,后者属于碱性酶,在ｐＨ７ ．５～１０ ．５ 范围内相当稳定．     

皮革废物铬革屑的微生物学处理研究Ⅱ:降解革屑微生物的发酵条件及其蛋白酶的降解研究

在以皮胶原为碳、氮源时其最适产酶条件为ｐ Ｈ７ ,３０ ℃,高产酶时间为４ ｄ ．经 Ｃａ（ Ｏ Ｈ）２ 预处理革屑不能有效促进该菌对革屑的降解,但可使大部分 Ｃｒ３ ＋ 沉淀而除去．经该株蛋白酶的粗提及性质实验,确定酶的最适反应条件为４０ Ｃ、ｐ Ｈ７ ．０ ～８ ．０ , Ｃｒ３ ＋ 对酶有轻度的抑制作用,以２ ．２６ ％ 的粗酶作用于革屑,水解率达５０ ％ 以上     

杀虫剂敌敌畏对黑眶蟾蜍蝌蚪的毒性影响

采用静态换水法研究了杀虫剂敌敌畏（dichlorvos，DDVP）对黑眶蟾蜍（Bufo melanostictus）蝌蚪的急性毒性和生长发育、生理活动的影响．结果表明，DDVP对黑眶蟾蜍蝌蚪的96h半数致死浓度（LC50，96h）为51．61mg／L．暴露于2．24mg／L的DDVP溶液中10d和20d，蝌蚪的体长日增长率分别降低24．9％和9．5％，并引起黑眶蟾蜍蝌蚪酯酶同工酶（EST）酶带数和强弱发生改变，抑制了蝌蚪的酯酶同工酶活性，而超氧化物歧化酶（SOD）比活受到的影响相对较小．暴露于6．72mg／L的DDVP溶液中10d和20d，蝌蚪的体长日增长率分别降低27．0％和38．8％，酯酶同工酶（EST）酶带的强弱发生明显的改变，SOD酶比活明显低于对照组．说明杀虫剂敌敌畏对黑眶蟾蜍蝌蚪可造成一定的毒性影响．图2表4参22     

高产脂肪酶菌株的筛选鉴定及酶学、转酯特性

从自然环境中筛选水解酶活高且酶学、转酯特性优良的产脂肪酶菌株,对脂肪酶工业化发酵生产及生物柴油制备的研究具有重要意义.采用罗丹明B平板初筛和摇瓶发酵复筛法,从70份含油脂丰富的样品中筛选产脂肪酶酶活较高的菌株进行16S rRNA鉴定,研究其酶学性质;用大孔树脂固定酶,在无溶剂体系中催化橄榄油制备生物柴油,研究其转酯特性.结果筛选到一株高产脂肪酶的菌株WZ10-3,通过p-NPP法测得其初始酶活为78.68 U/mL,经16S rRNA鉴定属于伯克霍尔德氏菌(Burkholderia sp.),与B.stabilis同源性达到99%.该菌在发酵48 h时达到产酶高峰,所产脂肪酶的最适作用温度为50℃,最适作用pH为7.0,70℃下的半衰期可达1 h,pH为7-9时稳定性良好.以大孔树脂NKA-9和HPD600为载体制备的2种固定化脂肪酶,催化橄榄油生产生物柴油的转酯率均可达到97%.综合表明,菌株WZ10-3脂肪酶的初始水解酶活高于大多数野生脂肪酶,热稳定性好且转酯特性优良,有很好的后续研究价值.图7表3参25     

大肠杆菌乙酰酯酶(AES)的酶学性质

以乙酸香叶酯为底物,对大肠杆菌乙酰酯酶(Acetyl esterase,AES)的酶学性质进行解析,实现将乙酸香叶酯生物转化为香叶醇.结果显示:大肠杆菌AES酶的最佳反应p H范围为6.0-7.5;最适反应温度为30℃;最佳催化时间为2 h;Mg~(2+)、Mn~(2+)、Co~(2+)对酶活没有太大影响,而Cu~(2+)、Zn~(2+)明显抑制酶的活性.对AES的动力学研究可知,其米氏常数Km、最大反应常数Vm分别为2.88 mmol/L、1.87 mmol/L.该酶同样可水解乙酸松油酯、乙酸薄荷酯、乙酸香茅酯,分别产生松油醇、薄荷醇和香茅醇.本研究得出了大肠杆菌乙酰酯酶的最适反应条件,可为后期香叶醇的生物合成优化和产量提高以及其他萜醇类化合物的生物合成提供参考依据.     

碱性β-聚糖酶产生菌选育及产酶条件优化

从碱性土样中分离到数十株产碱性β聚糖酶类的细菌,经摇瓶反复筛选后,得到一株碱性β聚糖酶产量较高的耐碱性细菌．经初步鉴定,属短小芽孢杆菌（Ｂａｃｉｌｕｓｐｕｍｉｌｕｓ）．其纤维素酶作用的最适ｐＨ为７．６,最适θ为６０℃,木聚糖酶的作用最适ｐＨ为９．０,最适θ为５５℃．该菌的最适生长ｐＨ为８．０,最适产酶θ为２８～３２℃．木聚糖与山梨糖分别是木聚糖酶和纤维素酶的良好诱导物．以麸皮为碳源,产酶的最适浓度为５％．添加尿素和（ＮＨ４）２ＳＯ４为氮源可提高纤维素酶酶活２倍,木聚糖酶酶活１倍．发酵周期为６０ｈ,纤维素酶酶活最高可达１．２１ＩＵｍＬ－１,木聚糖酶酶活可达４３ＩＵｍＬ－１．     

秸秆污泥堆肥产纤维素酶细菌的筛选及产酶条件优化

从添加秸秆进行堆肥处理的污泥中采集样品,通过富集培养和刚果红平板染色法筛选分离出具有纤维素降解能力的细菌,再通过酶活力测定从中分离筛选出1株相对高活性的产纤维素酶细菌CI;通过基于16S rRNA基因序列的系统发育分析,初步确定该菌株为Devosia sp..利用单因素试验对目的菌株C1进行产纤维素酶发酵条件优化,结果表明菌株C1产纤维素酶的最佳发酵时间、培养温度、摇床转速以及最适初始pH值分别为60 h、30℃、130 r·min^-1和7.2～7.5,且在该条件下其滤纸酶（FPase）和羧甲基纤维素酶（CMCase）活力分别达23.10和54.97 U·mL^-1.     

一株能产生聚乙烯醇降解酶的委内瑞拉链霉菌

以聚乙烯醇(PVA)为唯一碳源,从土壤中筛选到1株能产生胞外PVA降解酶的放线菌GY1.根据扩增出的该菌株的16SrDNA全序列在GenBank中的比较结果,结合生理生化实验、细胞化学成分及菌落形态分析,确定该菌为委内瑞拉链霉菌(Stretopmycesvenezuelae).GY1菌株以PVA为唯一碳源时,产生的PVA降解酶活性达到120UL-1,是以葡萄糖或可溶性淀粉为唯一碳源时的10倍.当在PVA培养基中添加1gL-1至3gL-1的葡萄糖时,该菌株细胞量和PVA降解酶总酶活随着葡萄糖添加量的增加而增加,最大细胞量是未添加葡萄糖时的2.4倍,最高总酶活是未添加葡萄糖时的2.6倍,而单位质量细胞产生PVA降解酶的能力提高不大.但当添加的葡萄糖浓度从3gL-1增至10gL-1时,总酶活随着细胞量的增加出现下降趋势,同时单位质量细胞产生PVA降解酶的能力也大大降低.在相同PVA聚合度下,高醇解度PVA比低醇解度PVA更有利于GY1菌株的生长及产生PVA降解酶.图5表1参16     

Alkaline phosphatase activity in subtropical Central North Pacific waters using a sensitive fluorometric method

This paper describes a fluorometric method for assaying low levels of the enzyme alkaline phosphatase in seawater. The assay is based on the hydrolysis of the monophosphate ester bond of 3-0-methylfluorescein phosphate. This enzyme is synthesized by many microorganisms when phosphate becomes limiting. Alkaline phosphatase activity was detected in phytoplankton from the nutrient-impoverished surface waters of the subtropical Central North Pacific Ocean. The presence of naturally occurring phosphatase suggests that phosphorus may be limiting to phytoplankton growth in these waters. The phytoplankton in water samples lacking enzyme activity at the time of collection produced phosphatase within 1 to 2 days of incubation at in situ temperatures.     

Catalytic urea hydrolysis by composite metal oxide catalyst towards efficient urea-based SCR process: performance evaluation and mechanism investigation

● Bimetallic oxide composite catalyst was designed for the urea-based SCR process. ● Surface chemical state and typical microstructure of catalyst was determined. ● Reaction route was improved based on intermediates and active site identification. ● TiO₂@Al₂O₃ presents an obvious promotion for urea hydrolysis. As a promising option to provide gaseous NH₃ for SCR system, catalytic urea hydrolysis has aroused great attention, and improving surface area and activity of catalysis are the crucial issues to be solved for efficient urea hydrolysis. Therefore, a composite metal oxide (TiO₂@Al₂O₃) catalyst was prepared by a simple hydrothermal method, with mesoporous alumina (γ-Al₂O₃) as substrate. The results verify the mesoporous structure and submicron cluster of TiO₂@Al₂O₃, with exposed crystal faces of (101) and (400) for TiO₂ and γ-Al₂O₃, respectively. The electronegativity difference of Ti⁴⁺ and Al³⁺ changes the charge distribution scheme around the interface, which provides abundant acid/base sites to boost the urea hydrolysis. Consequently, for an optimal proportioning with nano TiO₂ content at 10 wt.%, the hydrolysis efficiency can reach up to 35.2 % at 100 °C in 2 h, increasing by ~7.1 % than that of the blank experiment. ¹³C NMR spectrum measurements provide the impossible intermediate species during urea hydrolysis. Theoretical calculations are performed to clarify the efficient H₂O decomposition at the interface of TiO₂@Al₂O₃. The result offers a favorable technology for energy-efficiency urea hydrolysis.     

应用流式细胞技术研究铜对藻细胞膜完整性及脂酶活性的影响

应用流式细胞技术(FCM)及PI/FDA染色方法,在不同Cu2浓度处理后,从细胞膜完整性、脂酶活性两方面同时研究了Cu2 处理对微囊藻细胞的急性毒性作用.检测结果表明,在不同浓度Cu2 处理M.aeruginousa1h时,PI荧光检测显示藻细胞膜的完整性几乎没有受到影响,而FDA荧光检测则表明藻细胞的脂酶活性在一定浓度受到刺激.在Cu2 处理24h时,随着Cu2 浓度的增高,PI和FDA荧光强度变化的概率均呈明显的浓度抑制型变化,说明在此时Cu2 作用下FDA荧光的下降,不仅与细胞内脂酶活性受到抑制有关,而且也是高浓度Cu2 作用下细胞膜受损而导致细胞内含物外流的结果.图3参16     

一株菲降解菌的分离鉴定及其降解条件研究

以菲为研究对象,从克拉玛依稠油污染土壤中筛选到1株对菲具有较好降解效果的菌株JZ3-21。通过形态观察、生理生化指标及16S rDNA序列分析对该菌株进行了鉴定。该株菌的16S rDNA序列与Pseudomonas属的相似性达99%,结合分离菌株的形态、生理生化特征和16S rDNA基因序列的分析结果,初步鉴定该菌株为恶臭假单胞菌（Pseudomonas putida.）。对其降解条件进行了研究,结果表明：在40℃,pH 8.0,接种量为1.5%的条件下,菌株对初始质量浓度为100 mg.L-1的菲在64 h内的降解率高达94.2%。该菌对高质量浓度菲有较好的耐受性,其最高耐受质量浓度可达2 000 mg.L-1。     

不对称还原丙酮酸乙酯菌株的筛选及鉴定

以丙酮酸乙酯为底物,从成都某化工厂污水池及其附近土壤中分离到36株可将丙酮酸乙酯不对称还原成(S)-乳酸乙酯的菌株.经过多次复筛,最终获得了一株具有较高催化活性的酵母菌BTY18-6.在以该菌株静息细胞为催化剂,催化不对称还原丙酮酸乙酯合成(S)-乳酸乙酯的反应中,底物浓度为60 mmol/L时,底物转化率为86.9%,产物(S)-乳酸乙酯的ee值为88.7%.通过对其形态学、生理生化特征及其26S rDNA Dl/D2区域的分析表明,BTY18-6为胶红酵母.     

Isolation,identification, and the degradation characteristics of a thiobencarb-degrading bacterium Bacillus sp. T2北大核心CSCD

Thiobencarb, a thiocarbamate herbicide, is widely used to control weeds in rice paddies. Screening for highly efficient thiobencarb-degrading bacteria is important for the bioremediation of thiobencarb-contaminated environments. The aim of this study was to isolate and identify highly efficient thiobencarb-degrading bacteria and to identify the degradation pathway and the degrading properties. The thiobencarb-degrading strain was isolated using methods of microbiological acclimation and enrichment and was then identified using a 16S rRNA phylogenetic analysis. The degrading properties of the isolated bacterium were determined by single-factor experiments, and the degradation products were identified using gas chromatography-mass spectrometry (GC-MS). A thiobencarb-degrading strain T2, which can utilize thiobencarb as the sole source of carbon for energy and growth, was isolated from paddy soil. Strain T2 degraded more than 98.3% of 0.4 mmol/L of thiobencarb within 36 h. It was preliminarily identified as Bacillus sp. T2 according to the 16S rRNA gene analysis and from its morphological, physiological, and biochemical characteristics. The metabolic products of the thiobencarb degradation for strain T2 were identified as 4-chlorobenzyl mercaptan, 4-chlorobenzaldehyde, and 4-chlorobenzoic acid by the GC-MS. Based on metabolite identification, it was speculated that thiobencarb degradation in strain T2 was initiated by the hydrolysis of the thioester bond to produce 4-chlorobenzyl mercaptan, which was further oxidized to 4-chlorobenzaldehyde and 4-chlorobenzoic acid. The thiobencarb degradation that was initiated by the hydrolysis of the thioester bond by strain T2 is a new metabolic pathway, which provides valuable research material and reliable experimental data for revealing the metabolic process and mechanism of thiobencarb microbial degradation in soil. The strain Bacillus sp. T2 has a very high degradation efficiency, suggesting it is a good prospect for microbial remediation in thiobencarb-polluted environments. © 2018 Science Press. All rights reserved.     

Tertiary-butyl acetate metabolism,toxicity, and human health considerations

Tertiary-butyl acetate (TBAC) (CAS No. 540-88-5) is an organic solvent with a potential for occupational and environmental exposure as a result of its use in industrial coatings, adhesives, inks, and degreasers. The objective of these studies was to extend the toxicological database upon which health hazard and risk assessments of TBAC can be made. The metabolism of TBAC was studied in rats exposed by inhalation for 6?h to concentrations of 100 or 1000?ppm. There was an evidence of partial saturation of TBAC absorption and metabolism at some concentration below 1000?ppm. Approximately 5% of the low dose and 26% of the high dose was expired without change within 12?h, while the retained material was rapidly metabolised and excreted, mostly in the urine, within 24?h. Very little radioactivity remained in the tissues after day 7. The metabolism of TBAC appears to follow two major routes: hydroxylation of the tertiary-butyl moiety to form 2-hydroxymethylisopropyl acetate and ester hydrolysis to form tertiary-butyl alcohol (TBA). A minor route involves oxidation of the acetate moiety. Based on the proportion of metabolites that can clearly be assigned to one or the other major pathway, hydroxylation of the tertiary-butyl moiety prevails at 100?ppm, while hydrolysis of the ester bond predominates at 1000?ppm.

Based on nose-only inhalation exposure of rats to TBAC for 6?h, the LC50 for males and females combined is approximately 4200?ppm. Clinical signs included exaggerated breathing, staggering, tremors, and lethargy approximately 1?h after the exposure, but all surviving rats appeared normal from 24?h until the end of the 14?day observation period. An LC₅₀ was not identified for mice. After exposure of whole body for 6?h to 3000?ppm, the highest concentration tested, all mice were prostrate for most of the exposure time, but there were no deaths.

Groups of five male and five female Sprague-Dawley rats were exposed nose-only to 0, 100, 400, or 1600?ppm TBAC 6?h?day^?1 5 days?wk^?1 for 2?weeks. There were no effects on body weight, feed or water consumption, or necropsy findings. Male rats exposed to 1600?ppm had increased liver weights and hypertrophy of centrilobular hepatocytes. An increased proportion of cortical tubule cells with hyaline droplet accumulation was observed in all treated groups of males. Groups of five male and five female CD-1 mice were exposed whole body to 0, 190, 375, 750, or 1500?ppm TBAC 6?h?day^?1 for 14 consecutive days. There were no effects on body weight, feed consumption, or necropsy findings. Liver weights were increased in female mice at 750 and 1500?ppm. Minimal hypertrophy of centrilobular hepatocytes was found in female mice at 375, 750, and 1500?ppm and in male mice at 1500?ppm TBAC.

TBAC did not induce gene mutations in bacterial tests with strains of S. typhimurium and E. coli. Further, there was no evidence of clastogenic activity from tests either for the induction of chromosomal aberrations in human lymphocytes in vitro in the presence or absence of S9 mix or for the induction of micronuclei in bone marrow cells of rats exposed by inhalation for 6?h to 1600?ppm TBAC.

These results are relevant to human health risk assessment and are discussed in the context of previous studies. The weight of the scientific evidence supports the conclusion that TBAC has lower acute toxicity than previously suggested, that it is rapidly excreted when inhaled, and that neither TBAC nor its TBA metabolite are genotoxic or potential human carcinogens.     

油松毛虫感染白僵菌后体内蛋白质、酯酶和多酚氧化酶的变化

采用分光光度法测定了油松毛虫(Dendrolimus tabulaeformisTsai et Liu)3~5龄幼虫被病原物白僵菌(Beau-veria bassiana)感染后,其体内蛋白质的含量和多酚氧化酶活性的变化;结果表明,被白僵菌感染后1~8d,虫体内蛋白质含量持续下降,而未感染的则变化不大;多酚氧化酶(PPO)的活性呈现出先升高后下降的趋势.利用聚丙烯酰胺凝胶电泳技术,分析了染菌后1~7d幼虫体内酯酶同工酶的变化;结果显示,染菌后的3、4龄幼虫体内酯酶同工酶酶谱与对照相比,酶带数量变化较大,未染菌的为3条酶带,感染病菌后变为1条和2条.与其相比,5龄幼虫染菌后酯酶同工酶的酶带数量没有变化,只是酯酶的活性及含量比对照有明显减弱趋势.图2表5参16