Cd胁迫下城郊农业土壤微生物活性对生物炭输入的响应

为了探究Cd胁迫下生物炭输入对城郊农业土壤微生物活性的影响,通过室内培养试验,分析CK处理(风干土壤)、Cd处理(风干土壤+外源Cd)、CdBC处理〔风干土壤+外源Cd+2%生物炭,即生物炭与土壤(以湿质量计)质量比为2%〕、BC处理(风干土壤+2%生物炭)对土壤呼吸、土壤微生物数量及土壤酶活性的影响. 结果表明:整个培养期(0~60 d)内,各处理下土壤CO₂累积释放量表现为CK处理＜Cd处理＜CdBC处理＜BC处理. 与CK处理相比,CdBC处理下生物炭输入能显著增加土壤CO₂累积释放量(P＜0.05),增幅为43.6%,并且土壤中细菌、放线菌、真菌数量也有显著增加(P＜0.05),增幅分别达到12.7%、62.7%、18.7%. Cd胁迫对土壤酶活性的抑制表现为蔗糖酶＜脲酶＜中性磷酸酶,抑制率分别为3.5%、6.8%、18.0%. 生物炭输入可使受Cd胁迫的土壤脲酶、蔗糖酶的活性有所增强,增幅分别为15.0%、18.4%. 可见,生物炭输入可在不同程度上缓解Cd胁迫对蔗糖酶、脲酶活性及土壤微生物数量的影响.      

一种嗜热细菌来源角质酶的分离纯化及酶学性质

通过跟踪发酵液中pNPB水解酶活性,对角质诱导的Thermobifida fusca 口发酵液进行分离纯化.采用活性炭脱色、硫铵沉淀、Phenyl HP疏水色谱、DEAE sephamse阴离子交换色谱等方法,分离纯化得到电泳纯PNPB水解酶.该酶水解角质可得到角质单体,是一种角质酶.SDS-PAGE电泳结果显示,角质酶表观分子量约为29×10~3.该酶的最适温度为60℃.在40℃和60℃下均具有良好的热稳定性.最适pH为8.0,pH稳定范围为6.0～9.0.该角质酶的生化性质适合在纺织工业中应用.图8表2参17     

正交实验选择纤维素酶产生菌的最优综合培养条件

在复合碳源、30℃恒温培养条件下,用正交实验法对影响纤维素酶产生菌降解纤维素的5种单因素培养条件进行了优化,并将优化得到的条件应用于厌氧-好氧废水处理系统.结果表明,MgSO4用量等单因素对纤维素酶活性以及纤维素降解率有不同程度的促进作用;正交实验得到厌氧菌和好氧菌的最佳培养条件不完全一致;在废水处理系统中,5种单因素的最佳综合水平为:30mg/L MgSO4,20mg/L CoCl2,CNP配比为400:5:1,氮源为NH4Cl (28.7mg/L), pH=7.0,此时厌氧菌及好氧菌酶活性分别为4801U/L和4794U/L,酶稳定性分别达到91.0%和95.5%,纤维素降解率为31.9%和28.4% .     

河流湿地土壤芘的降解和生物有效性模型与酶活性动态变化(Model of Pyrene Degradation and Bioavailability and Dynamic Changes of Enzymatic Activities in the Riverine Wetland Soil)

在淹水和非淹水条件下,在河流湿地土壤中加入高浓度(10mg·kg-1)和极高浓度(200mg·kg-1)芘,研究了芘降解过程、芘生物有效性和土壤酶活性的长期动态变化.结果表明,培养91d后,高浓度芘处理的土壤中芘的残留率在淹水和非淹水条件下分别为79.0%和51.4%,而极高浓度处理的芘残留率在淹水和非淹水条件下分别为61.1%和33.9%.利用Tenax-ta树脂提取快速解吸态生物有效芘,结果发现,有效芘浓度在高浓度芘处理的两种土壤中的值比较接近,分别为1.01mg·kg-1和1.23mg·kg-1;而有效芘浓度在极高浓度处理的两种土壤的相应值差别较大,分别为20.31mg·kg-1和9.44mg·kg-1.采用四参数Logistic模型能够精确地拟合芘降解过程和生物有效性变化过程(p<0.0001).土壤蔗糖酶、脲酶和多酚氧化酶对芘污染敏感,而过氧化氢酶对芘污染不敏感.实验结果揭示了河流湿地土壤芘在淹水条件下降解活跃阶段持续时间短和芘生物有效性高的特征以及土壤蔗糖酶、脲酶和多酚氧化酶活性可以作为评估芘污染影响的候选指标.     

Enzyme-Mediated Reactions of Oligosaccharides and Polysaccharides

Two types of enzymatic reactions are given here as examples of synthetic problems encountered in industry. In the first case, commercially available -D-galactosidase from Escherichia coli was used as a catalyst to transfer galactose from -lactose to oligosaccharides. A preference for galactosyl transfer to the 3- or 4-position of the sugar moiety of the oligosaccharide was observed for the products. As expected, only the -anomer was produced. A wide variety of sugars, including disaccharides, trisaccharides, cellotetraose, and maltodextrins, has been shown to act as acceptors, yielding oligosaccharides. In the second example, -galactomannan that had been previously treated to contain cationic groups (cationic guar gum) was subjected to treatment with a series of inexpensive commercial enzymes such as lipases, protease, and cellulases. Some enzyme preparations showed significant changes in the viscosities of 1% cationic guar solution. For example, lipases from Aspergillus niger and Aspergillus saitoi and protease XIII from Rhizopus niveus produced a substantial viscosity reduction (0–20% of original viscosity). These examples demonstrate the utility of low-cost enzymes in manipulating polymer structures.     

Enzymatic treatment of estrogens and estrogen glucuronide

Natural and synthetic estrogens from sewage treatment systems are suspected to influence the reproductive health of the animals in the rivers.In this article we investigated the enzymatic treatment of three estrogens (estrone,17β-estradiol,and 17α-ethynyletstradiol) by a fungal laccase which oxidize phenolic compounds with dissolved oxygen.The elimination of the estrogenic activities by enzymatic oxidation was demonstrated by medaka vitellogenin assay.In addition,we developed an enzymatic treatment system comprised of β-D-glucuronidase and the laccase for 17β-estradiol 3-(β-D-glucuronide) degradation.The two enzymes eliminated 17β-estradiol 3-(β-D-glucuronide) and the intermediate,17β-estradiol,efficiently.     

废水处理系统中胞外水解酶的作用特性研究

从pH、温度、底物浓度和抑制剂等四方面的作用条件,对厌氧-缺氧-好氧废水生物处理系统中β-葡萄糖苷酶、碱性磷酸酶、亮氨酸氨基肽酶和脂肪酶的作用特性进行研究。试验结果表明,4种酶在60℃有最高酶活;偏碱性条件（pH=8-9）有利于酶促反应的进行;酶活随底物浓度的增加而增大;抑制剂PMSF对各酶抑制效果不尽相同,对葡萄糖、蛋白质和磷酸水解酶的抑制率分别为72．7％、26．1％和26．8％,而对脂肪酶的抑制率高达85．2％;最适作用条件下的各待测酶的活性可达日常作用条件的1．5～8倍;酶的活性与COD、氨氮、总氮和总磷等生化因子有较好的相关性。由此得出控制相关作用条件可最大限度地发挥酶的作用性能,提高废水处理效率。     

Soil enzymatic activities and microbial community structure with di erent application rates of Cd and Pb

This study focused on the changes of soil microbial diversity and potential inhibitory effects of heavy metals on soil enzymatic activities at different application rates of Cd andor Pb. The soil used for experiments was collected from Beijing and classified as endoaquepts. Pots containing 500 g of the soil with different Cd andor Pb application rates were incubated for a period of 0, 2, 9, 12 weeks in a glasshouse and the soil samples were analyzed for individual enzymes, including catalase, alkaline phosphatase and dehydrogenase, and the changes of microbial community structure. Results showed that heavy metals slightly inhibited the enzymatic activities in all the samples spiked with heavy metals. The extent of inhibition increased significantly with increasing level of heavy metals, and varied with the incubation periods. The soil bacterial community structure, as determined by polymerase chain reaction-denaturing gradient gel electrophoresis techniques, was different in the contaminated samples as compared to the control. The highest community change was observed in the samples amended with high level of Cd. Positive correlations were observed among the three enzymatic activities, but negative correlations were found between the amounts of the heavy metals and the enzymatic activities.     

黄土丘陵区撂荒农田土壤酶活性及酶化学计量变化特征

明确土壤胞外酶活性及酶化学计量比在农田撂荒过程中的变化特征及驱动因素,对揭示土壤养分可利用性随植被恢复的变化规律和阐明生态系统养分循环机制有重要意义.本文以黄土丘陵区不同撂荒年限坡耕地（0、10、20和30 a）为研究对象,通过测定土壤酶活性及酶计量比、土壤理化性质、植物多样性和科组成,探讨农田撂荒后土壤微生物养分限制状况及酶活性和酶计量比的主控因子.结果表明,β-1,4-N-乙酰氨基葡萄糖苷酶（NAG）、亮氨酸氨基肽酶（LAP）和碱性磷酸酶（ALP）的活性均随撂荒年限增加而显著增加,而β-1,4-葡萄糖苷酶（BG）活性则相反.土壤BG：（NAG+LAP）和BG：ALP呈现出与土壤BG活性相同的随撂荒年限增加而减小的趋势;而（NAG+LAP）：ALP呈先升后降趋势,在撂荒20 a时达到最高值.酶化学计量的向量长度随撂荒年限增加而显著减小,表明撂荒过程中土壤微生物受碳（C）限制程度的减弱.撂荒前10 a酶化学计量的向量角度小于45°,后20 a大于45°,说明撂荒前期微生物受氮（N）限制,后期受磷（P）限制.冗余分析结果揭示土壤有机碳含量、总氮含量、C：N、C：P、pH以及植被多样性是调控酶活性和酶计量比变化的主要因子.分类变异分析表明,土壤和植物因素可解释不同撂荒年限下土壤酶活性及酶计量比差异的62.0%,植被特征与土壤理化特性之间的交互作用是土壤酶活性及酶计量比变化的主控因子,解释度为37.1%.综上所述,黄土丘陵区农田撂荒过程中应考虑外源P的投入以缓解生态系统中有效P的不足,研究结果可为理解脆弱生境恢复生态系统中微生物介导的生物地球化学循环机制以及指导土壤养分管理和生态可持续发展提供理论依据.     

生物炭负载氨氮对土壤碳排放、酶活性及微生物群落的影响

土壤氮输入形式显著影响土壤CO₂ 排放.生物炭负载氨氮作为一种新型氮输入形式,既降低了农田化学氮肥投入,又减少了环境治理成本,其对推动国家化肥零增长、农田面源污染防治和实现国家“碳达峰”、“碳中和”目标意义重大.通过室内培养试验,设置不施肥（CK）、单施化学氮肥（CF）、生物炭配施化学氮肥（BF）和生物炭负载氨氮（BN）这4种处理,研究了不同氮输入形式对土壤碳排放、酶活性及微生物群落的影响.结果表明,与CF相比,BF显著提高了累计碳排放量（66.24 %）,而BN未见显著性差异.值得注意的是,BN累计碳排放量较BF处理显著降低了35.28 %.与CF和BF相比,BN处理β-葡萄糖苷酶,过氧化物酶,多酚氧化酶活性显著提高了20.25 %和5.20 %,36.72 %和36.19 %,90.36 %和61.36 %.与CF相比,BF处理提高了微生物群落丰富度和群落多样性,BN处理降低了微生物群落丰富度.与BF相比,BN处理变形菌门相对丰度降低了11.16 %,放线菌门和拟杆菌门相对丰度分别提高了8.12 %和5.83 %.对微生物群落结构影响最大的土壤因子是木糖苷酶活性,绿弯菌门相对丰度与纤维二糖水解酶活性极显著相关;芽单胞菌门相对丰度与β-葡萄糖苷酶活性极显著相关;变形菌门相对丰度与累计碳排放量呈极显著相关.综上所述,生物炭负载氨氮较生物炭配施化学氮肥显著减少了累计碳排放量,其减排效果更优.研究结果将有利于国家“双碳战略”落地、生物天然气产业健康发展、国家绿色种养循环农业体系构建和国家化肥零增长战略实现.