海洋弧菌几丁质酶的产酶条件及分离纯化研究

将产几丁质酶的海洋弧菌CY01菌株进行发酵培养，对产酶的培养条件等进行了优化。发酵液经硫酸铵分级盐析，几丁质亲和层析，Sephadex G-100、Sephacryl S-200凝胶分离纯化，分离出三种几丁质酶Chi1，Chi2，Chi3，采用SDS－PAGE测得三种酶的分子量分别为27kD，39kD和46kD。     

产脂肪酶海洋嗜冷菌的鉴定及酶学性质研究

从东海的深海底泥中筛选出一株产脂肪酶的海洋细菌 EastSeaG5-1415,该菌为革兰氏阴性好氧菌,短杆状,0.9～1.3μm×1.5～3.8μm,无鞭毛,无芽孢,无色素,菌落光滑不透明,过氧化氢酶和氧化酶阳性,甲基红实验阴性,氧化葡萄糖产酸,可耐受10%的NaCl.此菌最适生长温度为18℃,最高生长温度为35℃,在0℃也能生长,是典型的嗜冷菌.菌株脂肪酸种类为C17:1(28.2%),C18:1 9c(49.7%),辅酶Q-8是其主要的异戊烯醌类,DNA中G C含量为45.2mol%.以16SrRNA同源性为基础构建了相关种属细菌在内的系统发育树,在系统发育树中,分离菌株 EastSeaG5-1415 与 Psychrobacter glacincola 在同一分支,二者的序列相似性为97.6%,DNA 杂交显示与 P.glacincola 最为相近,达到87%.结合形态和生理生化试验,将其鉴定为嗜冷杆菌 P.glacincola.同时对其所产脂肪酶的性质进行了初步研究.该菌所产碱性脂肪酶最适反应温度为35℃,在5℃时仍有较高酶活,酶活达到23%,最适 pH 值为9,属低温碱性脂肪酶.     

高活性几丁质酶产生菌的筛选及鉴定

从四川、陕西、浙江等地食用菌栽培的土壤样品中,筛选到一株性能优良、产几丁质酶活力较强的菌株BLC08609,并结合菌落形态、生理生化指标和16S rDNA序列分析对其进行鉴定.结果显示,菌株BLC08609能以食用菌细胞壁(以几丁质为主)为唯一碳源生长,在菌株BLC08609个体形态和生理生化特性鉴定的基础上,通过16S rDNA测序鉴定,确定BLC08609为地衣芽孢杆菌(Bacillus licheniformis).     

低温纤维素酶产生菌的筛选、鉴定、生长特性及酶学性质

从北极楚科奇海分离出一株产纤维素酶的耐冷假交替单胞菌BSw20308。研究表明：该菌最适生长温度10℃,35℃不生长;在pH7．0～8．0、含2．0％～3．0％NaCl的培养基条件下最适宜菌株生长与产酶;可溶性淀粉、酵母浸出液是有利于菌株生长及产酶的碳源、氮源物质;蔗糖、可溶性淀粉、麦芽糖及麸皮对CMCase的合成具有明显诱导作用;CMC、麸皮、可溶性淀粉及麦芽糖对滤纸酶的合成有一定诱导作用,单糖与部分双糖(蔗糖、纤维二糖及乳糖)则起阻遏作用;在指数生长后期至稳定早期,大量产CMCase;发酵液含CMCase、滤纸酶及葡萄糖苷酶活性,以CMCase活力最高;胞外CMCase活力占总CMCase活力的74．1％左右;酶最适作用温度35℃,5℃时酶活保留50％左右;酶对热敏感,35℃半衰期为3h,25℃下酶活稳定;酶最适pH8．0。     

Analysis of deep excavations in clay under the undrained and plane strain condition with small strain characteristics

The nonlinearity and small strain characteristics of clay are predominant factors to affect the analysis accuracy of surface settlement induced by deep excavation in soft clay. In this study, we use a newly developed constitutive model, namely the undrained soft clay model, to simulate the nonlinearity of soft clay and to describe the degradation of elastic Young's modulus with the increasing stress level, ranging from small strain to near failure. The parameters of the formula can be obtained from conventional soil tests. One well-documented case history is then used to show the parameter determination procedure and validate the proposed model. The states of strain and stress paths for the soil in the excavation are also studied to validate the rationality of the model. Besides, two additional case studies are conducted to verify the model further.