Purification,characterization, and gene cloning of a new cold-adapted β-galactosidase from Erwinia sp. E602 isolated in northeast China

β-Galactosidases are widely used in industry for elimination of lactose from milk products. A new β-galactosidase was obtained from bacterial strain Erwinia sp. E602, newly isolated in northeast China. The enzyme was purified with the methods of ammonium sulfate fractionation, ion exchange, and gel filtration chromatography for further study of the enzymatic characteristics. The purified enzyme had a molecular weight of near 110 kDa. The optimum reaction temperature and pH of this enzyme was determined to be 40°C and 7.0, respectively, indicating that this enzyme was a mesophilic neutral β-galactosidase. Furthermore, the enzyme retained near 10% of the activity at 0°C, which also suggested its cold-adapted property. Kinetics of the β-galactosidase was studied, and the K_m (Michaelis constant) and V_max (maximum enzymatic reaction rate) of this enzyme were 0.21 mmol/L and 263.16 µmol/mg per minute, respectively. The effects of metal ions on the enzymatic activity and the lactose hydrolysis efficiency in milk, as well as its trans-glycosylation activity, were studied in this work. The β-galactosidase coding gene was cloned to be a 3-kb length fragment, which shared at most 81% of identity with the published sequences in NCBI Blast database (https://blast.ncbi.nlm.nih.gov). Results in this work suggested it is a new β-galactosidase and it has potential to be used in dairy and food processing.     

苦瓜果实中多糖的分离纯化及性质分析

以苦瓜果实为材料,经热水抽提、乙醇沉淀和Sevag 法去蛋白后获得了苦瓜果实粗多糖(MCP)。MCP 经DEAE- 纤维素柱离子交换柱层析分离得到4 个级分MCP-A、MCP-B、MCP-C 和MCP-D。MCP-A 经Superdex G-100 柱进一步纯化得到苦瓜果实多糖MCP-A1 组分。MCP-A1 经高效凝胶渗透色谱法(HPGPC)鉴定为均一组分,测定其平均分子量为93577D。经过对其理化性质鉴定表明,MCP-A1 不含蛋白质、核酸,含有糖醛酸,为非淀粉类多糖。红外光谱扫描结果表明,其具有典型的多糖吸收峰。     

五粮液酒醅中乳酸菌的分离鉴定

利用MRS培养基从五粮液酒厂窖池发酵酒醅中分离到1株产乳酸细菌,经鉴定为嗜酸乳杆菌,并对该乳酸菌的生理生化特性及产酸性能进行研究.结果表明,最高产酸量为1507 mg/100 mL,最适产酸温度为35℃,最适产酸pH值为6.0,最适产酸底物浓度(葡萄糖)为4％.     

传统发酵饮料博扎中酵母菌的分离和鉴定

实验从新疆伊宁市采集的3个博扎样品中分离纯化,得到了12株酵母菌,并对其进行属的鉴定：包括形态学和生化鉴定。依据《酵母菌的特征与鉴定手册》和《The yeast: a taxonomic study》将其归入3个属,其中隐球酵母属（Cryptococcus）5株、酿酒酵母属（Scerevisiae）3株、假丝酵母属（Candida）4株。     

一种新型产纤维素酶菌种的分离鉴定

从江西生产豆渣菌的作坊采样,检测到一株分解纤维素的真菌(MC1),分离纯化后,再利用以纤维素为唯一碳源的选择性培养基培养,根据形态特征可鉴定为面包串珠霉(MoniliasitophilaMont.)。摇床发酵产酶实验表明,在30℃、160r/min的条件下摇瓶培养6d后,其所产纤维素酶系中的以羧甲基纤维素钠为底物的CMC酶活为4119U/mL,以微晶纤维素为底物的C1酶活为6833U/mL,以水杨素为底物的βG酶活为451U/mL。     

四川冬菜中苯乳酸高产菌株的分离与鉴定

通过双层平板拮抗法和牛津杯琼脂扩散法抑菌试验,从传统发酵食品四川冬菜中分离筛选得到18株乳酸菌。结合反相高效液相色谱法得到1株苯乳酸高产菌株DL-13,其发酵上清液中苯乳酸含量为143mg/L。结合菌落形态、细胞形态、生理生化特性,最终确定菌株DL-13为植物乳杆菌。     

昆明酸浆米粉优势乳酸菌筛选及发酵性能研究

从昆明酸浆米粉中首次筛选适合于米粉发酵的优势乳酸菌菌株,研究不同培养温度对优势菌分离纯化效果的影响,探讨发酵性能。采用高通量筛选技术及应用产酸能力、发酵活力与酸浆米粉的感官评价程序,筛选发酵优势菌株,并利用微量生化反应对优势菌进行分类鉴定。结果表明:在37℃分离培养条件下乳酸杆菌较占优势,获得发酵性能优良的乳酸杆菌R1、R9、R11菌株。鉴定菌种结果:R1菌株为大双歧杆菌(Bifidobacterium magnum)、R9菌株为鼠李糖乳杆菌(Lactobacillus rhamnosus)、R11菌株为米酒乳杆菌米酒亚种(Lactobacillus sakei ss sakei)。其中R9菌株产酸能力最强,发酵活力最高,使酸浆米粉韧性高;R1菌株使酸浆米粉的米香风味最佳;R11菌株使酸浆米粉口感爽滑。可利用此3株发酵性能优良的乳酸杆菌人工制备酸浆米粉复合发酵剂,进一步开发研制优良品质的酸浆米粉。     

红茶菌中微生物的分离与鉴定

对某红茶菌中的微生物菌种进行分离,共得到70个菌株,其中酵母菌15株,醋酸菌30株,乳酸菌25株,经过初步鉴定得到6个菌种。分别为酿酒酵母Saccharomyces cerevisiae、粟酒裂殖酵母Schizosaccharomyces pombe、醋化醋杆菌木质亚种Acetobacterxylinum、液化醋杆菌A.liquefaciens、甲醇醋杆菌Acidomonas mnethanolica、乳杆菌Lactobacillus sp。     

茶枝柑皮多糖的分离纯化及单糖组成分析

采用酸水法从茶枝柑皮中提取多糖,经D-201阴离子交换树脂脱色、Sevag法脱蛋白,透析、冻干后得茶枝柑皮多糖,再用DEAE-Sepharose Fast Flow离子交换柱层析及Sephadex G-100凝胶柱层析分离得到组分CPA-Ⅰ。单糖经1-苯基-3-甲基-5-吡唑啉酮(PMP)衍生化后采用高效液相色谱法对多糖组成进行研究,凝胶分子排阻色谱法鉴定其纯度并测定其相对分子质量,紫外、红外光谱法对结构进行初步分析。结果表明：茶枝柑皮多糖CPA-Ⅰ不含蛋白,重均相对分子质量为7.96×104,主要由半乳糖醛酸和阿拉伯糖组成,是羧酸酯化的半乳糖醛酸多聚糖。     

青岛大剧院钢屋盖结构的稳定性和抗震性能分析

青岛大剧院屋盖钢结构采用非等高双向正交桁架体系,跨度85 m,最大悬挑长度达16 m.采用有限元非线性分析理论对该大跨空间钢桁架屋盖结构的整体稳定性进行了全过程跟踪分析,分别讨论了该大跨结构在有无初始安装偏差影响下的稳定性态;并对钢桁架屋盖结构进行了动力分析,研究了结构的自振特性,采用振型分解反应谱法对结构进行了抗震分析,给出了结构地震内力系数的分布规律,为结构设计提供了详细可靠的数据,为此类大空间结构提供了有价值的参考资料.