产过氧化氢酶菌株培养条件的优化

通过对溶壁微球菌培养基优化,确定最佳发酵培养基,并对发酵工艺条件进行了初步的优化.最适碳源是麦芽糖,最适氮源是蛋白胨和酵母膏,最近无机盐是MnSO4;该菌株产酶的最佳培养基配方为:60 g麦芽糖,13 g蛋白胨,8 g酵母膏,1 g MnSO4,5 g NaCl,2 g NaH2 PO4·2H2O,2 g K2HPO4·3H2O,0.5 g MgSO4·7H2O,0.5 g CaCl2,1 000 mL水.从该菌株发酵过程曲线发现,该菌株大量产酶期在12-14 h.摇瓶发酵最适初始pH值为7.0,250 mL三角瓶装液量为25mL,接种体积分数为5%,培养温度为37℃.     

鱼源藤黄微球菌三重PCR检测法的建立及耐药性分析

为鉴定感染黄颡鱼菌株fsznc-CL、建立一种快速检测的方法和探讨其耐药特性。采用形态学、理化特性及16S rDNA序列分析方法进行菌株鉴定,人工回归感染研究其致病性。通过对三对特异性引物的反应体系和条件进行优化,建立一种三重PCR检测法并应用到人工感染黄颡鱼的检测中。运用PCR方法扩增耐药基因,用琼脂纸片扩散法检测该菌的药敏特性。结果表明,分离菌株fsznc-CL为藤黄微球菌(Micrococcus luteus),该菌对黄颡鱼具有一定的致病性。三重PCR检测法可准确扩增出藤黄微球菌CBS、Sig和Pol三对目的基因,而其他菌株未扩增出,检测该菌的最低模板浓度为5.822×10^-3 ng/μL,该方法检测带菌样品的阳性率约为83.33%。该菌携带了TEM、aph(3')-Ⅱa、aac(6')-Ⅰ、Sul1和Sul2耐药基因。菌株fsznc-CL对诺氟沙星、苯唑西林、红霉素和呋喃唑酮耐药。本试验建立的三重PCR检测法具有较高的特异性和灵敏度,目前藤黄微球菌对少部分抗生素耐药。     

Bacterial biodegradation of phenol and 2,4‐dichlorophenol

Nine bacterial strains capable of utilising phenol and 2,4‐dichlorophenol (DCP) have been isolated from a mixed culture grown on substrates containing these compounds. One of these strains, a Micrococcus sp, was further investigated under aerobic conditions using phenol and DCP as sole carbon and energy sources at various pH values. Phenol degradation was enhanced under alkaline conditions, and up to 500 mg dm^?3 phenol was mineralised within 50 h at pH 10. DCP was more recalcitrant; however up to 883 mg g^?1 and 230 mg g^?1 were degraded within 10 days, when using initial DCP concentrations of 100 and 200 mg dm^?3, respectively. Biomass measurements showed cell growth, proving that both phenol and DCP are used as growth substrates for this isolate. Copyright © 2003 Society of Chemical Industry     

细菌对碳钢腐蚀的电化学研究

采用开路电位测量、极化曲线和电化学交流阻抗法（EIS）研究了小球菌对45＃碳钢的腐蚀行为。结果表明：（1）小球菌存在时试样表面上所形成的疏松、不均匀的生物膜加速了碳钢的腐蚀过程；（2）有菌存在时暴露2d、4d的Rpo值和Cc值非常接近，表明细菌的生长代谢过程已趋于稳定，两种暴露条件下所形成的生物膜趋向于成熟一致；（3）分别提出了不同暴露条件下EIS的等效电路，并计算了相应的等效元件参数；（4）小球菌影响下腐蚀反应的阻抗行为存在弥散效应。     

Effects of combined exposure of Micrococcus luteus to nisin and pulsed electric fields

Death and injury following exposure of Micrococcus luteus to nisin and pulsed electric field (PEF) treatment were investigated in phosphate buffer (pH 6.8, σ=4.8 ms/cm at 20°C). Four types of experiment were carried out, a single treatment with nisin (100 IU/ml at 20°C for 2 h), a single PEF treatment, a PEF treatment followed by incubation with nisin (as before) and addition of nisin to the bacterial suspension prior to the PEF treatment. The application of nisin clearly enhanced the lethal effect of PEF treatment. The bactericidal effect of nisin reduced viable counts by 1.4 log₁₀ units. Treatment with PEF (50 pulses at 33 kV/cm) resulted in a reduction of 2.4 log₁₀ units. PEF treatment followed by nisin caused a reduction of 5.2 log₁₀ units in comparison with a 4.9 log₁₀ units reduction obtained with nisin followed by PEF. Injury of surviving cells was investigated using media with different concentrations of salt. Sublethally damaged cells of M. luteus could not be detected by this means, following PEF treatment.     

经辐照杀菌的无菌袋中耐辐照微生物分离与鉴定

对某番茄酱生产企业提供的辐照杀菌（辐照剂量≥15 kGy）的5 L无菌袋进行菌落计数、分离和鉴定。3 L无菌水反复漂洗,滤膜过滤后进行平板菌落计数,分离纯化后采用16S rDNA和dnaJ序列分析分别鉴定到属和种。结果表明,5 批次的样品中均有细菌检出,数量在5～132 CFU/袋,9 个典型菌落经过16S rDNA序列分析后,分别属6 个属,其中栖水菌属（Enhydrobacter）、不动杆菌属（Acinetobacter）和考克斯菌属（Kocuria）各1 株,微球菌属（Micrococcus）、微杆菌属（Microbacterium）和芽孢杆菌属（Bacillus）各2 株;dnaJ序列分析则将一株葡萄球菌C8-3鉴定到种-表皮葡萄球菌（Staphylococcus epidermidis）。辐照杀菌的无菌袋虽然微生物数量不高,但是依然残留了一些耐辐照的细菌,它们或多或少会给内装食品带来一定的食品安全隐患或影响食品保质期。     

柠檬香蜂草精油的气相色谱-质谱联用分析及抑菌活性研究

该文采用水蒸气蒸馏萃取法(steam distillation,SD)对柠檬香蜂草提取精油,气相色谱-质谱联用(gas chromatograph-mass spectrometry,GC-MS)分析精油成分,制备成不同体积分数稀释液,通过纸片扩散法(kirby-bauer,K-B)测定柠檬香蜂草精油对3种食源性致病菌...     

Novel extracellular hyper acidophil and thermostable α‐amylase from Micrococcus sp.NS 211

Among several bacteria examined in this study, a hyper acidophil and thermostable Micrococcus sp.NS 211 designated as M.Amy NS 211 was selected for production of amylase using starch agar plates with following incubation at 85°C. Identification by 16SrRNA on selected bacterium disclosed the highest similarity for protean regions of this gene, 27 F and 1492R as Micrococcus sp.NS 211. Although activity of M.Amy NS 211 was established at temperatures between 70 and 110°C and pH ranges 1.2–8.0, the optimum temperature and pH was achieved at 85°C and 3.5 in sodium citrate buffer system respectively. Two‐step chromatography was performed using (CM Bio‐Gel A) and (Bio‐Gel A‐150) columns to purify 84 kDa hyper acidophil and thermostable α‐amylase. SDS‐PAGE analysis showed molecular mass and amylolytic activity as single band. Enhancement of enzyme activity was obtained in presence of 5 mM MnCl₂ (298%), CaCl₂ (347%), FeCl₂ (211%), MgCl₂ (253%), ZnCl₂ (146%), NiCl (142%), NaCl (141%), Na‐sulfate (153%) while inhibition was observed with (5 mM) EDTA, PMSF (3 mM), urea (8 M), and SDS (1%) at 143, 134, 43, and 119%, respectively. M.Amy NS 211 can be applied in laundry detergents, textile, and modern relevant industrial processes at extreme temperatures and under acidic conditions.     

Volatile compounds in cheeses made with Micrococcus sp. INIA 528 milk culture or high enzymatic activity curd

Volatile compounds were investigated in a semihard cheese made with lactic culture, lactic culture + Micrococcus sp. INIA 528 culture, and two levels of high enzymatic activity (HEA) curd made with this strain. The levels of acetaldehyde, 2‐methyl propanal, 3‐methyl butanal, ethanol, 2‐methyl propanol and 3‐methyl butanol were higher, and those of diacetyl and acetoin lower, in cheese made from milk with added Micrococcus culture. Free fatty acids and ethyl, propyl and isobutyl esters were at higher levels in cheeses with added HEA curd. Total esters increased up to 37‐fold in cheeses with added HEA curd.