Hygienic quality of commercial minced meat as indicated by aerobic micro-organisms and Coliform bacteria

 The hygienic quality of commercial beef and beef-pork minced meat was examined using aerobic micro-organisms and Coliform bacteria as indicator organisms. About 70% of the samples examined were of good quality and about 30% of tolerable quality. Aerobic micro-organisms can be recommended as an initial means of monitoring the hygienic quality of minced meat, being better for this purpose than Coliform bacteria. In about 7% of the samples the pH was more than 6.0 or below 5.3, and thus the meat was not suitable for consumption. Recommended amounts of micro-organisms for classification of commercially available minced meat as being of good, tolerable and bad hygienic quality are suggested as well as the associated pH values. Received: 25 October 1995/Revised version: 31 January 1996     

PCR-DGGE分析技术在环境科学研究中的应用

随着分子生物学和遗传工程技术的迅速发展,现代生物技术在环境科学研究中的应用越来越广泛.笔者较系统地综述了多聚酶链式反应结合变性梯度凝胶电泳（PCR-DGGE）分析技术的产生背景、基本原理和在环境科学中的应用现状,总结了该技术的优点和局限性,探讨其在环境科学中应用前景.     

传统豆腐微生物污染途径的研究

为了解豆腐制作全过程的微生物污染情况,在实验室模拟了市售豆腐制作工艺的各个加工工序和操作环节,通过对各个工序进行微生物检测,来描述各个工序对成品豆腐的污染情况。经研究发现,大豆经清洗后细菌总数比未清洗的大豆减少了70%,大肠菌群总数下降了75%。得出最佳的浸泡参数为:自来水清洗并浸泡,浸泡温度控制在12～15℃之间,浸泡时间为10h。检测并对比了豆浆煮浆前后的微生物变化情况,同时发现凝固剂中含有大量的微生物,这是造成豆浆二次污染的主要污染源。     

微生物净化污染地基土的理论分析与试验研究

通过理论分析及试验，证明了在净化碳氢化合物污染的地基土时，利用微生物对碳氢化合物的分解能力．可以提高其净化度．     

Microbial and "de novo" transformation of dicarboxylic acids by three airborne fungi

Micro-organisms and organic compounds of biogenic or anthropogenic origins are important constituents of atmospheric aerosols, which are involved in atmospheric processes and climate change. In order to investigate the role of fungi and their metabolisation activity, we collected airborne fungi using a biosampler in an urban location of Montreal, Quebec, Canada (45 degrees 28' N, 73 degrees 45' E). After isolation on Sabouraud dextrose agar, we exposed isolated colonies to dicarboxylic acids (C(2)-C(7)), a major group of organic aerosols and monitored their growth. Depending on the acid, total fungi numbers varied from 35 (oxalic acid) to 180 CFU/mL (glutaric acid). Transformation kinetics of malonic acid, presumably the most abundant dicarboxylic acid, at concentrations of 0.25 and 1.00 mM for isolated airborne fungi belonging to the genera Aspergillus, Penicillium, Eupenicillium, and Thysanophora with the fastest transformation rate are presented. The initial concentration was halved within 4.5 and 11.4 days. Other collected fungi did not show a significant degradation and the malonic acid concentration remained unchanged (0.25 and 1.00 mM) within 20 days. Degradation of acid with formation of metabolites was followed using high performance liquid chromatography-ultraviolet detection (HPLC/UV) and gas chromatography-mass spectrometry (GC/MS), as well as monitoring of (13)C labelled malonic acid degradation with solid-state nuclear magnetic resonance spectroscopy (NMR). Using GC/MS we identified two processes driving chemical modifications of organic aerosol solutions: (I) formation of metabolites within several days, and (II) rapid release (< or =2 min) of organic molecules from fungal species upon the insertion of taxa in organic aerosol solutions. Metabolites included aromatic compounds and alcohols (e.g. trimethylbenzene and butanol). Potential atmospheric implications of our results are discussed.     

Stable Foams and Sludge Bulking: The Largest Remaining Problems (Abridged)

The separation of activated sludge in secondary settling tanks is the crucial step in biological wastewater treatment from the point of view of both final effluent quality and operation of the aeration plant. The sludge-separation problems of bulking and foaming are connected with an excessive growth of filamentous micro-organisms in the biocenosis of activated sludge.
This paper (a) describes the methods which are used for the quantification of activated-sludge separation problems, and (b) summarizes the design recommendations for bulking and foaming control.     

球毛壳菌(Chaetomium globosum)cDNA文库的构建

以质粒pBluesciptIIsk( +)为载体,以E. coliDH5α为受体菌,通过加接头定向克隆的方法构建了球毛壳菌的cDNA文库. 该文库的滴度为 2. 25×l04pfu/ml, 重组率为 96. 4%.     

浅谈全面深入开展大气微生物污染监测的必要性

由于传染病控制非常迫切,全面深入地开展大气微生物监测就显得非常重要。介绍了大气微生物污染的特点及监测研究现状,给出了大气微生物污染监测实施的方法及措施。     

Microbial growth and colour of minimally processed shiitake mushroom stored at different temperatures

The effect of storage temperature on the microbiological and sensory characteristics of minimally processed shiitake was investigated. Shiitake mushrooms were washed, sanitised, packed in polystyrene trays, overwrapped with plastic film and stored at 7, 10 or 15 °C. Microbial counts, polyphenoloxidase activity, external lightness ( L* ) and acceptance tests were conducted. Mesophilic, aerobic psychrotrophic bacteria, yeasts and moulds predominated during storage. Pseudomonas was detected after 10 days' storage showing an increase of, approximately, 7 log cycles at 15 °C. Mushroom rejection occurred when the microbial population was lower than 10⁶ CFU g⁻¹, suggesting that, other factors, such as browning, affect mushroom spoilage more than microbial activity. Mushrooms treated with citric or ascorbic acids maintained high L * value during 10 days. The shelf life of minimally processed shiitake mushrooms was 10 days at 7 °C, but less than 5 days at 10 °C, and approximately 3 days at 15 °C.     

Photodegradation of sulcotrione in various aquatic environments and toxicity of its photoproducts for some marine micro-organisms

Photochemical behaviour of sulcotrione, a triketone herbicide, was studied in a variety of aqueous solutions including natural waters (sea and river) under laboratory conditions. Photodegradation experiments were carried out under two irradiation systems (UV-B and simulated solar radiation) in order to evaluate kinetics of active ingredient. The degradation kinetics, more rapid under UV-B radiation than solar simulator, followed a first-order reaction (photolysis half-lives ranged between 3 and 50 h) and appeared strongly dependent on water origin, pH value and molecular structure of the herbicide. Dissolved organic matter showed a retarding effect while low concentrations of nitrate ions had no effect on photolysis rate. Identification of photoproducts indicated that hydrolysis, a pH-dependent process (no degradation at pH >6 but at pH=3, k=0.0344 h(-1)), could be photoassisted. These results were compared to those of mesotrione, another triketone herbicide, which appeared more stable under UV-B irradiation. Toxicological studies on two marine heterotrophic bacteria and one cyanobacterium showed absence of effects up to 100 microgL(-1) for both sulcotrione and its photoproducts.