几种固定化耐冷菌载体的比较研究

向低温污水中投加耐冷菌，污水中有机物的去除率可大幅提高，但菌体流失快，重复使用性差．结合吸附法与包埋法，对聚胺脂泡沫、破碎陶粒、柱状活性炭等几种载体进行生物固定化，形成生物载体．实验结果表明固定化生物载体的效果取决于载体的孔径及表面的粗糙程度，载体固定化效果为：聚胺脂泡沫＞陶粒＞活性炭．经过60d的连续运行，载体上的耐冷菌的活性良好且有大量的增殖，生物载体对污水中有机物的去除效果为：聚胺脂泡沫＞陶粒＞活性炭。     

Characterization of Gram‐Negative Psychrotrophic Bacteria isolated from Italian Bulk Tank Milk

Eighty psychrotrophic bacterial strains, isolated from different northwest Italian bulk tank milks destined for Grana Padano cheese production, were identified by 16S rRNA gene amplification and partial sequence analysis of the rpoB gene. Pseudomonas spp. were the most commonly occurring contaminants, P. fluorescens being the predominant isolated species, along with Enterobacteriaceae, primarily Serratia marcescens. RAPD‐PCR was used to study genetic variability and distinguish closely related strains; a high degree of genetic heterogeneity among the strains was highlighted. All the strains were characterized for their ability to produce proteases, lipases and lecithinases at different temperatures (7, 22, and 30 °C). Forty‐one of the psychrotrophic strains were positive for all the enzymatic activities. The highest number of positive strains for all the incubation temperatures was found for lipolytic activity (59), followed by proteolytic (31) and lecithinase (28) activities, and the enzymatic traits varied among the Pseudomonas and Enterobacteriaceae strains. The proteolytic psychrotrophic strains were screened for the presence of the aprX gene, coding for a heat‐resistant metalloprotease in Pseudomonas spp. The aprX gene was detected in 19 of 63 Pseudomonas strains, and was widespread in the P. fluorescens strains (14/19).     

Oscillatory High Pressure Processing Applied to Mechanically Recovered Poultry Meat for Bacterial Inactivation

The effect of oscillatory high pressure processing on mesophile and psychrotroph populations of mechanically recovered poultry meat (MRPM) was evaluated. Vacuum‐packaged samples were subjected to cycles by alternating moderate pressure (60 MPa) and high pressure (450 MPa) at 20 °C, once or several times so that the total time under high pressure was 15 min. A continuous treatment at 450 MPa for 15 min at 20 °C was also performed. Oscillatory treatments did not generate significantly higher decreases in counts of both populations than continuous pressurization. Reductions from 3.2 to 3.8 log CFU g^–1 were found for mesophiles. Psychrotrophs proved more sensitive: one of the cyclic treatments induced a lethality of 5.2 log CFU g ^–1. Pressurization improves the microbiological quality of MRPM.     

利用耐冷菌处理低温污水的研究

生物法是目前污水处理中广泛采用的方法。但在我国北方地区冬季寒冷漫长、水温偏低,因此污水的生物处理普遍存在着处理效果差,出水难以达标的问题。通常解决的方法是降低污泥负荷,增加污水停留时间,但这样使污水厂的上中地面积增大,运转费用变高。本文从微生物角度对此进行了研究。从自然界中分离、筛选到了四种能在0-9℃下生长并能处理生活污水的耐冷菌。测定了它们的生长曲线同时也做了单菌和混合菌的降解试验。结果表明：与中温菌相比,耐冷菌在低温条件下能够生长并具有较高的降解能力。采用耐冷菌可提高低温污水的生物处理效果。     

耐低温生物脱氮机制与对策研究进展

废水处理系统中不可避免存在着低温环境,低温使得硝化菌和反硝化菌的活性下降,如何在低温条件下提高污水生物脱氮效果是废水处理研究工作中亟待解决的问题。本文对近年来研究发现的低温微生物耐低温机制进行了梳理,提出了最近发现的胞外聚合物（EPS）和聚羟基脂肪酸酯（PHA）的作用机理;介绍了几种已被研究证实能在低温下进行脱氮的功能菌与一些可以提高低温污水脱氮效果的新技术/工艺（包括使用新型填料、改变碳源投加方式、投加特定的重金属）;阐述了目前研究所遇到的一些问题,如缺乏工程实践、处理水质与研究菌株单一,研究结论与实际废水处理应用还有着差距。指出未来可以通过特异性功能菌的固定与使用、生物倍增技术与工程实践结合等方法来降低运行成本,提高低温污水的脱氮效果。     

极地微生物产海藻糖合成酶菌株的筛选

来源于极地的微生物经过筛选,得到能产海藻糖合成酶的耐冷菌株S1和S2,分别用TLC、DNS和HPLC的方法确证其酶反应的产物为海藻糖.以质量分数1%麦芽糖为底物,S1粗酶液能将麦芽糖转化为海藻糖,并且没有明显的葡萄糖生成,在pH值7.0的磷酸盐缓冲液下15℃反应48h,经过HPLC测定转化率最高达到75.2%.     

Psychrotrophs in dairy products: Their effects and their control

Health concerns and technological effects of psychrotrophic bacteria in dairy products are reviewed, as well as methods to control their presence and development. The various Gram‐negative and Gram‐positive psychrotrophic species are listed and, with respect to pathogenic psychrotrophs, emphasis is given on Listeria monocytogenes, Yersinia enterocolytica, and Bacillus cereus. The influence of psychrotrophic bacteria on the quality of raw milk, pasteurized and UHT milks, butter, ice cream, cheese, and powders is examined. Public health considerations of Listeria monocytogenes, Yersinia enterocolytica, and Bacillus cereus of these various dairy products are also presented. Methods that can be used to eliminate or control the development of psychrotropic bacteria include low or high temperatures, chemicals, gases, the lactoperoxidase system, lactic acid bacteria, microfiltration, bactofugation, lactoferrin‐related proteins, sanitation, flavors, and naturally occurring spore germinants.     

处理低温污水耐冷菌生物膜的研究

寒冷地区冬季生活污水生物处理效率低,处理后污水排放经常出现不达标的问题．为了提高低温生活污水的生物处理效率,采用孔隙结构发达的软性聚氨酯泡沫为固定化载体,对活性污泥中分离得到的高效耐冷菌群进行固定化,并投加到生物反应器中运行．污水处理系统运行到30d左右时,化学需氧量（COD）的去除率达到82％,生化需氧量（BOD）的去除率达到92％．耐冷菌在载体的多孔结构中形成直径10-30μm的成团簇状分布的生物膜,每克载体附着生物量平均可达800mg左右,位于载体外层空间的生物膜量和生物活性明显高于内层．生物膜中耐冷细菌种群呈多样性分布,主要为各种耐冷球菌和杆菌,少量丝状菌起着生物膜骨架作用．低温生物膜的这些微生物结构为稳定系统、高效处理低温污水提供了基础．     

Chitosan nanoparticle coatings reduce microbial growth on fresh‐cut apples while not affecting quality attributes

This study addressed the effects of chitosan‐based nanoparticles on microbiological quality, colour, polyphenol oxidase (PPO) and peroxidase (POD) and firmness of fresh‐cut ‘Gala’ apple slices during storage at 5 °C for 10 days. The treatments carried out were as follows: (i) slices pulverised with 110‐nm chitosan nanoparticles, (ii) slices pulverised with 300‐nm chitosan nanoparticles, (iii) 2 g L^?1 chitosan dissolved in 2% citric acid and (iv) noncoated samples. There was an increase in chroma and a proportional decrease in hue angle and lightness. Browning of the slices coated with conventional chitosan and control was slightly intense than those coated with chitosan nanoparticles of 110 and 300 nm. The PPO and PDO activities increased with time for all samples, with irrelevant difference among the treatments. Flesh firmness did not change for any treatment and period. Coatings with chitosan nanoparticles of 110 nm showed higher antimicrobial activity against moulds and yeasts, and mesophilic and psychrotrophic bacteria than the other treatments. No Salmonella, and total and faecal coliforms were detected. This investigation supports the potential use of chitosan nanoparticles as edible coatings in controlling microbial activity in fresh‐cut apples.