胶红酵母与酿酒酵母混合酒精发酵中酵母生长与糖苷酶活动力学

为了探索混合发酵中酵母生长动力学及糖苷酶活变化,评价优选的胶红酵母在葡萄酒增香酿造中的应用潜力,优化接种方案。以胶红酵母与酿酒酵母顺序接种发酵‘爱格丽’干白葡萄酒为处理,在发酵过程中,血球计数法测总酵母数量;p-NPG法测β-葡萄糖苷酶、鼠李糖苷酶、半乳糖苷酶及木糖苷酶活性;稀释平板法测2种酵母的生长变化,每24h取样,单一酿酒酵母发酵为对照。酵母生长动力学显示,顺序接种方案有助于减慢发酵速率,酿酒酵母接种时间越晚,胶红酵母的生长量随之升高且生存时间增长。4种糖苷酶主要在发酵早期表现较高的活性,混合接种发酵显著提升鼠李糖苷酶、半乳糖苷酶和木糖苷酶活性的累积量。可见顺序接种有助于降低发酵速率,增长胶红酵母生长时间,提升糖苷酶的活性,且顺序接种48h方案最具增香酿造的潜力。     

Effect of atmospheres combining high oxygen and carbon dioxide levels on microbial spoilage and sensory quality of fresh-cut pineapple

Fresh-cut fruit such as pineapple have a very limited shelf-life. The study aims at prolonging the shelf-life of fresh-cut pineapple by means of modified atmospheres (MAs). The effect of MAs combining high O₂ (21–70%) and CO₂ (21–50%) levels on microbial spoilage and sensory quality of fresh-cut pineapple was therefore evaluated. In the first part of the study, the behaviour of two spoilage yeasts (Candida sake and Candida argentea) and one lactic acid bacterium (Leuconostoc citreum), which had previously been isolated from spoiled commercial fresh-cut pineapple cubes, were monitored on pineapple agar separately. In the second part of the study, the shelf-life of commercial fresh-cut pineapple cubes packaged in selected MAs was evaluated at 7 °C. The results showed that MAs combining high O₂ and high CO₂ levels had a large inhibitory effect on the growth and volatile metabolite production of C. sake and C. argentea on pineapple agar. A MA with 50% O₂ and 50% CO₂ was in both cases the most inhibitive. Although MAs induced the production of ethyl acetate by the yeasts, the quantity of ethyl acetate was much lower in high O₂ and high CO₂ than that in air due to lower yeast population density in MAs. With regards to growth, L. citreum was not sensitive to high O₂ and CO₂ levels. The fresh-cut pineapple packaged in air had deteriorated and were not acceptable any more by day 7, while those packaged in 50% O₂ combined with 50% CO₂, which also retarded the growth of aerobes and yeasts on pineapple cubes during storage, were still acceptable. It can be concluded that a MA with 50% O₂ and 50% CO₂ shows the best potential for extension of the shelf-life of fresh-cut pineapple.     

流式细胞术及其在微生物学中的应用

流式细胞术(Flowcytometry ,FCM )是利用流式细胞仪对细胞或其他微小生物颗粒的多种物理、生物学参数同时进行定量检测,并对特定细胞群体进行分选的分析测量技术。它不仅快速、灵敏和准确,而且还具有客观、直接和同时进行多参数检测的优点。目前,该技术已成为工农业生产和研究、医药卫生和环境保护等方面的一个重要手段。在对FCM的发展简史简要介绍的基础上,对FCM在微生物学中的应用进行了综述。     

The importance and ecology of yeasts in soil

This review focuses on literature pertaining to the interactions of soil yeasts with biotic and abiotic factors in their environment. Soil yeasts not only affect microbial and plant growth, but may also play a role in soil aggregate formation and maintenance of soil structure. Serving as a nutrient source for bacterial, faunal and protistan predators, soil yeasts contribute to essential ecological processes such as the mineralization of organic material and dissipation of carbon and energy through the soil ecosystem. Some soil yeasts may also play a role in both the nitrogen and sulphur cycles and have the ability to solubilize insoluble phosphates making it more readily available for plants. Recently, the potential of soil yeasts as plant growth promoters and soil conditioners has been studied with the goal of using them in the field of sustainable agriculture.     

Fermented liquid feed for pigs: an ancient technique for the future

Fermented liquid feed is feed that has been mixed with water at a ratio ranging from 1:1.5 to 1:4. By mixing with water, lactic acid bacteria and yeasts naturally occurring in the feed proliferate and produce lactic acid, acetic acid and ethanol which reduces the pH of the mixture. This reduction in pH inhibits pathogenic organisms from developing in the feed. In addition, when this low pH mixture is fed, it reduces the pH in the stomach of pigs and prevents the proliferation of pathogens such as coliforms and Salmonella in the gastrointestinal tract. For piglets, the use of fermented liquid feed offers the possibility of simultaneously providing feed and water, which may facilitate an easier transition from sow’s milk to solid feed. Secondly, offering properly produced fermented liquid feed may strengthen the role of the stomach as the first line of defense against possible pathogenic infections by lowering the pH in the gastrointestinal tract thereby helping to exclude enteropathogens. Finally, feeding fermented liquid feed to pigs has been shown to improve the performance of suckling pigs, weaner pigs and growing-finishing pigs. In this review, current knowledge about the use of fermented liquid feed in pig diets will be discussed. This will include a discussion of the desirable properties of fermented liquid feed and factors affecting fermentation. In addition, advantages and disadvantages of fermented liquid feed will be discussed including its effects on gastrointestinal health, intestinal pH and the types of bacteria found in the gastrointestinal tract as well as the effects of fermented liquid feeds on pig performance.     

Microbial,chemical and physical changes during composting of a eucalyptus (Eucalyptus calophylla and Eucalyptus diversicolor) bark mix

Summary Physical, chemical, and population changes among microorganisms in a eucalyptus bark mix were examined during composting. The microbial succession was studied in detail by dilution plating. The CO₂ evolution corresponded to high microbial numbers. The pH increased rapidly, from 4 to 7.5, before stabilizing at approximately 6.5. Composting increased the availability of most nutrients. Initially, bacteria and filamentous fungi appeared to be the main decomposing organisms. With time, however, yeasts and actinomycetes increased in numbers. The numbers of spore-forming bacteria (Bacillus spp.) and pseudomonads also increased with time. The compost was initially phytotoxic, but ceased to be so within 76 days.     

Yeasts associated with soil invertebrates

The hindgut of the diplopod Pachyiulus flavipes is inhabited by specific yeast populations. The yeast communities consist almost exclusively of ascomycetes, viz., Debaryomyces hansenii, Torulaspora delbrueckii, and Zygowilliopsis californica. Evidence is provided that the yeasts isolated from the gut can be considered symbionts that remain in a steady state under different feeding and rearing conditions.     

Foal-Heat Diarrhea Is Not Caused by the Presence of Yeasts in Gastrointestinal Tract of Foals

The aim of this study was to evaluate whether a normal yeast flora is present in the intestine of healthy foals and whether establishing yeast flora or yeast overgrowth might be associated with foal-heat diarrhea. Among the sampled foals, 49% showed foal-heat diarrhea and 28.3% were positive for yeasts. Candida famata was isolated 9 times; Geotrichum sp., 6; Saccharomyces cerevisiae, 5; Cryptococcus laurentii, 4; Rhodotorula sp., 3; Zygosaccharomyces sp., 2; and Candida colliculosa, Candida globosa, and Candida pelliculosa 1 time, respectively. The colony-forming unit ranged from 1 to 10 in all positive cultures. Fifteen of 92 (16.3%) foals with heat diarrhea and 11 of 92 (11.9%) asymptomatic animals yielded positive samples for yeasts. None of the animals shed the same yeast more than 2 times consecutively, and yeasts were found in pure or mixed culture. Equine gastrointestinal tract did not appear to be colonized by yeasts during the first 15 days of life, and yeasts are not involved in foal-heat diarrhea.     

Yeast Flora in Oropharyngeal and Rectal Mucous Membranes of Healthy and Critically Ill Neonatal Foals

Little is known about the normal or pathologic yeast flora in healthy and critically ill neonatal foals. The aims of this study were to evaluate the yeast flora colonizing the mucous membranes of the digestive tract (oropharynx and rectum mucous membranes) of healthy and hospitalized foals and to find out risk factors involved in yeast colonization of foals referred to a neonatal intensive care unit. A total of 240 swabs were collected from 21 healthy (group A) and 39 sick (group B) foals. In 14 of the 60 foals, yeast was isolated in at least one sample (23.3%): 3 of the 21 foals (14.3%) were positive in group A and 11 of 39 foals (28.2%) were positive in group B. The yeasts were isolated from rectal swabs obtained from none in healthy foals, whereas 5 of the 39 sick foals were positive; however, this difference was not statistically significant. No significant difference was also detected regarding oropharyngeal swabs between healthy (3/21) and sick (10/39) foals. The risk factors significantly associated with the isolation of yeasts from rectal swabs were female sex, treatment with oral antibiotics, and stressful diagnostic–therapeutic procedures. The only risk factor significantly associated with the isolation of yeast from oropharyngeal swabs was the treatment with antacids and gastroprotectants. The results show that fungi present in the gastrointestinal tract of neonatal foals were mainly environmental yeasts and suggested the absence of a stable fungal colonization. Candida was the genus frequently isolated in hospitalized foals, just as it is isolated in critically ill human neonates.     

Biocontrol of fungi isolated from sour rot infected table grapes by Saccharomyces and other yeast species

Sour rot is an important disease of grapes caused by an etiologic complex of microorganisms in which filamentous fungi play a key role. Yeasts are used for biocontrol of pathogenic filamentous fungi on fruits. The major objective of this study was to assess in vivo on detached berries the effect of viticultural yeasts on phytopathogenic fungi involved in grape sour rot. Yeasts that were found to be effective in vivo against the fungi were assayed for their possible pathogenicity in humans: growth at 42 °C, pseudohyphal formation, adhesion, and phospholipase and protease activity. A total of 234 yeasts belonging to 14 genera were assayed against the following pathogens: Aspergillus caelatus, Aspergillus carbonarius, Aspergillus terreus, Aspergillus versicolor, Fusarium oxysporum, Penicillium comune, Rhizopus stolonifer and Ulocladium sp. Forty-three (16 Saccharomyces and 27 non-Saccharomyces) showed antagonistic properties against some of the fungi assayed in grapes at 25 °C. Yeast isolates determined as biocontrol agents under in vivo conditions were isolated from fermenting musts (35), viticultural soils (6) and grape berries (2). Twenty biocontrol agents did not show phenotypical characteristics associated with pathogenicity in humans.