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1.
Sixty-nine strains of bacteria isolated from murcha and ragi (amylase starters) were studied. These came from 14 different amylase starters from Java, Bali, and Nepal and were isolated from dilution plates incubated under aerobic and anaerobic conditions. Most belonged to Pediococcus , probably P. pentosaceus , and to Streptococcus faecalis. None were able to attack starch although they are used in starch fermentations. When inoculated on rice as pure cultures most of them failed to show visible growth unless yeasts and moulds were added at the same time. The roles of these bacteria are unknown but they may produce secondary products from the glucose formed by the amylolytic yeasts and moulds always found in the starters.  相似文献   

2.
Yeast were isolated from the intestine of farmed rainbow trout (Salmo gairdneri), turbot (Scophtalmus maximus), and free-living flat-fish (Pleuronectes platessa and P. flesus). The average number of viable yeasts recovered from farmed rainbow trout was 3.0 × 103 and 0.5 × 102 cells per gram homogenized intestine for white and red-pigmented yeasts, respectively. The dominant species were Debaryomyces hansenii, Saccharomyces cerevisiae, Rhodotorula rubra, and R. glutinis. In 5 of 10 free-lving marine fish, > 100 viable yeast cells per gram intestinal mucus were recovered. Red-pigmented yeasts dominated and composed >90% of the isolates. Colonization experiments were performed by inoculating rainbow trout and turbot with fish-specific, isolated yeast strains and by examining the microbial intestinal colonization at intervals. Inoculation of experimental fish with pure cultures of R. glutinis and D. hansenii HF1 yielded colonization at a level several orders of magnitude higher than before the inoculation. Up to 3.8 × 104, 3.1 × 106, and 2.3 × 109 viable yeast cells per gram intestine or feces were recovered in three separate colonization experiments. The high level of colonizing yeasts persisted for several weeks. The concentrations of yeasts in the tank water never exceeded 103 viable cells per milliliter. No traces of fish sickness as a result of high yeast colonization were recorded during any of the colonization experiments. For periods of the experiments, the concentration of aerobic bacteria in the fish intestine was lower than the intestinal yeast concentration. Scanning electron microscopy studies demonstrated a close association of the yeasts with the intestinal mucosa. The mucosal colonization was further demonstrated by separating intestinal content, mucus, and tissue. All compartments were colonized by >103 viable yeast cells per gram. No bacteria were detected on the micrographs, indicating that their affinity for the intestinal mucosa was less than that of the yeasts. Correspondence to: Thomas Andtid  相似文献   

3.
Cachaça (aguardente) is a rum-style spirit made from sugar cane juice by artisanal methods in Brazil. A study was made of the production, biochemistry and microbiology of the process in fifteen distilleries in Sul de Minas. Identification of 443 yeasts showed Saccharomyces cerevisiae to be the predominant yeast but Rhodotorula glutinis and Candida maltosa were predominant in three cases. Bacterial infection is a potential problem, particularly in older wooden vats, when the ratio of yeasts:bacteria can be 10:1 or less. A study of daily batch fermentations in one distillery over one season in which 739 yeasts were identified revealed that S. cerevisiae was the predominant yeast. Six other yeast species showed a daily succession: Kluyveromyces marxianus, Pichia heimii and Hanseniaspora uvarum were present only at the beginning, Pichia subpelliculosa and Debaryomyces hansenii were detected from mid to the end of fermentation, and Pichia methanolica appeared briefly after the cessation of fermentation. Despite a steady influx of yeasts from nature, the species population in the fermenter was stable for at least four months suggesting strong physiological and ecological pressure for its maintenance. Cell densities during the fermentation were: yeasts – 4 × 108/ml; lactic acid bacteria – 4 × 105/ml; and bacilli – 5 × 104/ml. Some acetic acid bacteria and enterobacteriaceae appeared at the end. Sucrose was immediately hydrolysed to fructose and glucose. The main fermentation was complete after 12 hours but not all fructose was utilised when harvesting after 24 hours.  相似文献   

4.
Freshly prepared pozol, a traditional Mexican fermented maize dough, contained (c.f.u./g wet wt): lactic acid bacteria, 104 to 106; aerobic mesophiles, 104 to 105; Enterobacteriaceae, 102 to 103; yeasts, 102 to 104; and mould propagules, <103. After 30 h at 28°C the numbers were, respectively: 109, 7×106, 5×105, 106 and 104. Soaking alkali-treated grains overnight allowed lactic acid bacteria, aerobic mesophiles and Enterobacteriaceae to grow and these then constituted the primary microbial flora of the pozol dough. Grinding in a commercial mill inoculated the dough with lactic acid bacteria, aerobic mesophiles, Enterobacteriaceae and yeasts. Other processing stages, including the nature of the surface upon which the balls were made, handling of the dough, and air, contributed only minor numbers of microbes compared with the two major sources, soaking and grinding. The pH of pozol fell from an initial value of 7.3 to 4.6 after 30 h incubation at 28°C. The numbers of Enterobacteriaceae and other aerobic mesophilic bacteria remained constant between 11 and 30 h incubation and there was no evidence of the acidic conditions having any lethal effects on these organisms.  相似文献   

5.
In this study Banh mensamples obtained from Vietnam were analysed in terms of pH, moisture content and fungal composition. The banh men pH proved to be acidic with a mean pH of 5.76. Moisture content was 13.6%. Total mould and yeast counts yielded 1.3 × 106 and 4.3 × 106 c.f.u./g-fresh sample, respectively. A total of 53 fungal isolates were obtained from 20 moulds and 33 yeasts. The mould isolates were identified as Rhizopus oryzae, Mucor indicus, Mucor circinilloides, and Amylomyces rouxii. The yeast isolates were identified as Saccharomyces cerevisiae, Hyphopichia burtonii, Saccharomycopsis fibuligera, Pichia anomala, and Candida sp. Based on the parameters used in this study, it can be deduced that banh men is similar to ragi and other Asian fermentation starters.  相似文献   

6.
Two separate 4 (bacterial concentrations)×6 (yeast concentrations) full factorial experiments were conducted in an attempt to identify a novel approach to minimize the effects caused by bacterial contamination during industrial production of ethanol from corn. Lactobacillus plantarum and Lactobacillus paracasei, commonly occurring bacterial contaminants in ethanol plants, were used in separate fermentation experiments conducted in duplicate using an industrial strain of Saccharomyces cerevisiae, Allyeast Superstart. Bacterial concentrations were 0, 1×106, 1×107 and 1×108 cells/ml mash. Yeast concentrations were 0, 1×106, 1×107, 2×107, 3×107, and 4×107 cells/ml mash. An increased yeast inoculation rate of 3×107 cells/ml resulted in a greater than 80% decrease (P<0.001) and a greater than 55% decrease (P<0.001) in lactic acid production by L. plantarum and L. paracasei, respectively, when mash was infected with 1×108 lactobacilli/ml. No differences (P>0.25) were observed in the final ethanol concentration produced by yeast at any of the inoculation rates studied, in the absence of lactobacilli. However, when the mash was infected with 1×107 or 1×108 lactobacilli/ml, a reduction of 0.7–0.9% v/v (P<0.005) and a reduction of 0.4–0.6% v/v (P<0.005) in the final ethanol produced was observed in mashes inoculated with 1×106 and 1×107 yeast cells/ml, respectively. At higher yeast inoculation rates of 3×107 or 4×107 cells/ml, no differences (P>0.35) were observed in the final ethanol produced even when the mash was infected with 1×108 lactobacilli/ml. The increase in ethanol corresponded to the reduction in lactic acid production by lactobacilli. This suggests that using an inoculation rate of 3×107 yeast cells/ml reduces the growth and metabolism of contaminating lactic bacteria significantly, which results in reduced lactic acid production and a concomitant increase in ethanol production by yeast.  相似文献   

7.
This survey uses a multivariate classification analysis to discriminate yeast strains with interesting biochemical activities for the processing of table olives among a collection of 32 isolates belonging to 16 different yeast species. Lipase, esterase and β-glucosidase activities (desirable characteristics) were quantitatively evaluated in both extracellular and cellular fractions for all isolates in different types of culture media. The study of the quantitative data by cluster and principal component analyses led to the identification of several Wickerhamomyces anomalus, Candida boidinii and Candida diddensiae isolates with promising characteristics (the best global activity levels), clearly differentiated from the rest of the yeasts. The results obtained in this work open up new alternatives to this methodology for the study, classification and selection of the most suitable yeasts to be used as starters, alone or in combination with lactic acid bacteria, during table olive processing.  相似文献   

8.
Mexican fermented maize dough, pozol, including traditional banana leaf-wrapped samples and material in plastic bags, was purchased. All samples were pH 4.7 to 5.7 approx. 12 h after preparation, pH declining to 3.6 to 3.9 after 6 to 9 days storage at ambient temperature. These latter samples had dry matter contents of 31% to 48% (w/w), 0.35% to 0.75% titratable acidity as lactic acid and lactic acid bacteria as predominant microbial flora at about 108 c.f.u./ml. The lactic acid bacteria included strains of Leuconostoc mesenteroides, Lactobacillus plantarum, Lactobacillus confusus, Lactococcus lactis and Lactococcus raffinolactis. Fungi were not found in the samples stored in plastic bags. The samples wrapped in banana leaf, however, developed a large surface mycoflora within 2 days. This included Geotrichum candidum, yeasts and moulds. The majority of the lactic acid bacteria and approx. 50% of yeasts hydrolysed starch to some extent. No Geotrichum isolate hydrolysed starch. Lactate was assimilated by all the Geotrichum isolates and by 17 of 39 yeast strains.  相似文献   

9.
The aim of this work was to describe the yeast populations present during the manufacturing of Minas cheese of the region of Serra da Canastra, Minas Gerais state, Brazil. Canastra cheese is produced from raw cow’s milk at the farmhouse level using artisanal procedures and natural whey cultures as starters. Samples from 10 farms were studied, and they included: raw milk, natural starter, cheese curd before salting and cheese after 5 days of ripening. The most frequent yeasts in whey, curd and cheese were Debaryomyces hansenii, Kluyveromyces lactis, Kodamaea ohmeri and Torulaspora delbrueckii. Many yeast isolates were able to produce proteases, lipases and β-galactosidades. Production of these enzymes by yeasts in the cheese would contribute to the development of the characteristic flavor and smell during the ripening process.  相似文献   

10.
Protoanemonin, a component of Ranunculus bulbosus, was tested as an antifungal agent on selected strains of dermatophytes and yeasts. The minimum inhibitory concentrations ranged from 2.0 to 7.5×10–4 M and the minimum lethal concentrations from 3.8×10–4 M to >1.0×10–3 M. The most sensitive dermatophyte tested was Epidermophyton floccosum, and the most sensitive yeast Rhodotorula glutinis. The effects of different culture media and of light on the sensitivity of Rhodotorula glutinis to protoanemonin were also tested. Structural analogies between protoanemonin and other cytotoxic unsaturated lactones, and the reversal by the amino acid cysteine of the antifungal action suggest a possible mechanism of action.  相似文献   

11.
Samples of camel's milk collected from different zones of Morocco were analysed to evaluate their microbiological quality and to identify predominating lactic acid bacteria (LAB). The following average colony-forming units (c.f.u.s) of aerobic total count, enterococci, faecal and total coliforms, LAB, yeasts,Staphylococcus aureus and spores of sulphite-reducing clostridia were recorded: 6.2 × 107, 2.9 × 104, 1.6 × 104, 7.0 × 106, 1.0 × 107, 3.8 × 104, 1.3 × 105 and 6.0 c.f.u./ml, respectively. The enumeration results were markedly variable and coliforms were not detected in 1 ml of some samples. Bacteriological identification revealed a definite dominance of enterococci with Enterococcus faecalis as the main representative species. Besides Enterococcus, other genera including Pediococcus (28.2%), Streptococcus (4%), Lactococcus (8%) and Leuconostoc(1%) were isolated on de Man, Rogosa and Sharp (MRS) agar.  相似文献   

12.
Ersho is a clear, yellow liquid that accumulates on the surface of fermenting teff-flour batter and is collected to serve as an inoculum for the next fermentation. The pH of ersho samples was about 3.5 and titratable acidity ranged between 3.1% and 5.7%. The mean aerobic mesophilic counts from four households varied between 6.9×106 and 1.3×108 c.f.u./ml and the aerobic bacterial flora consisted of Bacillus spp. Mean yeast counts ranged between 5.2×105 and 1.8×106 c.f.u./ml and comprised, in order of abundance, Candida milleri, Rhodotorula mucilaginosa, Kluyveromyces marxianus, Pichia naganishii and Debaromyces hansenii. Candida milleri was the most dominant isolate in all samples. About 90% of the teff flour samples had aerobic mesophilic counts 105 c.f.u./g and Gram-positive bacteria constituted about 71% of the total isolates. About 80% of samples had Enterobacteriaceae counts of 104 c.f.u./g.M. Ashenafi is with the Department of Basic Sciences, Awassa College of Agriculture, Addis Ababa University, PO Box 5, Awassa, Sidamo, Ethiopia.  相似文献   

13.
The initial interaction of Candida albicans with pulmonary tissue of B6D2/F1 mice was investigated. The LD50 for mice challenged intravenously (IV) was approximately 3 × 105 yeasts, whereas the LD50 by the intratracheal (IT) route was in excess of 108 yeasts. Mice challenged IV died of progressive yeast growth in the kidneys. In contrast, mice challenged IT rapidly eliminated the entire inoculum by the first day after challenge. Resident pulmonary alveolar macrophages (PAM) killed upwards of 70% of C. albicans in an in vitro killing assay. At effector: target ratios favoring the effector cell population resident PAM were able to restrict the formation of yeast germ tubes to only 30% of the yeasts, whereas at equivalent ratios virtually all of the intracellular yeasts produced germ tubes. Evaluation of the ability of PAM, harvested from genetically different strains of inbred mice, to kill C. albicans in vitro showed that killing ability was a property of resident PAM from mice with the black 6 background. It was discovered that during the initial stages of infection in vivo, the expression of the F4/80 surface molecule was down regulated, and the expression of the Mac 1 surface molecule upregulated. There were no quantitative changes in expression of either Mac 2, Mac 3, Ly 5 or the 5C6 surface epitopes. Taken together, the data show that pulmonary tissue is quantitatively very resistant to C. albicans infection, because of the ability of resident PAM to rapidly phagocytize and kill yeasts. Killing of C. albicans by resident PAM may be a property of a subset of this mononuclear phagocyte population and was accompanied by alterations in the expression of surface molecules.Presented as part of the Everett S. Beneke Symposium in Mycology, May 27, 1988.  相似文献   

14.
Lactic acid bacteria increased from 3.2 × 106 and 1.6 × 107 c.f.u./g (wet wt) to 2 × 109 and 1.6 × 109 c.f.u./g after 12 to 24 h of fermentation of home-produced mawè (a dough produced from dehulled maize) and commercial mawè, respectively. In commercial mawè, the yeast count increased from 1.3 × 105 to 2.5 × 107 c.f.u./g after 48 h of fermentation before decreasing, whereas in the home-produced mawè it increased from 2.5 × 104 to 3.2 × 107 c.f.u./g after 72 h of fermentation; the dominant yeasts were mainly Candida krusei, although C. kefyr, C. glabrata and Saccharomyces cerevisiae were also present. Enterobacteriaceae counts increased slightly during the initial stage ofthe fermentation, but decreased below the detection level after 24 to 48 h. Enterobacter cloacae was mostly found in commercial mawè and Escherichia coli mostly in homeproduced mawè.D.J. Hounhouigan and C.M. Nago are with the Université Nationale du Bénin, Faculté des Sciences Agronomiques, Département de Nutrition et de Sciences Alimentaires, BP 526, Cotonou, Benin; M.J.R. Nout and F.M. Rombouts are with the Agricultural University, Department of Food Science, Bomenweg 2, 6703 HD Wageningen, The Netherlands. J.H. Houben is with Utrecht University, Department of the Science of Foods of Animal Origin, Yalelaan 2, 3508 TD Utrecht, The Netherlands.  相似文献   

15.
The distribution of microorganisms in 10 samples of salted dried fish and the effects of irradiation of them were studied. The total aerobic bacteria in commercial dried fish were determined to be from 2 × 104 to 3 × 106 per gram. Mold counts were 1 × 102 to 7 × 103 per gram with a lower amount of yeasts. In spoiled dried fish, total aerobic bacteria were determined to be 4× 106 or 1 × 107 per gram with a few yeasts. Coliforms were not isolated on MacConkey agar plates from any of the samples. The predominant bacteria occurring in spoiled dried fish were Pediococcus halophilus, Vibrio costicola and Planococcus sp. More than 50% of the molds consisted of the Aspergillus niger group, whereas lower amounts of the A. flavus, A. fumigatus and A. ochraceus groups, Penicillium chrysogenum series, etc. were also isolated from many samples of dried fish. All kinds of putrefactive microorganisms were radiation sensitive, and a dose of ca. 500 krad appears to be sufficient for extension of the shelf-life of dried fish from 2 to 4 times.  相似文献   

16.
Pseudomonas aeruginosa was identified as a facultative pathogen of red palm weevil. Intra-haemocoelic injection of the pathogen within larvae and pre-pupae was more effective at killing the insects [with a median lethal dose (LD50) of 9×102 to 2×103 bacteria/insect] than inoculation by force feeding (LD50 of 105 to 4×105 bacteria/insect) or by wading the insects in a suspension of the pathogen (LD50 of 105 to 2×105 bacteria/insect). Injection of 3×103 bacteria/insect killed 69% of larvae; small larvae were more susceptible (LD50 of 9×105 bacteria/larva) than either larger larvae (LD50 of 103 bacteria/larva) or pre-pupa. The median time to death of the small larvae following injection of P. aeruginosa was about 6 days but that following force feeding or wading was about 8 days. A secondary invader, Serratia marcescens, had no effect on the pathogenicity of P. aeruginosa but hastened death of larvae by about 3 days.A. Banerjee and T.K. Dangar were with the Central Plantation Crops Research Institute, Regional Station, Kayangulam 690 533, Kerala, India. They are now with the Central Rice Research Institute. Cuttack 753 006, Orissa, IndiaCPCRI research paper no. 870.  相似文献   

17.
The potential of four yeasts (Debaryomyces hansenii, Rhodotorula minuta, Cryptococcus laurentii and Cryptococcus diffluens) and three bacteria (Bacillus amyloliquefaciens, Bacillus subtilis and Stenotrophomonas rhizophila) with antagonistic capacity against anthracnose caused by Colletotrichum gloeosporioides in mango cv. Ataulfo fruit was investigated. Germination of C. gloeosporioides spores was significantly inhibited by all marine yeasts and bacteria strains of an in vitro test. When yeasts and bacteria were tested on mango fruit, the marine yeast D. hansenii 1R11CB strain and marine bacteria S. rhizophilaKM02 strain were the best antagonists to anthracnose (C. gloeosporioides), which significantly decreased disease incidence by 56% and 89%, respectively, and reduced lesion diameter by 91% and 92%, respectively. All the isolated strains of the phytopathogen, yeasts and bacteria were molecularly identified. Our results from in vitro and in vivo experiments suggest that marine yeasts and bacteria strains can be used as some effective biological control agents for anthracnose in mango.  相似文献   

18.
Seasonal and depth variations of the abundance, biomass, and bacterivory of protozoa (heterotrophic and mixotrophic flagellates and ciliates) were determined during thermal stratification in an oligomesotrophic lake (Lake Pavin, France). Maximal densities of heterotrophic flagellates (1.9 × 103 cells ml–1) and ciliates (6.1 cells ml–1) were found in the metalimnion. Pigmented flagellates dominated the flagellate biomass in the euphotic zone. Community composition of ciliated protists varied greatly with depth, and both the abundance and biomass of ciliates was dominated by oligotrichs. Heterotrophic flagellates dominated grazing, accounting for 84% of total protistan bacterivory. Maximal grazing impact of heterotrophic flagellates was 18.9 × 106 bacteria 1–1h–1. On average, 62% of nonpigmented flagellates were found to ingest particles. Ciliates and mixotrophic flagellates averaged 13% and 3% of protistan bacterivory, respectively. Attached protozoa (ciliates and flagellates) were found to colonize the diatom Asterionella formosa. Attached bacterivores had higher ingestion rates than free bacterivorous protozoa and may account for 66% of total protozoa bacterivory. Our results indicated that even in low numbers, epibiotic protozoa may have a major grazing impact on free bacteria. Correspondence: C. Amblard.  相似文献   

19.
Yeast cell wall fractions have been proposed to bind enteropathogenic bacteria. The aim of this study was to develop a quantitative assay by measuring the optical density as growth parameter of adhering bacteria. The exponential growth phase of adhering bacteria was determined by optical density reading and compared with the colony count (CFU/mL). A linear regression was compiled and the bacterial number bound to the yeast cell wall product could be determined. Further focus was the investigation of a yeast cell wall from strain Trichosporon mycotoxinivorans (MTV) for its ability to bind gram negative Salmonella, E. coli and Campylobacter strains and gram positive probiotic bacteria of the genera lactobacilli and bifidobacteria as well as gram positive Clostridium perfringens quantitatively. The gram negative probiotic strain E. coli Nissle 1917 was also investigated. Seven out of 10 S. Typhimurium and S. Enteritidis strains adhered to the cell wall product with an amount between 103 and 104 CFU/10 μg. Four out of 7 E. coli strains showed an average binding capability (102 CFU/10 µg) whereas 4 × 103E. coli F4 cells bound per 10 μg yeast cell wall. E. coli 0149 K91, E. coli 0147 K89, C. jejuni and C. perfringens as well the genera lactobacilli and bifidobacteria did not bind to the yeast cell wall. E. coli Nissle 1917 was bound with 2 × 102 CFU/10 μg. These results demonstrate that cell wall from MTV can be used to differentially bind E. coli spp. and Salmonella spp. up to 8 × 104 CFU/10 μg. Thus certain yeast cell walls may prevent enteric infections caused by selective bacteria. This methodical approach would be an accurate tool in the feed industry for quality control of yeast cell wall products.  相似文献   

20.
A new process for recycling feedlot waste involves the fermentation of liquid from this waste combined with corn. Changes in the flora of this silage-like fermentation were followed. The fermentation was dominated by lactobacilli and yeasts, which initially constitute 1% or less of the natural flora. The species of yeasts and lactics involved were characterized. The fermentation has two phases. A single heterolactic species multiplied rapidly for the first 24 h until it represented 95% of the lactobacilli and more than 90% of the total microflora. It displaced the betabacterium predominant among lactics of the original waste; the acid produced killed coliforms and other organisms in feedlot waste; and the acetic acid produced probably caused the death of the dominant native yeast Trichosporon cutaneum (de Beurm., Gougerot et Vaucher) Ota. The peak lactobacillus count remained constant (about 2 × 109 organisms/g [wet weight]) throughout the rest of the fermentation. Homolactics dominated the later phase and yeasts increased to 9.5 × 107 organisms/g (wet weight). At 6 days, a stable mixture of three lactobacilli was present, one streptobacterium, one thermobacterium, and one betabacterium. Similarly, yeasts stabilized as a mixture of two Candida sp. and one Pichia sp. The dominant species of lactics were characterized. Information on the sequence of microorganisms provides a basis for enhanced protein synthesis in the fermentation.  相似文献   

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