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1.
Summary Sodium metabisulphite is traditionally used to control a non-microbiological spoilage symptom of prawns known as blackspot. This study was undertaken to evaluate the effect of sodium metabisulphite, at levels currently used to control blackspot, on the survival of V. cholerae on prawns during simulated commercial storage. Fresh prawns (Penaeus monodon) were divided into two batches, one of which was exposed to seawater while the other was treated with sodium metabisulphite (1%) in seawater. Two V. cholerae O1 strains were inoculated onto the prawns in separate experiments. Each of the batches were further sub-divided and stored either under chilled conditions (1.5 °C) for 14 days or under frozen conditions (−25 °C) for 49 days. At appropriate time intervals whole prawns were sampled and dilutions plated onto TCBS Cholera medium to determine numbers of V. cholerae. Experiments were performed in triplicate and uninoculated controls were included. Results indicated a significant (P < 0.05) decrease in numbers of V. cholerae on both chilled (~4 log units) and frozen (~2 log units) prawns over the storage period. A significantly (P < 0.05) greater decrease in numbers of the pathogen (up to 1.8 log units) on chilled sodium-metabisulphite-treated, as compared to chilled untreated, prawns was apparent. Sodium metabisulphite had a negligible effect on numbers of V. cholerae on frozen prawns. The use of sodium metabisulphite could be optimized and used to enhance the safety of chilled seafood in cholera-endemic countries.  相似文献   

2.
This study evaluated efficacy of 42 organic and inorganic salts as possible alternatives to synthetic fungicides for the control of Ilyonectria root rot of kiwifruit. Preliminary in vitro tests showed that ammonium bicarbonate, ammonium carbonate, potassium benzoate, potassium sorbate, sodium benzoate and sodium metabisulphite at 2% completely inhibited mycelial growth of the fungus. No significant differences were observed among these salts and disodium EDTA (P ≤ 0.05). However, the ED50, minimum inhibition concentration (MIC), and minimum fungicidal concentration (MFC) values indicated that sodium metabisulphite was more toxic to Ilyonectria liriodendri than these other six salts. Soil bioassays showed that sodium metabisulphite, sodium benzoate and potassium sorbate at 0.25% completely inhibited mycelial growth of the fungus, whereas potassium benzoate reduced the mycelial growth of fungus by 90.30%; however, the differences in inhibitory effects were statistically insignificant (P ≤ 0.05). Moreover, there was no significant difference between 0.1% sodium metabisulphite and 0.5% ammonium carbonate, 0.75% ammonium bicarbonate and 1.5–2.0% disodium EDTA (P ≤ 0.05). Unlike disodium EDTA, complete inhibitory was observed with ammonium carbonate and ammonium bicarbonate at higher concentrations. However, in root bioassays, applications of 2% ammonium bicarbonate, 1.5% ammonium carbonate and 2% disodium EDTA were phytotoxic to kiwifruit seedlings, but 0.25% four other salts were neither phytotoxic to kiwifruit seedlings nor did it adversely affect root length, root fresh weight and root dry weight of seedling. This study also showed I. liriodendri to be capable of growth in both acidic and basic environments. However, while the fungus showed uninhibited growth at pH values of 5–11, growth decreased significantly at both higher and lower pH values (P ≤ 0.05) and was completely inhibited at pH 12.  相似文献   

3.
Summary Physiological variants of Saccharomyces cerevisiae have been identified from burukutu and Raphia palm wine. Genomic DNA from the three S. cerevisiae variants had 38–40% G+C. Mixed fermentation of burukutu wort with each of the S. cerevisiae variants and bacterial species (Lactobacillus brevis, L. plantarum and Lactococcus lactis) produced burukutu of 3.1–4.0% alcoholic content.  相似文献   

4.
A study has been made on the possibility of replacing leucofuchsin by colored basic fuchsin for the histochemical demonstration of aldehydes. Several tissues from mammals and various pertinent fixatives were used. Aldehydes were freed from carbohydrates by oxidation and from thymonucleic acid by hydrolysis.

It was found that the colored form and not necessarily the leucoform of basic fuchsin can be used histochemically in demonstrating aldehydes. The technic used is as follows: (1) Treat with 1.0–0.5% H5IO6 (or in 1% KIO4 in M/1 H2SO4) for 5 to 10 min. and wash thoroughly. For thymonucleic acid hydrolize with N HCl 5 min. at room temperature, 10 min. at 60°C. and 5 min. at room temperature. (2) Stain for 2–3 min. with 0.05% basic fuchsin in 5% ethanol, 3% phenol. (3). Transfer immediately to 1 or 2 changes of 1% sodium bisulphite or potassium metabisulphite in 0.1–0.2 N H2SO4 for a total of 5 min. (4) Rinse with water and treat with M H2SO4 in 95% ethanol for 3–5 min. 6. Wash thoroughly in water and dehydrate, clear, and mount. For glycogen and mucin the following counterstaining solution is recommended: orange G, 0.25 g.; light green SFY, 0.10 g.; phosphotungstic acid 0.50 g.; 50% ethanol, 100 ml.; glacial acetic acid, 0.25 ml.  相似文献   

5.
During ripening, fleshy fruits undergo textural changes that lead to loss of tissue firmness and consequent softening due to cell wall dismantling carried out by different and specifically expressed enzymes. The effect of various chemical treatments on the ripening of mango fruit (Mangifera indica) was investigated at physiological and biochemical level. Based on changes in respiration, firmness, pH, total soluble sugar and a cell wall degrading enzyme pectate lyase (PEL) activity, treatment with 1-methylcyclopropene (1-MCP), silver nitrate (AgNO3), gibberlic acid (GA3), sodium metabisulphite (SMS) and ascorbic acid led to delaying of ripening process while those of ethrel and calcium chloride (CaCl2) enhanced the process. PEL of mango was found to be inhibited by certain metabolites present in dialysed ammonium sulphate enzyme extract as well as EDTA. Mango PEL activity exhibited an absolute requirement for Ca2+ and an optimum pH of 8.5.  相似文献   

6.
The essential oil of Satureja montana L. had a broad-spectrum of antimicrobial activity against 46 species of yeasts. This high and diffused activity could be used to control potential pathogenic and spoilage yeasts. The assay of MIC toward some pathogenic and spoilage yeasts showed a range values from 0.10 to 0.25 l ml–1. The MIC and growth rate reduction assay were effective tests for quantitative evaluation of antimicrobial activity.  相似文献   

7.
The effects of a range of plant growth regulators on callus production in various Ephedra species were examined. Species examined were E. andina, E. distachya, E. equisitina, E. fragilis var, camplyopoda, E. gerardiana, E. intermedia, E. major ssp procera, E. minima and E. saxatilis. All species produced callus on modified MS medium supplemented with 0.25 M kinetin and 5.0 M 2,4-dichlorophenoxyacetic acid or 1-naphthaleneacetic acid. Neither indole-3-acetic acid nor 3-indolebutyric acid induced significant callus formation but the latter maintained growth of established callus cultures in several species. Suspension cultures of several species were established in MS medium supplemented with 0.25 M kinetin and 5.0 M 2,4-dichlorophenoxyacetic acid or 1-naphthaleneacetic acid. Sustained fresh weight doubling times of 70±7h were recorded for cell suspension cultures of E. andina grown in a semi-continous air-lift bubble bioreactor and a minimum doubling time of 56 h was recorded for E. andina in batch culture. It also proved possible to immobilise E. andina batch cultures in sodium alginate beads.Neither parent plants or in vitro cultures of E. distachya, E. fragilis or E. saxatilis produced alkaloids. Trace quantities of 1-ephedrine and trace-0.14% dwt d-pseudoephedrine were produced by in vitro cultures of other species. The ability to produce alkaloid diminished to zero with successive subcultures.Abbreviations Eph 1-ephedrine - Peph d-pseudoephedrine - RGR relative growth rate - KIN kinetin - 2,4-d 2,4-dichlorophenoxyacetic acid - NAA 1-naphthaleneacetic acid - IBA 3-in-dolebutyric acid - IAA indole-3-acetic acid  相似文献   

8.
Dekkera and Brettanomyces yeast are important spoilage organisms in a number of food and beverage products. Isolates of both genera were cultured in a defined medium and supplemented with hydroxycinnamic acids and vinylphenols to investigate their influence on growth and the formation of ethyl phenol derivatives. The growth rate of Brettanomyces species in the presence of acids was reduced, and no significant conversion to vinyl or ethyl derivatives was observed. The growth rate and substrate utilisation rates of Dekkera anomala and Dekkera bruxellensis yeast differed depending on strain and the acid precursor present. Growth of D. bruxellensis was slowed by the presence of ferulic acid with the addition of 1 mM ferulic acid completely inhibiting growth. This study provides an insight into the spoilage potential of these organisms and possible control strategies involving hydroxycinnamic acids.  相似文献   

9.
Propionic acid and its sodium salt have long been used as additives in poultry feed to reduce microbial populations, including Salmonella spp. Propionic acids in poultry feed may have a potential role in inhibiting growth of Salmonella in the chicken intestine. In this study, we determined growth response of a Salmonella typhimurium poultry isolate to propionic acid and sodium propionate under aerobic and anaerobic conditions. Growth rate consistently decreased with the addition of greater concentrations of either propionic acid or sodium propionate. The extent of growth inhibition was much greater with propionic acid than the sodium form. Media pH decreased only with addition of propionic acid. Growth inhibition was more effective under anaerobic growth conditions with either propionic acid or sodium propionate. When determined at the same pH level, growth rate was significantly lowered by addition of 25 mM of either propionate or sodium propionate alone, and also by the decrease in pH levels (P<0.05). These results showed that growth inhibition of S. typhimurium by propionic acid or sodium propionate is greatly enhanced by pH decrease, and to lesser extent by anaerobiosis. We also found that sodium propionate was more inhibitory for growth of S. typhimurium than propionic acid when compared at the same pH levels.  相似文献   

10.
In order to monitor Lactobacillus plantarum and Oenococcus oeni in red wine produced with Italian grape (variety “Primitivo di Puglia”), a polymerase chain reaction– denaturing gradient gel electrophoresis (PCR-DGGE) approach using the rpoB as gene target was established. Wine was treated or not with potassium metabisulphite and supplemented with a commercial bacterial starter of O. oeni to encourage malolactic fermentation. Samples were taken from the vinification tanks at 4, 10, 16, 22, and 28 days after the start of alcoholic fermentation. Genomic DNA was directly isolated from wine and identification of lactic acid bacteria was performed using primers rpoB1, rpoB1O, and rpoB2 able to amplify a region of 336 bp corresponding to the rpoB gene. Amplified fragments were separated in a 30–60% DGGE gradient, and the ability of the PCR-DGGE analysis to distinguish L. plantarum and O. oeni was assessed. The results reported suggest that the PCR-DGGE method, based on the rpoB gene as molecular marker, is a reproducible and suitable tool and may be of great value for wine makers in order to monitor spoilage microorganisms during wine fermentation.  相似文献   

11.
Better preservation of oyokpo beer was obtained by treating it with sodium benzoate alone than by sodium metabisulphite, propionic acid, pasteurization or combinations of chemical preservatives and pasteurization.  相似文献   

12.
The effect of the addition of different concentratons of cystine and cysteine on sporulation and parasporal crystal formation inBacillus thuringiensis var.thuringiensis was studied. The effect was well pronounced when the cystine/cysteine additions were made after the stationary phase. Heat stable spores and crystals were formed when the culture was provided with a low concentration of cystine/cysteine (0.05 per cent w/v). At a moderate concentration of cystine or cysteine (0.15%), only heat labile spores were formed without the production of the crystal. When the cystine/cysteine concentration was high (0.25%), spore and crystal formation were completely inhibited. Partial reversal of inhibition of sporulation was brought about by sodium sulphate or Zinc sulphate and lead, copper, cadmium or cobalt acetate at 0.2 mM or at 0.2% of sodium or potassium pyruvate, citrate, cisaconitate, oxalosuccinate, ∞ -keto-glutarate, succinate, fumarate, malate, or oxalacetate. Glutamate (0.2%) overcame the inhibitory effect of cystine/cysteine completely. The structural changes observed using phase contrast microscopy were dependent upon the concentration of cystine/cysteine.  相似文献   

13.
Summary Diphenolases from Anoxybacillus kestanbolensis strains K1 and K4T, highly active against 4-methylcatechol were characterized in terms of pH- and temperature-optima, pH- and temperature-stability, kinetic parameters, and inhibition/activation behaviour towards some general polyphenol oxidase (PPO) inhibitors and metal ions. The temperature-activity optima, for Anoxybacillus kestanbolensis K1 and K4T catecholases in the presence of 4-methylcatechol, were 80 and 70 °C, respectively. Although catecholase from A. kestanbolensis K4T lost no activity after a period of 1 h incubation at its optimum temperature, the enzyme pH from K1 was stimulated by keeping at 80 °C. Both of the enzymes possessed pH optima at 9.5, and the pH-stability profiles showed that cathecholases from both preparations retained their activities at alkaline pH values. Both A. kestanbolensis K1 and K4T catecholase activities were totally inhibited by addition of 0.01 mM sodium metabisulphite, ascorbic acid and l-cysteine. 1 mM Mn2+ increased the activities of A. kestanbolensis K1 and K4T catecholases by 6.4- and 5.3-fold, respectively. These results indicate that both A. kestanbolensis K1 and K4T strains possess thermo- and alkalostable catecholases.  相似文献   

14.
Most commercially grown cacti can be easily propagated by seed and/or cuttings. A group of rare and endangered species does not fit into this category and is therefore a good candidate for in vitro propagation productions as a tool to overcome habitat and plant-destruction. The number of rare and endangered species of Cacti goes into about 100. Many show a low production and germination of seeds and plantlets are prone to damping-off, making the in vitro propagation a feasible alternative for the multiplication and conservation of their germplasm. The aim of the present investigation is to establish a protocol for the in vitro culture and plant regeneration of Notocactus magnificus, the blue cactus, a highly ornamental species, native to Brazil. The surface sterilization of the explants was achieved with immersion for 10 min in sodium hypochlorite solution for either seeds (0.25% v/v) or ribs segments (1% v/v). Callus formation was observed when explants were cultured on MS medium supplemented with sucrose at 2% (w/v), 2,4-dichlorophenoxyacetic acid 0.5 μM, benzylaminopurine 4.4 μM, thiamine HCl 0.4 mg l−1 and i-inositol 100 mg l−1. The regeneration of shoots was carried out on MS medium supplemented with either different concentrations of benzylaminopurine and 1-naphthaleneacetic acid, or kinetin and indole-3-acetic acid. The highest number of shoots occurred when MS medium was supplemented with benzylaminopurine 22.2 μM, sucrose 3% (w/v) and agar 0,6% (w/v). In vitro spontaneous rooting of shoots was observed after eight months under culture on MS medium. Only in vitro rooted shoots developed into normal plants under glasshouse culture conditions. This in vitro protocol should be useful for the conservation as well as mass propagation of Notocactus magnificus.  相似文献   

15.
In this work, Lactobacillus plantarum BP04 was employed as starter culture in dining-hall food waste storage with different inoculant levels at 0, 2 and 10% (v/w) to suppress the outgrowth of pathogenic and spoilage bacteria. Inoculation by Lactobacillus plantarum BP04 was effective in accelerating pH drop and reducing the growth period of enterobacteria to 9, 7 and 2 days, corresponding to inoculant levels at 0, 2 and 10% (v/w). Increasing inoculum levels were found to inhibit the growth of Lactobacillus brevis and Leuconostoc lactis. HPLC analysis revealed that lactic acid was the predominant organic acid during the treatment of dining-hall food waste. Its concentration varied among the fermented processes reflecting variations of microbial activity in the fermented media.  相似文献   

16.
Chemical induction of adventitious root formation in Taxus baccata cuttings   总被引:1,自引:0,他引:1  
The effect of some auxins (IBA and NAA), phenolic compounds (phloroglucinol, gentisic acid and coumarin), a combination of auxins and phenolics, and a systemic fungicide (Bavistin) have been examined for stimulatory effects on adventitious root formation in stem cuttings (current season's growth) of Taxus baccata L. In general lower concentration (0.25 mM) of both IBA and NAA was more effective in inducing rooting of cuttings taken from both male and female trees. The combined treatment of IBA+NAA (0.25 mM each) showed some success in cuttings from male trees only (55%, compared to 15% rooting in cuttings from female trees). Generally, the callus formation was quite high (70%) in all auxin treatments (alone or in combination). Among the phenolics, 40% rooting success was achieved with phloroglucinol only, while coumarin and gentisic acid were ineffective. The combined treatment of auxins and phenolics also failed to promote rooting. On the other hand, Bavistin was extremely effective for callusing (90%) as well as rooting (80%). The effectiveness of various compounds tested for rooting of young stem cuttings declined in the order: 0.25 mM IBA>0.05% Bavistin>0.25 mM NAA>1.25 mM IBA>15 mM phloroglucinol>IBA+NAA (0.25 mM each). In addition to the auxins, IBA and NAA that are widely used for commercial propagation, the auxin-like properties of the fungicide Bavistin could be exploited for adventitious rooting in T. baccata, and in other plant species.  相似文献   

17.
Okigbo RN 《Mycopathologia》2005,159(2):307-314
The potential of isolates of Bacillus subtilis from yam farm soil to control rot of yam in storage barns was investigated. Yam tubers inoculated in vivo with B. subtilis showed no rot while those inoculated with Aspergillus niger, Botryodiploidia theobromae or Penicillium oxalicum showed considerable rot. The set of yams in which B. subtilis and the fungi were simultaneously inoculated produced rot whereas those in which B. subtilis was inoculated a day before the fungi was inoculated were totally reduced or free of rot. Many fewer fungi were isolated from the surface of tubers treated with B. subtilis than from the untreated (control) and there was high recovery of B. subtilis (99–100%) throughout the period of storage. Rot build up was faster in uninoculated control tubers or those inoculated with a spoilage fungus, while those treated with the antagonist were totally reduced or free of rot. The culture filtrate of B. subtilis prevented spore germination in some spoilage fungi. The importance of this study in relation to farmers in developing countries is discussed.  相似文献   

18.
Aims: To assess the antimicrobial action of three natural‐derived products (essential oil, decoction and hydrosol of Satureja thymbra) against biofilms, composed of useful, spoilage and pathogenic bacteria (formed as monoculture or/and mixed‐culture), and to compare their efficiency with three standard acid and alkaline chemical disinfectants. Methods and Results: Two acids (hydrochloric and lactic, pH 3), one alkali (sodium hydroxide, pH 11), the essential oil of S. thymbra (1% v/v) and the two by‐products of the essential oil purification procedure (the decoction and the hydrosol fraction of essential oil, 100%), were tested against biofilms formed by five bacterial species, either as monospecies, or as mixed‐culture of all species. The tested bacterial species were Staphylococcus simulans and Lactobacillus fermentum (useful technological bacteria), Pseudomonas putida (spoilage bacterium), Salmonella enterica and Listeria monocytogenes (pathogenic bacteria). Biofilms were left to be formed on stainless steel coupons for 5 days at 16°C, before the application of disinfection treatments, for 60 and 180 min. The disinfection efficiency was evaluated by detaching the remaining viable biofilm cells and enumerating them by agar plating, as well as by automated conductance measurements (using Rapid Automated Bacterial Impedance Technique). Both these methods revealed that the essential oil and the hydrosol of S. thymbra exhibited a strong antimicrobial action against both monospecies and mixed‐culture biofilms. Surprisingly, the efficiency of the other three acid–base disinfectants was not adequate, although a long antimicrobial treatment was applied (180 min). Conclusions: The essential oil of S. thymbra (1%), as well as its hydrosol fraction (100%), presents sufficient bactericidal effect on bacterial biofilms formed on stainless steel. Significance and Impact of the Study: Use of natural antimicrobial agents could provide alternative or supplemented ways for the disinfection of microbial‐contaminated industrial surfaces.  相似文献   

19.
An actidione resistant yeast,Candida tropicalis, was isolated from fermenting custard apple juice. Though a slight inhibition of growth was observed on the first day with 5000 ppm of actidione, growth was equal to control after one week. Sorbic acid at 500 ppm and above inhibited the growth of this yeast while sodium benzoate and potassium metabisulphite were unable to suppress the growth even at 1000 ppm. Fermentation and assimilation of different carbon sources were delayed in the presence of 1000 ppm of actidione suggesting the disruption of protein synthesis by actidione. Contribution no. 985.  相似文献   

20.
Thirty-two isolates of Aspergillus flavus were obtained from various sources in Hungary. All isolates were morphologically identified as A. flavus and three atypical variants were confirmed as A. flavus by comparing their DNA with an ex type culture of A. flavus. None of these isolates produced aflatoxins when tested on coconut agar or grown on rice medium and culture extracts examined by thin layer chromatography. Also, none of the isolates converted sterigmatocystin, O-methyl sterigmatocystin, norsolorinic acid, or sodium acetate to aflatoxin. However, 59% of the isolates produced cyclopiazonic acid based on thin layer chromatographic analysis of culture extracts. The isolates that lack the ability to produce both aflatoxin and cyclopiazonic acid are potential candidates for use in bicontrol studies.  相似文献   

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