ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1991.tb02739.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

One of the main disadvantages of usingBacillus thuringiensisas an insecticide is that the spore and crystal preparations applied to foliage are readily washed away by rain and are inactivated by sunlight. Spores from some strains ofB. thuringiensishave been shown to be highly sensitive to u.v. light. This study has demonstrated how mutants with increased resistance to u.v., isolated by successive rounds of u.v. irradiation, and additionally with increased specific pathogenicity can be isolated. These techniques should be applied to strains that are frequently used in the industrial production ofB. thuringiensistoxin.

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1991.tb02740.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Ten actinomycetes isolated from various marine sediments were investigated for the production of tetrodotoxin (TTX). Tissue culture assay, high performance liquid chromatography and gas chromatography‐mass spectrometry confirmed that the nine strains produced TTX. Actinomycetes may be responsible for TTX accumulation in marine environment

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1991.tb02741.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Species ofLactobacillusandCarnobacteriumfrom meat and meat products could be separated by a few biochemical characteristics; presence ofmeso‐diaminopimelic acid in the cell wall, the isomers of lactic acid produced, production of citrulline from arginine and fermentation of some carbohydrates. This identification key was checked by DNA–DNA hybridizations stud

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1991.tb02742.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Lactobacillus sakeLb 706 can release a bacteriocin inhibitory toListeria monocytogenes. In MRS broth, viable counts decreased rapidly whenLact. sakeLb 706 was added, whereas growth of the listerias was not affected by a bacteriocin‐negative variant of the sameLactobacillusstrain. Inhibition ofL. monocytogeneswas also observed in pasteurized minced meat inoculated withLact. sakeLb 706. The bacteriocin produced is apparently effective in meat. However, the effect of the bacteriocin producer was less evident in minced meat than in broth. In comminuted cured raw pork filled into casings (German‐type ‘fresh Mettwurst’),L. monocytogeneswas able to grow at a pH of 6.3, but addition ofLact. sakeLb 706 prevented the growth of listerias during the first few days after manufacture. At normal pH (5.7)L. monocytogenesdid not multiply and addition ofLact. sakeLb 706 reduced viable counts of listerias by about one log cycle.Lactobacillus sakeLb 706 therefore may have some potential as a protective culture in meat p

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1991.tb02743.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

When shredded or sliced carrots were inoculated withListeria monocytogenesthe number of viable listerias decreased rapidly. On carrot slices stored at 8°C there was a decrease after 3 d followed by an increase, after 7 d, to numbers similar to those present initially. The numbers of spoilage micro‐organisms increased throughout storage at 8°C. Carrots macerated in a Stomacher Lab Blender also showed an antilisterial activity which resulted in a decrease in number of viable bacteria and in sublethal damage. The effect was shown by five carrot cultivars and acted on nine strains ofL. monocytogenesand single strains ofL. innocua, L. ivanovii, L. seeligeri, L. welshimeri. This antilisterial effect was heat‐labile, was inactivated after a few hours at 4°C or at 30°C and was active over the pH range 5.8 to 7.0. Maceration of carrots in an Atomix blender for 1 min or in liquid nitrogen destroyed the antilisterial a

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1991.tb02744.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Conventional heating was used to expose cells ofListeria monocytogenes, either in broth orin situon chicken skin, to the mean times and temperatures that are achieved during a 28 min period of microwave cooking of a whole chicken. HeatingL. monocytogenesby this method in culture broth resulted in a reduction in viable cell numbers by a factor of greater than 106upon reaching 70°C. Simulated microwave cooking ofL. monocytogenes in situ, on chicken skin, resulted in more variability in the numbers of survivors. Heating for the full cook time of 28 min, however, resulted in a mean measured temperature of 85°C and no surviving listerias were detected. This indicated a reduction in viable numbers of greater than 106. To reduce temperature variation, cells were heated on skin in a submerged system in which exposure to 70°C for 2 min resulted in a reduction in viable cell numbers of all strains of listerias tested of between 106and 108. These results show that when a temperature of 70°C is reached and maintained for at least 2 min throughout a food there is a substantial reduction in the numbers ofL. monocytogenes. The survival of this organism during microwave heating when temperatures of over 70°C are reported is probably due to uneven heating by microwave ovens resulting in the presence of cold spots in the product. The heat resistance ofL. monocytogenesis comparable with that of many other non‐sporing mesophilic ba

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1991.tb02745.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Artificial self‐purification (depuration) of mussels (Mytilus edulis) was undertaken at three temperatures, under conditions similar to those likely to be experienced in the commercial shellfish industry of the UK. During a 72 h depuration period, samples of mussel flesh were examined for three faecal indicator bacteria,Escherichia coli, Group D faecal streptococci and sulphite‐reducingClostridiumspores, and two types of bacteriophage. There was a statistically significant difference in the elimination rate of faecal indicator bacteria compared with the slower rate for both bacteriopha

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1991.tb02746.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

In a model system medium‐chain fatty acids (MCFA) C6–C12in coconut and palm kernel oil are converted to methyl ketones, one carbon atom less than the parent fatty acids, by two strains ofPenicillium crustosumThom. Conversion rates of up to 32% were seen for decanoic acid at 25°C. The optimum temperature for ketone production was 25°C in liquid suspension culture. Coconut oil contains 3.23 mmol/g MCFAs compared with 2.34 mmol/g for palm kernel oil. Coconut oil is more prone to fungal spoilage (growth and ketone production) than palm kernel oil. The main end product of fermentation was 2‐undecanone reflecting the high concentration of dodecanoic acid in the substrates. Ketonic rancidity is fungal engendered. The reaction can be controlled by reducing the temperature (4°C), reducing the water activity (0.91) or by addition of sorbic acid (20

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1991.tb02747.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

A study of the conjugal transfer of ColV,I‐K94 tn10 from acid‐treated donors suggested that acid‐habituated recipients repair acid‐damaged plasmid DNA better than those that are not habituated. The presence of an increased repair activity for acid‐damaged DNA in habituated cells was confirmed by isolating pBR322 from acid‐treated organisms; habituated cells produced more transformants when transformed by it than did non‐habituated ones. Additionally, agarose gel electrophoretic studies of pBR322 DNA isolated from acid‐damaged cells and tests of its transforming activity both indicated that plasmid DNA in habituated cells is less damaged by extreme acidity than is that in non‐hab

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1991.tb02748.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY