ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1989.tb02446.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1989.tb02447.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1989.tb02448.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The diurnal variations in the specific activities of polysaccharide‐degrading enzymes after feeding were monitored in adherent and non‐adherent microbial populations separated from bovine rumen liquor and digesta solids. There were marked differences in the activity profiles of the enzymes within the subpopulations. Enzymes involved in the degradation of soluble carbohydrates were more active in the non‐adherent populations, and in the liquor phase subpopulation activities increased in the 1–2 h post‐feed period. The muralytic enzymes were most active in the adherent population. Specific activities increased by up to 20‐fold over the 24 h period, with an initial five‐fold increase occurring between 8 h and 12 h after feeding. Enzyme levels in the three non‐adherent populations were similar at the end of the postprandial period. In the population recovered from the liquid associated with the digesta particles, however, the activities did not increase until the latter stages of the period, whereas in the non‐adherent population from the digesta solids the activities varied little during the diurnal cycle. The numbers of micro‐organisms associated with the digesta solids were similar at 2 h and 20 h after feeding; the variations in enzyme levels did not occur as a result of a population increase but were due to increased activities in an established population. The plant cell wall structural polysaccharides were degraded at different rates. There was no appreciable cellulose digestion during the first 8 h of the postprandial period and although hemicellulosic constituents were removed continuously the rate of loss of both polymers was increased in the later stages of the diurnal cycle when enzyme acti

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1989.tb02449.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The survival of several strains ofStaphylococcus aureusafter heat stress in different menstrua was not logarithmic and F‐values were determined to express their resistance to heat. Of the strains tested,Staph, aureus234 (enterotoxin B) was the most heat resistant andStaph. aureus790 (enterotoxin E) was the most heat sensitive. Buffalo milk gave the best protection to all the strains ofStaph. aureusagainst heat, followed by cow's milk; phosphate‐buffered saline gave the least protection. Soyabean casein digest agar gave maximum recovery of survivors followed by brain heart infusion and Baird‐Parker medium. At 50°C there was no marked variation in coagulase production by the surviving strains but at 55 and 62–5dE C there was complete loss of coagulase activity. There was a decreased deoxyribonuclease (DNase) production by all the strains ofStaph. aureusafter heat stress. Heat‐treatment at 55 and 62mD5dE C resulted in loss of enterotoxin production by all the survivors except S6and 234, the surviving cells of which still prodused enterotoxin B after heat treatment at 55dE C. Most of the survivors regained lost characteristics such as coagulase, DNase and enterotoxin production after four to five passages through BHI which suggests that subculture ofStaph. aureusrecovered from heat‐processed milk is necessary to avoid f

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1989.tb02450.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Gari starter cultures (Gastat) were developed by mixing pure single strains of the organisms that ferment cassava. They were propagated and maintained as granules on dried cocoyam slurry. The cultures were tested for fermentative and acid‐producing activity. The acidity produced at 30°C varied from 0.07% to 0.85% lactic acid with maximum levels occurring after 48 h. High levels of reducing sugar were produced during the first 24 h. The amounts produced were about 50% more than those from the self‐inoculated cassava. The quality of the gari produced by the starter cultures was good and well accepted. The texture was similar to that produced by natural fermentation. These results highlight the possibility of using starter cultures in the large‐scale production o

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1989.tb02451.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

A biotin‐labelled DNA probe was used in a dot‐blot hybridization test to demonstrate the presence ofEscherichia coliin a variety of artificially contaminated foodstuffs. Positive hybridization was detected by using a streptavidine/polyalkaline phosphatase conjugate to generate an insoluble coloured precipitate in the presence of an appropriate dye. The colour intensity was measured with a computer‐controlled image analysis system which assessed objectively the hybridization signal produced by each sample. The method was capable of distinguishing positive hybridization at cell concentrations exceeding 104cells/dot‐blot, equivalent to 2×107cells/g food, and had none of the drawbacks normally associated with the use of radioactively labelled DNA in hybridization techniques. The procedure is highly specific and takes less than 30 h. Many samples can be screened simultaneously and the procedure can be used to detect any species for which a suitable DNA probe is

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1989.tb02452.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

A two electrode system mounted as a single probe was developed to measure electrochemically the rate of reduction of a redox mediator (thionine) by bacteria. The system gave a rapid (2 min) bacterial‐dependent current above 2.5×105cfu/ml with pure cultures of bacteria, but when applied to the measurement of the bacterial contamination in samples of meat and milk it was unable to detect or quantify the contamination reliably. Incubation of samples for a few hours before examination enabled the system to detect bacteria in excess of 106cfu/

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1989.tb02453.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The summer prevalence ofVibrio parahaemolyticusand other halophilic vibrios in seafood from Hong Kong markets was investigated. Halophilic vibrios were isolated from all seven types of seafood examined, and comprised 9.1%, 8% and 6.1% of contaminating aerobic heterotrophic bacteria from mussels, clams and oysters respectively. Sucrose‐positive vibrios were more common than sucrose‐negative varieties.Vibrio alginolyticuswas the most frequently isolated species, followed byV. parahaemolyticus, V. harveyi, V.fluvialis, V. vulnificus, V. pelagius, V. campbellii, V. spendidus and V. marinus.Mussels contained the highest concentration ofV. parahaemolyticus(4.6×103/g); oysters and clams contained 3.4×104/g and 6.5×103/g respectively. The ubiquity and relatively high concentrations ofV. parahaemolyticusand other pathogenic vibrios in shellfish is a potential public health hazard in Hong Kong and other subtropical Asian cou

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1989.tb02454.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Rapid demonstration of mycobacteria in slaughter pigs is important for medical, epidemiological and economic reasons. The Bactec radiometric system detected more mycobacteria in less time than conventional culture on solid medium.

ISSN:0021-8847    

DOI:10.1111/j.1365-2672.1989.tb02455.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY