摘要:

The extracellular amylase produced byClostridium thermocellumstrain SS8 on starch was characterized as a β‐amylase based on blue value reduction test and the production of maltose from starch. The enzyme had a temperature and pH optima of 60°C and 6.0, respectively. Of the metal ions tested, Ca2 +and Mg2 +had little effect on enzyme activity, but their presence increased its thermal stability. Ca2 +displayed a higher stabilizing effect and at 10 mmol 1‐1Ca2 +, the enzyme retained 86% activity even after exposure at 70°C for 30 min. The amylase was induced on starch or maltose but was repressed strongly by g

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1994.tb00875.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

SeveralPediococcus acidilacticistrains produce a plasmid‐encoded bacteriocin, pediocin AcH. Previous studies have shown that this plasmid, designated as pSMB 74, encodes genes associated with the production of prepediocin, its post‐translation processing to pediocin AcH, transmembrane translocation of these molecules, and immunity of producer cells against pediocin AcH. We report here the complete nucleotide sequence of pSMB 74. The plasmid has a total of 8877 bp. Four genes have been located on pSMB 74. The genes are arranged in a gene cluster of 3500 bp and share a common promoter and rho‐independent stem‐loop terminator. The four genes, each with independent ribosome binding sites (rbs), initiation and termination codons and spacer sequences in between, were designated aspapA,papB,papC andpapD and encode respectively for proteins of 62, 112, 174 and 724 amino acids. The results of this study can be useful either to introduce a suitable marker at a unique restriction site in pSMB 74 and use it as a vector or to clone thepapgene cluster in a suitable plasmid and transform desirable strains for pediocin AcH production. The gene sequence has been submitted to Gene Bank (Acc. No.

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1994.tb00876.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

An undescribed bacterium capable of clearing tannic acid‐protein complexes has been isolated from ruminal contents of feral goats browsing tannin‐richAcaciaspecies. The bacterium is a Gram‐positive facultative anaerobe, characterized as aStreptococcus, but DNA‐DNA hybridization and 16S rDNA sequencing show that it is distinct from the common ruminal speciesStrep. bovis.We propose the nameStreptococcus caprinusfor this species. The type strain isStrep. caprinus2.3, Australian Collection of Microorganisms (ACM) 3969. The bacterium grows in media containing at least 2.5% w/v tannic acid or condensed tannin and produces zones of clearing around colonies on nutrient agar plates with added tannic acid.Streptococcus caprinusis not a major inhabitant of domestic livestock, but is found in feral goats browsing tannin‐richAcaciaspecies, at a population of up to 2 times 106cfu ml‐1of

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1994.tb00877.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The effectiveness of pressures ranging from 150 to 2000 bar, applied by means of a continuous homogenizer, on the cell viability of spoilage or pathogenic micro‐organisms, was evaluated. Moreover, the effects of microstructural modifications of food systems associated with the treatments on cell viability and on its subsequent evolution were investigated. Modulation of the homogenization pressure allowed strong instantaneous reductions of the initial numbers ofListeria monocytogenes, Yersinia enterocolitica, Bacillus subtilisand the yeastYarrowia lipolytica.The combined effects of the initial pressure treatment and space reduction, resulting from the microstructural modifications of food systems, increased the safety and the shelf‐life both of water in oil and oil in water emulsi

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1994.tb00878.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Nisin (NisaplinTM) was added to scald water and used to treatListeria monocytogeneswhich were either directly suspended in the water or attached to turkey skin. There was at least a 1 log decrease of listeria for the nisin treatments. This was followed by further reductions when the samples were stored under refrigeration. Heat exhibited a synergistic relationship with the nisin when the cells were directly suspended in the scald water. A 2 log decrease was observed immediately after this treatment and there was complete elimination of the listeria after 48 h of refrigeration. However, this relationship was not as obvious when the cells were first attached to the turkey skin. In these latter experiments, the nisin treatments resulted in reductions in the listeria levels but they were smaller than those observed when the cells were directly suspended in the scald water.

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1994.tb00879.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Certain members of the family Enterobacteriaceae developing on beef steaks packaged in modified atmospheres may grow on the medium CFC (Cephaloridine‐Fucidin‐Cetrimide), which is selective for pseudomonads. The addition of arginine (1% w/v) and the pH indicator phenol red (0.002% w/v) to this medium differentiated between the two groups. The pseudomonads produced ammonia from arginine, whereas Enterobacteriaceae generally did not use this substrate. The alkaline drift in pH in and around pseudomonad colonies gave a pink colouration with phenol

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1994.tb00880.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Sixty‐one different fortified wines, from the Douro valley, inoculated withLactobacillus hilgardiipreviously isolated from a spoiled fortified wine, were sampled progressively for 280 d. Samples were analysed for volatile acidity (acetic acid) and frozen for subsequent analysis where appropriate. After 280 d, 7/61 wines showed increases in volatile acidity of>0.5 g l‐1and were considered spoiled. Retrospective analysis of frozen samples of spoilage‐positive wines showed that all had apparently undergone a malolactic conversion before the onset of heterolactic activity (acetate production). It is suggested that the monitoring of L‐lactic acid might be a method of detecting activity of spoilage lactobacilli before the onset of s

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1994.tb00881.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Six suspensions of non‐culturableCampylobacterspp. were administered by gavage to day‐of‐hatch chicks. Four non‐culturable isolates ofCampylobacterspp. were found to colonize low numbers (5/79) of 1‐week‐old chicks, while two isolates did not (0/30). The original and recoveredCampylobacterspp. isolates were serotyped and examined by restriction enzyme analysis. Evidence of clonality of twoCamp, jejuniisolates was d

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1994.tb00882.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

A polyclonal antiserum against saxitoxin (STX) was used in a competitive enzyme immunoassay for the detection of paralytic shellfish poisoning toxins. The extent of cross‐reactions was determined from the amounts of neoSTX, decarbamoylSTX and gonyautoxin 2/3 (GTX2/3) that gave 50% inhibition in the assay. Horseradish peroxidase (HRP) conjugates of the toxins and a bovine serum albumin conjugate of STX (STX‐BSA) were used. When compared with STX‐BSA and STX as standard, the extent varied to which heterologous conjugates affected the binding values of the other toxins to the antibodies. The antibodies did not bind GTX2/3‐HRP. By use of neoSTX‐HRP or decarbamoylSTX‐HRP as the labelled antigen instead of STX‐HRP, the detection limit for neoSTX was improved t

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1994.tb00883.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

A strain ofBradyrhizobium japonicumwas isolated that accumulated anthranilic acid, indole, 3‐indoleacetic acid, 3‐indolelactic acid and 3‐indolepyruvic acid in culture. Such accumulations are indicative of altered tryptophan metabolism. Soybean plants inoculated with these bacteria formed more nodules (349vs159 per plant) and had more nodule mass (3.9vs2.2 g wet wt per plant) than plants inoculated with the wild‐type

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1994.tb00884.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY