摘要:

Cell‐free extracts from strains of leuconostocs and heterofermentative lactobacilli were tested for esterase activities using synthetic substrates. Results showed that esterases from both lactic acid bacteria groups preferentially degraded short‐chain fatty acids. Moreover, even though some similarities between strains of the same species were recorded, the observed differences were not strong enough to distinguish between species and therefore commend this technique as a tool for taxonomy of either leuconostocs or heterofermentative lactobaci

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1996.tb01338.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

The bacteriocin ofPseudomonassp. strain R10 was activein vitroagainst several enteropathogenic bacteria: enterotoxigenicEscherichia coli, Salmonella typhimurium, Salmonella typhi, Shigella flexneriandShigella sonnei. Pseudomonassp. R10 was studied for 5 d in an aquatic system in the presence of strains of the enteropathogenic species mentioned. All the target strains were inhibited in the presence of bacteriocinogenicPseudomonassp. R10 and the highest antibacterial action was observed on the second day. Similar results were obtained with the partially purified bacteriocin, although the greatest bactericidal action, in all the studied target strains, was observed on the first day and the bacterial recounts were slightly higher overall.

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1996.tb01339.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Mesophyllic lactobacilli cultures propagated in MRS broth were inoculated in goats' milk curd slurries and incubated at 30d̀C for 10 d. The micro‐organisms tested wereLactobacillus caseisubsp.caseiIFPL 731 and IFPL 99, andLactobacillus plantarumIFPL 3. Whole cells, cell‐free extracts and cell lysates were evaluated for acceleration of proteolysis in the curd slurries. Conversion of water‐soluble nitrogen to non‐protein nitrogen and amino acid nitrogen, reverse phase‐HPLC peak areas and ratio of hydrophobic to hydrophilic peptides, were all affected by the type of inoculum used as well as the strain under study. The results suggest that the accelerated‐ripening model system developed, containing cell lysates, may be suitable as a good and rapid indicator of the contribution of the strains to proteolysis during che

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1996.tb01340.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

A rapid procedure based on the gas chromatographic analysis of cellular fatty acids was used to differentiate between strains ofLactobacillus sakeandLact. curvatusisolated from dry salami. All strains had very similar fatty acid profiles except four of them which lacked C19 cycl acid, but neither this feature nor other differences in single fatty acid contents could be successfully correlated with the biochemical discrimination ofLact. sakefromLact. curvatus. When, however, strains were compared on the basis of the total content of fatty acids with 18 carbon atoms divided by that with 16 carbon atoms, a very good correlation with strain characterization by classical methods was achieved. It was concluded that selected cellular fatty acid ratios might be useful for characterizing phylogenetically related strains of lactic acid bacteria.

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1996.tb01341.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Nineteen strains of lactic acid producing bacteria of the generaLactobacillusandStreptococcuscollected from different culture collections were screened for the production of extracellular phytase. A number of them exhibited the enzyme activity in the fermentation medium butLactobacillus amylovorusB4552 produced the maximum amounts of phytase ranging from 125 to 146 units ml‐1extracellularly under the submerged cultivation conditions. The optimum glucose and inorganic phosphate levels for highest phytase production were found to be 1% and 24% mg, respectively.Lactobacillus amylovorushas potential in improving nutritional qualities of cereal and pulse‐based food fermentati

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1996.tb01342.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Large entodiniomorphid ciliates taken from the rumen cannot be reliably keptin vivo, and cryopreservation was investigated as an alternative approach to storage. Three species of large entodiniomorphid ciliates (Polyplastron multivesiculatum, Epidinium ecaudatumformacaudatumandOphryoscolex caudatusformatricoronatus) were cryopreserved by one‐step freezing, with mean recoveries of 43, 51 and 80%, respectively. ForOphryoscolex caudatusformatricoronatustwo‐step freezing was investigated. The mean recovery was 30%, and of tested parameters, the equilibration time and temperature of the cryoprotective additive of dimethyl sulphoxide and the length of holding phase at –40d̀C were found to be critical for the success of the

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1996.tb01343.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

AnAcidiphilium cryptumstrain and twoAcidiphilium symbioticumstrains exhibited extremely high tolerance to CdSO4, growing at a concentration of 700 mmol l‐1or more in MGY medium (g l‐1composition: KCl, 0.1; MgSO4.7H2O, 0.25; (NH4)2SO4, 2.0; K2HPO4, 0.25; glucose, 1.0; yeast extract, 0.1) of pH 3. Fairly high concentrations of ZnSO4(200>125 mmol l‐1), NiSO4(50>20 mmol l‐1) and CuSO4(25>15 mmol l‐1) were also tolerated by these strains.Acidiphilium multivorumgrew in the presence of NiSO4(400>350 mmol l‐1), ZnSO4(50>40 mmol l‐1), CdSO4(40>20 mmol l‐1) and CuSO4(20>10 mmol l‐1) while anAcidiphiliumstrain GS18h tolerated ZnSO4(100>60 mmol l‐1), NiSO4(50>30 mmol l‐1), CuSO4(30>15 mmol l‐1) and CdSO4(20>10 mmol l‐1) in the same medium.Acidiphilium angustum, on the other hand, was found to be metal sensitive—growth inhibition being observed at concentrations of 10 mmol l‐1ZnSO4, 10 mmol l‐1CuSO4, 20 mmol l‐1NiSO4and 0.2 mmol l‐1CdSO4in MGY medium.Acidiphilium organovorumalso exhibited tolerance to these metal sulphates in this medium at the levels of 70>60 mmol l‐1for Zn, 20>10 mmol l‐1for Cd and Ni, and 10>5 mmol l‐1for Cu. This strain, interestingly enough, showed a much higher level of tolerance in MAGY medium (g l‐1composition: KCl, 0.15; MgSO4.7H2O, 3.36; K2HPO4, 0.15; (NH4)2SO4, 0.15; Al2(SO4)3.18H2O, 2.25; CaCl2.2H2O, 0.97; MnSO4.H2O, 0.12; glucose, 1.0; yeast extract, 0.1) of pH 3 than in MGY medium. Replacement of carbon source, however, did not affe

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1996.tb01344.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Growth at low positive temperatures and induced phenotypic resistance to extreme cold temperature (freezing/thawing cycles) ofEnterococcus faecaliswere investigated. The effect of low temperatures on the specific growth rates was studied; use of Arrhenius profile and Ratkovsky ‘square‐root’ model allowed determination of the ‘temperature characteristic’ (μ≅ 13 800 cal mol‐1), the critical temperature (Tcrit≅ 17.9d̀C) and the notional minimum growth temperature (To≅ 3.6d̀C). Preincubation ofEnt. faecaliscells at low temperatures (8–16d̀C) during periods corresponding to their generation time resulted in an increased ability of the bacterial cells to withstand short periods of freezing/thawing (‐20d̀C/+37d̀C) challenge. Moreover, the increase of the incubation period at low positive temperature led to a

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1996.tb01345.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Glucoamylases produced byAspergillus nigergrown on wheat bran in solid cultures were purified. Four different forms, GA I, GA I', GA II and GA III, were found having apparent molecular weights of 112 000, 104 000, 74 000 and 61 000 Da respectively. The enzymes are glycoproteins with a carbohydrate content of 16%, and optimal activity at 60d̀C and pH 4.4. Activity was strongly inhibited by Hg2+while Mn2+and Fe2+were stimulatory. The Kmvalues for the degradation of starch and maltose were 3.5 and 7.8 mg ml‐1, respective

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1996.tb01346.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

Heating spores of non‐proteolyticClostridium botulinumat 85d̀C for 2 min followed by plating on a standard laboratory medium reduced the count of viable spores by a factor of greater than 104. A similar result was obtained when the plating medium was supplemented with juice from courgette, carrot or mung bean sprout. When plating was on media supplemented with hen egg white lysozyme or juice from turnip, swede, flat bean, cabbage or potato, heating at 85d̀C for 10 min did not reduce the viable count by a factor of 104. Thus these vegetable juices increased the measured heat resistance of spores of non‐proteolyticCl. botulinum. These findings are relevant to the safety of minimally processed (e.g.sous‐vide

ISSN:0266-8254    

DOI:10.1111/j.1472-765X.1996.tb01347.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY