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E R Vedamuthu

Publications and source records attributed to E R Vedamuthu.

8 recordsLinked to original sources
PubMed1988

Inhibition of Listeria monocytogenes by using bacteriocin PA-1 produced by Pediococcus acidilactici PAC 1.0.

The bacteriocin produced by Pediococcus acidilactici PAC 1.0, previously designated PA-1 bacteriocin, was found to be inhibitory and bactericidal for Listeria monocytogenes. A dried powder prepared from PAC 1.0 culture supernatant fortified with 10% milk powder was found to contain bacteriocin activity. An MIC against L. monocytogenes and lytic effects in broth cultures were determined. Inhibition by PA-1 powder occurred over the pH range 5.5 to 7.0 and at both 4 and 32 degrees C. In addition, inhibition of L. monocytogenes was demonstrated in several food systems including dressed cottage cheese, half-and-half cream, and cheese sauce.

Bacteriocins↗
PubMed1987

Phage resistance in Streptococcus lactis ssp. diacetylactis transconjugant SLA3.2501 and its derivatives.

Phage 18-16, which was virulent for Streptococcus lactis ssp. diacetylactis SLA3.25 was used to study phage-resistant characteristics of mucoid S. lactis ssp. diacetylactis transconjugant SLA3.2501 obtained through conjugative cotransfer of pSRQ2201 (Lac-plasmid) and pSRQ2202 (Muc-plasmid) to SLA3.25 (15). Interaction of phage 18-16 with SLA3.2501 and its derivatives showed that phage resistance was not related to either the lack of phage adsorption or restriction-modification. Suppression of phage replication in SLA3.2501 and its derivatives was not completely relieved by curing of either pSRQ2201 or pSRQ2202 or both.

Bacteriophages↗
PubMed1975

Beta-galactosidase of Propionibacterium shermanii.

Ten strains of Propionibacterium shermanii were tested for beta-galactosidase (beta-gal) activity. Of these ten strains, five yielded enhanced enzyme activity when cell suspensions were treated with toluene-acetone; on solvent treatment, the remaining five lost a considerable portion of the activity found in whole-cell suspensions. By using a strain yielding decreased activity upon solvent treatment, explanations for the loss in activity were sought through assays for possible alternative beta-galactoside utilization mechanisms. When this strain was assayed for beta-D-phosphogalactoside galactohydrolase by using orthonitrophenyl-beta-D-galactopyranoside-6-P04 as a substrate, the activity was wither lower or indiffernt as compared with beta-gal activity determined simultaneously. Cell suspensions of P. shermanii 7 and 22 (strains chosen for further work) grown separately on the individual substrates (lactose, glucose, galactose, and sodium lactate) did not show significant differences in beta-gal activity. Optimal temperature for beta-gal activity in untreated and toluene-acetone-treated cell suspensions of strain 7 was 52 C. With strain 22, of the temperatures tested, maximal activity in untreated cell suspensions was noted at 58 C and with solvent-treated cells at 32 C. In the cell-free extract (CFE) system, both strains exhibited maximal activity at 52 C. Optimal pH for untreated and solvent-treated cell suspensions of both strains was around 7.5. In the P. shermanii 22 CFE system, maximal activity occurred at pH 7.0; pH had very little effect on enzyme activity in P. shermanii 7 CFE. Sodium or potassium phosphate buffers in the assay system yielded the best activity. In the CFE system of these two strains, Mn2+ was definitely stimulatory, but in untreated and solvent-treated cell systems of these strains presence or absence of Mn2+ in the assay system had variable effects on enzyme activity. Maximal beta-gal activity was noted in P. shermanii 7 cells harvested after 28 h of growth at 32 C in sodium lactate broth. Sulfhydryl-group blocking agents inhibited enzyme activity in P. shermanii 22 CFE; the inhibition was partly reversed by dithiothreitol.

Acetone↗
PubMed1971

Isolation of inhibitory factor in raw milk whey active against propionibacteria.

Preparative isolation of the active component(s) in skim milk whey inhibitory for propionibacteria was made by using (NH(4))(2)SO(4) salt fractionation. The crude preparation was further purified by Sephadex G-100 column separation. Disc-gel electrophoresis of the active peak from the Sephadex elution pattern (peak I) showed that this fraction contained almost all of the immune globulin in the column sample. The biologically inactive peaks did not contain any immune globulin. Starch-gel electrophoresis of the active peak revealed the presence of three separate immune globulin fractions. A correlation was also observed between hemolytic reaction of propionibacterial strains and relative resistance to whey inhibition. The investigation showed that one of the immune globulins of milk, pseudoglobulin, was mainly responsible for the suppressive activity of whey.

Ammonium Sulfate↗
PubMed1969

Differential agar medium for separating Streptococcus lactis and Streptococcus cremoris.

The characteristic ability of Streptococcus lactis and inability of Streptococcus cremoris to hydrolyze arginine formed the basis for the development of a differential agar medium to separate these species in pure and mixed cultures. Ammonia liberated from arginine was detected by the pH changes occurring in the medium. The agar contained milk as the sole source of carbohydrate, arginine as the specific substrate, diffusible (K(2)HPO(4)) and nondiffusible (CaCO(3)) buffer systems, and a suitable pH indicator in addition to other ingredients. The nondiffusible buffer system afforded the localization of pH changes, and, hence, the indicator color changes immediately around individual colonies appearing on the medium. S. cremoris produced yellow colonies surrounded by yellow zones on this purple medium because of their ability to produce acid from lactose in the milk. S. lactis, on the other hand, first produced colonies similar to S. cremoris, but subsequent color reversal of pH indicator with the liberation of NH(3) resulted in the discharge of the yellow color. Hence, S. lactis colonies were white and devoid of zones. The difference in their colony color allowed the identification of the species in a mixture of S. cremoris and S. lactis strains. The medium was found suitable for both qualitative and quantitative differentiation.

Agar↗