| 1. |
- Andersson, Rolf E.
(författare)
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Inhibition of Staphylococcus aureus and spheroplasts of Gram-negative bacteria by an antagonistic compound produced by a strain of Lactobacillus plantarum
- 1986
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Ingår i: International Journal of Food Microbiology. - : Elsevier BV. - 0168-1605 .- 1879-3460. ; 3:3, s. 149-160
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Tidskriftsartikel (refereegranskat)abstract
- A strain of Lactobacillus plantarum was examined for production of an extracellular antagonistic compound. Cellfree preparations, dialyzed to remove organic acids, were used in inhibition studies which revealed that Gram-positive bacteria were sensitive. Among these, Staphylococcus aureus was chosen for further characterization of the agent. The antagonistic compound was susceptible to breakdown by proteolytic enzymes and its effect was completely lost after heat treatment at 121°C for 15 min. Ultrafiltration studies indicated that the agent had a molecular weight of over 100, 000, suggesting a complex protein-containing aggregate. The antagonistic effect was found to be highest at low pH values and S. aureus was shown to be able to adapt to the agent. Most Gram-negative bacteria were resistant to the compound. However, after their transformation to spheroplasts, which removed most of the cell envelopes, these bacteria were sensitized. The conclusion is that the antagonistic mechanism probably includes agent influence on the cell surface. © 1986.
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| 2. |
- Andersson, Rolf E.
(författare)
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Nitrate reduction during fermentation by Gram-negative bacterial activity in carrots
- 1985
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Ingår i: International Journal of Food Microbiology. - : Elsevier BV. - 0168-1605 .- 1879-3460. ; 2:4, s. 219-225
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Tidskriftsartikel (refereegranskat)abstract
- Carrots were subjected to lactic acid fermentation through the action of a starter culture, Lactobacillus plantarum, and changes in the amount of both the naturally present and added nitrate were recorded. The nitrate content in the carrots decreased to about 10% of the original amount during the initial stage of the fermentation process. By using irradiation-sterilized carrots it was shown that the decrease in the nitrate content is a result of the activity of the Gram-negative bacteria, which dominate the flora during the initial stage of the fermentation process, and that the lactic acid bacteria present were unable to affect the nitrate content. The nitrite concentration was also determined and was found not to exceed 0.2 mg/kg on any occasion. The conclusion is that if the nitrate content of carrots is to be lowered in a fermentation process, this process must be controlled in such a way as to allow the original Gram-negative flora to reduce the nitrate amount before the starter organism takes over. © 1985.
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