Experimental Studies on the Formation of Volatile Nitrogen Compounds Induced by Pseudomonas Fragi in A Synthetic Medium with Amino Acids as Source of Nitrogen

Abstract

The influence of the growth of Pseudomonas fragi strain F 111 was studied in a synthetic medium. It was shown that volatile nitrogen compounds were rapidly liberated as a result of the decomposition at 5°C of arginine and histidine. A later and slower increase of TVN was observed in media, which contained lysine or urea. From the other 7 amino acids which were included in the test, no increase of TVN was observed to be caused by the strain F 11.

It was shown that within the range of 0.05 to 0.8 % histidine added to the basic salt solution the amount of TVN liberated was correlated to the amount of histidine included in the media. At the TVN maximum approx. 50 % of the amino acid nitrogen of the medium was recovered as TVN.

It was further shown that the liberation of TVN was correlated to the added amount of arginine and histidine included in the growth medium. The presence of lysine also influenced on the TVN maximum which was reached. In the synthetic medium to which arginine or histidine was added the growth of strain F 111 was stimulated by the presence of glucose. The acids produced by the oxidative breakdown of glucose were neutralized partly by the volatile bases produced in the decomposition of amino acids.

The ability of the Pseudomonas fragi to grow in anaerobic conditions and to produce enzymes which could decompose histidine was studied. It was concluded that the anaerobic breakdown of histidine was similar to the anaerobic breakdown of arginine reported by other authors.

Sammanfattning

Inverkan av tillväxten av Pseudomonas fragi, stam F 111, på aminosyror studerades i ett syntetiskt medium. Det visades att flyktiga kvävebaser bildades snabbt vid nedbrytningen av arginin och histidin vid inkubering i 5° C. En senare och långsammare ökning av TVN observerades i media som innehöll lysin eller urinämne. Ingen ökning av TVN förorsakad av stam F 111 påvisades i media som innehöll någon av de sju övriga aminosyror som ingick i prövningen.

Inom gränserna 0,05 till 0,8 % histidin visades mängden frigjort TVN vara korrelerad till den mängd av aminosyran som tillfördes bassubstratet. Vid maximihalten av TVN kunde ungefär 50 % av aminosyrans kvävehalt återfinnas som flyktigt kväve.

Det visades också att halten bildat flyktigt kväve var korrelerad till summan av mängden histidin och arginin. Närvaron av lysin påverkade också TVN maximum. I det syntetiska mediet till vilket arginin eller histidin hade tillsatts stimulerades tillväxten av Pseudomonas fragi av närvaron av glykos. De syror som producerades vid den oxidativa nedbrytningen av glykos neutraliserades av flyktiga baser som producerades vid nedbrytningen av aminosyror.

Förmågan hos Pseudomonas fragi att växa under anaeroba förhållanden och att producera enzym som kan bryta ned histidin under dessa förhållanden studerades. Det påvisades att nedbrytningen av histidin liknade den anaeroba nedbrytningen av arginin som rapporterats av andra författare.