Studies of Bacteria from Fermenting Egg White and the Production of Pure Culture Fermentations.

In a previous study (1942) an investigation was made of the bacterial and chemical changes taking place during the natural fermentation of egg white, a preliminary step in the commercial processes for preparing dried egg albumen. This study established rather conclusively that predominance of bacteria of either the Aerobacter or Escherichia genus is necessary from the standpoint of the production of a high quality dried albumen from naturally fermented egg white. Other bacterial types were occasionally encountered in experimental laboratory fermentations but it was found that when species of Proteus or Pseudomonas were present in large numbers during such fermentations, a dried albumen of inferior quality was usually obtained. The cultures isolated in this investigation have been studied more thoroughly with the object of confirming the tentative classifications originally made, and determining their effects on sterile egg white in pure culture. The results of microscopic and cultural studies on twenty strains tentatively classified in the genus Aerobacter are given in Table 1. From the data given in this table it appears that 12 of these cultures are strains of the species Aerobacter aerogenes (Bergey, 1939). They produce acid and gas from glycerol and do not liquefy gelatin. Seven strains were motile and five were non-motile. Eight strains were encapsulated. They all fermented glucose, mannose, and galactose, the three sugars known to be present in egg white. They also fermented sucrose, maltose, arabinose, raffinose, cellobiose, mannitol and starch, although six strains failed to ferment dulcitol. They all brought about acid coagulation in litmus milk and produced nitrites from nitrates. Only one strain produced indole in tryptone broth. The remaining eight strains may also be Aerobacter aerogenes since they are not exactly typical of the other species in this genus, namely, Aerobacter cloacae (Bergey, 1939). They do not liquefy gelatin. Neither do they ferment glycerol, starch or dulcitol. They are all actively motile by virtue of peritrichous flagella and none have capsules. It is believed, therefore, that they resemble Aerobacter cloacae more closely than Aerobacter aerogenes and should be classified as strains of the former. All eight ferment glucose, mannose and galactose, with the production of acid and gas, fully as vigorously as the 12 typical strains of Aerobacter aerogenes. The results of similar studies with 13 isolations tentatively classified as belonging to the genus Escherichia are given in table 2.