Properties of Crude Ethylester-forming Enzyme Preparations from Some Lactic Acid and Psychrotrophic Bacteria

Ester-forming enzyme preparations were obtained from 48 h cultures of Streptococcus diacetilactis ATCC 15346, S. lactis ML3, Lactobacillus No. 81 and two strains of psychrotrophic bacteria belonging to the genus Pseudomonas (Strains No. 50 and 53).Optimum pH's of the enzyme preparations of Lactobacillus No. 81 and two strains of the lactic streptococci for the production of ethylbutyrate and ethylhexanoate were 6.5 and 7.0 to 7.5, respectively. Enzymes of Strains No. 50 and 53 had their maximum activities at pH 8.0. The optimum temperature was 32 C for all strains. Enzymes were generally stable below 35 C at pH 7.0, but their activities were rapidly lost at higher temperature. When the esterases were incubated at 4 C for 24 h, Lactobacillus No. 81, the lactic streptococci (Strains ML3 and ATCC 15346), and the psychrotrophic bacteria (Strains No. 50 and 53) were most stable at pH 6.0, 7.0, and 8.0, respectively. Copper, manganese, and cobalt salts inhibited all the enzymes. The inhibitory effect of cobalt on enzyme activities of Strains ML 3, No. 50 and 53 and that of copper on Strain No. 81 were especially significant.