Formation of Acidic Carbonyl Compounds by Some Homofermentative Lactic Acid Bacteria

HUBERand Staphylococcus aureus (Anderson et al., 1958); Brettanomyces schanderlii (Nelson et al., 1960), and the mold Absidia orchidis.The tendency of all microorganisms to contain similar amounts of these amino acids, coupled with the un- likely possibility of altering the amino acid composition of integral cell proteins, indicates that the use of micro- organisms as concentrated sources of specific essential amino acids may be limited to those organisms which also produce amino acids extracellularly.The formation of such uncombined amino acids is more amenable to modification than is the formation of constitutive cellular amino acids.Further study of those organisms which form the greatest amounts of cellular amino acids may disclose strains which liberate the desired amino acids extracellularly.Such an organism would make a particularly valuable source of amino acids for feed supplementation. SUMMARYThe nitrogen, lysine, methionine, and tryptophan contents of 131 species of molds grown in shaken culture were determined.The average nitrogen content was 6.4 i 1.4 per cent of the dry weight; the average amounts of lysine, methionine, and tryptophan in the cells, expressed as grams of amino acid per 16 g of nitrogen, were 6.8 14 1.5, 1.2 ± 0.4, and 0.8 i 0.3, respectively.The molds were similar to the yeasts with respect to methionine: nitrogen and tryptophan: nitrogen ratios and like the bacteria with regard to the lysine:nitrogen ratio.The variability of the groups, as indicated by the coefficients of variation, was lowest for the yeasts; it was about equal for bacteria and molds, except that the bacteria showed somewhat more variability in lysine content.