The fermentation of l-threonine, l-serine, l-cysteine and acrylic acid by a Gram-negative coccus

Abstract

Washed suspensions of LC3 strain of a gram-negative, anaerobic organism isolated from sheeps'' rumen contents, ferment L-serine, L-threonine, L-cysteine and acrylate with the formation of H2, CO2, ammonia and volatile fatty acids. Small amounts of an acid with the same retention volume as formic acid were produced from all 3 amino acids but not from acrylate. Propionate and smaller amounts of acetate, butyrate and valerate were formed from threonine. The predominant acids formed from serine and cysteine were acetate and butyrate. Acetate, propionate and some valerate were the major acidic end products of acrylate fermentation. Acetone powders of LC3 decompose L-threonine and L-serine but not L-cysteine. At pH 6.5 the main products from threonine were H2, CO2, propionate and alpha-oxobutyrate. Acetate, pyruvate, H2 and CO2 were produced from serine at pH 6.5. At pH 9.5 more of the oxo-acids accumulated. Acetone powders of LC3 metabolize acrylate. Under a hydrogen gas-phase, H2 is taken up and some CO2 is produced, along with propionate and an amount of acetate approximately equivalent to the CO2 formed.