Production of Lactic Acid and an Iodine Staining Substance by Bovine Rumen Bacteria

Abstract

The effect of some conditions on the in vitro formation of an iodine staining substance (ISS) and lactic acid by rumen bacteria was investigated. Most of the conditions studied conceivably could occur in the rumen at some time; included were alteration of pH, change of substrate concentration, addition of salt mixtures, and inhibitors. Production of ISS by rumen bacteria is probably a mechanism which enables them to store a reserve energy supply. It is doubtful whether this reaction is confined solely to rumen microorganisms. Lactic acid is produced from glucose, fructose, maltose, and cellobiose but not from xylose or arabinose. Accumulation of lactic acid occurred when carbohydrate in excess of 200u Moles/11 ml or cell preparations from high speed centri-fugation were used. Lactic acid was detected from glucose (200u Moles) after 2 hours incubation but not after 24 hours regardless of the method of cell preparation. Pyruvate, malate, and succinate yield scant amounts of lactic acid even when 2,000u Moles are used.