Yeast fermentation of pentose phosphoric acids

Abstract

D-Ribose-5-phosphoric acid was readily fermented by Lebedew macerate of dried beer yeast with the formation of 1 mol. alcohol, 1 mol. CO2, 1 mol. free phosphoric acid and an as yet unidentified product. Other pentose-5-phosphoric acids were very little fermented (d-arabinose and xylose esters were used). The rate of fermentation of ribose phosph. was similar to that of glucose or hexose monophosphate (Robison ester), when allowance was made for the fact that these substances both gave 2 mol. CO2 and alc., instead of only the 1 given by ribose phosp. Intact yeast cells hardly fermented ribose or its phosphoric ester. An enzyme prep. free from coenzyme and phosphate required the addition of cozymase and phosphoric acid before fermentation set in. An activator (hexose diphosphate, acetaldehyde, glycollalde-hyde) was needed to remove the delay in onset of fermentation, as with hexose phosphate fermentation in similar preps. The products of the reaction with the dried enzyme, cozymase, inorg. P, Mg and Mn salts, were the same as with Lebedew as far as the alc., CO2 and inorg. P were concerned. The expts. are being continued to determine the nature of the remaining product. It did not reduce alk. Cu reagent was not precipitated by neutral Pb acetate and contained 2 or more adjacent unsubstituted hydroxyl groups.