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COMMUNICATIONS TO THE EDITOR ACTION OF DINITROCRESOL ON YEAST FERMENTATION AND OXIDATION
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in amount of alcohol produced aerobically; in fact, any alcohol initially present was oxidized. Sir: (5) Since part of the carbon dioxide produced The details of a study of the effect of 4,6- aerobically resulted from fermentation, an amount dinitro-o-cresol (DNC) on the metabolic activi- of carbon dioxide equimolar to the alcohol proties of yeast will be presented in a paper now be- duced aerobically was subtracted from the total ing prepared for publication. The present com- to get the oxidative carbon dioxide. In several munication gives a summary of certain of these experiments where this was done the ratio of oxiexperiments conducted with normally fermenting dative carbon dioxide to oxygen consumed was yeast which bear on the mechanism of DNC ac- not significantly influenced by the presence of tion. These experiments were conducted in Janu- 10-5 M DNC. M , DNC increased not only the ary, Februaiy and March, 1935, with yeast ob(6) At tained from Xnheuser-Busch, Inc. rate of aerobic oxygen consumption and anaerobic (1) The rate of anaerobic carbon dioxide pro- carbon dioxide production, but also the total duction by yeast in a glucose-phosphate medium amount of glucose oxidized or fermented as dr(pH 4.45) was increased by DNC in concentra- termined from the products of reaction. tions from to 10-4 molar. Greater concen(7) The amount of glucose disappearing, as trations of 13NC caused a subnormal anaerobic determined by analysis, was greater than that carbon dioxjde production. Maximum stimula- accounted for by the products of oxidation and,'or M DNC with fermentation. DNC had no effect on the amount tion occurred at lov5 to 2 X yeast in a concentration of 6 mg. per cc. In a of glucose which disappeared. (8) Actual count showed no increase in number normal system Qg& was, in two experiments, 74.5 and 78; after addition of 2 X M DNC of yeast cells during the period of the experiment. Qg& was increased to 159 and 157, respectively. (9) At optimum concentration, DNC stimulated Analysis showed that an amount of alcohol anaerobic carbon dioxide and alcohol production equimolar to the anaerobic carbon dioxide was to a greater degree than it stimulated oxygen produced in the presence of optimum concentra- consumption in a corresponding aerobic system, tion of DNC. and caused increased anaerobic utilization of ( 2 ) The rate of oxygen consumption by buffer sufficient sugar to account for excess oxygen conwashed yeast was increased by DNC in concen- sumed and excess alcohol produced in the aerobic trations from lov6 to 2 x molar. Greater system. These results are not incompatible with the concentrations of DNC caused a subnormal oxygen consumption. Maximum stimulation (50 view that the principal metabolic effect of DNC to 100%) occurred a t 10-6 M DNC. With 1 to is to accelerate one of the anaerobic processes oc6 mg. of yeast per cc., oxygen consumption was curring early in the series of reactions concerned stimulated by DNC in a medium containing with the formation of (a) substances subsequently glucose or alcohol as substrate but not in a me- oxidized by the cell, and (b) products of anaerobic fermentation. dium containing pyruvate as substrate. (3) The rate of reduction of cytochrome (549 mp We wish to express our indebtedness to Miss band) in buffer washed yeast was increased by A. K. Keltch for her cooperation. DNC in concentrations from 10" to 2 X M. LILLYRESEARCH LABORATORIES M. E. KRAHL INDIANA G. H. A. CLOWES Greater concentrations of DNC lengthened the INDIANAPOLIS, RECEIVED APRIL11, 1935 reduction time. The greatest shortening of reduction time (from one hundred and five to THE RELATIVE RATES OF COMBINATION OF M DNC. thirty-two seconds) was effected by LIGHT AND H Z A V Y HYDROGEN WITH ETHYLENE (4) With (a concentration of DNC M), which caused the optimum rise in oxygen con- Sir: Preliminary determinations of the rate of comsumption of yeast in a glucose medium, an increased aerobic alcohol production occurred only bination of heavy hydrogen with ethylene have a t high glucose concentrations and for limited been made. The reaction has been carried out times. At low glucose concentrations, and over both on a copper catalyst and homogeneously, the extended time periods, DNC effected no increase rate of these reactions being compared with the
