American journal of pharmacy . The methods used by the physical chemist to measure rates ofchemical reactions can be applied to investigate the process of alco-holic fermentation by living and growing yeast cells. The resultsobtained in this way are valuable, for they not only give new informa-tion, but also make is possible to bring into line results obtained byother methods. In this communication yeast growth and alcoholicfermentation are considered from this point of view. The subject matter may be explained by describing the growthof yeast cells in a nutrient medium, and by pointing out th
American journal of pharmacy . The methods used by the physical chemist to measure rates ofchemical reactions can be applied to investigate the process of alco-holic fermentation by living and growing yeast cells. The resultsobtained in this way are valuable, for they not only give new informa-tion, but also make is possible to bring into line results obtained byother methods. In this communication yeast growth and alcoholicfermentation are considered from this point of view. The subject matter may be explained by describing the growthof yeast cells in a nutrient medium, and by pointing out the mainfactors which determine the rate of growth and rate of fermentationat different stages of the of cells per Cc. Diagram of Yeast = lag phase in growth; B = logarithmic phase; C = retarded growth;D = yeast crop; E = death of yeast cells. If a trace of yeast is seeded into malt wort, which is a medium * Reprinted from Journal of Society of Chemical Industry, Oct. 31, 1919. By Arthur Slator. Time ?. io6 Yeast Growth. (Am. Jour. Pharm.\ February, 1920. containing all foods necessary for yeast growth and also large amountsof fermentable sugars, the yeast cells bud and grow. If the num-ber of cells is plotted against the time a curve of the type given inthe diagram is obtained. After a certain initial disturbance (lag-phase) the cells multiplyregularly, the number increasing logarithmically with the the usual equations employed to calculate the rate of unimolecu-lar chemical reactions can be applied to yeast growth over thisperiod, if note is made that the reaction is increasing in rate insteadof decreasing as is the case with ordinary chemical reactions. Thereare several methods of measuring this logarithmic constant of growth(K.) or the generation time (G. T.) which is a number inverselyproportional to K. (G. T. X K. = log. 2). Some of them de-pend on counting yeast cells under the microscope, and others onmeasuring rates of fermentation from
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Keywords: ., bookcentury1800, bookidamerica, booksubjectpharmacy, bookyear1835
