THE VALUE OF CANE JUICE AS A YEAST NUTRIENT MEDIUM

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1 Administrative and technical viewpoints are often widely divergent, but mutuality of purpose should provide adequate and effective arrangements whereby the technical staff and operators clearly understand the need for advancement along sound economic lines and towards this end be furnished with necessary data, costs, cooperation and support. The improvement illustrated by chart B, as compared to chart A, representing a net gain of $0.475 per ton of cane, was the only basic improvement in the earning position of this company in a number of years. The gain in margin of security is fundamentally important and, in effect, the increased recovery represents a gain in the market position of approximately $0.35 per 100 lbs. of output. We are, at this juncture, closely approaching the reasons why so many producers fail to avail themselves of technical advancement. The administrative office can not undertake the solution of strictly technical problems with dependable effectiveness (although it has often been tried), but it should recognize full responsibility for extending to the technical staff every facility and encouragement for bringing about improvements. In this, few things are more helpful than an interesting and impressive analysis of costs and losses, together with comprehensive studies of other factors which affect the earnings of the concern. Unified treatment of problems can result only from mutual understanding of the objectives. To bring this condition into general effectiveness it is essential that we employ means for establishing a better understanding of possibilities and the advantages of their attainment. In general it may be said that the penalty for not applying useful improvements assumes the aspect of an accumulative loss of earnings and profits. 'A paper prepared by Kazuo Yamafuji and Kano Ohtsu was presented by the chairman. PAPER THE VALUE OF CANE JUICE AS A YEAST NUTRIENT MEDIUM K~zuo YAMAFUJI and KANO OHTSU Government Sugar Experiment Station, Tainan, Formosa INTRODUCTION Many studies have been reported on the different nutrient media which affect the propagation and fermentation of yeast. In our experience, the fermenting power of an excellent yeast is decreased by cultivation in an unsuitable nutrient medium. The culture of yeast is a very important problem not only from a scientific standpoint but also on account of its practical relation to the fermentation industry. There are two nutrient media widely used in yeast culture: (1) malt decoc- 880

2 tion in the West, and (2) kodi decoction in the East. The former has been developed primarily for beer yeast and the latter for Japanese sakc yeast. Both are alcoholic yeasts. Sugarcane is common in the tropics and for a great many years has been the source of cane sugar. No experiments have been brought to our attention, however, regarding the value of cane juice as a yeast nutrient medium. The experiments here reported relate to the value of cane juice as a nutrient medium for the yeasts of commercial interest and include comparative trials with the nutrient media in common use. EXPERIMENT 1 Yeast. We used three species of yeast which are employed commonly in the fermenting industry. '1. Saccharomyces formosensis, a yeast having a strong power to ferment molasses. 2. Saccharomyces cereviseae, the beer yeast. 3. Saccharomyces sake', the Japanese sakk yeast. Nutrient media. We used cane juice, comparing it with malt decoction and kodi decoction as the yeast nutrient media. These three media were prepared by the following methods: 1. Cane juice. The cane stalks (5-10 months old) were pressed at the test mill. The density of the cane juice thus obtained was about 5-12 Bllg. The juice was heated and concentrated up to 30 Bllg. The clear, filtered cane juice was then diluted with water as desired for use and sterilized in the ordinary way. 2. Kodi decoction. Two kilograms of kodi (a product formed by the action of Aspergillus oryzae on steamed rice) were added to 8 liters of water. This was incubated for 4 hours at 55O C. It was then boiled and filtered. 3. Malt decoction. Two kilograms of malt were crushed and stirred into 6 liters of water. This was incubated for 4 hours at 63O C. It was then boiled and filtered. The chemical analyses of these nutrient media were as shown in table 1. Measurement of reproduction and fermentation. Five-day agar streak cultures of Saccharomyces formosensis and Saccharomyces sake' were used as inoculum for the kodi decoction and similar cultures of Saccharomyces cereviseae were used with the malt decoction. The decoctions were incubated for 40 hours at 330 C., 300 C., and 230 C. in the thermostat. The precipitated yeasts were then suspended in 50 ccm. sterilized water. One-ccm. lots of these yeast suspensions were then used as inocula in 50 ccm. of nutrient media in fermentation bottles. The weight of C02 gas formed, the amount of alcohol, the number of yeast cells and the weight of the dried yeast from each nutrient medium were carefully measured. The results are brought together in table 2. I

3 TABLE 1. Total acid in ccm. N Nutrient media Degree Total Total N Ash NaOHper ph Balling sugar % % % 100 ccm. juice Cane juice Kodi decoction Malt decoction TABLE 2. Weight of Degree Fermen- Dried Yield of Weight of Fermen- NutPient Medium Balling tation Yeast in Alcohol COz gas tation Hours 50 ccm. (Volume in 50 ccm. Recovery (gms.1 in %O (gms.1 % - Saccharomyces formosensis (CULTURE TEMP. 33OC.O 882

4 TABLE 2. Continudd Weight of Cane Juice.... Kodi decoction..... Saccharomyces cereviseae (CULTURE TEMP. 30 C.) ; ' % Malt decoction Saccharomyces saki: (CULTURE TEMP. 23 C.) ' Cane Juice , I2O Kodi decoction Malt decoction I I The results presented in table 2 indicate that all three of th duce and ferment better in the cane juice than in the malt deco kodi decoction. The indicated optimum density of cane juice for fe the respective species is as follows:

5 S. formosensis Bllg. S. cereviseae Bllg. S. sake' Bllg. On the other hand, the indicated optimum density of the cane juice for reproduction is as follows: S. formosensis ~11~. S. cereviseae Bllg. S. sake' Bllg. The results further indicate that S. formosensis could ferment up to 90% of the sugar of the cane juice, whereas it was rather difficult for it to ferment as much as 20% of the sugar of the malt decoction. This phenomenon does not appear to be due to the difference of sugar in the nutrient media, because 70% of the sugar of the kodi decoction was fermented by the same yeast. The fermenting power of the yeasts grown in the different nutrient media was carefully observed in a second set of experiments in which series of cross transfers were made to the media indicated. The 5-day agar streak cultures of yeast were used as inocula for the cane juice, the malt decoction, and the kodi decoction of Bllg. After keeping these yeasts for 72 hours at 33O C., 300 C., and 23O C., respectively, in the thermostat, 1 ccm. of these yeast suspensions was added to each 50 ccm. of three different nutrient media and their fermenting powers were carefully observed. The results have been brought together in table 3. The results given in table 3 indicate that the yeasts cultured in cane juice. have the greatest fermenting power. It has been recognized that differences in nutrient media have much to do with the reproduction and fermentation of yeast. In the experiments here reported, the value of cane juice as a yeast nutrient medium has been compared with malt decoction and kodi decoction, using S. formosensis, S. cereviseae, and S. sake', yeasts which are important in the alcoholic fermentation industry. These yeasts reproduced and fermented better in cane juice than in the malt decoction or in the kodi decoction. The precipitated yeast cultured in the cane juice has a much more active fermenting power than precipitated yeast cultivated in either of the other two nutrient media.

6 The first The Fermen- Yield nutrient secondary tation of Alcohol medium nutrient hours (volume medium %) Weight of COs gas in Fermentation 50 ccm. Recovery (gms.1 (%I Total acid in com. N NaOH in 100 ccm..juice ph Saccharomyces formosensis (FERMENTATION TEMP. 3s0c.) Cane juice Kodi decoc Cane Juice Malt decoc Cane Juice Kodi decoc... Kodi decoc Malt decoc Cane Juice Kodi decoc... Malt decoc Malt decoc Saccharomyces cereviseae (FERMENTATION TEMP. 30 c.) Cane Juice Kodi decoc... Cane Juice Malt decoc Cane Juice... Kodi decoc... Kodi decoc... Malt decoc Cane Juice Kodi decoc... Malt decoc Malt decoc Saccharomyces sake (FERMENTATION TEMP. 24Oc.) Cane Juice Kodi decoc... Cane Juice Malt decoc Cane Juice... Kodi decoc Kodi decoc Malt decoc Cane Juice Kodi decoc... Malt decoc ' Malt decoc