Microbiological Aspects of Arrack Production in Batavia [Excerpted]

The following excerpts were published under the title 'Mikrobiologisches über die Arrakfabrikation in Batavia' in the German medical journal Centralblatt für Bakteriologie und Parasitenkunde (Band XVI, pages 97-103) in 1894 by C. Eijkman, director of the Bacteriology Laboratory in Batavia [now Jakarta], Indonesia.

This NIH library translation (NIH-95-429) from German into English was provided by Ted Crump, translator. Copyright restrictions apply. This translation is for exclusive use of Frans Hochstenbach, and has been edited by Frans Hochstenbach and Norman Hu.

In this article, Eijkman describes the production of an alcoholic liquor, called arrack, which, in Batavia, involves fermentation of cane sugar molasses, a brown-black syrup that remains after separation of crystalizable sugar during sugar manifacture. Eijkman describes that during the fermentation process so-called Chinese yeast is added, which consists of a Mucor fungus. In addition, a second organism contributes to the fermentation, namely a rod-shaped yeast. In 1897 Beijerinck classified this arrack yeast as Schizosaccharomyces asporus, since spore formation was not observed. Under this name, J. Smit submitted in January of 1923 an isolate of arrack yeast from an Batavian arrack factory to the Centraalbureau voor Schimmelcultures, the Central Depository for Fungi Cultures in the Netherlands. After analyzing this strain, denoted CBS 352, Stelling-Dekker reclassified in 1932 arrack yeast as Schizosaccharomyces pombe.

[Eijkman Article Title]

Microbiological Aspects of Arrack Production in Batavia [Excerpted]

By Dr. C. Eijkman in Batavia.

Arrack production is pursued in Batavia and in other locations in Java by the Chinese. The process may certainly be modeled after that used in their motherland for centuries; however, these [processes] differ substantially from each other in one main respect, namely local circumstances. While arrack in China and in many other areas inhabited by Chinese (here, for example, on the island of Banka) is prepared, as is well known, from fermented rice, here [the rice] is used only as a supplement, and the otherwise almost-useless cane molasses [discarded by] sugar factories is used as the actual fermentation material.

The process is basically as follows: Hulled rice kernels are cooked thoroughly in water, then spread out in a thin layer on a mat, and, after they have cooled sufficiently, they are mixed well with pulverized Chinese yeast. Then the mixture is placed in a cylindrical keg, open at the top, with holes in the bottom, covered with a mat, and left to stand. After 2 days, the rice turns into a soft juicy coherent mass (Malayan tapei). Weighing some 30 kg, this is removed entirely, and suspended in already fermenting molasses in a 2-3 hectoliter fermentation cask. The next day the contents of this cask, after the tapei cakes have been pulverized, are poured into a second, larger fermentation cask, which is more than half-filled with diluted molasses (approximately one part molasses to 2 parts river water). The first cask is then refilled with this, in order to be charged with a new tapei mass. However, the remainder stays in the second vessel until the next morning, and is then distributed among several fermentation casks. The fermentation continues in these casks with gradual addition of new, correspondingly diluted quantities of molasses. On the 8th to 10th day, the almost completely fermented liquid is poured into pot-bellied clay pots of roughly 15-L capacity, in which a weak secondary fermentation occurs and a sediment is formed. After another 8 days the liquid, which now is no longer sweet but rather acidulous, is distilled. The distillate contains approximately 50% alcohol by weight, and is marketed as arrack. It is relatively free of bad alcohol, and differs from rice wine in its peculiar, sweetish-burned odor. This is because of the molasses, as is evident when unfermented molasses is diluted w

ith water and distilled.

1. Chinese Yeast and Rice Fermentation

The [Chinese] yeast, with which the cooked rice is mixed in the fermentation process, originated from China, but has completely made its home here in the domestic household. It is prepared and sold everywhere in the form of whitish to grayish, flat, mealy balls, approximately the size of a thaler. [A.G. Vorderman, inspector of the public health service for Java and Madoera, reported in 1893 that these Chinese yeast balls were called 'ragi' in Malay.]
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Our fungus seems very similar in description to that first found by Calmette in Chinese yeast and named Amylomyces rouxii. While Calmette remained completely in the dark as to the position of his fungus in the botanical system, I had more luck, because I can say with certainty that it is a Mucor species.

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2. Molasses Fermentation

After all that has been said, one whould expect that fungi play the main role in fermentation of molasses. This, however, is not so. During the entire course of the fermentation, an overwhelming quantity of a rod-shaped microbes not present in [Chinese] yeast is found in the fermenting liquid; it reproduces by division and is a strong alcohol fermentation fungus. It is 0.005 - 0.006 mm thick and 0.020 - 0.040 mm long. Its double-contoured wall of cellulose clearly stands out from its fine-granular contents. Division takes place along a transverse membrane that forms in the middle. The released ends round off, but the daughter cells nevertheless remain linked to each other at an angle. These V-shaped double-rods were compared aptly to the shape of a flail by Vorderman (Geneesk. Tijdschr. v. Ned. Indië. 1893) who was the first to describe them.

[Eijkman illustration]

I would not venture to address with certainty the systematic position of the microorganisms in question. According to previous findings, they would be included among the schizomycetes, where they would stand out with their colossal dimensions. From time to time, however, as is evident from the adjoining illustration, [pseudo-hyphal] growth forms reminiscent of simple hyphomycetes are also to be found.

My investigations have revealed the following biological properties, which until now have not been studied in detail:

The rods can be readily recultivated on suitable solid substrates, namely those containing sugar or starch. They do not thrive on gelatin and agar nutrient media commonly used for bacteria cultures; neither can peptone nor glycerin serve as their carbon source. Lactose also offers them nothing. On cane sugar gelatin plates they form whitish, spherical, sharply outlined, non-liquefying colonies. On sugar agar, rice, and potatoes, etc., they form thick, white to yellowish-white cultures that are not characterized by any conspicuous traits.

Spore formation was never observed; also, the rods died relatively quickly in cultures.

They are totally lacking in any noteworthy diastatic effect [of converting starch into sugar], but they invert cane sugar and ferment it. In addition to the alcohol fermentation, a rather substantial acid formation takes place.

After a pure culture of the rods has been placed in molasses diluted with water and then heat-sterilized, a vigorous foaming occurs after 2-4 days, depending on the amount used; [the foaming] lasts for 1-2 weeks, until the sugar is fermented. The distillate has all the properties of good arrack; it has only a very small quantity of cheap alcohol, and its characteristic odor, as has already been pointed out, is reminiscent of molasses. The distillation residue is rather acidic. I found lactic acid in it, among other things, but I did not pursue this further.

As to the origin of the rods, they are not encountered either in [Chinese] yeast or in fermenting rice, as Vorderman (Geneesk. Tijdschr. v. Ned. Indië. 1893) has already pointed out from his microscopic observation, and which I can confirm on the basis of repeated culture experiments.

If diluted molasses that has been sterilized previously is mixed with [Chinese] yeast or fermenting rice, the fermentation does in fact run its regular course, and at the end an arrack-like distillate is obtained. However, in the fermenting liquid, apart from numerous microorganisms of no further interest here, only fungi are to be found along with the deteriorating tubes of the Mucor. These are not absent from fermenting molasses of the arrack factories; however, as has been pointed out already, they are found in minute quantities compared to the flail-shaped rods.

Where these rods originate from could not be determined with certainty. One suggestions is that they were already present either in the molasses or in the river water used for its dilution. The experiments in this direction, however, have not provided any unequivocal results. Only once were organisms found that were very similar but not identical to the flail microbes of the arrack factories. In this experiment, following the process used in the arrack factories, the mixture of molasses and river water was mixed with tapei for fermentation without preliminary sterilization. However, nothing of this nature was observed in spontaneously fermenting, diluted molasses, despite repeated examinations.

In the local arrack factories, the flail microbes appear as a constant accompaniment to molasses fermentation. Once present in the fermentation casks, their continuous existence is guaranteed by the usual fermentation procedure of repeatedly mixing the molasses to be fermented with already fermenting molasses. The hypothesis that Batavian arrack perhaps owes its acknowledged superiority to the described microorganism has proven to be inaccurate. I also found the organisms in question in overwhelming abundance in the samples of fermenting molasses I examined from other localities in Java (Surabaya, Tegal, Cheribon).

Finally, the alcohol yield in the local arrack production is never less than desired. It amounts to only approximately 20% by weight of the fermented sugar. Similar results were produced by fermentation experiments with pure cultures of the flail microbes. The acidic reaction that appears in the fermentation indicates that other transformations still take place.

Even among microorganisms usually encountered in the fermenting molasses or in the [Chinese] yeast, no particularly effective alcohol-fermentation fungi were found. Most even proved to be incapable of completely fermenting concentrated sugar solutions, and their [lack of] effectiveness became evident with an alcohol content of [merely] 4-6% by volume.

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