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Development of the Butyl-Acetonic Fermentation Industry’ C. L. Gabriel and F. M . Crawford COMMERCIAL SOLVENTS CORPORATION, 230 PARKAvE., NEWYORK,N. Y.
A brief history of the butyl-acetonic fermentation H E fact that n-butyl quent high prices, until new industry is presented, covering the discovery of the plantings had reached a suffialcohol is produced by fermentation, its first use as a source of raw material certain forms of microcient stage of development to for synthetic rubber, its exploitation during the war as begin to yield. It is only o r g a n i s m s has long been a source of acetone, and its subsequent development known. Wurtz, in 1852, was natural, therefore, that such for the production of lacquer solvents. The present a condition should immediapparently the first investicommercial process is outlined and the economics of ately put the synthetic org a t o r t o n o t e t h a t butyl the industry are discussed. ganic chemist on his mettle. alcohol was one of the reml a r c o n s t i t u e n t s of fusel Investigations in Rubber Synthesis oil, which in turn had been discovered by Scheele in 1785. The first record of the discovery of butyl alcohol as a ferThe problem of synthesizing rubber had occupied the mentation product rather than as a constituent was an- attention of chemists for a great many years, and work of a nounced by Pasteur in 1862, who found that this material rather desultory character had been carried on continuously was a normal product of the butyric fermentation of lactic since rubber was first successfully synthesized in 1860. The acid. Several years later Fitz began work on fermenta- greatest amount of work on this subject was probably done tions while bacteriology was in a very rudimentary state, in 1909 by groups of workers in England, Germany, and and published a series of papers on this subject during the Russia. Our present interest lies in the work done by the years 1876 to 1884. He obtained by accident a ferment English group. It is interesting to note in passing that the capable of forming butyl alcohol from glycerol, a culture amount of work done on the subject of synthetic rubber fell which he stated was a mixture of two bacteria, one producing off rather rapidly after the peak year mentioned above, butyl alcohol and the other ethyl alcohol. This ferment, doubtless owing to the fact that production of plantation however, unfortunately would not attack starch. This work rubber was beginning to catch up with consumption and was followed by investigations by Beijerinck, Bredemann, prices were such that the margin of profit became too ?mall Schardinger, Pringsheim, and others. for the synthetic product t o compete successfully. Although of value in pointing out to later investigators the The greater portion of the work done in England during possibilities of research in this new field, the work done by this period was under the direction of the firm of Strange & these pioneers was far from being adaptable to the require- Graham, Ltd., promoted primarily for the study of synthetic ments of a successful commercial process for the production rubber. This company employed, among others, Professor of butyl alcohol by fermentation. The first real indications Perkin of Manchester University and his assistant, Ch. that such a process was feasible came less than two decades Weizmann, and Professor Fernbach of the Pasteur Institute ago and in a manner similar to that responsible for a great and his assistant, hlr. Schoen. The studies of these investimany of our most important scientific developments-that gators led them to believe that their best chances for the is t o say, as the result of a search for a new material or a synthesis of rubber lay through the polymerization of isocheaper source of an old material which is required by an prene or butadiene. While these compounds might be preentirely different industry. pared in a number of ways, the most feasible methods apThe automobile industry has frequently been given credit peared to be from isoamyl alcohol and n-butyl alcohol, during recent years for the remarkable industrial growth and respectively. The method of synthesizing rubber originally prosperity of the Cnited States and, to a lesser extent, of selected by the “English group” as being the most promising certain other nations. Be this as it may, it is certain that was that in which fusel oil containing approximately 87 per the tremendous and rapid growth of this one industry has cent of isoamyl alcohol was used as the basic raw material. created many new demands, which in turn have led to the Since fusel oil was produced only as a by-product in the ethyl birth and growth of other new industries. New wealth thus alcohol fermentation industry and only to the extent of created has brought about the establishment of still other about 0.8 per cent of the total fermentation products, it was new industries to furnish luxuries TThich become necessities highly desirable to locate additional sources of fusel oil or for the creators of this new wealth. And thus the “vicious of isoamyl alcohol. Later the same group of investigators circle” of industry ever widens. This modern industrial decided that the synthetic rubber from butadiene obtained monster and Mars, the god of war, took the seed of an idea in turn from 11-butyl alcohol possessed more desirable properconceived by Kurtz, Fitz, and their fellow workers and ties than even the isoprene condensation product. created from it one of the modern romances of fermentation chemistry-the butyl-acetonic fermentation industry. Fermentation Studies During the first decade of the present century the automobile industry began to grow apace, and soon it was apI n studying the available sources of isoamyl and n-butyl parent that rubber from the native forests of Brazil, Asia, alcohols, consideration m-as devoted to the pioneer bacterioand Africa was available in hardly sufficient amounts t o logical work mentioned a t the beginning of this paper. and meet the rapidly increasing demands for this important raw it was decided that the best chances of ultimate success lay material needed in the production of tires. A number of in obtaining their ram materials by fermentation methods. years must elapse after a rubber tree is planted before it Research was accordingly started along such lines. By the begins to yield appreciable amounts of latex. Hence a early part of 1911 Fernbach and Weizmann had found a rapid and unexpected demand meant a shortage, with conse- mixture of bacteria which fermented the starch in potatoes and yielded amyl alcohol among other products. A few 1 Received September 30, 1930.
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months later it was discovered that n-butyl alcohol was produced in the fermentation and the energies of the “group” were then diverted to the best method of obtaining this product. About the same time it was noted that acetone and ethyl alcohol were also produced in substantial quantities by the microorganism which Fernbach designated as a “bacillus of the type of Fitz.” The use of this organism for the production of acetone and higher alcohols was patented by Fernbach and Strange in 1913. During the summer of 1912 Doctor Reizmann left the services of the “group” and after a time concluded t o continue independently his investigations upon fermentation processes of this character. After a detailed study of all the prior work and after extensive search, he succeeded in isolating a form of bacteria which differed n-idely from the organisms described by Fernbach or any of the prior investigators and possessed superior properties from the standpoint of a commercial fermentation. Among the outstanding advantages over Fernbach’s organism were the ability of Reizmann’s bacteria to ferment starch other than that of potatoes without preliminary treatment and the ability to produce markedly higher yields of the desired products. Erection of Butyl Alcohol Plants
I n the meantime Strange and Graham, Ltd., in continuation of its original plan to manufacture synthetic rubber, erected a plant a t Rainham for the production of n-butyl alcohol. This plant, using potatoes as the raw material, was put into operation in the middle of the year 1913, and was used until about June, 1914. Previous to the latter date, however, a second fermentation plant had been established at King’s Lynn, also in England. Fermentation Process Applied to Acetone Production
At this point another important factor enters the picture. The outbreak of the World War and the beginning of artillery warfare on an unprecedented scale necessitated the use of greatly increased amounts of acetone in the manufacture of cordite, one of Great Britain’s most important explosives. The available supplies of acetone from the usual sources were quickly drained and a search for new sources was then instituted. I n this quest the Government’s attention was called to the fact that acetone was produced in appreciable quantities in the Strange-Graham or Fernbach process. Accordingly, a demonstration was conducted in the early fall of 1914 at King’s Lynn before a representative of Sobel’s Explosives Company, and a contract Tvas later entered into to furnish the Government v-ith acetone. Since this process operated only on potatoes, the company was never able to furnish even the minimum quantities of acetone contracted. I n the meantime an official of Manchester University, where Doctor Weizmann was employed, called the Government’s attention to Doctor Weizmann’s work and an investigation of his fermentation was made. This investigation resulted so favorably, as compared with the process of Strange and Graham, Ltd., that the Government took over the plant of the latter and installed the Weizmann process, using maize as the raw material. This resulted immediately in a yield of about four times as much acetone as was formerly available from this source, and operation was so successful that the Government made plans t o take over a number of distilleries in which to employ the Weizmann process. Successful fermentations were being carried out in some of the new plants when the shortage of foodstuffs occasioned by the submarine blockade made it imperative to locate plants nearer the sources of raw material. Two distilleries a t Toronto, Canada, were then taken
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over and suitably modified for use of the Weizmann process. An additional plant was begun in India, but was never operated except for a short period after the conclusion of the war. Shortly after the United States entered the war, the Bllied War Board began operation of the Weizmann process in tiyo distilleries purchased a t Terre Haute, Ind., and thus in a comparatively short time the butyl-acetonic fermentation was operated on a large scale in still another country. At the conclusion of the war the great demand for acetone immediately ceased and consequently the Weizmann plants throughout the world were closed. Butyl Alcohol in Lacquer Manufacture
As has been indicated, the Reizmann process was developed originally as a source of n-butyl alcohol for the synthesis of rubber. but during the war it was operated primarily for the production of acetone. Since, however, the bacteria TTork the same way in war time as in peace, it was necessary to produce twice as much n-butyl alcohol and onethird as much ethyl alcohol in order to obtain the large quantities of acetone needed. Furthermore, the countries where these materials were being produced a t that time had no need for synthetic rubber. Consequently, there was almost no demand for the product obtained in the largest quantity-i. e., the n-butyl alcohol-although a small amount was used in the production of methylethyl ketone as a substitute for acetone. Hence, a t the conclusion of the war there mere large supplies of this former laboratory curiosity available in a number of places in the world with practically no market for it. Soon chemists were seeking valiantly for suitable uses for this “waste material.” The pendulum swung again, and the demand for n-butyl alcohol for automobile lacquers occasioned the reestablishment of the fermentation on a commercial scale and put it firmly on the road to success. Thus it may safely be said that the butyl-acetonic fermentation industry is doubly indebted to the automobile. Although other finishes were known, up to the end of the war practically every automobile was coated with oleoresinous varnishes, which were disadvantageous from a number of standpoints. The most undesirable feature of these finishes was their slow drying, necessitating a period of about 3 weeks for finishing a car and thus increasing very materially the manufacturing cost. It had long been known that nitrocellulose rarnishes gave quick-drying and generally satisfactory finishes which were admirably suited for such purposes, but their use was not regarded as practical, for two reasons. An ideal solvent at a reasonable price was not available and, equally important, with the grades of nitrocellulose then available it was difficult to obtain a sufficiently concentrated solution t o serve as a satisfactory finish, which would not a t the same time be too viscous to be easily applied. Suitable grades of lowviscosity nitrocellulose became commercially available coincident with the search for uses for n-butyl alcohol. It mas forecast from the knowledge of Steven’s early work on the use of amyl acetate as a nitrocellulose solvent that n-butyl acetate would also be suitable for this purpose, and actual trial proved this forecast t o be more than true. For general lacquer formulation n-butyl acetate was found to be, not only equal to, but in many respects even superior to amyl acetate. With the discovery of a large potential market for the n-butyl alcohol, several large lacquer manufacturers bought up the available supplies and began the production of the present-day lacquers which have speeded up so many lines of manufacture and at the same time added variety and beauty in finishing where formerly much less pleasing effects were possible. I n order to supply the new demand for n-
November, 1930
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butyl alcohol thus created, a n American corporation was organized to carry out the butyl-acetonic fermentation in this country. This corporation took over from the Allied War Board tlie plants located a t Terre Haute, Ind., and acquired the world-wide basic patent rights to both the Weizniann and Ricard processes for the production of n-butyl alcohol and acetone by fermentation. The plants a t Terre Haute were reopened aiid the process was operated this time primarily for the production of n-butyl alcohol, with acetone as the by-product. Tlie rapid growth of the nitrocellulose lacquer iiidustrg Poon required additional plant capacity and a new and much larger plant was built a t Peoria, Ill.. in the heart of the Corn Belt, where the basic raw material required could be obtained most cheaply. The past few years have seen a continued expansion of thiq new industry, which is now producing solvents a t approxiniately 9400 per cent the rate in 1914, when the procesq first operated on a commercial scale in England.
this culture is used as the source of inoculum for about 500 cc. of mash, which is also incubated for 24 hours a t 36" C. and serves in turn as the inoculum for about 10 liters of sterile mash. After the sterile mash has been incubated for the customary 24 hours, it is transferred to the plant and serves as the inoculum for about 80 gallons of sterile mash. The latter in turn is used to inoculate a n 800-gallon fermenter and the mash from the fermenter serves as the inoculum for about 42,000 gallons of sterile mash in the plant-size fermenters. During all of this operation the cultures are carefully studied by both chemists and bacteriologists, aiid only a final culture which has satisfactorily passed every test is employed as the inoculum for the large-scale fermenters. From 48 to 72 hours after the mash has been inoculated, the fermentation is generally complete, and the products are recoi-ered by the usual methods of fractional distillation.
Fermentation Process
Little has been said about one of the most important features of the butyl-acetonic fermentation industry-namely, the economic side. X familiar adage of the packing indust,ry is that it employs everything of the hog except the squeal. I t is believed that it can soon be said with a n equal degree of veracity that the butyl-acetonic fermentation industry utilizes everything from the maize plant except the smell produced during the fermentation-and who knows but that a use for that as a perfume base may not be found? Many economies have been effected in the process during the coinparatively few years of its existence, resulting ir; lower prices for bhe basic products, and further improvements are still heing made by a large staff of chemists and bacteriologists. previously indicated, the solvents produced in the process are n-butyl alcohol. acetone, and ethyl alcohol in the ratios of approximately 6:3: 1, respectively. I n the beginning only these products were recovered from the fermentation. aiid the tremendous volumes of hydrogen, carbon dioxide, and other materials formed during the process were allowed to go to waste. The importance of the loss involved in not recovering the gases is easily visualized from the fact that for every pound of mixed solvents about 1',./?pounds of gases are obtained. At present. hmvever, this, as well as practically every other waste, has been eliminated. Lill of the hydrogen and a portion of the carbon dioxide are now being converted into synthetic methanol, aiid the remainder of the carbon dioxide is finding a use as Dry-Ice. The maize germ which was formerly allowed to go to waste is now caved; the oil extracted from it is used for food purposes, and the residual-oilcake meal is used as cattle feed. These product,s, together with the distillery slop, account for ahout 96 per cent of the original dry weight of the corii, the remaining 4 per cent representing synthetic water formed in tlie methanol synthesis, and a very small percentage of unaccoiuited-for material. By transforming the carbon dioxide to carbon monoxide prior to the methanol synthesis the loss as synthetic water may be eliminated and a practically complete recovery obtained. The distillery slop is too dilute to warrant an evaporation to dryness, but it has recently been found that this material has promise in certain other fermentation processes. It, is hoped in the near future to utilize the slop in the production of acetic acid, d i i c h in turn will be used in producing butyl acetate from t,he ht,anol, thus reuniting in one chemical compouncl t,he elements o€ the original maize plant, which had been taken apart and variously acted upon by the agency of infinitesimal organisms pursuing t,lieir ordinary functions of living and reproducing themselves.
The fermentation as carried out a t the present time differs only in certain minor details from the process originally discovered and patented by Doctor Keizmann. A carbohydrate, such as maize, kaffir corn, rice, rye, wheat, cassava, etc., is first, reduced to the form of a coarse meal. With forms such as maize it is desirable to remoi-e t,he germ, which is not utilized during the fermentation and coiisequent'ly ~ o u l be d lost. By degerniinatirig the maize before subjecting it to fermentation and recovering tlie oil from the germ, a considerable saving is effected. For fermeiit,ation purposes, however, it is not necessary t,o subject the carbohydrate to any part,icular treatment other than to reduce it to the form of meal. This meal is added in suitable amount to water to give a mash containing approximately G to 8 per cent concentration by weiglit. Tlie mash is then subjected to "cooking" n-itli live steam for about 2 hours at approximately 30 pounds pressure n-hile vigorously agitating to prevent 1)alling of the meal. This operation has for its object the complete sterilization of the mash and a t the same time the conversion of tlie starch in the meal to a smooth paste n-liich may be more readily acted upon hy the bacteria. K h e n the cooking has been completed. the mash is blown through coolers, where the temperature is dropped to approximately 9'7" F.. and thence into closed, sterilized fermenters of approximately 50.000 gallons capacity, where it is ready for inoculation with the bacteria. It should be noted that, from tlie time tlie mash is sterilized until it is inoculated, every possible precaution is taken to see that it is maintained absolutely sterile. All pipe lines, connections, fermenters, etc., are frequriitly sterilized with live steam and, if necessary. with chemicals. The so-called Keizmann bacteria may be obtained from a rather wide variety of sources-as, for example. soil, fruits, cereals, et(,. Alfterhaving been isolated from any of these sources. they may he stored for years without losing any of their fermentative powers. Being "spore formers," they go into a dormant stage when a suitable supply of food is no longer available. Aismall flask of sterile soil d i i c l i lias been impregnated with these spores will give sufficient "wed" to operate a large plant for many months. Whenever it is desired to start a fermentation, a few grains of this sporeimpregnated sand are added to a test' tube containing a few cubic centimeters of sterile mash of suitable concentration. The mash is then subjected to a "heat' shock," 100" C. for 1 or 2 minutes, a procedure which has been foulid to increase the speed of germination of the spores and also to yield a more virile culture. After incubation at, 36" C. for 24 hours,
Economic Considerations
