THE HYDROLYSIS OF CORN-STARCH BY COMMERCIAL PAiWREATIN.

BY JAMES H. WALTON AND HARRY R. DITTMAR.

(Received for publication, September 7, 1926.)

The hydrolysis of potato starch by pancreatin has been the subject of much investigation, particularly by Sherman and his pupils (I), who have studied the action of both malt and pancreatic amylase upon potato starch, especially with reference to optimum concentration of enzyme, substrate, pH value, and concentration of activating salts. The best conditions of hydrolysis were at (2) 40” in the presence of sodium chloride and disodium phosphate which acted as promoters or activators to the diastase. The favor- able infiuence of these two salts is explained by the maint’enance of a hydrogen ion concentration most favorable to the activity of the amylase. Potassium and ammonium chlorides are mentioned as exerting the same influence as the sodium chloride, while the combined effect of sodium carbonate and disodium phosphate was found to be the same as when the latter salt was used alone.

The hydrolysis of potato starch proceeds more rapidly and com- pletely than the hydrolysis of corn-starch. This fact, which was brought to the attention of t’he authors by Dr. David Klein, led to the present investigation, which deals with the most favorable conditions for the hydrolysis of corn-starch.

Method.

The method used in following the hydrolysis was to add a definite amount of pancreatin, usually dispersed in a definite amount of water, to the starch solution at 40”, from which portions were withdrawn from time to time for analysis.

713

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714 Hydrolysis of Corn-Starch

The hydrolyses were always made on 98 cc. of a 2 per cent starch solution. The per cent of moisture in the starches was first determined by drying them in a vacuum oven at 60’. The amount of starch taken was such as to give a 2 per cent solution of the dried substance. The starch was placed in a 200 cc. Erlenmeyer flask, and in case salts were introduced, solutions of them were added at this point, together with an amount of water necessary to make 98 cc. of the substrate solution after the introduction of the solution of pancreatin. The contents of the flask were then brought slowly to boiling under a reflux condenser, and kept at the boiling point for 20 minutes. At the end of this time, the flask was immersed in a water thermostat regulated at 40” where it was allowed to attain the temperature of the bath.

The pancreatin was always added in solution. The desired amount of enzyme was carefully weighed, and was then introduced into a definite volume of water at 40”. If activating salts had been added to the starch, the enzyme was introduced into water con- taining the same concentration of activants. Aliquots were then withdrawn from the pancreatin solution and added to the starch solution. The concentration of enzyme solution was so adjusted that 10 cc. contained 5 mg. The substrate solution was always of such concentration that after the addition of the water containing the enzyme, the total volume was 98 cc. As the hydrolysis pro- ceeded, 5 cc. portions of the substrate were pipetted off from time to time, and the maltose content (anhydrous) determined. The reducing sugars were determined volumetrically by the method of Shaffer and Hartmann (3).

Materials.

The corn-starch used in this investigation was a commercial product manufactured by the Corn Products Refining Company under the trade name of Pearl Globe (No. 144), and was furnished by courtesy of this company. The potato starch was untreated starch sold by the Central Scientific Company, Chicago. The pancreatin preparation was a commercial product of the Wilson Laboratories, Chicago, generously donated by Dr. David Klein. Its diastatic power was carefully determined and found to have a value of 66 on Sherman’s new scale (4). The water used was all redistilled over alkaline permanganate and carefully protected from

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J. H. Walton and H. R. Dittmar 715

the air. Salts added with the panereatin were always of the high-- est purity obtainable.

Results.

Before attempting to study the saccharogenic power of pan- creatin on corn and potato starches, a preliminary microscopic study was made in order to ascertain the extent of “solution” of the boiled substrate solutions with the idea of determining if differences of dispersion would influence very greatly the saccha-

TABLE I.

HY~TO~YS~S of Corn and Potato Starches by 6 Mg. of Enzyme.

Time,

- I

hrs.

0.75 1.50 2.50 3.50 5.00 6.25 8.00 8.50

10.50 11.00 21.00

Maltose content in 5 cc. Maltose content in 5 cc. (no sctivants). (activants added).

Potato starch.

mg.

25.9

38.8

48.2

53.9 64.5

(64.5 per cent starch.)

- --

-

Corn-starch.

15.8

29.3

40.4

44.4

54.4 (54.4 per cent

starch.)

-

-

Potato &arch.

mff. 42.2 56.2 61.0

71.2 (71.2 per cent

starch.)

Corn-starch.

mg. 36.0 49.4 53.9

62.3 (62.3 per cent.

starch.)

rogenic power of the enzyme in its action on corn and potato starches. Upon studying a boiled 2 per cent solution of potato starch microscopically, the granules were found to be greatly enlarged. A granular structure was still apparent, especially after staining with iodine. A corn-starch solution of the same concen- tration, and similarly treated, gave the same general appearance especially in regard to the existence of granules, although the latter did not appear to be swollen to the same extent as the potato starch granules. A 2 per cent corn-starch solution was prepared from the corn-starch after it had been rendered soluble according,

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716 Hydrolysis of Corn-Starch

to the formula of Lintner (5). When this solution was studiedunder the microscope, the starch granules could not be detected even after staining with iodine. Autoclaving gave similar results; the granules were disrupted upon boiling. Having been able appar- ently to disperse the two starches completely, a quantitative study

FIG. 1. Rates of hydrolysis of corn and potato starches by 5 mg. of pan- creatin.

was undertaken to determine the rate of conversion of the two, as well as the effect of dispersion.

In determining the rates of conversion of corn and potato starches, 98 cc. of a 2 per cent solution of each starch were hydro- lyzed by 5 mg. of pancreatin without the addition of sodium chlo-

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J. H. Walton and H. R. Dittmar 717

ride and disodium phosphate. The potato starch was hydrolyzed not only more rapidly, but also more completely. If, on the other hand, 300 mg. of sodium chloride and 7 cc. of fiftieth molar disodium phosphate were added to the substrates, the rate of conversion was increased enormously; the potato starch, however, was still more readily acted upon than the corn-starch. This can be seen from the results given in Table I and Fig. 1.

The rates of conversion of the two starches were next studied when the amounts of pancreatin added were 3 and 1 mg. per 98 cc. of a 2 per cent substrate solution containing the 300 mg. of sodium

TABLE II.

Hydrolysis of Corn and Potato Starches by Different Amounts of Pancreatin.

Time.

h-s.

0.50

1.50 2.00 4.50 5.00 7.50

26.00

Hydrolysis by 3 mg. of panorerutin (&&ants added).

Potato starch.

mg.*

21.4 46.6

Corn-starch. Potato starch. Corn-starch.

mg.’

18.1 40.4

61.0 52.7

71.7 64.0 (71.7 per cent (64.0 per cent

of total of total starch.) starch.)

- I Hydrolysia by 1 mg. of panoreatin

(aotivanta added).

mg: mg.’

6.9 5.7

25.9 22.6

47.6 41.0 55.6 47.6 63.4 58.9

(63.4 per cent (58.9 per cent of total of total starch.) starch.)

* Maltose per 5 cc. of solution.

chloride and 7 cc. of fiftieth molar disodium phosphate. Results are given in Table II and Fig. 2.

It will be seen that in each of the above cases the rate of con- version of potato starch was more rapid than the rate for the corn- starch; also that the speed increased with the concentration of pancreatin.

If after the hydrolysis of corn-starch by 1 mg. of pancreatin, 2 more mg. were added and the reaction was allowed to proceed for 20 hours more, the maltose content rose from 58 to 65 per cent of the total starch first present. An additional 2 mg. increased the yield to 67 per cent.

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718 Hydrolysis of Corn-Starch

Having established the fact that corn-starch is converted into maltose more slowly than the same amount of potato starch, attempts were next made to increase the rate of hydrolysis of the former starch. Corn-starch was rendered soluble according to the formula of Lintner. Microscopic examination of a solution of this

80

I 20 I

IO

FIQ. 2. Rates of hydrolysis of corn and potato starches with different amounts of pancreatin.

soluble corn-starch showed no starch granules. If this substrate was hydrolyzed more rapidly than the untreated starch, it would tend to demonstrate that the speed of conversion was dependent upon the degree of dispersion of the starch granules, provided that the material did not undergo any deep seated chemical changes during the process of rendering it soluble.

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J. H. Walton and H. R. Dittmar

98 cc. of a 2 per cent solution of this soluble corn-starch con- taining sodium chloride and disodium phosphate were hydrolyzed by 5, 3, and 1 mg. of pancreatin, respectively. A blank run was always made to obtain the reducing power of the starch. In no case was the speed of conversion increased over the speed of the untreated corn-starch. Table III shows the results obtained in the hydrolysis by 5 mg. of enzyme.

The dry corn-starch was next treated with steam for 30 minutes under a pressure of 3 atmospheres. The starch so treated ap- peared to be partially dextrinized, but upon the hydrolysis of 98 cc. of a 2 per cent solution by 5,3, and 1 mg. of enzyme, no increase in the rate was observed. This can be seen in Table IV in which

TABLE III.

Effect of Starch Rendered Soluble According to Lintner on the Rate of Enzymatic Conversion.

Time. Untreated corn-starch. Maltose per 5 cc.

Starch rendered soluble according to Lintner.

Maltose per 5 cc.

hrs. I mg.

0.75 36.0 1.50 49.4 2.50 53.9

21.00 62.3

NaCl + NapHPOa added in each case.

mg.

37.2 49.3 53.9 64.0

comparisons in the maltose formation of untreated and auto- claved corn-starch by 3 mg. of enzyme are made.

The fact that the hydrolysis of the autoclaved starch proceeded more rapidly at the very first of the conversion was, no doubt, due to the fact that the starch was partially hydrolyzed into dextrins. Treating the dry starch under pressure, however, did not increase the rate of conversion. Results of identically the same order were obtained when the hydrolysis took place with both 5 and 1 mg. of enzyme.

The effect of freezing a starch solution was also tried. The 2 per cent solution of corn-starch was first boiled, after which it was frozen solidly and left for an hour. After melt’ing it was again boiled, cooled to 40”, and the necessary amount of sodium chloride and phosphate added together with 5 mg. of pancreatin. The

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720 Hydrolysis of Corn-Starch

result’s in Table T; show that the freezing does not increase the rate of conversion; in fact, there is a slight decrease in speed.

A study was also made upon the hydrolysis of corn-starch which had been extracted wit,h et’her, since it was possible for the corn- starch to contain a slight amount of oil, a fact which might account for its slower enzymatic hydrolysis. From this ether-extracted starch the usual amount of a 2 per cent solution was prepared. This was then hydrolyzed with 5 mg. of enzyme after the usual

TABLE IT.

Effect ofdutoclnving Dry Corn-Starch wpon the Rate of Enzymatic Hydrolysis.

Time. Untm?dod corn-starch. Maltose per 5 cc.

his. mg.

0.50 18.1 1.50 40.4 4.50 52.7

26.00 64.0

NaCl + Na2HPOd added in each case.

Auto&wed corn-starch. Maltose per 5 cc.

mv.

21.4 39.8 52.2 64.0

TABLE v. E$+ect of Freezing and of Ether-Extracting Corn-Starch upon the Rate of

Enzymatic H&rolysis.

Time. Unaltered corn-starch. Frmen corn-starch. Maltose per 5 cc. Maltose per 5 cc.

70-s. m!3.

0.75 36.0 1.50 40.4 2.50 53.0

21.00 64.0

mg. mQ.

35.5 36.0 46.2 49.3 50.2 54.0 63.4 64.0

activants had been added. The results of the conversion of starch so treated are also given in Table V.

From these results it can be seen that neither freezing nor ether- extracting the corn-starch increased Dhe rate of conversion. A solution of the starch was next autoclaved for 5 hours under a pressure of 5 atmospheres. By this treatment the substrate was made soluble. When first boiled n-ith water, the solut’ion was slightly cloudy, but after the treatment under pressure it became clear. No starch granules could be observed. In preparing the

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J. H. Walton and H. R. Dittmar 721

solution 2 gm. of starch were boiled with 82 cc. of water, auto- claved, and 7 cc. of fiftieth molar disodium phosphate were added with 300 mg. of sodium chloride in 5 cc. of water. 1 mg. of enzyme was then added in 4 cc. of water, and 5 cc. aliquots were used for analysis from time to time. The pressure treatment converted some of the substrate into products which reduced Fehling’s solu- tion so that two blanks were always run. Table VI compares the rate of hydrolysis with that of the unautoclaved starch solution.

These results show that the rate of hydrolysis of the autoclaved solution was at first greater than the untreated substrate. This was probably due to the fact that the pressure treatment converted some of the starch into dextrins which were more readily acted upon by the enzyme. This point was substantiated by the fact

TABLE VI.

Ejkct Which Autoclaving Corn-Starch Solution Has upon the Rate of Enzyme

Time. Unautoclaved corn-starch. Maltose per 5 cc.

hrs. ml.

0.50 5.7 2.00 22.6 5.00 41.0 7.50 47.6

28.00 58.9 -

Hydrolysis.

r --

-

lutoclaved solution of corn-starch. Maltose rmr 5 DC.

mg.

9.8 25.2 34.2

52.5

that the addition of alcohol precipitated a white substance from the autoclaved starch.

In the above case the activants were added after pressure treat+ ment. When they were added before autoclaving the starch, the rate of hydrolysis was decreased enormously; at the end of 5 hours, 5 cc. of substrate solution contained only 12 mg. of sugar, while at the end of 26 hours the total quantity of maltose formed was only 33 per cent of the total weight of starch. In attempting to find an explanation for this result, the hydrogen ion concen- tration of the starch solutions was taken after hydrolysis was complete. The pH of the solution in which the sodium chloride and phosphate were added after pressure treatment was found to be 7.0 (determined by indicator method), a pH which Sherman (6) found to be most favorable for conversion with pancreatic

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722 Hydrolysis of Corn-Starch

amylase. If, on the other hand, the activants were added before autoelaving, the solution at the completion of the action had a pH of 5.0 to 5.2, a concentration of hydrogen ions which is not very favorable to the activity of pancreatin. This difference in pH probably accounts for the large variation in the rate of conversion. If the starch solution was prepared by merely boiling the substrate with water, the pH as well as the rate of hydrolysis was identically the same whether the activants were added before or after boiling. This treatment of a starch solution did not affect its speed of hydrolysis except slightly at the beginning of the hydrolysis, while toward the end of the hydrolysis the rate was decreased.

In all the hydrolyses, except that of the autoclaved solution of corn-starch, an insoluble white residue remained in the flask after conversion. This residue did not reduce Fehling’s solution. Upon being hydrolyzed by concentrated hydrochloric acid, how- ever, it reduced Fehling’s solution. It was insoluble in water, alcohol, and ether, and gave a bluish violet coloration with iodine. It appeared as if the amount of this residue varied in different hydrolyses, depending upon the enzyme concentration and the substrate used. In order to determine whether or not this ob- servation was correct, the weights of residues formed in the hydrolysis of potato and corn-starch were compared. 98 cc. of a 2 per cent solution of each starch (activants added) were hydro- lyzed with 5 mg. of pancreatin. At the end of 24 hours, the amounts of sugar in the supernatant liquids were determined by analysis, after which the solutions were filtered through weighed Gooch crucibles, the residue washed several times with water, dried at loo”, and weighed. The weight of maltose formed from potato starch was 1.4240 gm., the weight of residue being 0.0113 gm. The corn-starch gave by the enzyme hydrolysis 1.2800 gm. of maltose, and an insoluble residue weighing 0.1602 gm. These residues were then hydrolyzed on a water bath for 5 hours with hydrochloric acid (sp. gr. 1.12). The large excess of acid was then neutralized by ammonium hydroxide, the solution filtered through asbestos, and the residue washed. The filtrate was collected in a. 250 cc. volumetric flask and aliquots used for analysis. The dextrose formed was calculated to anhydrous maltose. The quantity of this sugar so obtained from the potato residue was 0.0156 gm., from the corn residue 0.1434 gm. (the residues were

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J. H. Walton and H. R. Dittmar 723

obtained from 2 gm. of starch in each case). The total amount of maltose obtained from the potato starch (sum of maltose from acid and enzyme action) was 1.4396 gm., and from starch 1.4243 gm., the difference being only 0.0153 gm. If corn-starch was hydrolyzed by 100 mg. of enzyme, 1.7020 gm. of maltose were formed, while the weight of the residue was 0.0722 gm., showing that the weight of residue was dependent upon the enzyme concen- tration, or, in other words, that the residue was diacultly hydro- lyzable. The data obtained are given in Table VII.

TABLE VII.

Comparison of Maltose Formed after Acid Hydrolysis of Residues.

Potato starch.

Maltose. 100 mg. of enzyme.. . 1.7040 gm.

85.02 per cent of total starch.

Corn-starch.

Maltose. 100 mg. of enzyme.. . . . . 1.7020 gm.

85.01 per cent of total starch.

I

Mixed hydrolysis.

Maltose. c-m.

5 mg. of enzyme.. . . 1.4240 Hydrolysis of residue. 0.0156

Total. . . . . . . . . . . . . . 1.4396 71.98 per cent of total starch.

Maltose. !3m-

5 mg. of enzyme.. . . . . . 1.2800 Hydrolysis of residue. . . 0.1434

Total.. . . . . . . . . . . 1.4234 71.17 per cent of total starch.

These data not only tend to demonstrate the fact that the maximum yield of maltose is approximately 85 per cent, but that the corn-starch appears to contain more of some substance diflicultly hydrolyzed by enzymes, while the total amount of mal- tose formed from the enzyme hydrolysis of the starch and the acid hydrolysis of the residue is the same for each case.

Attention was now turned toward the salts which were used to accelerate the hydrolysis, namely sodium chloride and disodium phosphate, with the hope that possibly other activants would increase the speed of conversion to a greater extent than the salts named above. The effect of substituting 7 cc. of a fiftieth molar solution of various salts for the 7 cc. of fiftieth molar disodium phosphate, was determined, the salts used being sodium acetate,

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724 Hydrolysis of Corn-Starch

sodium potassium tartrate, sodium citrate, sodium succinate, sodium ammonium hydrogen phosphate, monosodium phosphate,

TABLE VIII.

E$ect of Substituting Various Salts for Disodium Phosphate in Enzyme Hydrolysis of Corn-Starch.

The mg. of maltose in 5 cc. of substrate are given at various intervals of time.

Time.

Ars. 0.50 2.00 2.25 2.50 4.00 5.00 5.50 6.00 7.50

21.00

-

--

NC% acetate.

ml.

3.7 14.2

-

I

_L

NaK ;&rate.

w7.

4.2 10.8

-

_-

Nl% citrate.

%7.

5.0 24.5

29.3 38.2

33.8 47.6

59.9 38.1 51.5 56.0 59.6

1

-

1

- _

-

mg. 5.0

24.7 28.7

46.0 46.6

59.9 57.3 -

-

1

_-

-

m?. 5.7

22.6 25.9

37.1 41.0

47.6 58.9

-

1.7

4.6

19.2

TABLE IX.

Efect of Substituting Various Salts for Sodium Chloride in Enzyme Hydrolysis of Corn-&arch.

The maltose content per 5 cc. of substrate solution is given at various intervals of time.

Time.

hrs.

0.50 2.50 3.50 5.50 6.00

21.00

-

--

-

No;h&anta

m9.

2.50 5.00

10.00 32.1

.-

-

KC1 NH&l LiCl N&l (alone).

.w. ml. w3. ma.

6.4 5.4 5.4 5.7 30.9 20.8 19.8

36.5 47.1 46.0

36.5 41.5 58.3 56.7 52.7 58.3

0.00513 mol of sodium sulfate practically stopped the hydrolysis. At the end of 6.5 hours, 5 cc. of substrate contained but 4.2 mg. of maltose.

and disodium phosphate. In place of 300 mg. of sodium chloride equimolecular quantities (0.00513 mol) of the following salts were used together with the requisite amount of disodium phosphate:

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J. H. Walton and H. R. Dittmar 725

potassium chloride, ammonium chloride, lithium chloride, and sodium sulfate. The sodium chloride and the phosphate were each tried alone. In all of the hydrolyses in which these salts were used, they were added after boiling the 2 gm. of corn-starch with 82 cc. of water under a reflux condenser. 1 mg. of pancreatin

70

60 -

0 5 3o

bY FIG 3. Effect of different salts upon the rate of hydrolysis of corn-starch 1 mg. of pancreatin.

was then added in 4 cc. from water containing the same concen- tration of salts at 40”, making a total volume of 98 cc. Table VIII gives the data obtained in studying the speed and extent of the hydrolyses where the substitutes mentioned above for the disodium phosphate were used

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726 Hydrolysis of Corn-Starch

By comparing the results with those of the common activants, sodium chloride and disodium phosphate (next to the last column), the relative efficiencies of the other activants can be seen. Sodium acetate, sodium potassium tartrate, and disodium phosphate (this latter when used alone) are not as favorable to the enzymatic hydrolysis as the disodium phosphate; on the other hand, sodium succinate, microcosmic salt, and sodium citrate were as efficient as the disodium phosphate, sodium citrate being even a trifle better. The curves showing the influence of Rochelle salts, sodium citrate, .and the phosphate when used alone as compared to the normal

TABLE X.

Summary of E$ect of Various Salts upon the Rate of Hydrolysis of Corn-Starch.

Activants used. Effect on hydrolysis.

KC1 and Na2HPOb. NH&l “ “ LiCl “ “ NaCl “ NaK tartrate.

“ “ Na acetate. “ (only). ‘6 and NaHQPOa. ‘I “ Na citrate.

CL c< “ succinate. “ “ microcosmic salt.

Na2HP04 (only). NazSOa and Na2HP04.

Same as NaCl and Na2HP04. ‘I <‘ ‘I <‘ ‘I

Less than “ “ “ “ “ I‘ “ l‘

Slightly less than NaCl and Na2HP04. Less than NaCl and Na2HP04. Much less than NaCl and NanHPOt. Slightly greater than NaCl and

Na?HPOa. Same as NaCl and NazHP04.

‘I “ “ “ “ Very little hydrolysis. No hydrolysis.

curve are given in Fig. 3. The influence of the salts which were substituted for the sodium chloride are given in Table IX.

By comparing the results with those in which the sodium chloride was added with the disodium phosphate (sixth column, Table VIII) it will be seen that both potassium and ammonium .chlorides were as favorable to enzymatic activity as the sodium chloride, while the lithium chloride and the sodium chloride (the latter when used without disodium phosphate) did not exert the same influence.

Fig. 4 shows the curves for the rate of conversion in which potassium and lithium chlorides were used, as well as the one in

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J. H. Walton and H. R. Dittmar 727

which only the sodium chloride was added. Also the curve in which no activants were employed.

Table X shows the effect of all the salts used.

oe I I I I I I 0 5 10

Time in” hrs. 20 25 50

FIQ. 4. Effect of different salts upon the rate of hydrolysis of corn-starch with 1 mg. of pancreatin.

SUMMARY.

1. Potato starch is hydrolyzed more rapidly than corn-starch by pancreatin, this being due to a difference in the chemical nature of the two, for the corn-starch was found to contain a material of a hemicellulose nature which was very slowly hydrolyzed by pancreatin.

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Hydrolysis of Corn-Starch

2. The enzymatic action was found to stop when the maltose content was 85 per cent of the total weight of the starch, a fact which is in accord with the results of Sherman and his co- workers.

3. The rate of conversion of corn-starch was not increased after the starch had been rendered soluble according to Lintner, autoclaved dry, autoclaved in solution, frozen, or ether-extracted.

4. In an attempt to increase the speed of conversion of corn- starch by substituting other salts besides the disodium phosphate and sodium chloride, it was found that potassium and ammonium chlorides would act, as well as the sodium chloride, while sodium citrate, sodium succinate, and sodium ammonium hydrogen phosphate could be used in place of the disodium phosphate. None of these salts increased the rate of hydrolysis more than the sodium chloride and phosphate except sodium citrate which, when used with the sodium chloride, showed a slightly more favorable effect.

BIBLIOGRAPHY

1. Sherman, H. C., and Thomas, A. W., J. Am. Chem. Sot., 1915, xxxvii, 623. Sherman, H. C., and Punnet& P. W., J. Am. Chem. Sot., 1916, xxxviii, 1877. Sherman, H. C., and Walker, F., J. Am. Chem. Sot., 1919, xli, 1866; 1921, xliii, 2461. Sherman, H. C., and Naylor, N. M., J. Am. Chem. Sot., 1922, xliv, 2957. Sherman, H. C., and Caldwell, M. L., J. Am. Chem. Sot., 1922, xliv, 2926.

2. Kendall, E. C., andsherman, H. C., J. Am. Chem. Sot., 1910, xxxii, 1087. Sherman, H. C., and Baker, J. C., J. Am. Chem. Sot., 1916, xxxviii, 1885. Sherman, H. C., Thomas, A. W., and Baldwin, M. E., J. Am. Chem. Sot., 1919, xli, 231. Sherman, H. C., and Thomas, A. W., J. Am. Chem. Sot., 1915, xxxvii, 623. Sherman, H. C., and Schlesinger, M.D., J. Am. Chem. Sot., 1912, xxxiv, 1104; 1911, xxxiii, 1195.

3. Shaffer, P. A., and Hartmann, A. F., J. Biol. Chem., 1920-21, xiv, 365. 4. Sherman, H. C., Kendall, E. C., and Clark, E. D., J. Am. Chem. Sot.,

1910, xxxii, 1082. 5. Lintner, C. J., J. prakt. Chem., 1886, xxxiv, 378. 6. Sherman, H. C., Thomas, A. W., and Baldwin, M. E., J. Am. Chem. Sot.,

1919, xli, 231.

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James H. Walton and Harry R. DittmarBY COMMERCIAL PANCREATIN

THE HYDROLYSIS OF CORN-STARCH

1926, 70:713-728.J. Biol. Chem. 

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