T H E EFFECT OF TEMPERATURE UPON T H E GROWTH OF YEAST I N VARIOUS MEDIA BY F. F. SHERWOOD AND E. I. FULMER”
----
Introduction In previous communications from this laboratory’ it has been shown that the rate of growth of yeast depends not only upon the kinds of nutrients present but also upon their concentrations. In the case of ammonium salts there are optimum concentrations which shift with temperature, a higher concentration being required for optimum results with rise in temperature. This is true not only in a synthetic medium but holds likewise for beer wort, The optimum concentrations of ammonium salt for the growth of yeast in the medium at any temperature is that concentration in which a protein, wheat gluten, is least swollen. The generalization was made2 that “if the addition of ammonium salt to a medium increases its ability to dehydrate wheat gluten, the addition will likewise improve the medium for the growth of yeast, the effect being a maximum in any combination in which the gluten is least swollen”. It was likewise pointed out in a preliminary communication on the subjecta that since there are a t least two optimal concentrations of ammonium salt for the growth of yeast at a given temperature it follows that for a given concentration of the salt there are at least two optimal temperatures. In Table I are given the values of the optimum temperatures for several standard media for yeast growth. TABLE I Calculated Optimum Temperatures for Several Standard Media for the Growth of Yeast Investigator
Pasteur Nageli Mayer Amand Raulin MacDonald Laurent Cohn
Ammonium salt
tartrate tartrate nitrate chloride nitrate and sulfate sulfate sulfate tartrate
Normality 0.0010g 0.00435 0.00936
0.0187 0.0359 0.0454 0.0713 0.109
Optimum Temperatures - 29.5 -26.0 - 23.8 -2j.4 - 15.0 -24.2 1.4 -21.9
+ + 31.6 + 48.2
+ 93.7 +I59.
-=7.9
-15.5
- 9.5 - 0.47
* From the Laboratory of Biophvsical Chemistry, Chemistry Department, Ames. Fulmer, Nelson and Sherwood: J. Am. Chem. Soc., 43, 191 (1921); Ind. Eng. Chem., 16, 921 (1924); Fulmer: “Colloid Symposium Monograph’, 2, 204 (1924). Fulmer, Sherwood and NelBon: Ind. Eng. Chem., 16, 921 (1924). Fulmer: “Colloid Symposium Monograph”, 2, 204 (1924).
EFFECT O F TEMPERATURE UPON GROWTH OF YEAST
739
In only one instance, that of Raulin’s medium, is an optimum temperature within the viable range. A rise in temperature in a medium with a given concentration of ammonium salt is equivalent in the effect upon the growth of yeast to the lowering of the concentration of the salt a t a given temperature. Evidently the term “optimum temperature” for the growth of an organism has no general meaning but is a function of the kinds of materials present and of their concentrations. Data obtained regarding the effect of temperature up& the growth of an organism in a medium of constant composition are the resultant of two factors, the effect of temperature per se and its effect upon the physical chemical environment. This may be illustrated as follows. If the growth of yeast in Amand’s medium be studied between IO’ and 30’ the growth rate will be increased by rise in temperature but also retarded due to the increasing “distance” from the optimum of +1.4’; with MacDonald’s medium the growth rate will be accelerated by the increase in temperature and likewise by that fact of the approach to an optimum of +48.2’; with a medium such as that of Cohn the effect will be complex for with rise in temperature the growth rate will be accelerated by the increase in temperature but retarded as the temperature goes away from the medium of - 1 . 7 ’ and accelerated as the optimum of + I 59 is approached.
It would seem then that the effect of temperature per se upon the growth of yeast in a medium of a given composition can be determined only on the basis of growth rates in the medium with the optimum concentrations of the components for each temperature. Data are here presented on the growth of yeast a t various temperatures in media whose composition is adjusted to optimum conditions and the results compared to those obtained in media not SO adjusted as well as with data obtained by other investigators. The yeast used had been growing continuously in a synthetic medium for five years and came originally from a cake of Fleischmann’s yeast and is identical with the yeast described previously1 as No. I I . The number of cells in each case was determined by means of the Thoma-Zeiss counting chamber and is indicated as “count”. The “count” is the number of cells in sixteen small squares so that when the count is one there are 250,ooo cells per cubic centimeter. In every case the flasks were inoculated so that the initial count was one, the inoculation being made from an actively growing culture in order to reduce any “lag phase” to a minimum. In the determination of the growth rates the flasks were gently rocked after the method described by Clark2 and for reasons discussed by him. The beer wort was made by mashing, at g j ’ , 3 6 0 grams of distiller’s malt with 1 1 5 0 cc. of distilled water for 24 hours. The mixture was filtered through towelling, then through filter paper and heated for thirty minutes under 15 Fulmer and Christensen: J. Phys. Chem., 29, 1415 (1925) Clark: J. Phys. Chem., 26, 42 (1922).
F. F. SHERWOOD AND E. I. FULMER
7 40
m. w.
.
4
h
00 N
%I N
"W N
N
0
* N O H N N K )
00
U H
2 121 I I I I I I I : W W Q \ D
l o l o c i
P l K ) m * N
d-\D
* K ) W H
t Z N
H N C Q M d N 0 K)\D o \ O 0 Y H N H H N N N N K ) K ) K ) K ) K ) M K ) K ) M * * * * 3 * U H
? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? C
N
C
h C
o o o o o o o o o o o o o o o o o o o o o c
EFFECT O F TEMPERATURE UPON GROWTH O F YEAST
74=
~.
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
*
0
0 M W n ) O W W M W O a m H * W \ 0 h * W * M N N M K , . . f N N N N N M N N N N N N N 0
0
* 3
u w
\ o e M N
N
N
742
F. F. SHERWOOD AND E . I. FULMER
pounds pressure. After standing for three days to permit coagulated matter to settle out, the liquid was filtered and sterilized in live steam for thirty minutes. The basal medium was Medium El which for 30’ has the following 0.100g. K2HP04, 0.100g. amounts of materials per IOO cc.: 0.188 g. “&I, CaC12,0.04 g. CaC03, I O g. sugar. The Determination of Optimum Concentrations of Ammonium Chloride in Medium E and in Wort I n Tables 11, I11 and IV are given typical data showing the effects of various concentrations of ammonium chloride upon the growth of yeast in Medium E and in beer wort a t several temperatures. It will be noted that with both media there are two optimum concentrations of the salt. With both media the largest crops were obtained at 42’, a temperature considerably higher than that usually considere< optimum for the growth of yeast. Slate? states that above 40’ the enzymes are destroyed. In the synthetic medium the growth at 42’ is as good as at 40’ but there is a sharp break at 43’. It would seem than that with a properly adjusted medium of the given components that 40’-42’ marks the temperature for the maximum growth of yeast and that a profound change takes place between 42’ and 43’. The ammonium salt may be said to act as a ‘‘temperature buffer”. The term “thermal” death point of an organism may have as little general meaning as “optimum temperature” unless expressed in terms of the composition of the medium. The effect of ammonium salts upon the death rate of yeast and change in permeability to methylene blue3 is being studied in this laboratory. The data on wort confirm a previous statement4 that whatever the role of bios may be in beer wort it is not the same as that of the ammonium salt. In Table IV are assembled the optimal concentrations of the ammonium chloride for the media studied. In each instance the optimum normality of the salt is a linear function of the temperature, the appropriate equations being given in the table. By means of equations ( I ) and ( 2 ) may be calculated the optimum concentrations of the salt for a given temperature for the synthetic medium while equation (3) and (4) may be used for the beer wort employed in this work. Since latter medium may vary considerably in composition, depending upon the malt and method of mashing, these equations could not be promiscuously used. The equation should be determined for each sample. Similarly by means of the equations ( j , 6, 7 , and 8) may be calculated the optimum temperatures for a given normality of the ammonium salt, Equations (5) and (6) were used in calculating the data in Table I. Fulmer, Nelson and Sherwood: J. Am. Chem. SOC., 43, 191 (1921); Ind. Eng. Chem. 16, 921 (1924);Fulmer: “Colloid Symposium Monograph,” 2, 204 (1924). Slator: J. Chem. SOC., 89, 128 (1903). Miller: J. Phys. Chem., 24, 564 (1920);Fraser: J. Phys. Chem., 25, I ; Fulmer: I O (1921). 4 Fulmer, Sherwood and Nelson: Ind. Eng. Chem., 16, 921 (1924).
EFFECT O F TEMPERATURE UPON GROWTH O F YEAST TABLE
7 43
Iv
The Effect of Ammonium Chloride upon the Growth of Yeast in Medium E-Second Maximum Temperature IO 20 Normal- Count ity of 30 hr. NH,Cl 0.00oo 48 0.059 53 0.118 61 0.1298 72 0.1475 80 0.1534 92* 0.1593 0.1652
Normal- Count ity of 35 hr. NH,Cl 0.000
0.059 0.118 0.1475
0.177 0.182 0.194 0.206 0.236 0.354
79 60
55 0.236. 40 0.2950 38 * Optimum. 0.177
Kormalit,y of ?;Hac1
Count 2 8 hr.
58
0.000
61
65
0.118
75
0.177
84 89
71 80 86 89
.
0.2263 0.236 0.295 0,354 0.472 1.118 1.483
IOO*
88 65 56
IO^* 84 76 63
58 50
40 Normal- Count ity of 30 hr. NHdCl 0.000 67 0.118 76
0.177
84
0.2265 0.236 0.265 0.278
91 94 97
0.287
79
0.295 0.354 0.4720
65 59
TABLE V Optimum Concentrations of Ammonium Chloride in Medium E and in Wort Medium E Wort Temp. 11(2) I?) 0
0.0118
IO
0.0236 0,0295 0.0319 0.0354 0.0383 0.0413 0.042 5 0.0431
20 25
30 35 40 42
43
0 . I534
0.0141 0.0188
0 . I940
--
0.106
0.278
0.0283 0.0294
0.123
0.00057t f 0.0179; ti
N2
=
o.oo42t
0.111;
tz
Wort
N2
= O.OO~O
0.0649 0.0826
0.0236
=
NI
U4)
0.236
s i
+
72
-~
N = normality of ammonium chloride t = temperature Medium E
2
III*
+ o.oosot: ti
- 0 . 0 1 79 0.00057 N-O.III -= 0.0042
=
N -0.0090 0.0050
N -0.0475 0.0475 +O.O0177t;tz = 0.00177
0.
I18
F. F. SHERWOOD AND E. I. FULMER
744
The Optimum Concentrations of K2HP04,CaClz and CaC03 Data showing the effect upon the growth of yeast a t several temperatures of various concentrations of K2HP04, CaClz and CaC03 in Medium E are found in Tables VI, VI1 and VIII. The results confirm our previous findings, 1
TABLE VI Growth of Yeast, varying KLHP04 25OC. Normality KzHPOi
I = 1
I = 1
Count 30 hr.
Count 06 hr.
Count 42 hr. 60 162 165
0.0000
180
93
0.00232 0.003480 0.00464* 0.00696 0.00928 0.01 160 0.01392 * Optimum.
222
227
I = 1
280
305 302 304 303
204 203 202
I90 189 187 188
262
302
203
187
Count Count 24 hr. 72 hr.
26 98 126 I59 158 I57
27
172
261 260 259 261
I=r
1 = 1
Count 24 hr.
2 46
205
4oOC.
35 O C .
3oOC.
I = 1
181
91 183 241 269 267 268 269 267
L
158 I59
TABLE VI1 Growth of Yeast, varying CaCL 25OC.
Normality of
CaCls 0.000
0.00180 0.00360 0.00540 0.00720
o.00900 0.0108 0.0126 0.01440 0.01620 o .01800* 0.0216 0.0217
0.0324 0.0360 * Optimum.
I = 1 I = 1 Count Count 24 hr. 48 hr. 61 92
73 91
106
105
129 136 156 I73 196 218 278 334 333 335 335
130 140 158 219 256 286 379 375 378 376
117
30°C. I=1 I = 1 Count Count 72 hr. 48 hr. 217 186 235 198 247 202 289 246 295 266 304 290 312 298 310 310 318 318 335 342 386 388 387 388 388 389 387 389
Refers to first reference given on page 742.
3 5°C. I=1 I = r Count Count 42 hr. 98 hr. 157 202
4oOC.
I=r
I = 1
Count Count 24 hr. 48 hr. 160 2IO
161
257
209
269
177
260
212
272
191
274
226
285
243
299
251
275 276 274 275 276
325 328 326 324
EFFECT O F TEMPERATURE UPON GROWTH O F YEAST
745
TABLE VI11 Growth of Yeast, varying CaCOs Normality of CaCOa
25OC.
3oOC.
3 5OC.
4ooC,.
I = r Count 32 hr.
I = 1 Count 48 hr.
I = 1 Count 36 hr.
Count 46 hr.
1 = 1
0.000
42
130
65
0.0040
115
I 79
170
70 I96
0.0060 0.0080"
I2 j
2 98
192
2 IO
170
371
220
251
0.0100
IO0
238
215
226
0.0160
80 65
180 164
206
150
140
0.020
52
I48
I39
0.024
51
186 I75
0.0120
I90
I3 9
* Optimum. It will be noted that the optimum concentrations of the salts above studied do not vary with temperature as do those for the ammonium chloride. In Table IX are given the concentrations for the best possible medium for the growth of yeast a t any temperature with the given components.
TABLE IX The Concentrations of Salts in Medium E Optimum for Any Temperature Salt
Normality
NHdC1
K 2 H P 0 4 (anhyd) (anhyd) CaCL CaC03 (ppted)
Grams per
+ or + o.oo42t
(I)
0.0179
(2)
0.111
0.00057t
IOO cc.
+ 0.60306t or 0.595 + o.67jt
0.0960
0.00464
0.0260
0.01800
0 . IO0
0.0080
0.040
The Growth of Yeast in Various Media In Table X will be found data showing the growth of yeast in wort without added ammonium chloride while data on the growth of yeast in wort to which had been added the optimum concentration of the ammonium salt for each temperature will be found in Table XI.
F. F. SHERWOOD AND E. I. FULMER
746
TABLE X Growth of Yeast in Wort without ISHdC1 2 oo
IO0
O0
Time (Hours)
Count
Time
Count
Time
Count
28
2.2
26
I3
I7
57
35 48
2.7
29
I9
I9
92
3.9
36
35
21
I49
64
4.3 4.4
40 52
53 128
23 25
243 281
76
4.6
62
162
29
792
77
164
39 48
1165 1190
63
1205
52
40° Time Count (Hours) 6
8 9.5
4.5 25
I2
67 223
I3 I4
320 505
23.5 29 37 48 60
837 872 I342 I345 I332
72
I342
42O Time Count 9 11
53 83 131
I3
308
I5
316
I7 33 41.5
340 355 408 521
56 68
625 630
IO
21
Time
43 Time
Count
I2
1.6
18
2.2
24
2.8
30 38
3.6 3.7
45 68
3.8
3.8
30° Count
EFFECT O F TEMPERATCRE UPON GROWTH O F YEAST
747
TABLEXI Growth of Yeast in Wort with Optimum Concentrations of NH4C1 3 oo
40°
Count
Count
Count
Count
1st 2d Opt.
1st
1st 2d Opt.
IO0
20°
Time (Hours)
2d
opt.
8
29
25
IO
56
I1
87
54 82
42O
2d
1st
Opt.
9
3.4
I5
4.8
4.6
I7 18
6.0
5.7
I9
7.2
130
122
59
131
113
209
178
161 146
332
217
255
1107
980
13
228
406 356
6.8
21
72
63
92
83
119
107
196
I75
21.5
I437 1300 600
23 384
25
I330
26
15
14.0
32
28
26 1059 1040
34
525
342
25.j
I200
1470 1390 652 617
35 43 45 47 48 50
1st 2d opt.
64
3.5
I2
Count
1301 1180 I09
98 1465 1380 667 655
I53
I33
237
206
55 59 62
670 662 I449 1296
67 69
1705 156,;
70
151j
74 75
2 44
2 IO
81
2 46
212
I444 1300
1400
F. F. SHERWOOD AND E . I. FULMER
748
In Table XI1 are given the data showing the growth of yeast on the synthetic media. The figures in the columns marked A were obtained by using Medium E with the optimum concentration of ammonium salt for each temperature while in the experiments designated B Medium E was used with the concentration of the ammonium salt optimum for 30'.
TABLE XI1 Growth of Yeast' in Medium E. -4.Opt. for Each Temp. B. Opt. for 30' Temp. oo Time A 6
IO0
A
20°
B
A
B
30' A B
40°
A
42O
B
A
B
I3
7.5
43' A
7 8
I1
9
I7
IO
21
I1
30
33 45 45
I2
I3 I4 I5 16
77 3
I37 34 24
23
91
41 26
I. j
77
I 1 0 I10
I7 I8
13.5
43 2 8 63 38
70
I12
55
97 1.31
1.8
24
4.2
19
49 74
21:
42
162
22
5.5
23
I11
24
72 128
25 26 28
I1
80
2.1
16
20
30 32 33 34 35 36
37
J
I2
2.6 28
49
89
EFFECT O F TEMPERATURE UPON GROWTH OF YEAST
749
TABLE XI1 (Continued) Growth of Yeast in Medium E. A. Opp. for each Temp. B. Opt. for 30’ Temp. Time 38 39 40 41 42 43 45 46 48
oo
A
B
A
42 18
224
B
A
B
40’
A
43 O
B
A
132 332 188
254 258
3.5 395
261 2 80
3.6
261 184 I39
3.8
I Oj
274 37
56
I95
58 59
349
3 93 274 I34 4.2
67 345
270
399
3.4 196
71
270
69
72
73
75
A
191 192 I74
55
60 62 63 64 65 68 69
42’
B
3.4
50
51 52 54
3 oo
20°
100
A
398 4.1
I37
203
202
The data above presented permit an analysis of three growth phases of yeast in various media a t several temperatures. Buchannn’ describes and discusses in detail seven growth phases in a culture of a microorganism. I. Initial Stationary Phase during which the number of cells remains constant. 2. Lag Phase or Positive Growth Acceleration Phase in which the “average rate of increase in numbers per organism increases with the time”. 3. The Logarithmic Growth Phase during which “the rate of increase per organism remains constant”. Buchanan: J. Infect. Dis., 23, 109 (1918).
F. F. SHERWOOD AND E. I. FUIjMER
750
3. Phase of Negative Growth Acceleration in which “the rate of growth per organism decreases”. 5 . Maximum Stationary Phase during which “there is practically no increase in the numbers of organisms”. 6. Phase of Accelerated Death in which the numbers of cells is “decreasing with increasing rapidity”. 7. Logarithmic Death Phase during which the “rate of death per organism remains constant”.
The Logarithmic Growth Phase of Yeast in Several Media at Different Temperatures During the logarithmic or maximum rate of growth the number of cells increases a certain fraction of itself each instant, that is if C = count
(2)
/ ’
=
k
LA
/
“
dt 1
and ( 3 ) log Cz - log C1 = k(t2 - tl) During this phase of growth the generation time, that is, the time required for one cell to become two will be:
log
2
(4) g.t. = -
k
From the growth data previously given values of k were obtained as the slope of the straight lines resulting from the graph of log I O C plotted against time. The following discussion will deal then with the effect of temperature upon the value of k per various media, A summary of such values is given in Table XIII.
TABLE XI11 Values of k for Various Media at Different Temperatures Temperature 0
Wort KO NH&1 added
Wort 1st Optimum
Wort 2d Optimum
0.0122
0.0453 0.1092 0.1780
0 * 0443 0.1068 0.1740 0.1992 0.1964
IO
0.0430
20
0.1035
30 40 42 43
0.1686 0.1936 0,1923 0.0180
PjHaCl
0.2051 0.~005
NH4C1
Medium E Optimum
Medium E Optimum for each Temperature
0.0324 0.0777 0.1361 0.1316 0.1098
0.0405 0.0883 0.1361 0.1452 0.1239 0.0143
for 30’
0.0113
EFFECT OF TEMPERATURE UPON GROWTH O F YEAST
751
I n Table XIV the values of k for the various media are compared to that for wort as standard.
TABLE XIV The Value of K for Various Media Where K = Temperature
Wort 1st Optimum NH4C1
0
3.7=
IO
2.54
20
1.72
30 40 42
1.22 1.03
43
k(Medium Used) k (Wort)
Wort 2d Optimum
Medium E Optimum
"4Cl
for 30"
-
3.63 2.48 1.68 1.18
0.75 0.75 0.807
Rledium E Optimum for each Temperature
0.93 0.94 0.85 0.807
I .OI
0.54
0.75
__
__
0.57
0.64
-
--
-
0.79
The jncrease in growth rate in wort due to the addition of the optimum concentrations of the ammonium chloride is especially striking a t the lower temperatures. The above points are shown clearly on the graphs in Fig. I where the values of k are plotted against temperature. With a rise in temperature the advantage of the salt decreases with practically no effect a t 40'. The two optimum concentrations for the wort give practically identically results. In the synthetic medium again is seen the advantage of using the optimum concentrations for each temperature as compared to results obtained by use of a medium optimum for the one temperature of 30'. The Temperature Coefficients for the Growth of Yeast in Several Media at Various Temperatures Using the values for k found in Table X the temperature coefficients are calculated on the usual basis where Qlo = k(tl Io)/k(tz). Values for & l o are listed in Table XVI. In the same table are listed values for "p" calculated from the van't Hoff equation as follows:*
+
In every instance through a range of 10-40there is a smaller "spread" of values for in cases where optimum conditions are maintained compared to values for unadjusted media. With wort the differences in value of Qlo for adjusted and non-adjusted medium is greatest a t the lower temperatures. In Table XVII are found average values of Qlo obtained by various investigators.
F. F. SHERWOOD AND E. I. FULMER
4
H
H
'?
0 0
0 0 0 0 0 0 0 0 N) 00, '0,
H
H
N
H
o m
c= ha
0 0
0' v )
0 0 0 0 0- 0, W *
w"
0 0
4
00, 0
w"
B 4 i
0 O
0 d-
M
N
H
0 0
:-% H
t N
0 0
a ?
N
0 0
00, ch
H
E
?
H
t N
1 0 0 *
. .
H
N
H
EFFECT O F TEMPERATURE UPON GROWTH O F YEAST
753
TABLE XVII Average Values of Investigator
&IO
Temperature Range
Average Qlo
10-35 I4-28 12-33 10-40 10-40 10-40
2.97
Slatorl Herzog2 Abersona Sherwood and Fulmer
2.88 2.72
2.18 I .go 2.Oj
W o = wort without ammonium chloride. W1 = wort with optimum concentration of ammonium chloride. El = medium E optimum for each temperature.
t
I
I
I
I
lo
20
30
YO
50
to+ FIG.I
-
An examination of this table shows the widely differing values for &IO obtained by various investigators of yeast growth. It is evident that the lowest average values obtained are typical of media whose composition has been adjusted in an appropriate manner for each temperature thus eliminating certain variables discussed in the Introduction. Slator: J. Chem. Soc., 89, 128 (1903). Herzog: Z. physik. Chim., 37, 149 (1902). a Aberson: Rec. Trav. chim., 22, 78 (1903). 2
754
F. F. SKERWOOD AND E. I. FULMER
The Phase of Negative Growth Acceleration and the Maximum Stationary Growth Phase of Yeast I n studies on temperature coefficients for the growth of yeast use has usually been made of the phase, the logarithmic phase. However environment may not influence the growth phases equally or even in the same direction. For example; with reference to the logarithmic phase and the Maximum Stationary Phase or “total crop” a change of environment may cause one of nine effects as follows:
I T
I I
1
I
I
Tcme--.
FIG.2
TABLE XVIII
I ogarithmic Phase I. Increase 11, Increase 111. Increase IV. Decrease V. Decrease VI. Decrease VII. No effect VIII. No effect IX. No effect
Total Crop
No effect Decrease Increase No effect Decrease Increase No effect Decrease Increase
From the graphs of growth data given above a study may be made of the effect of ammonium chloride and of temperature upon the phase of negative growth acceleration and the total or maximum crop. The former phase is represented by the count at the inflection of the curve between thelogarithmic phase and the maximum stationary phase, that is, the count a t which the growth just ceases to be logarithmic. These points are designated on a typical curve on Fig. 2. Values for the above functions are given in Table XIX.
EFFECT OF TEMPERATURE UPON GROWTH O F YEAST
TABLE
755
XIX
Maximum Crop and Critical Count for the Growth of Yeast in Various Media a t Several Temperatures
W1
Medium Wo Temp. A B
A
w2
A
B
B
A
Eo B
EI A 4.2
0 IO
20
30 40
102 161 290 1218
153 246 384 1442
133 212 342 1300
1245 1350 950 1555
1437 1515 1380 1710
1300 1400
450
42
622
600
665
1200
1560
525
660
37 69 80 203
4.2
128
137 282
202
137 223
280 394
89 138
131
343
156 97
10.5
270
43
3.3
A
B
3.4
W1 and W2 = Wort with 1st and 2d opti-
= Inflection count.
mum NH4C1. Eo = Medium E optimum for 30’. E1 = Medium E with optimum NH4C1.
B = Total crop. Wo = Wort with NH4C1.
The data show that the effect of the ammonium salt falls into class I11 given in Table XVIII that is the salt increases both the logarithmic growth rate and the total crop. It is also apparent that the salt leads to an increased count a t the inflection point in the logarithmic curve. However, the figures given in Table XX show that the inflection count and the total crop are not increased equally. At 20’ in all the media used with the possible exception of E1 the phase of negative growth acceleration is more extended than a t any other temperature. The maximum logarithmic growth rate, inflection count, and total crop occur at 40’ for all the media used except Medium E optimum for 30’.
TABLE XX Ratio of “Inflection Count” to “Total Crop”, B/A Medium Temp.
Wo
171
w2
Eo
E1
IO
I
.6 3.8
.6 3.8
1.8
1.3
20
1.6 4.6
2 . 5
2.2
30
1.1
1.1
1.1
1.7
2
40
1.6
1.2
1.3
2.1
1.8
42
1.4
1.1
1.2
1.6
2.6
I
.o
756
F. F. SHERWOOD AND E. I. FULMER
Summary A detailed study has been made upon the growth of yeast a t various I. temperatures in several media. The optimal concentrations of ammonium chloride in the synthetic 2. medium have been formulated. 3. Temperature coefficients for the growth of yeast were determined in media adjusted to optimum concentrations for each temperature and compared to those obtained in media not so adjusted. 4. A quantitative study was made of the phase of negative growth acceleration and the maximum stationary growth phase of yeast in several media at different temperatures.
