532

Journal of Health Science, 57(6) 532–539 (2011)— Research Letter —Safety Study of Yeast Hydrolysate
with below 10 kDa Molecular
Weight in Animal Models
Eun Young Jung, a Sung Sun Park, a
Jay Hwan Kim, a Un Jae Chang, b
Song Hwan Bae, c Jang Won Choi, dand Hyung Joo Suh∗, aaDepartment of Food and Nutrition, Korea University, 1Jenongneung-dong, Sungbuk, Seoul 136–703, Republic of Korea, b Department of Food and Nutrition, Dongduk Women’s
University, 23–1 Hawolgok-dong, Sungbuk-gu, Seoul 136–714,
Republic of Korea, c Department of Food and Biotechnology,
Hankyong National University, 327 Seokjeong-dong, Anseongsi, Gyeonggi-do 456–749, Republic of Korea and d Departmentof Bioindustry Daegu University, Jillyang-eup, Gyeongsan-si
712–714, Republic of Korea(Received July 14, 2011; Accepted August 9, 2011)

The aim of this study was to obtain data on
the safety of yeast hydrolysate with below 10 kDa
molecular weight. The acute [at a single dose of
5000 mg/kg body weight (BW)] and subacute (at adose of 1000 mg/kg BW for 14 consecutive days)
oral toxicity of yeast hydrolysate from Saccharomyces
cerevisiae was assessed in Sprague-Dawley (SD) rats.
The yeast hydrolysate acute treatment via the oralroute at the dose of up to 5000 mg/kg did not produce
any signs of toxicity or death in the rats. The yeast
hydrolysate with below 10 kDa molecular weight did
not induce any damage to the internal organs of therats as examined by hematological and biochemicalparameters. The macroscopic analysis of the treatedanimals did not show significant changes in color andtexture. These results show that yeast hydrolysate
with below 10 kDa molecular weight possesses very
low toxicity as indicated in this SD rat model.
Key words —— Saccharomyces cerevisiae, yeast, safety,
acute toxicity, subacute toxicity∗

To whom correspondence should be addressed: Department
of Food and Nutrition, Korea University, 1 Jenongneung-dong,Sungbuk, Seoul 136–703, Republic of Korea. Tel.: +82-2-9402853; Fax: +82-2-940-2850; E-mail: suh1960@korea.ac.kr

INTRODUCTION
Yeast is a unicellular fungus and probably oneof the most commercially exploited microorganisms. The yeast species Saccharomyces cerevisiae(S. cerevisiae) has been used in baking and fermenting alcoholic beverages for thousands of years.1) It
is also extremely important as a model organism
in modern cell biology research, and is one of themost thoroughly researched eukaryotic microorganisms.2, 3)
Yeast hydrolysate, which is acquired from S.
cerevisiae through protein hydrolysis, showed effectiveness in reducing the emotional, physical, andbehavioral symptoms of premenstrual syndrome.4)
Furthermore, yeast hydrolysate has displayed physiological effects on reproductive function5) and antistress and immunopotentiating activities.6, 7) Recently, yeast hydrolysate has revealed various physiological effect of according to molecular weight.
In Kim et al. study,8) yeast hydrolysate with 10–
30 kDa molecular weight increased longitudinalbone growth and growth hormone secretion in adolescent Sprague-Dawley (SD) rats. And yeast hydrolysate with below 10 kDa molecular weight has
displayed the anti-obesity effects in SD rats fed ahigh fat diet and obese women.9–11) It is needed
the detailed toxicological information of yeast hydrolysate at the different stage of the molecularweight for safety-in-use of yeast hydrolysate witheach molecular weight in an industrial context as afunctional material for the health and diet food market.
In our previous study,12) we found that the yeast
hydrolysate with 10–30 kDa molecular weight wascomparatively nontoxic when oral acute and subacute toxicity were examined in SD rats. In thisstudy, we tried to obtain data on the safety of yeast
hydrolysate with below 10 kDa molecular weight byassessing its acute and subacute oral toxicity following Organization of Economic Co-operation andDevelopment (OECD) guideline. The acute (at asingle dose of 5000 mg/kg body weight)/subacute(at the dose of 1000 mg/kg body weight for 14
consecutive days) oral toxicity of yeast hydrolysate
with below 10 kDa was assessed in SD rats of both
sexes. In the subacute toxicity study, the effects onbiochemical, hematological, and histopathologicalparameters were evaluated.
C 2011 The Pharmaceutical Society of Japan

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MATERIALS AND METHODS
Preparation of Yeast Hydrolysate with below
10 kDa Molecular Weight —— The yeast used
was S. cerevisiae (IFO 2346; strain Kyokai 6;
MCYC 3175; LSUrDNAD1D2) obtained fromthe Institute for Fermentation Osaka (IFO, Osaka,
Japan). S. cerevisiae was incubated in medium
containing 2% molasses, 0.6% (NH4 )2 SO4 , 0.1%
MgSO4 ·7 H2 O, 0.2% KH2 PO4 , 0.03% K2 HPO4 ,and 0.1% NaCl for 3 days at 30◦ C. After incubation, the culture was centrifuged at 10000 × g for
20 min. The cells were suspended in 20 mM phosphate buffer (pH 7.0) and hydrolyzed with 1000
units of bromelain at 30◦ C for 4 hr. The hydrolysate
was subsequently centrifuged at 10000 × g for
20 min. Next, the supernatant was passed througha 10 kDa molecular weight cut-off membrane(Satocon cassette, Sartorius, Gottingen, Germany)and lyophilized.
Experimental Animals —— The experimental
protocol was reviewed and approved by the Korea
University Animal Care Committee. Female andmale SD rats were obtained at 8 weeks of age
from Nara Biotech (Kyonggi-do, Korea). They
were individually housed in plastic cages withgrated stainless steel floors. The colony room wasmaintained at 24 ± 1◦ C with 60% atmospherichumidity and a 12 hr light/12 hr dark cycle. The rats
had ad libitum access to water and to a commercial
diet (Samyang Co., Seoul, Korea) containing thefollowing (g/kg of diet): moisture, 80; protein, 230;
fat, 35; fiber, 50; carbohydrate, 600; and water.
Acute Toxicity —— According to OECD guidelines for the testing of chemicals, TG420 (OECD)
guideline for testing of chemicals, TG420,13) therats were randomly divided into 2 groups per
sex. The yeast hydrolysate at a single dose of
5000 mg/kg of body weight was given orally to thetreated group (1st group), whereas an equal volume
of water vehicle was given to the control group (2ndgroup). Observations were made and recorded systematically 1, 2, 4, and 6 hr after test substanceadministration. The visual observations included
changes in the skin, fur, eyes and mucous membranes; the respiratory, circulatory, autonomic, andcentral nervous systems; as well as somatomotor activity and behavioral patterns. The number of survivors was noted after 24 hr and these rats were thenmaintained for another 14 days with once daily observations. On day 15, all the rats were fasted for
16–18 hr and then anesthetized with ethyl ether andsacrificed.
Subacute Toxicity —— According to OECD
TG407,14) the rats were divided into 4 groups per
sex. The yeast hydrolysate was administered to thetreated group (1st group) at the dose of 1000 mg/kg
of body weight for 14 days, whereas an equal volume of water vehicle was given to the control group(2nd group). In order to assess reversibility and thedelayed occurrence of toxic effects, satellite groups
were employed by giving the yeast hydrolysate (3rdgroup) at the dose of 1000 mg/kg of body weightor an equal volume of water vehicle (4th group)for 14 days and then the rats were maintained foranother 14 days after treatment. During the periodof administration, the animals were weighed andobserved daily to detect signs of toxicity. Daily
visual observations similar to those performed in
the acute toxicity study were made and recorded
systematically. At the end of the period, all rats
were fasted for 16–18 hr and then anesthetized with
ethyl ether and sacrificed.
Hematological and Biochemical Analysis ——Blood samples were collected from a common
carotid artery into heparinized and dry nonheparinized centrifuge tubes. The heparinizedblood was used for hematological examinations
and the serum separated from the non-heparinizedblood was assayed for biochemical analyses. Hematological analysis was performed using an automatic hematological analyzer, KN-21N (Sysmex
Co., Kobe, Japan). The parameters included:
red blood cell (RBC) count, white blood cell(WBC) count, hematocrit (Hct), hemoglobin (Hgb),
mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), and mean corpuscularhemoglobin concentration (MCHC). For biochemical analysis, the blood was centrifuged at 1500 ×
g for 10 min to obtain the serum and the following parameters were determined using a FUJI DRICHEM 3500 analyzer (Fuji Photo Film Co., Osaka,
Japan): glucose, blood urea nitrogen (BUN), creatinine, total protein, albumin, aspartate aminotransferase (AST), and alanine aminotransferase (ALT).
Morphological Study —— After blood collection,
the rats were sacrificed for tissue studies. The animals were perfused with saline solution followedby 10% buffered formalin solution for 10 min andthen their organs such as the liver, kidneys, spleen,lungs, heart, and sex organs were removed, blotted
free of blood, and weighed immediately on an electronic balance for subsequent analysis. The organ
weights were expressed in relative terms (g/100 g

534Vol. 57 (2011)

Fig. 1. Body Weight Gain and Daily Intake of SD Rats Treated Orally with Yeast Hydrolysate with below 10 kDa Molecular Weight
for Acute and Subacute Toxicity
Bars are means ± S.D. for 5 rats/group. The group for acute toxicity was given water vehicle or yeast hydrolysate with below 10 kDa molecularweight at 5000 mg/kg once followed by no treatment for 14 days. The group for subacute toxicity was given water vehicle or yeast hydrolysate withbelow 10 kDa molecular weight at 1000 mg/kg daily for 14 days. The satellite group for subacute toxicity was given water vehicle or yeast hydrolysate
with below 10 kDa molecular weight at 1000 mg/kg daily for 14 days followed by no treatment for 14 days. The differences between the control andtreated groups were evaluated by Student’s t-test.

of body weight). After fixation in 10% phosphatebuffered formalin, the liver and kidneys were processed in a routine manner, embedded in paraffin,
and sectioned. Then, to perform light microscopic
evaluation, the liver was stained with hematoxylin
and eosin (H & E), and the kidneys were stainedwith periodic acid schiff (PAS).
Statistical Analysis —— All statistical analyses
were performed using the Statistical Package forSocial Sciences (SPSS) version 12.0 (SPSS Inc.,
Chicago, IL, U.S.A.). The differences between thecontrol and treated groups were evaluated by Student’s t-test and p values less than 0.05 were considered significant. All data are reported as means± standard deviations (S.D.).

RESULTS
Acute Toxicity
Acute oral toxicity refers to the adverse effects
that occur following the oral administration of a

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Table 1. Hematological Parameters of SD Rats Treated Orally with Yeast Hydrolysate with below 10 kDa Molecular Weight for Subacute Toxicity
Hematologicalparameters
RBC (×106 /µl)
WBC (×103 /µl)
Hct (%)
Hgb (g/dl)
MCV (fl)
MCH (pg)
MCHC (g/dl)
Platelets (×103 /µl)
Hematologicalparameters
RBC (×106 /µl)
WBC (×103 /µl)
Hct (%)
Hgb (g/dl)
MCV (fl)
MCH (pg)
MCHC (g/dl)
Platelets (×103 /µl)

FemaleGroup for subacute toxicitya)
Satellite group for subacute toxicityb)
Control
Yeast hydrolysate
Control
Yeast hydrolysate
7.33 ± 0.52
7.21 ± 0.19
7.47 ± 0.30
7.12 ± 0.17
8.57 ± 1.55
8.08 ± 1.24
8.00 ± 1.34
7.20 ± 0.22
43.77 ± 3.75
43.98 ± 2.27
44.73 ± 2.74
45.10 ± 1.37
13.51 ± 1.52
13.49 ± 0.94
14.50 ± 0.87
14.47 ± 0.35
56.77 ± 1.45
58.42 ± 1.26
59.83 ± 1.37
58.90 ± 1.20
18.34 ± 0.58
18.21 ± 0.88
19.33 ± 0.50
19.47 ± 0.65
31.12 ± 1.23
31.55 ± 1.59
32.37 ± 0.21
32.50 ± 1.00
845.26 ± 54.42
898.87 ± 49.99
728.00 ± 41.52
823.67 ± 38.94
MaleGroup for subacute toxicitya)
Control
Yeast hydrolysate
7.06 ± 0.78
7.24 ± 0.86
11.21 ± 1.02
11.00 ± 0.89
45.15 ± 3.35
46.66 ± 4.32
13.99 ± 0.98
14.28 ± 1.01
57.78 ± 1.24
57.62 ± 1.08
17.49 ± 0.52
18.00 ± 0.15
31.07 ± 1.01
31.22 ± 1.75
721.42 ± 58.87
705.66 ± 61.41

Satellite group for subacute toxicityb)
Control
Yeast hydrolysate
7.96 ± 0.38
7.98 ± 0.41
10.47 ± 0.31
10.82 ± 0.95
47.25 ± 2.35
47.00 ± 4.48
14.97 ± 0.21
15.00 ± 0.78
58.93 ± 1.11
58.83 ± 2.68
18.50 ± 0.52
18.73 ± 0.06
31.27 ± 0.21
31.90 ± 1.44
692.67 ± 60.34
695.00 ± 60.22

Values are means ± S.D. for 5 rats/group. a) The group for subacute toxicity was given water vehicle or yeast hydrolysate
with below 10 kDa molecular weight at 1000 mg/kg daily for 14 days. b) The satellite group for subacute toxicity was given
water vehicle or yeast hydrolysate with below 10 kDa molecular weight at 1000 mg/kg daily for 14 days followed by notreatment for 14 days. The differences between the control and treated groups were evaluated by Student’s t-test.

single dose of a substance or multiple doses given
within 24 hr. The results indicated that the yeast
hydrolysate with below 10 kDa molecular weightacute treatment via the oral route at the dose of up
to 5000 mg/kg did not produce any signs of toxicity
or death in the rats during 14 days of observation.
Therefore, an LD50 could not be estimated, and it
is possibly higher than 5000 mg/kg. LD50 is a statistically derived single dose of a substance that canbe expected to cause death in 50 percent of animals
when administered by the oral route.13) No significant differences were found between the initial andfinal body weights of the control and treated rats. A
similar absence of toxic effects was observed in thecase of food and water consumption (Fig. 1).
Subacute Toxicity
No toxicity signs, such as piloerection, alterations in locomotor activity or diarrhea, or deaths,
were recorded during the 14 consecutive days ofyeast hydrolysate with below 10 kDa molecularweight treatment via the oral route at doses of1000 mg/kg. The body weight gain of the rats

treated with yeast hydrolysate with below 10 kDa
molecular weight was significantly lower comparedto that of the control (p < 0.05); yeast hydrolysate
with below 10 kDa molecular weight induced a decrease in body weight gain in relation to the control
group (p < 0.05). There were no significant differences in daily food and water intake between thecontrol and treated rats (Fig. 1).
Hematological and Biochemical Parameters
The hematological profiles of the treated andcontrol groups are presented in Table 1. No statistically significant differences were recorded in anyof the hematological parameters analyzed. Table 2
shows the biochemical profiles of the treated andcontrol groups. The BUN test is a measurement of
the amount of nitrogen in the blood in the form ofurea, and BUN values are affected by dietary protein.15) The BUN values of the control rats wereslightly lower than the normal range of BUN values
for SD rats, and the BUN values of the rats treatedwith yeast hydrolysate with below 10 kDa molecular weight, which is a rich source of protein and536Vol. 57 (2011)

Table 2. Blood Biochemical Parameter of SD Rats Treated Orally with Yeast Hydrolysate with below 10 kDa
Molecular Weight for Subacute Toxicity
Blood biochemicalparameter
Glucose (mg/dl)
BUN (mg/dl)
Creatinine (mg/dl)
Total protein (g/dl)
Albumin (g/dl)
Total bilirubin (mg/dl)
AST (U/l)
ALT (U/l)
Blood biochemicalparameter
Glucose (mg/dl)
BUN (mg/dl)
Creatinine (mg/dl)
Total protein (g/dl)
Albumin (g/dl)
Total bilirubin (mg/dl)
AST (U/l)
ALT (U/l)

FemaleGroup for subacute toxicitya)
Satellite group for subacute toxicityb)
Control
Yeast hydrolysate
Control
Yeast hydrolysate
89.67 ± 8.02
94.67 ± 13.65
114.00 ± 9.70
116.33 ± 10.23
8.57 ± 0.50
10.37 ± 0.32∗∗
13.40 ± 1.40
13.45 ± 1.22
0.30 ± 0.01
0.30 ± 0.01
0.27 ± 0.05
0.28 ± 0.05
5.27 ± 0.06
6.00 ± 0.10
5.81 ± 0.13
5.84 ± 0.14
3.53 ± 0.12
3.80 ± 0.01
3.79 ± 0.15
3.80 ± 0.13
0.47 ± 0.06
0.53 ± 0.15
0.58 ± 0.08
0.58 ± 0.09
85.33 ± 5.08
89.33 ± 6.21
90.00 ± 6.97
92.92 ± 7.80
27.67 ± 4.16
29.33 ± 2.53
29.33 ± 4.18
30.92 ± 4.23
MaleGroup for subacute toxicitya)
Control
Yeast hydrolysate
102.00 ± 8.89
102.33 ± 4.93
7.03 ± 0.32
11.80 ± 0.26∗∗
0.30 ± 0.01
0.37 ± 0.06
5.40 ± 0.20
5.63 ± 0.15
3.50 ± 0.01
3.60 ± 0.17
0.47 ± 0.06
0.47 ± 0.05
95.00 ± 5.01
98.33 ± 13.02
37.33 ± 2.16
35.00 ± 2.61

Satellite group for subacute toxicityb)
Control
Yeast hydrolysate
118.67 ± 4.04
125.00 ± 6.24
13.00 ± 0.56
13.43 ± 0.31
0.30 ± 0.01
0.30 ± 0.01
5.60 ± 0.20
5.83 ± 0.06
3.53 ± 0.06
3.62 ± 0.10
0.47 ± 0.06
0.53 ± 0.06
96.33 ± 8.13
99.33 ± 6.79
41.67 ± 2.58
39.01 ± 2.00

Values are means ± S.D. for 5 rats/group. a) The group for subacute toxicity was given water vehicle or yeast hydrolysate
with below 10 kDa molecular weight at 1000 mg/kg daily for 14 days. b) The satellite group for subacute toxicity was given
water vehicle or yeast hydrolysate with below 10 kDa molecular weight at 1000 mg/kg daily for 14 days followed by no treatment
for 14 days. ∗∗ Significantly different from the control, p < 0.01. The differences between the control and treated groups were
evaluated by Student’s t-test.

amino acids, were increased to normal range.
Morphological Parameters
The representative microscopic findings in theliver and kidneys of the rats for the acute and subacute oral treatments of yeast hydrolysate with below 10 kDa molecular weight are shown in Figs. 2
and 3. The macroscopic analysis of the treated animals did not show significant changes in color andtexture when compared to the control group in boththe male and female rats. Also, the microscopicalfindings did not suggest histological alterations in
the liver and kidneys.

DISCUSSION
Generally, the reduction of internal organ
weight is a simple and sensitive index of toxicity after exposure to a toxic substance.16) In this study, therelative internal organ weights of the rats were notaltered by the yeast hydrolysate with below 10 kDa

molecular weight (Table 3). Furthermore, gross examination of the internal organs of all rats revealed
no detectable abnormalities. Yeast hydrolysate withbelow 10 kDa molecular weight did not induce any
damage to the internal organs as examined by blood
parameters. Thus, it can be concluded that yeast
hydrolysate with below 10 kDa molecular weight isvirtually nontoxic.
Substances fermented by S. cerevisiae are generally recognized as safe (GRAS). For example, theacute oral toxicity of wheat germ powder fermented
by S. cerevisiae was found to very low, in which theLD50 is 1868 mg/kg, the highest dose tested in miceand rats. Its subacute toxicity is also very low, as no
toxicity was observed at the highest dose tested inrats, 1868 mg/kg.17)
Kim et al.11) tried to assess the anti-obesity effect of yeast hydrolysate with below 10 kDa molecular weight and found that it reduced body weightin SD rats fed a high fat diet. To investigate the effects of yeast hydrolysate with below 10 kDa molecular weight on appetite regulation mechanisms in

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Table 3. Relative Organ Weights of SD Rats Treated Orally with Yeast Hydrolysate with below 10 kDa Molecular Weight for Subacute
Toxicity
Relative organ
weight (g/100 gof body weight)
FemaleLiver
KidneySpleen
Lung
Heart
Ovary
Male
Liver
KidneySpleenLung
Heart
TestisGroup for acute toxicitya)
Control
Yeast hydrolysate

Group for subacute toxicityb)
Control
Yeast hydrolysate

Satellite group for subacute toxicityc)
Control
Yeast hydrolysate

3.93 ± 0.35
0.98 ± 0.05
0.32 ± 0.01
0.51 ± 0.02
0.38 ± 0.01
0.08 ± 0.01

4.02 ± 0.24
0.99 ± 0.09
0.30 ± 0.01
0.49 ± 0.03
0.36 ± 0.03
0.09 ± 0.01

3.77 ± 0.16
0.89 ± 0.05
0.26 ± 0.03
0.48 ± 0.03
0.34 ± 0.01
0.06 ± 0.01

3.79 ±0.14
0.87 ± 0.04
0.26 ± 0.03
0.47 ± 0.02
0.34 ± 0.01
0.07 ± 0.01

3.72 ± 0.20
0.84 ± 0.11
0.23 ± 0.02
0.42 ± 0.04
0.30 ± 0.01
0.05 ± 0.01

3.73 ± 0.10
0.86 ± 0.06
0.25 ±0.05
0.43 ± 0.04
0.32 ± 0.02
0.04 ± 0.01

4.77 ± 0.38
1.06 ± 0.13
0.40 ± 0.08
0.44 ± 0.01
0.38 ± 0.01
0.76 ± 0.09

4.88 ± 0.44
1.05 ± 0.08
0.36 ± 0.09
0.45 ± 0.03
0.36 ± 0.03
0.74 ± 0.08

3.80 ± 0.13
0.87 ± 0.07
0.24 ± 0.01
0.41 ± 0.02
0.34 ± 0.01
0.71 ± 0.07

3.72 ± 0.26
0.89 ± 0.01
0.20 ± 0.05
0.40 ± 0.01
0.34 ± 0.01
0.72 ± 0.04

3.37 ± 0.10
0.82 ± 0.01
0.20 ± 0.01
0.36 ± 0.04
0.30 ± 0.01
0.68 ± 0.05

3.31 ± 0.29
0.86 ± 0.06
0.19 ± 0.04
0.38 ± 0.01
0.32 ± 0.02
0.69 ± 0.04

Values are means ± S.D. for 5 rats/group. a) The group for acute toxicity was given water vehicle or yeast hydrolysate at 5000 mg/kg once
followed by no treatment for 14 days. b) The group for subacute toxicity was given water vehicle or yeast hydrolysate at 1000 mg/kg daily for
14 days. c) The satellite group for subacute toxicity was given the water vehicle or yeast hydrolysate at 1000 mg/kg daily for 14 days followed by notreatment for 14 days. The differences between the control and treated groups were evaluated by Student’s t-test.

Fig. 2. Representative Microscopic Findings in the Liver of SD Rats Treated Orally with Yeast Hydrolysate with below 10 kDa Molecular Weight for Acute and Subacute Toxicity (Hematoxylin-eosin Stain, × 400)
(A) Water vehicle group for acute toxicity, (B) Yeast hydrolysate group for acute toxicity, (C) Water vehicle group for subacute toxicity, (D) Yeast
hydrolysate group for subacute toxicity, (E) Water vehicle (satellite) group for subacute toxicity and (F) Yeast hydrolysate (satellite) group for subacutetoxicity.

the central nervous system, Jung et al.10) measured
nitric oxide synthase (NOS) expression and vasoactive intestinal peptide (VIP) immunoreactivity inthe paraventricular nucleus (PVN) and ventromedial hypothalamic nucleus (VMH) of the hypothalamus using histochemical methods. They sug-

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Fig. 3. Representative Microscopic Findings in Kidneys of SD Rats Treated Orally with Yeast Hydrolysate with below 10 kDa Molecular Weight for Acute and Subacute Toxicity (Periodic Acid Schiff Stain, × 400)
(A) Water vehicle group for acute toxicity, (B) Yeast hydrolysate group for acute toxicity, (C) Water vehicle group for subacute toxicity, (D) Yeast
hydrolysate group for subacute toxicity, (E) Water vehicle (satellite) group for subacute toxicity and (F) Yeast hydrolysate (satellite) group for subacutetoxicity.

gested that administering yeast hydrolysate with below 10 kDa molecular weight to SD rats reduced
body weight gain by altering neuropeptide Y (NPY)and tryptophan hydroxylase (TPH) expression. Furthermore, Jung et al.18) examined the anti-obesity
effects of yeast hydrolysate with below 10 kDa
molecular weight on obese women. The results
also showed that this yeast hydrolysate with below
10 kDa molecular weight caused a higher reduction of body weight compared to placebo. Therefore, it is considered that due to the anti-obesity effect of yeast hydrolysate with relative low molecular weight, the body weight gains of the rats treatedwith yeast hydrosylate with below 10 kDa molecular weight were lower compared to those of the control (p < 0.05).
In the present study, no deaths or signs of toxicity were observed in the rats that received yeast hydrolysate with below 10 kDa molecular weight up
to an oral acute dose of 5000 mg/kg, thus establishing its safety for use. In conclusion, these results show that yeast hydrolysate with below 10 kDa
molecular weight possesses very low toxicity, as indicated in our rat model. However, a chronic toxicity study is needed to further support the safety-

in-use of this yeast hydrolysate with below 10 kDa
molecular weight
Acknowledgements This work (Grants No.
00041607-1) was supported by Business for International Cooperative R&D between Industry,
Academy, and Research Institute funded Korea
Small and Medium Business Administration in
2011.

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