GELLAN GUM
First draft prepared by Dr F.S.D. Lin,
Division of Toxicological Review and Evaluation,
Center for Food Safety and Applied Nutrition,
US Food and Drug Administration.
1. EXPLANATION
Gellan gum has not been previously evaluated by the Joint
FAO/WHO Expert Committee on Food Additives.
Gellan gum is a high molecular weight polysaccharide gum
produced as a fermentation product by a pure culture of Pseudomonas
elodea. The production organism is an aerobic, gram-negative
bacterium, which has been very well characterized and demonstrated
to be non-pathogenic. Chemical structure of the polysaccharide has
been determined. It has a tetrasaccharide repeat unit consisting of
two glucose (Glc) residues, one glucuronic acid (GlcA) residue, and
one rhamnose (Rha) residue:
-> 3)-ßD-G1c-(1->4)-ß-D-G1cA-(1->4)-ß-D-G1c-(1->4)-L-Rha-(1->
The glucuronic acid is neutralized by the presence of
potassium, calcium, and magnesium ions. The relative concentrations
of these ions will control the physical properties of the gum
material such as gel strength, melting point and setting point. The
molecular weight of the polysaccaride is greater than 70 000 with
95% above 500 000. The gum has been proposed for use as a
stabilizer and thickener in foods.
There are three basic forms of gellan gum product which have
been characterized and are distinguished by their 1) polysaccharide
content, 2) the percent of o-acetyl substitution on the
polysaccharide and 3) the protein content (including nucleic
residues and other organic nitrogen sources).
It is noted that a relatively pure (>95% polysaccharide) non-
acetylated gum product was used in the acute toxicity studies, the
13-week oral rat study and the genotoxicity studies. For the
remaining toxicological studies, a blend of 5 products with lower
purities and varied degrees of acetylation was used. This blend,
which contained 58.5% polysaccharide, was intended to represent the
complete range of possible compositions of the gum product and was
considered as the "worst case" in terms of purity.
2. BIOLOGICAL DATA
2.1 Biochemical aspects
2.1.1 Absorption, distribution and excretion
The absorption, distribution and excretion of gellan gum was
studied using a dually radiolabelled (3H and 14C) preparation.
The use of dual labelling allowed simultaneous quantitation of both
polysaccharide and "protein" fractions of gellan gum.
The gellan gum was prepared in separate fermentations using
3H-glucose and 14C-glucose as carbon source. The 3H product was
subjected to multi-stage purification process to give a relatively
pure 3H-polysaccharide. This was added to the media of the 14C
fermentation, which was then precipitated in isopropanol to yield a
product with the polysaccharide fraction labelled with both isotopes
and the non-polysaccharide (or "protein") fraction labelled only
with 14CO2.
One male and one female Sprague-Dawley rat were gavaged with
single doses of the 3H/14C-gellan gum (ca. 960 mg/kg; ca. 4 µCi).
Expired air was collected for 24 hours after dosing. Less than
0.55% of the given radioactivity was detected as 14C.
Four male and 3 female Sprague-Dawley rats were dosed with
single gavage dose of 3H/14C-gellan gum (ca. 870 mg/kg; 2.9 - 4.1
µCi 14C; 0.7 - 0.9 µCi 3H). Urine and faeces were collected for 7
days, at which time the animals were sacrificed and their tissues
analyzed for residual radioactivity. Females excreted 86.8% and
1.9% of the given 14C in their faeces and urine, respectively.
Males excreted 86% of the dosed 14C in the faeces and 3.3% in the
urine. Females excreted 4.1% of the dosed 3H in their urine and
100.1% in their faeces, while males excreted 3.6% of the total 3H
in their urine and 99.6% in their faeces. In all animals, the
activities of 3H in tissues (blood, brain, liver, kidney, lung,
muscle, skin, heart and carcass) were too low to be quantitated
accurately. Tissue and carcass radioactivity for 14C averaged 3.8%
of dose for male rats and 3.0% of dose for female rats.
A male and four female Sprague-Dawley rats were gavaged with
about 1 g/kg of radiolabelled gellan gum and blood samples collected
from the tail vein at different time intervals over a 7-day period.
Data were reported as 14C dmp/ml blood (3H dmp/ml blood was not
reported). The peak level of radioactivity, which amounted to about
0.4% of the administered radioactivity, occurred about 5 hours after
dosing (Selim, 1984a).
2.2 Toxicological studies
2.2.1 Acute toxicity
LD50
Species Sex Route (mg/kg b.w.) Reference
Rat M&F oral >5000 Wolfe & Bristol,
1980
M&F inhalation >5.09 mg/l Coate et al.,
1980
Gellam gum is practically non-toxic to rats when administered
as a single large dose (5 g/kg b.w.) in diet or via gavage.
2.2.2 Short-term studies
2.2.2.1 Rat
Male and female Sprague-Dawley rats (20/sex/group) were fed
dietary levels of GG ranging from 0-6% for 13 weeks. Although the
animals on this study experienced symptoms of a sialodacryoadenitis
viral infection, all animals survived treatment and there were no
adverse effects associated with the feeding of GG (Batham et al.,
1983).
2.2.2.2 Monkey
Prepubertal rhesus monkeys (2/sex/group) were dosed by oral
gavage with GG at levels of 0, 1, 2 or 3 g/kg/day for 28 days.
There were no overt signs of toxicity reported (Selim, 1984b).
2.2.3 Long-term/carcinogenicity studies
2.2.3.1 Mouse
Groups of 50 male and 50 female Swiss Crl mice were fed GG
admixed in the diet at 0, 1,0, 2.0 and 3.0% for 96 and 98 weeks for
males and females, respectively. All animals were examined twice
daily for mortality and morbidity. Physical examination for the
presence of palpable masses was initiated on a weekly basis starting
in week 26. Bodyweights and food consumption were measured for 7-
day periods on a weekly basis for the first 26 weeks of treatment
and every 2 weeks thereafter. At necropsy, a complete gross
pathological examination was performed on the following organs and
tissues of the animals from the control and 3.0% groups: adrenals,
aorta (thoracic), bone (sternum), brain (fore-, mid- and hind-),
caecum, colon, duodenum, epididymis, oesophagus, eyes, Harderian
gland, heart, ileum, jejunum, kidneys, lacrimal gland, liver (sample
of 2 lobes), lung (sample of 2 lobes), lymph nodes (mandibular and
mesenteric), mammary gland (inguinal), nasal turbinates, optic
nerves, ovaries, pancreas, pituitary, prostate, rectum, salivary
gland, sciatic nerve, seminal vesicles, skeletal muscle, skin,
spinal cord, spleen, stomach, testes, thymus, thyroid lobes (and
parathyroids,), tongue, trachea, urinary bladder, uterus, vagina,
Zymbal's gland and all gross lesions. Only the liver, kidneys,
ovaries, testes, adrenals, pituitary, lungs and heart were examined
for animals of the 1.0 and 2.0% groups. There were no effects
attributable to the feeding of GG on either body weight gain or food
consumption. There were no neoplastic or non-neoplastic changes
which were associated with the feeding of GG (Batham et al.,
1987).
2.2.3.2 Rat
Groups of 50 F1 generation Sprague-Dawley rats of each sex
were exposed to GG in utero and continued on GG diets for
approximately 104 weeks. The dietary levels of GG were 0, 2.5, 3.8
and 5.0%. The rats were observed daily for the first 4 weeks of
treatment and weekly thereafter for clinical signs of toxicity.
Individual bodyweights and food consumption were measured on a
weekly basis for the first 26 weeks of treatment and every two weeks
thereafter. Funduscopic and biomicroscopic examinations were
conducted on the control and 5% groups during weeks 1, 13, 26, 52,
78 and 103. Clinical chemistry and haematological samples were
collected at weeks 13, 25, 39 and 51. After 104 weeks,
ophthalmoscopic examinations, haematology, clinical chemistries and
organ weight data revealed no changes which could be attributed to
the feeding of GG. Survival of male treated rats was poor when
compared to controls whereas female treated rats exhibited better
survival than their concurrent controls. Male rats, fed GG at the
3.8 and 5.0% dietary levels, exhibited lower bodyweights after 76
weeks. The initial bodyweights were 5.2 and 3.4% lower than the
control values for the 3.8% and 5.0% dietary levels, respectively.
The authors concluded that in spite of the initial bodyweight
deficit, the growth pattern for these treated groups was identical
to that of the control. In addition, this effect was not seen in
either the females or any other species tested. There is no basis
to suggest that the lower bodyweights, observed in the male rats,
are indicative of toxicity.
Organs and tissues as those listed in the above mouse study
were examined for histopathological changes at study termination.
There were no neoplastic or non-neoplastic changes that could be
associated with the feeding of GG. The authors concluded that under
the conditions of this bioassay, GG was non-carcinogenic to Sprague-
Dawley rats (Batham et al., 1985).
2.2.3.3 Dog
Diets containing 0, 3, 4.5 and 6% GG were fed to groups of 5
beagle dogs per sex for a period of 52 weeks. The dogs were
observed daily for clinical signs of toxicity and were measured for
bodyweights and food consumption. Ophthalmoscopic examinations were
performed during pretreatment and after 12 , 24, 39 and 51 weeks.
Haematology and clinical chemistry were measured during pretreatment
and after 6, 13, 25, 39 and 50 weeks. After 52 weeks all animals
were killed and grossly examined. The following organs and tissues
were removed, processed and examined for histopathological lesions:
adrenals, aorta, bone and marrow, brain, caecum, colon, duodenum,
epididymis, oesophagus, eyes, gall bladder, heart, ileum, jejunum,
kidneys, liver, lungs, lymph nodes, mammary gland, optic nerves,
ovaries and ovariducts, pancreas, pituitary, prostate, rectum,
salivary gland, sciatic nerve, skeletal muscle, skin, spinal cord,
spleen, stomach, testes, thymus, thyroid and parathyroid, tongue,
trachea, urinary bladder and uterus.
All animals survived treatment. Food intake was higher in the
treated groups compared to the controls. There were no adverse
effects associated with the feeding of GG to beagle dogs for a
period of one year (Batham et al., 1986).
2.2.4 Reproduction studies
Groups of 26 male and 26 female CD (Sprague-Dawley) rats were
administered GG in their diets at doses of 0, 2.5, 3.8 or 5.0%.
Males were treated for 70 days prior to mating and for three weeks
after mating. Females were treated for 14 days prior to mating and
throughout mating, gestation and lactation. Selection was made for
the pups (F1) of this mating and they were allowed to mature and
were mated to form the F2 generation.
There was no treatment-related effect on mating or fertility
index, conception rate, length of gestation, length of parturition,
number of live pups, number of dead pups, post-implantation loss
index, survival index on day 4, 7, 14 or 21 or lactation index for
any of the generations (Robinson et al., 1985a).
2.2.5 Teratology studies
GG was fed to groups of 25 pregnant female Sprague-Dawley rats
at dietary levels of 0, 2.5, 3,8 or 5.0% during days 6-15 of
gestation. GG had no fetotoxic or teratogenic effects on rats when
ingested in the diet at levels up to 5.0% ( Robinson et al.,
1985b).
2.2.6 Genotoxicity studies
Results of genotoxicity assays on gellan gum
Test system Test object Concentration of Results Reference
gellan gum
Ames test (1) S. typhimurium 10, 30, 100, 300 and Negative Robertson et al.,
TA98, TA100 1000 œg/plate 1985a
TA1535 TA1537
TA1538
DNA repair test Rat hepatocyte 3, 5, 10 & 20 mg/ml Negative Robertson et al.,
1985a,b
V-79/HGPRT Chinese hamster 3, 5, 10 & 20 mg/ml Negative Robertson et al.,
lung fibroblasts 1985c
(1) Both with and without rat liver S-9 fraction.
2.3 Observations in humans
Five female volunteers and five male volunteers, all normal in
health and free from gastrointestinal disease, participated in the
clinical study. Following a 7-day control period, each of the
volunteers consumed the test substance at a daily dose level of 175
mg/kg for 7 days, then the dose was increased to 200 mg/kg/day for a
further 16 days. Plasma biochemistry parameters, haematological
indices, urinalysis parameters, blood glucose and plasma insulin
concentrations and breath hydrogen concentrations were monitored on
the first day of the control period and repeated on the last day of
the treatment period.
The authors concluded that the ingestion of gellan gum at the
given dose levels caused no adverse dietary nor physiological
effects in any of the volunteers on the study. There were no
allergenic nor other subjective untoward manifestations, reported by
or observed in any of the human subjects. The ingestion of gellan
gum, at the stated daily intake levels, did not cause any adverse
toxicological effects. However, gellan gum does act as a faecal
bulking agent, increases faecal bile acid, decreases faecal neutral
sterols, and decreases serum cholesterol (Eastwood et al., 1987).
3. COMMENTS
Gellan gum was shown to be poorly absorbed and did not cause
any deaths in rats which received a single large dose (5 g per kg of
body weight) in the diet or by gavage. Short-term (90-day) exposure
of rats to gellan gum at levels up to 60 g/kg in the diet did not
cause any adverse effects. In a 28-day study in prepubertal
monkeys, no overt signs of toxicity were observed at the highest
dose level of 3 g per kg of body weight per day. In reproduction
and teratogenicity studies in rats in which gellan gum was given at
dose levels up to 50 g/kg in the diet, there was no evidence of
interference with the reproductive process, and no embryotoxic or
developmental effects were observed. Gellan gum was also shown to
be non-genotoxic in a battery of standard short-term tests.
In a study in dogs, which were treated for 1 year at dose
levels up to 60 g/kg in the diet, there were no adverse effects that
could be attributed to chronic exposure to gellan gum. In long-term
carcinogenicity studies, gellan gum did not induce any adverse
effects in mice or rats at the highest dose levels of 30 g/kg and 50
g/kg in the diet, respectively.
Results from a limited study on tolerance to gellan gum in
humans indicated that oral doses of up to 200 mg per kg of body
weight administered over a 23-day period did not elicit any adverse
reactions, although faecal bulking effects were observed in most
subjects.
4. EVALUATION
The Committee allocated an ADI "not specified" to gellan gum,
and pointed out that its potential laxative effect at high intakes
should be taken into account when it is used as a food additive
(Annex I, ref. 88, Section 2.2.3).
5. REFERENCES
BATHAM, P., RAINEY, S., BIER, C., LOSOS, G., OSBORNE, B.E. &
PROCTER, B. (1983). A 13-week toxicity study of a polysaccharide
gum (K9A50) during dietary administration to the albino rat.
Unpublished project No. 81274 from Bio-Research Laboratories Ltd.,
Montreal, Canada. Submitted to WHO by Kelco (Division of Merck &
Co., Inc.), San Diego, CA, USA.
BATHAM, P., PINSONNEAULT, R.T. & PROCTER, B.G. (1985). An in
utero/chronic toxicity/carcinogenicity study of gellan gum
administered in the diet to the rat (in utero phase). Unpublished
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Canada. Submitted to WHO by Kelco (Division of Merck & Co., Inc.),
San Diego, CA, USA.
BATHAM, P., KALICHMAN, S.G. & OSBORNE, B.E. (1986). A 52-week oral
toxicity study of gellan gum in the beagle dog. Unpublished project
No. 81779 from Bio-Research Laboratories Ltd., Montreal, Canada.
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Diego, CA, USA.
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Co., Inc.), San Diego, CA, USA.
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SELIM, S., FULLER, G.B. & BURNETT, B. (1984b). A 28-day subchronic
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