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 project No. 81835 from Bio-Research Laboratories Ltd., Montreal, 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. Submitted to WHO by Kelco (Division of Merck & Co., Inc.), San Diego, CA, USA. BATHAM, P., ENGEL, D., OSBORNE, B.E. (1987). A dietary carcinogenicity study of gellan gum in the albino mouse. Unpublished project NO. 81833 from Bio-Research Laboratories Ltd., Montreal, Canada. Submitted to WHO by Kelco (Division of Merck & Co., Inc.), San Diego, CA, USA. COATE, W.B., KEENAN, D.L., VOELKER, R. & HARDY, R.J. (1980). Acute inhalation toxicity study in rats. Unpublished project No. 2123-105 from Hazelton Laboratories America, Inc., Vienna, VA, USA. Submitted to WHO by Kelco (Division of Merck & Co., Inc.), San Diego, CA, USA. EASTWOOD, M.A., BRYDON, W.G., & ANDERSON, D.M.W. (1987). The dietary effects of gellan gum in humans. Unpublished report from Wolfson Gastrointestinal Laboratory, Edinburgh, U.K. Submitted to WHO by Kelco (Division of Merck and Co., Inc.), San Diego, CA, USA. ROBERTSON, R.T., NICHOLS, W.W., BOKELMAN, D.L. & BRADLEY, M.O. (1985a). Microbial mutagenicity test. Unpublished report No. 83- 870 from Merck Sharp & Dohme Research Laboratories, West Point, PA, USA. Submitted to WHO by Kelco (Division of Merck & Co., Inc. ), San Diego, CA, USA. ROBERTSON, R.T., NICHOLS, W.W. & BOKELMAN, D.L. (1985b). Unscheduled DNA synthesis in rat hepatocytes: Auto-radiographic assay. Unpublished report No. 84-8403 from Merck Sharp & Dohme Research Laboratories, West Point, PA, USA. Submitted to WHO by Kelco (Division of Merck & Co., Inc.), San Diego, CA, USA. ROBERTSON, R.T., NICHOLS, W.W. & BOKELMAN, D.L. (1985c). Gellan Gum: V-79 mammalian cell mutagenesis. Unpublished report Nos. 84- 8531 and 83-8530 from Merck Sharp & Dohme Research Laboratories, West Point, PA, USA. Submitted to WHO by Kelco (Division of Merck & Co., Inc.), San Diego, CA, USA. ROBINSON, K., THIBAULT, C. & PROCTER, B.G. (1985a). A two generation reproduction study of gellan gum administered in the diet to the rat. Unpublished project No. 81834 from Bio-Research Laboratories LTD, Montreal, Canada. Submitted to WHO by Kelco (Division of Merck & Co., Inc.), San Diego, CA, USA. ROBINSON, K., THIBAULT, C. & PROCTER, B.G. (1985b). A teratology study of gellan gum administered in the diet to the rat. Unpublished project No. 81890 from Bio-Research Laboratories LTD, Montreal, Canada. Submitted to WHO by Kelco (Division of Merck & Co., Inc.), San Diego, CA, USA. SELIM, S. (1984a). Rat balance study, tissue distribution and blood level of 14C and 3H labelled gellan gum. Unpublished study No. KE-162r from Primate Research Institute, Holloman Air Force Base, New Mexico, USA. Submitted to WHO by Kelco (Division of Merck & Co., Inc.), San Diego, CA, USA. SELIM, S., FULLER, G.B. & BURNETT, B. (1984b). A 28-day subchronic toxicity study in rhesus monkeys. Unpublished project No. KE-170m from Primate Research Institute. Holloman Air Force Base, New Mexico, USA. Submitted to WHO by Kelco (Division of Merck & Co., Inc.), San Diego, CA, USA. WOLFE, G.W., & BRISTOL, B.A. (1980). Acute oral toxicity study in rats. Unpublished project NO. 2123-103 from Hazelton Laboratories America, Inc. Vienna, VA, USA. Submitted to WHO by Kelco (Division of Merck & Co., Inc.), San Diego, CA, USA.
See Also: Toxicological Abbreviations GELLAN GUM (JECFA Evaluation)