Soybean Fiber Research Articles

Statistical optimization of thermo-tolerant xylanase activity from Amazon isolated Bacillus circulans on solid-state cultivation

A 2 2 factorial design was performed to find the best conditions of pH and temperature for xylanolytic activity of Bacillus circulans BL53 isolated from the Amazon environment. Solid-state cultivation was carried out on an inexpensive, abundant agro-industrial soybean residue. The central composite design (CCD) used for the analysis of treatment combinations showed that a second-order polynomial regression model was in good agreement with experimental results, with R 2 = 0.9369 ( P < 0.05). The maximum activity was obtained at a high temperature (80 °C) and over a large pH range (4.0–7.0). Enzymatic activity was maintained in heated extracts up to 50 °C, suggesting that the xylanases of B. circulans BL53 are thermo-tolerant biocatalysts, being of interest for industrial processes. The crude enzyme extract hydrolyzed rice straw, sugar cane bagasse and soybean fiber and its activity was stimulated by Co 2+, Fe 3+, and β-mercaptoethanol but inhibited by Mn 2+, Cu 2+, Ca 2+, Zn 2+, Ba 2+, Mg 2+ and by EDTA.

Soluble soybean fiber: a 3-month dietary toxicity study in rats

Soluble soybean fiber (SSF) is a food ingredient intended for human consumption. SSF was administered in the diet to Sprague–Dawley CD® rats at concentrations up to 40,000 ppm for three months. Unformed stool was detected during the early and middle part of the treatment period and was considered an exaggeration of a normal physiological response to the fibre content in the diets, to which the animals appeared to adapt. This finding has been reported with other water-soluble fibres and was not considered an adverse effect. Decreased weight gain and food intake during the first half of the treatment period are possible sequelae of increased intestinal throughput. Adaptation was indicated by subsequently improved weight gain and food consumption. Decreased serum cholesterol occurred in males receiving 30,000 or 40,000 ppm and this has been reported before in rats fed soluble fibre. Haemoconcentration (indicated by increased erythrocyte count, haematocrit and haemoglobin concentration) and decreased spleen weight are likely related to minor fluid imbalances during exposure to high concentrations of dietary fibre and occurred at all SSF concentrations. The spleen was microscopically normal. In conclusion, the no-observed-adverse-effect level (NOAEL) for SSF in this study was 40,000 ppm (equivalent to 2.43 g/kg bodyweight/day for males and 2.91 g/kg bodyweight for females).

Energy metabolism and protein balance in growing rats fed different levels of dietary fibre and protein

A study was performed to investigate the effect of different levels of dietary fibre (DF) and dietary protein on visceral organ size, digestibility, nitrogen balance and energy metabolism in rats. Thirty-six male Wistar rats, initial body weight about 76 g, were used in a factorial design consisting of three levels of DF (low, 100 g/kg DM; medium, 250 g/kg DM and high, 290 g/kg DM) and two levels of dietary protein (low, 120 g/kg DM and high, 223 g/kg DM). The added fibre source was soybean hulls and Danish fish meal was used as sole source of dietary protein. Measurements of gas-exchange were done on six rats (one group) while urine and faeces were collected individually. The ratio of food/empty body gain increased (P < 0.05) with increasing DF and decreasing levels of dietary protein. The weight of the digestive tract was larger (P < 0.05) in rats fed the high fibre diet than in those fed the low fibre diet. The digestibility of nutrients and energy decreased linearly with increasing level of soybean fibre (P < 0.05). An increased intake of DF was associated with a concomitant loss of protein and energy to faeces. The microbial degradation of NSP and other unabsorbed carbohydrates caused considerably changes in N metabolism of the colon. In rats fed the low protein diets increased levels of DF decreased N excretion in urine and increased N excretion in faeces, while the ratio of retained/digested protein remained constant. When rats were fed the high protein diet protein retention dropped in response to DF both absolute and relative to digested amount, indicating that energy intake could be a limiting factor. Heat production as a percentage of metabolizable energy (HP/ME) was higher (P < 0.05) in rats fed the low protein diet than in rats fed the high protein diet, but no significant difference was found among DF levels.

Ingestion of Water-Soluble Soybean Fiber Prevents Gastrectomy-Induced Iron Malabsorption, Anemia and Impairment of Voluntary Running Exercise Performance in Rats

We examined the effects of feeding water-soluble soybean fiber (WSSF), a highly fermentable dietary fiber, on gastrectomy-induced iron malabsorption, anemia and impairment of exercise performance in rats in two separate experiments. The study was designed as a 2 x 2 factorial arrangement with operation (total gastrectomy) and diet (WSSF) under sedentary (Experiment 1) and exercised (Experiment 2) conditions. In Experiment 1, gastrectomy reduced net iron absorption, hemoglobin concentration, hematocrit and hemoglobin regeneration efficiency (P < 0.01). However, in rats fed a WSSF diet (50 g/kg diet), iron absorption and the hematological variables of the gastrectomized rats were comparable to those in the sham-operated rats, demonstrating that ingestion of WSSF promotes iron absorption and prevents anemia after gastrectomy. Feeding WSSF increased pools of organic acids and soluble iron in cecal contents and decreased the pH of the cecal contents (P < 0.001). Of the many cecal variables measured, net iron absorption in gastrectomized rats was most closely correlated (r = 0.614, P < 0.01) with the short-chain fatty acid pool in the cecum. Cecal fermentation of WSSF may contribute to improvements in gastrectomy-induced nutritional defects. In Experiment 2, we examined voluntary running exercise performance in totally gastrectomized rats fed diets with or without WSSF. Total gastrectomy severely impaired running performance (P < 0.001), and WSSF feeding largely restored the lowered performance. We conclude that feeding WSSF improves anemia and impaired voluntary running performance in totally gastrectomized rats.

Ingestion of water-soluble soybean fiber prevents osteopenia and hypercholesterolemia induced by ovariectomy in rats.

This study examined the effects of feeding water-soluble soybean fiber (WSSF), a highly fermentable dietary fiber with low viscosity, on intestinal calcium (Ca) absorption, bone mineral content, and serum total cholesterol levels using female Sprague-Dawley rats (5 weeks old) with or without ovariectomy (OVX). The rats in each group were fed a WSSF (50 g/kg of diet) or WSSF-free diet for 4 weeks. Ca absorption was higher in OVX rats fed the WSSF diet than in OVX rats fed the WSSF-free diet. Femoral Ca content in both sham and OVX rats fed the WSSF diet was higher than that in rats fed the WSSF-free diet. The serum total cholesterol levels were elevated after OVX compared with that in the sham rats, and this elevation was prevented by the WSSF diet. In conclusion, ingestion of WSSF prevented osteopenia and hypercholesterolemia induced by ovariectomy in rats.

Ingestion of water-soluble soybean fiber improves gastrectomy-induced calcium malabsorption and osteopenia in rats

OBJECTIVE: Total gastrectomy produces calcium malabsorption and osteopenia. We examined the effects of feeding water-soluble soybean fiber (WSSF), a highly fermentable dietary fiber with low viscosity, on calcium absorption and bone characteristics in totally gastrectomized rats. METHODS: Male Sprague-Dawley rats were assigned to two groups: sham operation and gastrectomy. After the postoperative recovery period, rats of each group were fed diets with or without WSSF (50 g/kg diet) for 4 wk. RESULTS: Net calcium absorption and femoral dry weight and calcium content and maximum breaking force were lower in the gastrectomy groups than in the sham groups. In the gastrectomy groups, calcium absorption and these femoral parameters were higher in rats fed the WSSF diet than in rats fed the WSSF-free diet. Feeding WSSF increased the concentrations of short-chain fatty acids and soluble calcium and decreased the pH in cecal contents. Net calcium absorption in gastrectomized rats correlated positively with the concentration of total short-chain fatty acids (the sum of acetic, propionic, and butyric acids) in cecal contents ( r = 0.545, P < 0.05) and negatively with cecal pH ( r = −0.628, P < 0.05). CONCLUSIONS: These findings indicate that ingestion of WSSF partly prevents the diminished calcium absorption after total gastrectomy in rats, resulting in the improvement of postgastrectomy osteopenia. The increase of calcium absorption may be associated with cecal fermentation of WSSF.

Ｐｒｏｓｋｙ変法により調製した大豆食物繊維画分の人工消化性と加熱による影響

Prosky変法により処理した生および乾熱・電子レンジ加熱・蒸煮大豆のIDF, SDF区分の人工消化性を調べると共に,加熱が多糖に及ぼす影響について検討した.その結果IDF区分では,胃液,膵液でわずかに消化性が認められた.SDFでは生大豆区分で胃液,膵液および腸液に,電子レンジ加熱大豆から抽出した区分においては膵液,腸液で消化性が認められた.一方唾液から腸液までの連続消化ではIDF, SDF区分共に消化性が認められ,その割合は全体的にIDFよりSDFで大きかった.また消化性は蒸煮大豆から抽出した食物繊維区分で最も高く,次いで乾熱,電子レンジ加熱,生大豆区分の順であった.HPLCによる連続消化後の糖の分析結果からはIDF,SDF区分共にエリスリトールが最も高く次いでアラビノースとグルコースが検出された.SDF区分ではスクロース,スタキオース,フラクトース,ガラクトースが検出され大豆中のアラビノガラクタンやセルロース,ペントザンなどの低分子化が示唆された.

Physiological effects of water-soluble soybean fiber in rats.

Four-week-old rats were fed on diets containing either no dietary fiber (DF) or a DF source (WSSF, ISF or cellulose) for 4 weeks. The DF level was adjusted to 5%. The WSSF diet contained 3% and 2%, respectively, of WSSF and cellulose. No rat in any group experienced diarrhea, and none of the experimental diets suppressed the growth of rats, the apparent absorption of major nutrients being almost 100%. However, the rate of degradation of DF during the digestive process was significantly different (p < 0.05, cellulose, 23.6%; WSSF with cellulose, 64.5% (WSSF degradation only was 91.8%); and ISF, 77.6%). The plasma and liver lipid levels were within normal ranges, although the liver cholesterol level in those rats fed on WSSF and ISF was significantly lower (p < 0.05) than in those fed on cellulose. The cecal organic acid contents were in the order of WSSF > ISF > cellulose > DF-free. Furthermore, WSSF was effective in shortening the gastrointestinal transit time. The results indicate that WSSF seems to have favorable effects on the intestinal functions.

Effect of Dietary Fiber on Fecal Excretion of Polychlorinated Dibenzo-p-dioxins in Rats.

The effect of dietary fibers on the liver distribution and fecal excretion of polychlorinated dibenzo-p-dioxins (PCDDs) congeners in the causal rice-bran oil of Yusho was examined in male rats. The fibers used were rice-bran fiber, spinach fiber, burdock fiber, cabbage fiber, soybean fiber, Japanese-radish (root) fiber, carrot fiber, corn fiber, Japanese-radish (leaves) fiber, Chinese cabbage fiber, azuki bean fiber and barley fiber. The animals were administered 4 g of each diet containing 0.5 ml of the rice-bran oil and kept on the same fiber for another 5 d. The oil was contaminated with 1, 2, 3, 7, 8-P5CDD (6.86 ng/ml), 1, 2, 3, 6, 7, 8-H6CDD (31.4 ng/ml), 1, 2, 3, 7, 8, 9-H6CDD (22.4 ng/ml) and 1, 2, 3, 4, 6, 7, 8-H7CDD (121.7 ng/ml). The fecal excretion of 1, 2, 3, 7, 8-P5CDD in the group fed with rice-bran and spinach fibers were promoted 3.3 and 3.1 times, respectively, than that in the group fed with a non-fiber diet. The excretion of 1, 2, 3, 6, 7, 8-H6CDD, 1, 2, 3, 7, 8, 9-H6CDD and 1, 2, 3, 4, 6, 7, 8-H7CDD were 2.1, 1.9 and 1.6 times higher, respectively, in the groups fed with rice-bran and spinach fibers than that in the group fed with the non-fiber diet. The present results suggest that the dietary fibers are useful agents for the treatment of patients exposed to the lipophilic contaminants.

EFFECTS OF EMULSIFIER AND SOY FIBER ADDITION ON SENSORY PROPERTIES OF CORN MEAL EXTRUDATE

ABSTRACTYellow dent corn meal was extruded in a twin‐screw extruder with a monoacylglycerol (MAG) and soybean fiber. A ten member descriptive analysis panel was employed to study the effects of four extrusion treatment variables on the textural properties and microstructure of extruded corn meal products. The treatment variables studied included MAG and soybean fiber contents in the feed, extruder screw speed, and feed rate. The microstructure of extruded samples was also studied to support the sensory texture evaluations. MAG addition was found to be the most significant factor affecting texture. Low levels of MAG (0.375%) and soybean fiber additions (5%) resulted in improved overall texture quality. Higher screw speeds were associated with higher cohesiveness and adhesiveness, and feed rate had the least influence. Most of these effects could be attributed to the microstructural property changes under the treatments.

Intake of 25 g of Soybean Protein with or without Soybean Fiber Alters Plasma Lipids in Men with Elevated Cholesterol Concentrations

Twenty-one mildly hypercholesterolemic men consumed a diet that was low in fat (< 30% of energy) and cholesterol (300 mg/d) and were given muffins containing 25 g protein + 20 g dietary fiber daily from either isolated soybean protein + soybean cotyledon fiber, isolated soybean protein + cellulose, casein + soybean cotyledon fiber or casein + cellulose. All subjects progressed through the low fat, low cholesterol baseline period, lasting 2 wk, and then through all four dietary treatments, lasting 4 wk each, according to a Latin square design. Plasma concentrations of total, LDL, HDL and VLDL cholesterol, total and VLDL triacylglycerols, and apolipoprotein A-I and B were measured at the end of each period. When data from all subjects were analyzed, dietary treatments did not influence lipemia; however, in subjects with initial total cholesterol concentrations > 5.7 mmol/L, both isolated soybean protein treatments resulted in significantly lower total cholesterol compared with the two casein treatments (P < 0.05). In addition, a negative linear relationship was observed when a subject's total or LDL cholesterol change after each of the soybean treatments was regressed against the subject's baseline cholesterol concentration (P < 0.05). Apolipoprotein A-I varied dependent on baseline cholesterol with no apparent pattern, whereas apolipoprotein B levels were not affected. Results indicate that consumption of 25 g soybean protein/d is associated with lower total cholesterol concentrations in individuals with initial cholesterol concentrations > 5.7 mmol/L.

Ten Different Dietary Fibers Have Significantly Different Effects on Serum and Liver Lipids of Cholesterol-Fed Rats

The comparative effects of 10 different dietary fibers on serum and liver lipids were investigated by feeding male Sprague-Dawley rats diets containing 10 g cholesterol + 2 g cholic acid/kg diet, with 60 g fiber/kg diet. Diets were fed for 3 wk; cellulose was the control fiber. Rats fed psyllium (rich in soluble fiber) had the lowest serum and liver cholesterol concentrations. Rats fed other soluble fiber-rich fibers (oat gum, guar gum and pectin) also had significantly lower serum and liver cholesterol concentrations than rats fed cellulose. Although feeding diets containing both soluble and insoluble fibers (soybean fiber and oat bran) did not significantly alter serum cholesterol, liver cholesterol values were significantly lower than those of cellulose-fed rats. Rats fed rice bran, predominantly an insoluble fiber source, had significantly higher liver cholesterol and significantly lower body weight gains and serum triglyceride concentrations than cellulose-fed rats. Values for serum and liver cholesterol were similar for rats were fed insoluble-rich fibers (corn bran, cellulose and wheat bran). These observations indicate that feeding dietary fibers rich in soluble fiber produces lower serum and liver cholesterol concentrations than does feeding commonly available sources of water-insoluble fiber.

Corn Meal Extrusion with Emulsifier and Soybean Fiber

Twin-screw extrusion of corn meal with monoacylglycerol (MAG) and soy fiber was investigated. The treatment variables studied were MAG and soy fiber contents, screw speed, and feed rate. MAG addition reduced torque, specific mechanical energy, and dough temperature, but increased die pressure. The significant increase in die pressure was caused by an increased length in filled flights. Die pressure and dough mass temperature increased with soy fiber addition at lower MAG contents (<0.4 g/100 g). The trends were reversed at higher MAG contents (>0.4 g/100 g). Moreover, MAG-starch complexation increased with MAG addition but was impeded by soy fiber addition.

Effect of Soy Products on Methotrexate Toxicity in Rats

Several experiments were conducted to determine the effect of various soy products on methotrexate (MTX) toxicity. Products tested included soybean meal, soybean concentrate, soybean isolate and soybean fiber, which were provided as replacements for casein or cornstarch in a semipurified diet. Soybean meal and soybean concentrate offered the greatest protection, completely alleviating MTX-induced anorexia and diarrhea when included as the sole protein source and fed 14 d prior to and 7 d following intraperitoneal MTX injection at 20 mg/kg body weight. Positive responses also were observed with soybean isolate and soybean fiber. Histological examination of the small intestine of MTX-injected animals revealed that soybean concentrate and soybean isolate prevented the necrosis observed in animals fed the casein-based semipurified diet. Methotrexate levels in plasma were similar for animals fed semipurified diets in which protein was supplied by casein, soybean concentrate or soybean isolate. Thus, altered plasma MTX levels did not explain the differences among protein sources in ameliorating MTX-induced anorexia and gut toxicity. White blood cell counts were depressed by MTX in animals fed all diets.

Dietary Fiber Sources Lower Blood Cholesterol In C57BL/6 Mice

Five sources of dietary fiber were compared for their effect on blood and liver cholesterol. The effects of soybean fiber, rice bran (full fat), oat bran, barley bran and mixed bran on total blood cholesterol concentrations and liver cholesterol concentrations were measured in beef-fed C57BL/6 male mice. Each diet contained cooked beef, beef tallow, corn starch and 7% dietary fiber from one of the five fiber sources. A control group consumed a fiber-free diet. Dietary cholesterol was provided by the beef and beef tallow only. The experimental diets were fed for 3 wk; blood and liver were collected when the mice were 18 wk old. The liver cholesterol concentration in the rice bran-fed group was the lowest of the six diet groups and was significantly different than concentrations in the oat bran-fed group and the barley bran-fed group (P less than 0.05). The oat bran, mixed bran, and barley bran did not significantly lower blood cholesterol in the mice. Both the soybean fiber and rice bran diet groups had significantly lower total blood cholesterol than did the fiber-free controls (P less than 0.05). The soybean fiber group also had significantly lower blood cholesterol than the mixed-bran group.

Effects of Soybean Fiber on Cecal Digestion in Rats Previously Adapted to a Fiber-Free Diet

This study was conducted to study digestion in rats of a diet containing soybean fiber (chiefly hemicellulose). The animals were first fed a fiber-free high starch diet for 7 d before receiving a 30% soybean fiber diet. There was a progressive change in the cecal pool of volatile fatty acids (VFA), up to approximately 1000 mumol, due to the enlargement of the cecum in conjunction with the rise of the VFA concentration, and the decrease in the cecal pH to 6. In rats fed the soybean fiber diet, the cecal concentrations of acetate and propionate increased with propionate reaching a very high value (approximately 50 mmol/L) after 22 d of dietary treatment. Butyrate concentrations first increased, then declined to about 10 mmol/L. Absorption of VFA was enhanced fivefold between d 2 and d 21 and was then 10-fold higher than in rats fed the fiber-free diet. The transfer of blood urea to the cecum increased in parallel with the enlargement of the cecum and there was a large rise of ammonia absorption after 8 d. There was a rapid increase in the cecal pool of phosphorus, whereas the cecal pools of calcium and magnesium significantly increased only after 8 d. The cecal absorption of calcium and magnesium increased very early, even when the cecal pool of these cations was not enhanced. The soybean fiber diet also elicited a strong induction of ornithine decarboxylase (ODC) in cecal mucosa, which was attenuated after 21 d of dietary treatment. Thymidine kinase was smaller than for ODC.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of Diets Rich in Fermentable Carbohydrates on Plasma Lipoprotein Levels and on Lipoprotein Catabolism in Rats

This study was conducted to examine the effects of a combination of several dietary fibers (5% guar gum, 5% apple pectin, 15% wheat bran, 22% soybean fiber) and crude potato starch (23%) on plasma lipids and lipoproteins and on liver lipid concentration in rats fed a diet containing either 15% lard or 5% oil with or without dietary cholesterol/cholic acid. Male Wistar rats ate the test diets for 3 wk. The incorporation of fiber and crude potato starch into the diet resulted in a significant enlargement of the cecum; it also increased the concentration of volatile fatty acids and the pool of acetate, propionate and butyrate. Feeding this fermentable carbohydrate decreased plasma cholesterol and triglyceride levels in rats given a low fat diet and prevented the expected rise in plasma cholesterol and triglycerides in rats fed cholesterol/cholic acid or lard. Further studies of high density lipoprotein (HDL) composition, 3-hydroxy-3-methyl-glutaryl coenzyme A reductase (HMG-CoA reductase) activity and 125I-labeled human low density lipoprotein (LDL) turnover were done in the group fed the low fat diet without added cholesterol/cholic acid. The study of the HDL fraction in rats fed a diet rich in fermentable carbohydrates demonstrated a decrease in the HDL1 subpopulation and in the proportion of apolipoprotein E. Plasma clearance of intravenously injected 125I-labeled LDL was faster in rats fed this diet than in rats fed the fiber-free diet. In the liver, cholesterol and triglyceride levels were depressed whereas the activity of HMG-CoA reductase was increased.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of soybean fiber and phytate on serum zinc response

Changes in serum zinc levels after oral zinc administration was used as an index of zinc absorption. Ten adult males received a single dose of zinc gluconate on 5 separate occasions, either alone (control) or with 1 of 4 aifferent soybean treatments. The soybean treatments consisted of a high-fiber, high-phytate treatment (ground soybeans); a high-fiber, low-phytate treatment (dephytinized ground soybeans); a low-fiber, high-phytate treatment (tofu); and a low-fiber, low-phytate treatment (dephytinized tofu). The dephytinized soybean treatments yielded significantly higher postingestive serum zinc values than did the non-dephytinized treatments whereas no differences were observed between the high- and low-fiber treatments. These data suggested zinc absorption is more inhibited by soy phytate than by soy fiber.

Effect of Consuming Soybean Dietary Fiber on Fasting and Postprandial Glucose and Insulin Levels in Type II Diabetes

The effects of diet enriched soybean fiber on glucose and insulin curves were studied in non-insulin-dependent diabetic human subjects. Postprandial glucose levels following a meal tolerance test in which fiber was given in powder form were lower in all subjects irrespective of the form of fiber intake. Consumption of fiber-rich bread for 12 weeks significantly reduced glucose levels at 0, 30, and 60min following a meal tolerance test in subjects with fasting blood glucose levels of 130mg/dl and over. Each patient consumed, during a 12-week period, 40g of fiber either in bread or as a powder suspended in milk. Following the consumption of fiber for 12 weeks, a reduction of plasma insulin was observed, but without a statistical significance. Body weight and plasma lipid levels did not change throughout the study period.

In Vitro Binding of Potent Mutagenic Pyrolyzates to Intestinal Bacteria

The ability of 22 strains of intestinal bacteria to bind the mutagenic pyrolyzates--3-amino-1,4-dimethyl-5H-pyrido-[4,3-b]indole [(Trp-P-1) CAS: 62450-06-0], 3-amino-1-methyl-5H-pyrido [4,3-b]indole [(Trp-P-2) CAS: 62450-07-1], 2-amino-6-methyldipyrido[1,2-a:3',2'-d]imidazole [(Glu-P-1) CAS: 67730-11-4], 2-aminodipyrido[1,2-a:3',2'-d]imidazole [(Glu-P-2) CAS: 67730-10-3], 2-amino-3-methylimidazo[4,5-f]quinoline [(IQ) CAS: 76180-96-6], 2-amino-3,4-dimethylimidazo[4,5-f]quinoline [(MeIQ) CAS: 77094-11-2], and 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline [(MeIQx) CAS: 77500-04-0]--was investigated and compared to their ability to bind to some dietary fibers (corn bran, apple pulp, soy bean fiber, cellulose, chitin, and chitosan). The pyrolyzates are potent mutagenic and carcinogenic heterocyclic amines formed during cooking. Solution of these amines was mixed with aqueous suspension of bacterial cells or dietary fibers, and removal of these amines from the reaction mixture by centrifugation was defined as the binding. Trp-P-1 and Trp-P-2 were effectively bound to all gram-positive and some gram-negative bacterial cells, corn bran, apple pulp, and soy bean fiber. Binding of Trp-P-1 and Trp-P-2 to Escherichia coli, Klebsiella pneumoniae, and cellulose was moderate, and to chitin and chitosan it was little. None but corn bran bound Glu-P-1 and Glu-P-2 effectively. Corn bran effectively bound all mutagens tested. The quantity of the binding of IQ, MeIQ, and MeIQx was dependent on the strain of bacteria and the kind of fiber. The mechanism of binding of Trp-P-2 to freeze-dried feces, Lactobacillus casei YIT 9018 (LC9018), and corn bran was investigated. The binding was pH dependent, occurred instantaneously, and was inhibited by the addition of metal salts. These results indicate that the binding was mostly due to a cation-exchange mechanism, but some irreversible binding of Trp-P-2 was observed, most notably to freeze-dried feces. The mutagenicity of Trp-P-2 for Salmonella typhimurium TA98 in the presence of S9 mix was inhibited by the addition of LC9018 or corn bran to the reaction mixture. The results indicate that bound Trp-P-2 did not cause mutation under the assay conditions.