Formation mechanism of cross‐linking Maillard compounds in peptide–xylose systems

The formation mechanism of Maillard peptides was explored in Maillard reaction through diglycine/glutathione(GSH)/(Cys‐Glu‐Lys‐His‐Ile‐Met)–xlyose systems by heating at 120 °C for 30–120 min. Maximum fluorescence intensity of Maillard reaction products (MRPs) with an emission wavelength of 420~430 nm in all systems was observed, and the intensity values were proportional to the heating time. Taken diglycine/GSH–[¹³C₅]xylose systems as a control, it was proposed that the compounds with high m/z values of 379 and 616 have the high molecular weight (HMW) products formed by cross‐linking of peptides and sugar. In (Cys‐Glu‐Lys‐His‐Ile‐Met)–xylose system, the m/z value of HMW MRPs was not observed, which might be due to the weak signals of these products. According to the results of gel permeation chromatography, HMW MRPs were formed by Maillard reaction, especially in (Cys‐Glu‐Lys‐His‐Ile‐Met)–xylose system, the percentage of Maillard peptides reached 52.90%. It was concluded that Maillard peptides can be prepared through the cross‐linking of sugar and small peptides with a certain MW range. Copyright © 2012 European Peptide Society and John Wiley & Sons, Ltd.     

Effect of Maillard reaction products on the growth of selected food-poisoning micro-organisms

The activity of the Maillard reaction products (MRP) prepared by heating (15 h at 90°C) a solution of 1·71 mol/l glucose and 2·05 mol/l glycine at pH values 6·0 and 8·8, against food-poisoning micro-organisms, including Staphylococcus aureus, Listeria monocytogenes, Salmonella typhimurium, Salmonella enteritidis and Aeromonas hydrophila , was investigated. High and low pH MRPs strongly inhibited A. hydrophila , whereas Staph. aureus and L. monocytogenes were slightly inhibited by the high pH MRPs only and Salmonella strains were resistant to both.     

Biosynthesis of Threonine from Homoserine by Mixed Rumen Microorganisms: An In Vitro Study

The biosynthesis of threonine (Thr) by using the main biosynthetic pathway involving homoserine (Hser) was quantitatively investigated by mixed rumen bacteria (B), protozoa (P), and their mixture (BP) in an in vitro system. Rumen contents were collected from fistulated goats to prepare the microbial suspensions and were incubated anaerobically at 39°C for 12 h with or without Hser (2 mm) as a substrate. Thr and other related compounds produced in both the supernatants and hydrolysates of the incubation were analyzed by HPLC. During a 12-h incubation period, 84.2%, 58.1%, and 92.0% of Hser disappeared in B, P, and BP suspensions, respectively. Rumen bacteria and the mixture of rumen bacteria and protozoa were demonstrated for the first time to produce Thr from Hser, and the production of Thr from Hser in BP (371.9 and 297.2 μmol/g MN) (MN, microbial nitrogen) was about 13.0% and 9.1% higher than that in B alone (329.2 and 272.5 μmol/g MN) during 6- and 12-h incubations, respectively. On the other hand, mixed rumen protozoa were unable to synthesize Thr from Hser. Other metabolites produced from Hser were found to be glycine (Gly) and 2-aminobutyric acid (2AB) in B and BP. In P, Gly and 2AB were not found. The results mentioned above indicated the abilities of rumen bacteria and the mixture of rumen bacteria and protozoa to synthesize Thr de novo from Hser and appeared as first-time report. Received: 24 May 2000/Accepted: 4 August 2000     

Microorganisms and Maillard reaction products: a review of the literature and recent findings

Research on the impact of Maillard reaction products (MRPs) on microorganisms has been reported in the literature for the last 60 years. In the current study, the impact of an MRP-rich medium on the growth of three strains of Escherichia coli was measured by comparing two classic methods for studying the growth of bacteria (plate counting and optical density at 600 nm) and by tracing MRP utilisation. Early stage and advanced MRPs in the culture media were assessed by quantifying furosine and N ^ε -carboxymethyllysine (CML) levels, respectively, using chromatographic methods. These measures were performed prior to and during bacterial growth to estimate the potential use of these MRPs by Escherichia coli CIP 54.8. Glucose and lysine, the two MRP precursors used in the MRP-rich medium, were also quantified by chromatographic means. Compared to control media, increased lag phases and decreased growth rates were observed in the MRP-rich medium for two out of the three Escherichia coli strains tested. In contrast, one strain isolated from the faeces of a piglet fed on a MRP-rich diet was not influenced by the presence of MRPs in the medium. Overall, CML as well as the products obtained by the thermal degradation of glucose and lysine, regardless of the Maillard reaction, did not affect the growth of the three strains tested. In addition, no degradation of fructoselysine or CML was found in the presence of Escherichia coli CIP 54.8.     

Characterisation of manganese peroxidase and laccase producing bacteria capable for degradation of sucrose glutamic acid-Maillard reaction products at different nutritional and environmental conditions

Maillard reactions products (MRPs) are a major colorant of distillery effluent. It is major source of environmental pollution due to its complex structure and recalcitrant nature. This study has revealed that sucrose glutamic acid-Maillard reaction products (SGA-MRPs) showed many absorption peaks between 200 and 450 nm. The absorption maximum peak was noted at 250 nm in spectrophotometric detection. This indicated the formation of variable molecular weight Maillard products during the SGA-MRPs formation at high temperature. The identified aerobic bacterial consortium consisting Klebsiella pneumoniae (KU726953), Salmonella enterica (KU726954), Enterobacter aerogenes (KU726955), Enterobacter cloaceae (KU726957) showed optimum production of MnP and laccase at 120 and 144 h of growth, respectively. The potential bacterial consortium showed decolourisation of Maillard product up to 70% in presence of glucose (1%), peptone (0.1%) at optimum pH (8.1), temperature (37 °C) and shaking speed (180 rpm) within 192 h of incubation. The reduction of colour of Maillard product correlated with shifting of absorption peaks in UV–Vis spectrophotometry analysis. Further, the changing of functional group in FT-IR data showed appearance of new peaks and GC–MS analysis of degraded sample revealed the depolymerisation of complex MRPs. The toxicity evaluation using seed of Phaseolus mungo L. showed reduction of toxicity of MRPs after bacterial treatment. Hence, this study concluded that developed bacterial consortium have capability for decolourisation of MRPs due to high content of MnP and laccase.     

Important role of Maillard reaction in the protective effect of heat-processed ginsenoside Re-serine mixture against cisplatin-induced nephrotoxicity in LLC-PK1 cells

The aim of the present study was to verify the important role of Maillard reaction in the protective effect of heat-processed ginsenoside Re-serine mixture against oxidative stress-induced nephrotoxicity. The free radical-scavenging activity of ginsenoside Re-serine mixture was increased by heat-processing. Ginsenoside Re was transformed into less-polar ginsenosides such as Rg(2), Rg(6) and F(4) by heat-processing, and the glucose molecule at carbon-20 was separated. The improved-free radical-scavenging activity by heat-processing was mediated by the generation of antioxidant Maillard reaction products (MRPs) from the reaction of glucose with serine. Moreover, MRPs from ginsenoside Re-serine mixture showed protective effect against cisplatin-induced renal epithelial cell damage.     

Antioxidant effects of Maillard reaction products obtained from ovalbumin and different D-aldohexoses

Nonenzymatic glycation between ovalbumin (OVA) and seven D-aldohexoses was carried out to study the chemical and antioxidant characteristics of sugar-protein complexes formed in the dry state at 55 degrees C and 65% relative humidity for 2 d through the Maillard reaction (MR). The effects of Maillard reaction products (MRPs) modified with different aldohexoses on radical scavenging, lipid oxidation, and tetrazolium salt (XTT) reducibility were investigated. The results showed that the degree of browning and aggregation and the tryptophan-related fluorescent intensity of glycated proteins displayed a noticeable difference that depended on the sugars used for modification. All the glycated proteins exhibited higher antioxidant activity as compared to a heated control and native OVA, and the antioxidant activity was well correlated with browning development. Furthermore, the order of antioxidant activities for the seven complexes was as follows: altrose/allose-OVAs > talose/galactose-OVAs > glucose-OVA > mannose/glucose-OVAs. This implies that sugar-protein complexes with two sugars known as epimers about C-2 showed a similar antioxidant capacity. From these results, the configuration of a hydroxyl (OH) group about position C-2 did not influence the advanced cross-linking reaction, but the configuration of OH groups about C-3 and C-4 might be very important for formation of MRPs and their antioxidant behaviors.     

Effects of protozoa on Methane production in rumen and hindgut of calves around time of weaning

Effects of the presence or absence of ciliate protozoa on methanogenesis in the rumen and hindgut were investigated in young calves during a 7-week period. Ten Holstein calves, aged 7 days, were divided in two groups (n = 5) and fed an increasing amount of a commercial milk replacer and small amounts of a calves starter. One group was inoculated with ciliate fauna on two occasions, week 5 and 6, while the second remained ciliate-free. The absence of protozoa in the rumen decreased rumen empty weight ( ? 23%, P < 0.01), and rumen pool size of N ( ? 36%, P < 0.01) and crude fat ( ? 37%, P < 0.05). Rumen bacteria of non-faunated calves contained a higher proportion of total amino acid-N per 16 g N ( + 3%, P < 0.01) and D-alanine-N per 16 g N ( + 13%, P < 0.05) compared to faunated calves. Further results contain a reference for a higher bacterial mass in the ciliate-free rumen with an increased number of bacteria adherent to rumen mucosa. The CH₄ production in the rumen increased exponentially with the increase in protozoa population size (R² = 0.68). In presence of 46 · 10⁴ protozoa per ml rumen fluid, the in vitro CH₄ production of rumen fluid per mol total VFA was about 34% higher in faunated than in non-faunated calves (P < 0.001). Hydrogen (2H) recovery of rumen fermentation was positively correlated (R² = 0.55) to the CH₄ production rate. Methanogens were attached on rumen mucosa. Methanogenesis, induced by rumen mucosa attached bacteria, was stimulated by ruminal protozoa. In the absence of protozoa in the rumen, the acetate - propionate ratio and butyrate proportion of VFA were reduced. In vivo in the absence of protozoa not only the whole animal CH₄ production ( ? 30%, P < 0.05) but also the digestibility of carbohydrates ( ? 4%, P < 0.05) was reduced. Thereby no difference was observed in the intake of ME per kg DM between the groups. In conclusion, the methanogenesis in the rumen, but not in hindgut, is associated with the development of the ruminal protozoa population. The level of methanogenesis (mol/mol VFA) in the hindgut amounts to 20% of the ruminal methanogenesis.     

Production of tyrosine and other aromatic compounds from phenylalanine by rumen microorganisms

Summary Rumen contents from three fistulated Japanese native goats fed Lucerne hay cubes (Medicago sativa) and concentrate mixture were collected to prepare the suspensions of mixed rumen bacteria (B), mixed protozoa (P) and a combination of the two (BP). Microbial suspensions were anaerobically incubated at 39°C for 12h with or without 1 MM ofl-phenylalanine (Phe). Phe, tyrosine (Tyr) and other related compounds in both supernatant and microbial hydrolysates of the incubations were analyzed by HPLC. Tyr can be produced from Phe not only by rumen bacteria but also by rumen protozoa. The production of Tyr during 12h incubation in B (183.6 mol/g MN) was 4.3 times higher than that in P. One of the intermediate products between Phe and Tyr seems to bep-hydroxyphenylacetic acid. The rate of the net degradation of Phe incubation in B (76.O mol/g MN/h) was 2.4 times higher than in P. In the case of all rumen microorganisms, degraded Phe was mainly (>53%) converted into phenylacetic acid. The production of benzoic acid was higher in P than in B suspensions. Small amount of phenylpyruvic acid was produced from Phe by both rumen bacteria and protozoa, but phenylpropionic acid and phenyllactic acid were produced only by rumen bacteria.     

Conjugated linoleic acid producing potential of lactobacilli isolated from the rumen of cattle

Lactobacilli isolated from the rumen of cattle were subjected to morphological and biochemical characterizations followed by PCR-based identification. Among isolates, Lactobacillus brevis was found to be the most prevalent species in the rumen. For in vitro conjugated linoleic acid (CLA) production, the two isolates of L. brevis and one each of Lactobacillus viridescens and Lactobacillus lactis were selected. The sunflower oil (i.e., 0.25, 0.5 and 1.0%; a rich source of linoleic acid) was added to skim milk as a substrate for CLA production by isolates at 37 °C/12 h. L. brevis 02 was found to be the most potential CLA producer (10.53 mg CLA/g fat) at 0.25% concentration of sunflower oil followed by L. brevis 01 (8.27 mg CLA/g fat). However, at higher level of sunflower oil (i.e., 1.0%), L. lactis was the highest CLA producer (9.22 mg/g fat) when compared to L. brevis and L. viridescens. The results indicated that L. brevis and/or CLA production was inhibited with increasing concentration of sunflower oil in skim milk. In contrast, L. lactis and L. viridescens could tolerate the increasing concentrations of sunflower oil and produced higher CLA. Overall, L. brevis extends a possibility to be used as a direct-fed microbial for ruminants to increase the CLA content in milk, however, in vivo trials are needed for validation of results obtained.     

The metabolic, nutritional and toxicological consequences of ingested dietary Maillard reaction products: a literature review

The field of Maillard reaction in food has recently re-emerged. This reaction which takes place between carbohydrates and proteins at a high cooking temperatures and causes the formation of flavor and yellow to brown colors was already well documented. Little is known, however, about the formation of other Maillard reaction products (MRPs) which may be toxic: the so-called glycotoxins. It is well recognized that only 10% of these have been identified so far, and improved analytical methods are needed for the discovery of more of the neo-formed contaminants. Only a few studies as yet have focused on the digestion, metabolism and excretion of fructoselysine, carboxymethyllysine, pentosidine, acrylamide, the MRPs which have already been identified. MRPs have been shown to be present at significant amounts in a variety of industrially and domestically heat-treated foodstuffs but their absorption appears to be limited and they are readily excreted. Clinical studies indicate, none the less, that the typical Western diet, which contains a high MRPs content, may have an impact on human health. The main effects are observed on the glucose and lipid metabolisms, and on inflammatory mediators. However, the physiopathological role of the ingested MRPs has yet to be investigated in detail, so no conclusive recommendations can be given at present regarding their possible toxic effects.     

Bioconversion of waste office paper to hydrogen using pretreated rumen fluid inoculum

In this study, a microbial consortium from an acid-treated rumen fluid was used to improve the yields of H₂ production from paper residues in batch reactors. The anaerobic batch reactors, which contained paper and cellulose, were operated under three conditions: (1) 0.5 g paper/L, (2) 2 g paper/L, and (3) 4 g paper/L. Cellulase was added to promote the hydrolysis of paper to soluble sugars. The H₂ yields were 5.51, 4.65, and 3.96 mmol H₂/g COD, respectively, with substrate degradation ranging from 56 to 65.4 %. Butyric acid was the primary soluble metabolite in the three reactors, but pronounced solventogenesis was detected in the reactors incubated with increased paper concentrations (2.0 and 4.0 g/L). A substantial prevalence of Clostridium acetobutylicum (99 % similarity) was observed in the acid-treated rumen fluid, which has been recognized as an efficient H₂-producing strain in addition to ethanol and n-butanol which were also detected in the reactors.     

In Vitro Metabolism of the Stereoisomers of 2,6-Diaminopimelic Acid by Mixed Rumen Protozoa and Bacteria

Formation of lysine from stereoisomers (SI) of 2,6-diaminopimelic acid (DAP) and the epimerization between the three SI of DAP (DAP-SI) by rumen protozoa and bacteria were examined. Mixed rumen protozoa (P) and bacteria (B) were isolated from the rumen of goats given a concentrate and hay cubes and incubated separately with and without a mixture and a single one of the three DAP-SI. In P suspensions, mixed DAP-SI decreased by 10.59% as a whole and converted mainly to lysine by 8.41% during 12 h incubation. When meso-, L- and D-DAP were added singly to the media, the results showed that each DAP-SI interconverted and produced lysine. This means that mixed rumen protozoa have an ability to synthesize lysine from not only meso-DAP but also from D- and L-DAP, though probably via meso-DAP, and hence have DAP epimerase activities for the reversal conversion of each DAP-SI. This is the first discovery to show the interconversion of DAP-SI and synthesis of lysine from them by protozoa. In B suspensions, mixed DAP-SI decreased by 10.92% as a whole and converted to lysine by 4.20% during 12 h incubation. When a single DAP-SI was added to the media, meso-, L- and D-DAP were interconverted and then converted to lysine by the rumen bacteria as well as the protozoa. This also means that mixed rumen bacteria have DAP epimerase activities to interconvert DAP-SI and have an ability to synthesize lysine from not only meso-DAP but also from L- and D-DAP, and this is also the first finding in rumen bacteria. Received: 16 March 1996 / Accepted: 14 May 1996     

The chemical and hydroxyl radical scavenging activity changes of ginsenoside-Rb1 by heat processing

The chemical and hydroxyl radical (*OH) scavenging activity changes of ginsenoside Rb(1) (Rb(1)) by heat processing were investigated in this study. Rb(1) was changed into 20(S)-Rg(3), 20(R)-Rg(3), Rk(1), and Rg(5) by heat processing through glucosyl elimination and epimerization of carbon-20 by SN1 reaction. The glucosyl moiety, separated from Rb(1), made Maillard reaction product (MRPs) with glycine. The generations of 20(S)-Rg(3) and MRPs were related to the increased OH scavenging activity of Rb(1) by heat processing.     

Comparison of nisin and monensin effects on ciliate and selected bacterial populations in artificial rumen

The effect of daily supplementation of nisin (2 mg/L), monensin (5.88 mg/L) and nisin and monensin (2 + 5.88 mg/L) on ovine ruminal ciliates and bacteria was investigated using the artificial rumen RUSITEC. Major groups in RUSITEC were Entodinium spp. and Dasytricha ruminantium. The supplementation of nisin significantly increased the population of both major ciliate groups. The supplementation of monensin significantly decreased the population of both groups. The combined effect of nisin and monensin was similar to the effect of monensin. Monensin had strong antiprotozoic effects in contrast to the stimulatory effects of nisin. D. ruminantium followed by Entodinium spp. appeared more resistant to tested compounds than other rumen ciliates. Tested additives did not significantly influence the presence and growth of amylolytic streptococci and enterococci but nisin showed a tendency to decreasing the concentration of Escherichia coli and lactobacilli.     

Health effects of dietary Maillard reaction products: the results of ICARE and other studies

In food science the Maillard reaction is well known to cause degradation of amino acids and an overall decrease in the nutritional value of foods that have been subjected to heat in processing. There has been evidence more recently of the endogenous formation of some Maillard reaction products (MRPs) in biological systems and their association with pathophysiological conditions including diabetes, renal disease and cardiovascular disease. Several studies have suggested that dietary MRPs increase the in vivo pool of MRPs after intestinal absorption and contribute to the development of diabetes and related complications. This review focuses on the animal and human studies which have assessed the eventual implications of dietary MRPs on human health, highlighting the different diets tested, the experimental designs and the biomarkers selected to estimate the health effects. The results of these studies are compared to those of the recently published ICARE study. In this latter study an accurate determination of the MRP content of the diets was achieved, allowing the calculation of the contribution of individual food groups to daily MRP intakes in a regular western diet.     

体外法添加苹果酸与饱和脂肪酸对瘤胃功能菌群数量的影响

本试验在添加饱和脂肪酸即硬脂酸(Stearic acid, SA)的基础上添加不同水平的苹果酸(Malic acid, MA), 采用体外法对瘤胃微生物进行培养, 通过实时定量(Real-time)PCR方法检测在添加脂肪酸和苹果酸后, 对瘤胃功能微生物如纤毛虫、产甲烷菌, 纤维分解细菌、氢化细菌以及脂肪分解菌的数量的影响。实验结果表明, 添加硬脂酸后对脂解厌氧弧杆菌(Anaerovibrio lipolytica) 和产琥珀酸丝状杆菌(Fibrobacter succinogenes)数量产生了显著影响, 脂解厌氧弧杆菌数量减少了95.8%(P<0.001), 产琥珀酸丝状杆菌数量增加了52.5%(P<0.05)。添加苹果酸后, 添加5 mmol/L MA处理组的脂解厌氧弧杆菌数量减少了91.2%(P<0.001), 添加10 mmol/L MA处理组, 减少了94.8% (P<0.001), 而MA10组比MA5组的该菌数量减少了41.3%(P<0.05)。本研究结论是硬脂酸和苹果酸分别对瘤胃部分微生物产生了显著的影响。二者对瘤胃微生物的互作影响并不显著。     

Evidence against nitric oxide-quenching effects of chemically defined Maillard reaction products

Direct interaction between Maillard reaction products (MRPs) and nitric oxide (NO) has been suggested as a pathophysiological mechanism involved in enhanced diabetic arteriosclerosis. Only MRPs without structural characterization have been studied to date. Using chemically synthesized and analytically well defined individual MRPs, we investigated whether the native nitric oxide concentration is directly affected by the Amadori compound N-epsilon-fructosyllysine or the advanced glycation end product N-epsilon-carboxymethyllysine. MRPs were incubated with nitric oxide solution or NO donors (SNAP, spermine-NONOate). Changes in the nitrite (oxidative metabolite of NO) concentration served as indicator of NO availability. MRPs, either as free amino acids or covalently bound to bovine serum albumin (BSA), had no influence on nitrite concentration when using NO solution. In contrast, incubation of the respective NO donors with several covalently protein-bound MRPs as well as native BSA significantly reduced nitrite concentration. If SNAP was co-incubated with EDTA or with Fe (2+) ions, nitrite concentration was decreased or increased, respectively, suggesting a metal ion-dependent alteration of the NO liberation rate. Native NO concentration was not affected by the MRPs tested. Substitution of native NO by NO-releasing substances may be inadequate as a model of NO-MRP interaction, as metal ions or chelators present in compound preparations may affect the NO-liberating mechanism of the donor.     

Studies on the utilization of methionine sulfoxide and methionine sulfone by rumen microorganisms in vitro

Summary.  An in vitro experiment was conducted to test the ability of mixed rumen bacteria (B), protozoa (P), and their mixture (BP) to utilize the oxidized forms of methionine (Met) e.g., methionine sulfoxide (MSO), methionine sulfone (MSO₂). Rumen contents were collected from fistulated goats to prepare the microbial suspensions and were anaerobically incubated at 39°C for 12 h with or without MSO (1 mM) or MSO₂ (1 mM) as a substrate. Met and other related compounds produced in both the supernatants and hydrolyzates of the incubation were analyzed by HPLC. During 6- and 12-h incubation periods, MSO disappeared by 28.3 and 42.0%, 0.0 and 0.0%, and 40.6 and 62.4% in B, P, and BP suspensions, respectively. Rumen bacteria and the mixture of rumen bacteria and protozoa were capable to reduce MSO to Met, and the production of Met from MSO in BP (156.6 and 196.1 μmol/g MN) was about 17.3 and 14.1% higher than that in B alone (133.5 and 171.9 μmol/g MN) during 6- and 12-h incubations, respectively. On the other hand, mixed rumen protozoa were unable to utilize MSO. Other metabolites produced from MSO were found to be MSO₂ and 2-aminobutyric acid (2AB) in B and BP. MSO₂ as a substrate remained without diminution in all-microbial suspensions. It was concluded that B, P, and BP cannot utilize MSO₂; but MSO can be utilized by B and BP for producing Met. Received December 28, 2001 Accepted May 21, 2002 Published online October 14, 2002 Acknowledgements The authors are extremely grateful to Professor H. Ogawa, the University of Tokyo, Japan and Dr. Takashi Hasegawa, Miyazaki University, Japan for inserting permanent rumen fistulae in goats. We would like to thank MONBUSHO for the award of a research scholarship to Mamun M. Or-Rashid since 1996–2001. Authors' address: Shaila Wadud, Laboratory of Animal Nutrition and Biochemistry, Division of Animal Science, Miyazaki University, Miyazaki 889-2192, Japan, Fax. +81-985-58-7201, E-mail: rafatkun@hotmail.com