Galacturonic Acid Concentrations Research Articles

Enzymatic production, physicochemical characterization, and prebiotic potential of pectin oligosaccharides from pisco grape pomace

The prebiotic capacity of Pectin Oligosaccharides (POS) is influenced by structural factors such as molecular size, composition, and degree of esterification, which affect their interaction with the gut microbiota. While existing literature has predominantly examined POS derived from apple and citrus pectins, the extrapolation of these findings to other pectin sources remains complex due to variations in their composition. This study focused on obtaining POS with prebiotic potential from pisco grape pomace through controlled enzymatic hydrolysis, resulting in three molecular size fractions: <3 kDa, 3–10 kDa, and > 10 kDa. The POS fractions were analyzed using FTIR, HPSEC, HPLC, and MALDI-TOF-MS techniques to characterize their physical-chemical properties. Each fraction presented distinct compositions, with the <3 kDa fraction showing a higher concentration of galacturonic acid and glucose, while the >10 kDa fraction was also composed of rhamnose and arabinose. Notably, the <3 kDa fraction supported greater biomass growth of the probiotic strain Lactobacillus casei ATCC 393 compared to the other fractions. In contrast, the non-probiotic strain Escherichia coli ATCC 25922 achieved the lowest biomass with this fraction. Consequently, the <3 kDa POS fraction exhibited the highest prebiotic index. This fraction, composed of oligomers from the rhamnogalacturonan region and arabino-oligosaccharides with a degree of polymerization between two and five, highlights its potential for further research and applications. Therefore, investigating other sources and optimizing extraction conditions could lead to developing novel prebiotic formulations that supply specific probiotic strains for a symbiotic product.

Star anise (Illicium verum Hook. F.) polysaccharides: Potential therapeutic management for obesity, hypertension, and diabetes

This study explores the extraction of polysaccharides from star anise (Illicium verum Hook. f.) with its anti-obesity, antihypertensive, antidiabetic, and antioxidant properties. The aim is to optimize the extraction conditions of star anise polysaccharides (SAP) utilizing propane alcohols-based deep eutectic solvents and microwave-assisted methods. The optimized conditions resulted in an extraction yield of 5.14%. The characteristics of acidic pectin-like SAP, including high viscosity (44.86 mPa s), high oil-holding capacity (14.39%), a high degree of esterification (72.53%), gel-like properties, highly amorphous, a high galacturonic acid concentration, and a highly branching size polysaccharide structure, significantly contribute to their potent inhibition of pancreatic lipase (86.67%), angiotensin-converting enzyme (73.47%), and α-glucosidase (82.33%) activities as well as to their antioxidant properties of azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS, 34.94%) and ferric ion reducing antioxidant power (FRAP, 0.56 mM FeSO4). Therefore, SAP could be used as a potential therapeutic agent for obesity, hypertension, and diabetes mellitus management.

Characterization of Banana Peel Pectin (Musa acuminata Colla) as a Potential Halal Pharmaceutical Excipient

Indonesian Halal Product Assurance Law No. 33 of 2014 states all products circulating in Indonesia must be halal-certified, including pharmaceuticals. Banana peel waste has the potential to produce pectin compounds as pharmaceutical excipients. This study is aimed at determining the characteristics of banana peel pectin as a potential halal pharmaceutical excipient. It has involved qualitative tests and established characteristics of extract pectin by organoleptic test, acidity (pH) test, solubility, equivalent weight, methoxyl concentration, galacturonic acid concentration, esterification degree, moisture content, and ash content. The yield of pectin produced was 17.19%. The qualitative test showed positive pectin, the characteristics of a white powder that is slightly ash, odorless, has a pH of 6.02, is soluble in water, insoluble in ethanol 96%, has an equivalent weight of 5,000 mg, methoxyl concentration of 2.6%, galacturonic acid concentration of 73.92%, esterification degree of 20.19%, moisture content of 7.139% and ash content of 1.6%. Based on the characterization results, banana peel pectin is, by pectin quality standards, a pharmaceutical excipient, especially as a raw material for manufacturing capsule shells, thickeners, and coating and gelling agents.

Cold and exogenous calcium alter Allium fistulosum cell wall pectin to depress intracellular freezing temperatures.

De-methyl esterification of homogalacturonan and subsequent cross-linking with Ca2+ is hypothesized to enhance the freezing survival of cold acclimated plants by reducing the porosity of primary cell walls. To test this theory, we collected leaf epidermal peels from non- (23/18 °C) and cold acclimated (2 weeks at 12/4 °C) Japanese bunching onion (Allium fistulosum L.). Cold acclimation enhanced the temperature at which half the cells survived freezing injury by 8 °C (LT50 =-20 °C), and reduced tissue permeability by 70-fold compared with non-acclimated epidermal cells. These effects were associated with greater activity of pectin methylesterase (PME) and a reduction in the methyl esterification of homogalacturonan. Non-acclimated plants treated with 50mM CaCl2 accumulated higher concentrations of galacturonic acid, Ca2+ in the cell wall, and a lower number of visible cell wall pores compared with that observed in cold acclimated plants. Using cryo-microscopy, we observed that 50mM CaCl2 treatment did not lower the LT50 of non-acclimated cells, but reduced the lethal intracellular ice nucleation to temperatures observed in cold acclimated epidermal cells. We postulate that the PME-homogalacturonan-mediated reduction in cell wall porosity is integral to intracellular freezing avoidance strategies in cold acclimated herbaceous cells.

Isabgol (Plantago ovata) and lentil (Lens culinaris) intercrop responses to arbuscular mycorrhizal fungi inoculation

ABSTRACT Intercropping medicinal plants with grain legumes provides an excellent opportunity for small-scale farmers to generate more income and move towards sustainable cropping systems. The effect of arbuscular mycorrhizal fungi (AMF) inoculation on yield, quality and nutrient uptake of isabgol and lentil, when grown as monocrops or in various intercropping ratios, were evaluated. Inoculation with AMF resulted in positive effects on AMF root colonisation, yield components and seed yields (significant for lentils only) of both crops, especially in the intercropping systems, as well as in the nutrient uptake in isabgol. The highest seed yields of isabgol (743 kg ha−1) and lentil (684 kg ha−1) were obtained when these species were grown as monocrops and inoculated with AMF. The highest mucilage content (20.9%) and swelling factor (16.9 ml) of the isabgol seeds were found when the two secies were grown in the intercropping ratio of 2I:2L (2 rows isabgol: 2 rows lentil) and treated with AMF. Regarding the composition of the isabgol seed mucilage, the highest concentrations of galacturonic acid (9.0%), galactose (11.8%), glucuronic acid (18.3%), and xylose (39.0%) were recorded in intercropping with AMF treatment. AMF inoculation also increased soil basic microbial respiration, soil substrate-induced respiration and soil microbial biomass carbon. Overall, the highest land equivalent ratio (LER = 1.67) was recorded in the 4I:2L intercropping pattern with AMF inoculation. The results indicated that intercropping of isabgol and lentil together with AMF inoculation was an effective system to increase the use efficiency of resources for smallholder farmers in semi-arid regions.

Bioethanol production from cactus cladode biomass: considerations of harvesting time, dry matter concentrations, and enzymatic hydrolysis

Cactus pear biomass has the potential for bioethanol production in dry regions. However, its low solids concentration and pH variations may hinder the process of alcoholic fermentation. The objectives of this study were as follows: (1) to evaluate the effects of harvest time and season on biomass pH and dry matter concentration of cladodes of two cactus pear species commonly used as forage (Nopalea cochenillifera and Opuntia stricta); (2) to compare the hydrolysis of fresh and dried biomass (10% w v−1 solids); (3) to compare increasing periods of two temperatures (65 °C or 105 °C) to concentrate the biomass to 10% and 30% solids; and (4) to perform enzymatic hydrolysis and fermentation of biomass dried to 30% solids. Biomass pH ranged from 3.0 to 5.6, from early morning to late afternoon, with higher diurnal variation during the dry season, when their solids concentrations were higher than in the rainy season (12–16% × 7–10%). Hydrolyzed fresh and dried biomass had similar glucose, xylose, and galacturonic acid concentrations. Drying at 105 °C for 12 h was the best temperature and period to reach 30% of solids. The enzymatic hydrolysis of the biomass dried to 30% solids yielded 65.3 and 80.0 g of glucose L−1. After fermentations (33 °C; 8 h; Saccharomyces cerevisiae), ethanol was produced to 29.4 and 37.5 g L-1 from N. cochenillifera and O. stricta biomasses, respectively. Therefore, early morning during the dry season is the best moment to harvest the cladodes, whose biomass can be partially dried at 105 °C for 12 h to 30% solids load before being hydrolyzed and fermented for bioethanol production. This procedure reduces the time, energy, and inputs needed in the process.

Effect of metal nanoparticles on the accumulation and structure of rapeseed carbohydrates

The purpose was to conduct field tests of the most active metal nanoparticles of iron, cobalt and copper to realize the maximum accumulation of polysaccharides in plants; to develop a method for obtaining and studying the structure of polysaccharides obtained from plants treated before sowing with metal nanoparticles; to study the physical-chemical characteristics of polysaccharides and the monosaccharide composition under the influence of metal nanoparticles. Before sowing, seed treatment was carried out with suspensions of nanoparticles with a concentration of 0.5 g/ha (hectare seed sowing rate). Observed under the influence of copper nanoparticles, the yield increased by 15 % comparison to the control one. When determining the monosaccharide composition, in addition to changing the quantitative content of monosaccharides, a high concentration of galacturonic acid was observed, especially when treating seeds with copper nanoparticles before sowing.

Online evaluation of the metabolic activity of Ustilago maydis on (poly)galacturonic acid

BackgroundPectin is a rather complex and highly branched polysaccharide strengthening the plant cell wall. Thus, many different pectinases are required for an efficient microbial conversion of biomass waste streams with a high pectin content like citrus peel, apple pomace or sugar beet pulp. The screening and optimization of strains growing on pectic substrates requires both, quantification of the residual substrate and an accurate determination of the enzymatic activity. Galacturonic acid, the main sugar unit of pectin, is an uncommon substrate for microbial fermentations. Thus, growth and enzyme production of the applied strain has to be characterized in detail to understand the microbial system. An essential step to reach this goal is the development of online monitoring tools.ResultsIn this study, a method for the online determination of residual substrate was developed for the growth of the plant pathogenic fungus Ustilago maydis on pectic substrates such as galacturonic acid. To this end, an U. maydis strain was used that expressed a heterologous exo-polygalacturonase for growth on polygalacturonic acid. The growth behavior on galacturonic acid was analyzed by online measurement of the respiration activity. A method for the online prediction of the residual galacturonic acid concentration during the cultivation, based on the overall oxygen consumption, was developed and verified by offline sampling. This sensitive method was extended towards polygalacturonic acid, which is challenging to quantify via offline measurements. Finally, the enzymatic activity in the culture supernatant was calculated and the enzyme stability during the course of the cultivation was confirmed.ConclusionThe introduced method can reliably predict the residual (poly)galacturonic acid concentration based on the overall oxygen consumption. Based on this method, the enzymatic activity of the culture broth of an U. maydis strain expressing a heterologous exo-polygalacturonase could be calculated. It was demonstrated that the method is especially advantageous for determination of low enzymatic activities. In future, it will be applied to U. maydis strains in which the number of produced hydrolytic enzymes is increased for more efficient degradation.

The interaction of induction and repression mechanisms in the regulation of galacturonic acid-induced genes in Aspergillus niger

Aspergillus niger is an important industrial fungus expressing a broad spectrum of pectinolytic genes. The main constituent of pectin, polygalacturonic acid (PGA), is degraded into galacturonic acid (GA) by the combined activity of endo- and exo-polygalacturonases some of which are specifically induced by GA. The regulatory mechanisms that control the expression of genes encoding PGA-degrading enzymes are not well understood. Based on available genome-wide expression profiles from literature, we selected five genes that were specifically induced by GA. These genes include three exo-polygalacturonases (pgaX, pgxB and pgxC), a GA transporter (gatA), and an intracellular enzyme involved in GA metabolism (gaaB). These five genes contain a conserved motif (5′-TCCNCCAAT-3′) in their promoter regions, which we named GARE (galacturonic acid-responsive element). Promoter deletion studies and site-directed mutagenesis of the conserved motif of the pgaX gene showed that the conserved element is required for GA-mediated induction. A set of promoter reporter strains was constructed by fusing the promoter region of the five above-mentioned genes to the amdS reporter gene. Expression of the amdS gene is quantitatively correlated with ability to utilise acetamide as an N-source, hence higher expression of amdS improves growth of the strain on acetamide and therefore can be used as an in vivo reporter for gene expression. Growth analysis of the reporter strains indicated that four genes (pgaX, pgxB, pgxC, and gatA) are specifically induced by GA. The in vivo promoter reporter strains were also used to monitor carbon catabolite repression control. Except for gaaB, all promoter–reporter genes analysed were repressed by glucose in a glucose concentration-dependent way. Interestingly, the strength of glucose repression was different for the tested promoters. CreA is important in mediating carbon catabolite repression as deletion of the creA gene in the reporter strains abolished carbon catabolite repression for most promoters. Interestingly, the pgxC promoter was still repressed by glucose even in the creA null background, suggesting a role for alternative repression mechanisms. Finally, we showed that low concentrations of GA are required to induce gene expression of pgaX, pgxB, and pgxC even under derepressing conditions. The results obtained are consistent with a model in which a GA-specific transcription factor is activated by GA or a GA-derivative, which binds to the conserved motif, possibly in combination with the HAP-complex, to drive GA-specific gene expression.

Enzymatic hydrolysis and fermentation of crushed whole sugar beets

Pectinase and cellulase enzymes were used for hydrolysis of whole sugar beets and the hydrolyzates were fermented with Escherichia coli KO11 and Saccharomyces cerevisiae via simultaneous saccharification and fermentation (SSF). Ethanol production rate was significantly higher for S. cerevisiae than for E. coli KO11. The combined effect of pectinase and cellulase loadings on ethanol production as well as residual galacturonic acid and arabinose concentrations were modeled for fermentations with S. cerevisiae. Ethanol yields of more than 92% were reached with moderate to high cellulase and pectinase loadings at 0.51 FPU g−1 and 51 U g−1 of dry biomass, respectively. Ethanol yields of 85% were achieved without any enzyme addition. However, addition of cellulase and pectinase enzymes increased effluent arabinose and galacturonic acid concentrations and reduced total suspended solids. This study demonstrated the yield potential of fermentation of crushed, whole sugar beets with or without the addition of cellulase and pectinase enzymes.

Pengaruh Ion-ion Logam terhadap Aktivitas Pektinase dari Aspergillus niger pada Penjernihan Sari Buah Jambu

Pectinase can be used on various fruit juices clarification; however, the activities can be affected by their metal ions content. The purpose of this study was to determine the type of metal ions inhibition i.e. Zn 2+ ; Mg 2+ and Ca 2+ on the pectinase activity of Aspergillus niger , and its potential application in guava juice clarification. Activity assays performed at pH 5, temperature 50°C during 55minutes and each ion concentration were 2-10 mM. Galacturonic acid concentration, as the product of pectin substrate hydrolysis, used as the basis for determining its activity and analyzed by visible spectrophotometry. The results showed that the ions concentration of Zn 2+ and Mg 2+ more than 4 mM were inhibitor for pectinase activity while Ca 2+ ion concentration was 6mM. K I values for the metal ions Zn 2+ ; Mg 2+ and Ca 2+ at concentrations of 6mM were 176.99; 326.09 and 280.37 mM respectively. Pectinase from Aspergillus niger were able to reduce 18% of pectin of guava juice.

Galacturonic Acid Inhibits the Growth of Saccharomyces cerevisiae on Galactose, Xylose, and Arabinose

The efficient fermentation of mixed substrates is essential for the microbial conversion of second-generation feedstocks, including pectin-rich waste streams such as citrus peel and sugar beet pulp. Galacturonic acid is a major constituent of hydrolysates of these pectin-rich materials. The yeast Saccharomyces cerevisiae, the main producer of bioethanol, cannot use this sugar acid. The impact of galacturonic acid on alcoholic fermentation by S. cerevisiae was investigated with anaerobic batch cultures grown on mixtures of glucose and galactose at various galacturonic acid concentrations and on a mixture of glucose, xylose, and arabinose. In cultures grown at pH 5.0, which is well above the pK(a) value of galacturonic acid (3.51), the addition of 10 g · liter(-1) galacturonic acid did not affect galactose fermentation kinetics and growth. In cultures grown at pH 3.5, the addition of 10 g · liter(-1) galacturonic acid did not significantly affect glucose consumption. However, at this lower pH, galacturonic acid completely inhibited growth on galactose and reduced galactose consumption rates by 87%. Additionally, it was shown that galacturonic acid strongly inhibits the fermentation of xylose and arabinose by the engineered pentose-fermenting S. cerevisiae strain IMS0010. The data indicate that inhibition occurs when nondissociated galacturonic acid is present extracellularly and corroborate the hypothesis that a combination of a decreased substrate uptake rate due to competitive inhibition on Gal2p, an increased energy requirement to maintain cellular homeostasis, and/or an accumulation of galacturonic acid 1-phosphate contributes to the inhibition. The role of galacturonic acid as an inhibitor of sugar fermentation should be considered in the design of yeast fermentation processes based on pectin-rich feedstocks.

Influence of growing area and harvest date on the organic acid composition of olive fruits from Gemlik variety

Organic acids (oxalic, citric, galacturonic, tartaric, malic, lactic and succinic) contents of Gemlik variety olive fruits from five different cultivation areas of South Anatolia (Turkey), harvested in six collection dates (September, October and November of crop years 2006 and 2007), were determined by HPLC/DAD. Citric acid was the major compound (∼45%), followed by succinic (19%) and galacturonic acids (∼16%). The olive fruits of Antalya location showed the lowest and Karaman, Alanya and Hatay locations had the highest levels of total organic acids, especially on the early and late harvest. Significant interactions between “ location”, “ harvest date” and “ crop year” were found, regarding the concentrations of citric, lactic, oxalic, tartaric and malic acid (3-way and 2-way interactions), which means that the effect of one factor (e.g. “ location”) on an acid's concentration is not constant across the levels of the other factor. For succinic and galacturonic acids's concentrations, all interactions between the considered factors were statistically significant, except the 2-way interaction between “ harvest date” and “ crop year” which was no significant, meaning that the effect of factor “ harvest date” on the succinic and/or on the galacturonic acid's concentrations does not vary significantly from one level of factor “ crop year” to other. Significant mean differences were found in the concentrations of individual organic acids according to harvest time, which indicated generally a decline as harvest date moved on or no significant changes in some cases. Our results showed that rainfall and altitude of the location seemed to have more marked effects than temperature, on the levels of some organic acids such as malic, oxalic and succinic acids. The grouping of locations formed in Principal Component Analysis were quite different according to crop years, as for the first crop year (2006) “oxalic, citric, tartaric and succinic” and “lactic, malic, galacturonic” acids were the two groups of variables mainly responsible for discrimination, while for the following crop year (2007) “galacturonic, tartaric, oxalic, lactic”; “succinic, citric” and “malic” acids were the three groups responsible for the formation of clusters.

Statistical optimization of hydrolysis process for banana peels using cellulolytic and pectinolytic enzymes

Dried and ground banana peels (BP) were pretreated and hydrolyzed using a combination of cellulolytic and pectinolytic enzymes. Central composite design (CCD) was used to optimize cellulase, β-glucosidase and pectinase concentrations and hydrolysis time for production of glucose and reducing sugars. Design expert software was used to analyze and evaluate the data. The interactions between filter paper cellulase and β-glucosidase concentrations were statistically significant at a 95% confidence level in production of glucose and reducing sugars from BP. The validation experiment was carried out with cellulase, β-glucosidase and pectinase at 8FPU/g cellulose, 15IU/g cellulose and 66IU/g pectin, respectively, for 15h in a laboratory fermenter. The glucose and reducing sugars concentrations of 28.2 and 48g/l, respectively, obtained through the validation experiment were higher than the theoretical values for glucose and reducing sugars predicted by the software. Glucose, galactose, arabinose, xylose and galacturonic acid concentrations increased with time, but a significant increase in fructose concentration was not observed. Process optimization also led to about 40% savings in hydrolysis time, indicating scale-up potential for the process.

Determination of galacturonic acid content in pectin from fruit juices by liquid chromatographydiode array detection-electrospray ionization tandem mass spectrometry

Abstract A reversed-phase high-performance liquid chromatographic (HPLC) method is applied for the determination of galacturonic acid (GA) of pectins in different commercial fruit juices. The separation was carried out on a C18 column using precolumn derivatization with p-aminobenzoic acid (p-ABA) and UV detection at 304 nm. The identification of GA was confirmed by high-performance liquid chromatography/electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS) in positive ion mode. The concentration of GA in the samples analyzed ranged from 12.9 ± 0.5 to 49.4 ± 0.5 mgGA L−1. Amongst the samples analyzed, mango juice was found to be richest in GA content, and therefore a good source of pectins. Detection and quantification limits of the described methodology were 1.2 and 3.9 mg L−1, respectively. Quantitative GA recoveries in the beverages had a range between 90 and 98%. The results showed that the HPLC method proposed was precise and suitable for the identification and quantification of GA in commercial fruit juices.

Effect of maturity and storage temperature on the development of peteca in lemons ( Citrus limon (L.) Burm. F.) cv. Eureka

To evaluate the effect of maturity and storage temperature on the development of the physiological disorder peteca, lemons cv. Eureka were harvested from a grove with northern exposure located in Mallarauco (33°45′ Latitude South) Metropolitan Region of Chile, at 2 levels of maturity (silver or yellow). After storage for 60 d at 3 or 7 °C, under 90% R.H., fruits were evaluated visually for incidence of epidermal and subepidermal peteca. At that time, the concentration of galacturonic acid and degree of methylation were measured in the albedo, and calcium, hydrogen peroxides and total oxalate concentrations, peroxidase and polyphenoloxidase (PPO) activities were determined in the juice and albedo. Yellow lemons at 3 °C developed more epidermal peteca than fruit stored at 7 °C, and that silver fruit stored at 3 and 7 °C, with these last lemons presenting a higher pectin quality than fruit stored at 3 °C. Maturity and temperature interacted significantly on the concentrations of peroxide and calcium in the albedo, which in average were much higher than in the juice, while for PPO and peroxidases, this interaction was highly significant both in juice and albedo, with higher activity in the albedo. These biochemical evaluations suggest that peteca is a result of some kind of stress on the fruit. It is concluded that yellow lemons are more prone to develop peteca than silver fruit. They will develop greater incidence of the disorder when stored at temperatures as low as 3 °C for 60 d, and that this condition affects the degree of methylation in the albedo, which would end up altering the quality of pectins.

An Effective Combination of Carbohydrases That Enables Reduction of Dietary Protein in Broilers: Importance of Hemicellulase

After observing the effects of purified cellulase (C), hemicellulase (H), pectinase (P), and their combinations on the in vitro digestibility of a corn-soybean meal broiler diet, we examined the associations between pectin breakdown and the digestibilities of CP and DM by using free galacturonic acid (GA) as an index of pectin breakdown. There was no significant effect of the single enzymes except for H. However, the enzyme combinations H + P, C + H, and C + H + P significantly increased CP and DM digestibilities, whereas the combination of C + P was not effective. Because H has activities of both H and P, these enzymes were considered to be important in stimulating digestion. Furthermore, when the enzymes increased CP and DM digestibilities, GA concentration was significantly higher, and clear correlations between CP and DM digestibilities and GA concentration were observed, whereas correlations between the digestibilities and concentration of glucose or xylose + mannose as indices of cellulose and hemicellulose breakdown, respectively, were not significant. From these observations, we hypothesized that a mixture of enzymes could increase the protein digestibility of broiler feed. Thus, in the in vivo experiment, low-protein (19% CP) diets made mainly of corn and soybean meal with or without mixed enzymes were prepared and given to broiler chicks. The birds given the diet containing mixed enzymes showed significantly higher BW gain, with higher CP and DM digestibilities than the birds given the diet without the mixed enzymes. Moreover, the growth rate was same as that of the birds given the normal (21% CP) diet. The results indicate that the mixed enzyme preparation can effectively degrade indigestible cell constituents and thus enable the protein of the broiler feed to become more digestible. Furthermore, the results indicate the importance of H as a rate-limiting factor of cell wall breakdown.

Comparison of the amount of pectin in the human terminal ileum with the amount of orally administered pectin

Objective Dietary fiber by definition is resistant to digestion and absorption in the human small intestine, and it should naturally reach the large intestine. To date, there have been several reports that have examined in vivo how much dietary fiber actually reaches the terminal ileum in human subjects using glucose, with large differences in results. We compared the amount of pectin in the human terminal ileum with that of orally administered pectin. Methods Seven healthy male volunteers ages 20 to 27 y were given a test meal containing 4.05 g of pectin. A double-lumen tube was placed in the terminal ileum by using the endoscopic retrograde bowel insertion method, and the ileal contents were aspirated through the tube. Amounts of pectin orally administered and collected from the terminal ileum were estimated as galacturonic acid concentrations (Englyst’s method) and were compared with each other. Results The mean ± standard deviation amount of pectin collected in the terminal ileum was 3.58 ± 0.43 g, or 88.4 ± 10.5% of pectin administered. Further, there were large individual differences in recovery, ranging from 76.8% to 105.1%. Conclusions Approximately 90% of ingested pectin was recovered in the terminal ileum in this study. Ten percent may have been degraded by bacteria within the digestive tract, especially the terminal ileum.

Quantification of uronic acids in tea polysaccharide conjugates and their antioxidant properties.

A technique of high-performance liquid chromatography (HPLC) was described for the measurement of total uronic acids in tea polysaccharide conjugates. This method was applied to polysaccharide conjugate extracts obtained from green tea after most of the components that produce interference were removed. The preliminary extraction process was according to the procedure of isolation of polysaccharide conjugates. The uronic acid content of different polysaccharide conjugate fractions was quantified by HPLC on a Sugar-Pak I column with a 1.0 x 10(-)(4) mol x L(-)(1) calcium disodium ethylenediaminetetraacetic acid solution as the mobile phase and refractive index detection. The validation study showed high recoveries (>97.0%) and low coefficients of variance (<3.0%). The minimum detectable limit concentration of uronic acid was 10 microg x mL(-)(1). The analysis of a standard range of galacturonic acid concentrations (100-4000 microg x mL(-)(1)) yielded linear results. The use of the method on different polysaccharide conjugate fraction samples confirmed its effectiveness. With the high content of uronic acids in polysaccharide conjugates, the stronger reactive oxygen species scavenging activities were found.

Kinetics of galacturonic acid release from sugar-beet pulp

Extracted sugar-beet pulp was studied as a source of galacturonic acid. For this purpose a commercial enzyme mixture (Pectinex ® 100 l from Novo Nordisk) was used to degrade extracted sugar-beet pulp to galacturonic acid in high yields and at short retention times. Because sugar-beet is a very complex substrate with a varying, non-standardisable composition, the kinetics of this enzyme mixture were studied at first with citrus- and sugar-beet pectin as model substrates, in order to define a starting point for a comparison. The degradation of the citrus- and sugar-beet pectin was carried out in acetate buffer (pH 4) and the decomposition of extracted sugar-beet pulp in water (pH 4.4), with a view to an industrial application. It was found, that for all substrates no substrate inhibition, but a strong product inhibition is given. Therefore, the use of extracted sugar-beet (and other related compounds) can enzymatically yield only low concentrations of galacturonic acid.