Galactomannans from Brazilian seeds: characterization of the oligosaccharides produced by mild acid hydrolysis

Efficient production of High-Purity manno-oligosaccharides from guar gum by citric acid and enzymatic hydrolysis

Currently, the production of manno-oligosaccharides (MOS) from guar gum faces challenges of low oligosaccharide enzymatic hydrolysis yield and complicated steps in separation and purification. In this work, a potential strategy to address these issues was explored. By combining citric acid pretreatment (300 mM, 130 °C, 1 h) with β-mannanase hydrolysis, an impressive MOS yield of 61.8 % from guar gum (10 %, w/v) was achieved. The key success lay in the optimizing conditions that completely degraded other galactomannans into monosaccharides, which could be easily removable through Saccharomyces cerevisiae fermentation (without additional nutrients). Following ion exchange chromatography for desalination, and concluding with spray drying, 4.57 g of solid MOS with a purity of 90 % was obtained from 10 g of guar gum. This method offers a streamlined and effective pathway for obtaining high-yield and high-purity MOS from guar gum by combining citric acid pretreatment and enzymatic hydrolysis.

Seed gum-based polysaccharides hydrogels for sustainable agriculture: A review

Globally, water scarcity in arid and semiarid regions has become one of the critical issues that hinder sustainable agriculture. Agriculture, being a major water consumer, presents several challenges that affect water availability. Hydrogels derived from polysaccharides seed gums are hydrophilic polymers capable of retaining substantial moisture in their three-dimensional network and releasing it back into the soil during drought conditions. Implementation of hydrogels in the agricultural sectors enhances soil health, plant growth, and crop yield. Furthermore, the soil permeability, density, structure, texture, and rate of evaporation and percolation of water are modified by hydrogel. In this review, hydrogels based on natural plant seed gum like guar, fenugreek, Tara and locust beans have been discussed in terms of their occurrence, properties, chemical structure, method of synthesis, and swelling behavior. The focus extends to recent applications of modified seed gum-based natural hydrogels in agriculture, serving as soil conditioners and facilitating nutrient delivery to growing plants. The swelling behavior and inherent structure of these hydrogels can help researchers unravel their maximum possibilities to promote sustainable agriculture and attenuate the obstacles propounded by our dynamic nature. The current review also examines market growth, prospects, and challenges of eco-friendly hydrogels in recent times.

Structural characterization of chia seed polysaccharides and evaluation of its immunomodulatory and antioxidant activities

This study aims to extract an active heteropolysaccharide Chia seed polysaccharide (CSP-A) and further purified by DEAE Sepharose Fast Flow and Sepharose CL-6B chromatographic column, characterize its structure, and evaluate its antioxidant and immunomodulatory activities. Structural analysis revealed that CSP-A was composed of d-mannose, d-glucuronic acid and d-xylose in a molar ratio of 1:3:4 with molecular weight of 1.688 × 105 Da, owning 4 sugar residues of β-d-Manp-(1→, →4)-α-d-GlcpA-(1→, →2,4)-β-d-Xylp-(1→, and → 4)-β-d-Manp-(1 →. Congo red assay and microscopic characteristics showed that CSP-A in its solution may possess a helical conformation. In vitro experiments showed that CSP-A had moderate DPPH· and OH· scavenging activities. CSP-A also enhanced the phagocytosis ability of RAW 264.7 cells and prompted the release of NO, TNF-α, IL-6 and IL-1β from RAW 264.7 cells, which indicated CSP-A had immune regulation effect. This experiment provides scientific basis for further utilization and development of chia seeds, a kind of functional food.

An efficient protocol for preparing linear β-manno-oligosaccharides

Linear β-manno-oligosaccharides (l-β-MOS) are widely used to investigate oligo- and poly-saccharide structures and mannanolytic enzyme activities. l-β-MOS are also being used as prebiotic agents with potential bio-active properties. In this study, we developed an efficient protocol to prepare a series of l-β-MOS by hydrolyzing cassia gum (CG) using mannanolytic enzymes (endo-1,4-β-mannanase, α-galactosidases and β-glucosidases). By using medium pressure liquid chromatography (MPLC), we purified l-β-MOS with different degrees of polymerization (DPs). HPAEC-PAD, MALDI-TOF-MS and NMR studies confirmed that these l-β-MOS species ranged from 1,4-β-d-mannobiose to 1,4-β-d-mannononaose (DP 2-9) with >95% purity. Our results provide a robust approach to preparing l-β-MOS, thus enabling l-β-MOS to be further used in the fields of chemistry, life science, and nutritional food.

Production of manno-oligosaccharide from Gleditsia microphylla galactomannan using acetic acid and ferrous chloride

A novel and efficient method for manno-oligosaccharides (MOS) production has been proposed by utilizing Gleditsia microphylla galactomannan as the starting material. This co-operative hydrolysis using ferrous chloride (Fe²⁺) and acetic acid (HAc) effectively improved the MOS yield and meanwhile decreased the amount of monosaccharide and the 5-hydroxymethyl-furfural (HMF). The highest yields under the optimum conditions were 46.7% by HAc hydrolysis (5 M HAc at 130 °C for 120 min); 37.3% by Fe²⁺ hydrolysis (0.1 M Fe²⁺ at 150 °C for 120 min); and 51.4% by co-operative hydrolysis (2 M HAc, 0.05 M Fe²⁺ at 160 °C for 10 min). From the changes in the value of M/G (mannose/galactose) ratios, it was deduced that Fe²⁺ predominantly cleaves the main chain, and HAc assists in the breakage of the side chain, thus resulting in the high-efficient co-operative hydrolysis for the production of MOS.

Production and purification of mannan oligosaccharide with epithelial tight junction enhancing activity

Background

Mannanan oligosaccharide (MOS) is well-known as effective supplement food for livestock to increase their nutrients absorption and health status, but the structure and identification of bioactive MOS remain unclear. In this study, MOS production was accomplished, using enzymatic hydrolysis of pretreated coconut meal substrate with recombinant mannanase.

Methods

The mannanase gene was cloned from Bacillus subtilis cAE24, then expressed in BL21. Purified Mannanase exhibit stability over a wide range of pH and temperature from pH 6-8 and 4 °C to 70 °C, respectively. SEM analysis revealed that sonication could change the surface characteristic of copra meal, which gave better MOS yield, compared to untreated substrates. The separation and purification of each MOS were achieved using Biogel-P2 column chromatography. Determination of biological active MOS species was also investigated. T84 cells were cultured and treated with each of the purified MOS species to determine their tight junction enhancing activity.

Results

Scanning electron microscope imaging showed that pretreatment using sonication could disrupt the surface of copra meal better than grinding alone, which can improve the production of MOS. Pentamer of MOS (M5) significantly increased tight junction integration of T84 cells measured with TEER (p < 0.0001).

Galactomannan: a versatile biodegradable seed polysaccharide

Polysaccharides have been finding, in the last decades, very interesting and useful applications in the biomedical and, specifically, in the biopharmaceutical field. Galactomannans are a group of storage polysaccharides from various plant seeds that reserve energy for germination in the endosperm. There are four major sources of seed galactomannans: locust bean (Ceratonia siliqua), guar (Cyamopsis tetragonoloba), tara (Caesalpinia spinosa Kuntze), and fenugreek (Trigonella foenum-graecum L.). Through keen references of reported literature on galactomannans, in this review, we have described occurrence of various galactomannans, its physicochemical properties, characterization, applications, and overview of some major galactomannans.

Chemical characterization of the immunomodulating polysaccharide of Aloe vera L

The polysaccharide isolated by alcohol precipitation of Aloe vera mucilaginous gel was found to have a Man:Glc:Gal:GalA:Fuc:Ara:Xyl ratio of 120:9:6:3:2:2:1 with traces of Rha and GlcA. Linkage analysis of the endo-(1-->4)-beta-d-mannanase-treated sample yielded Manp-(1--> (approximately 26%), 4-Manp (approximately 53%), 2,4-Manp (approximately 3%), 3,4-Manp (approximately 1%), 4,6-Manp (approximately 1%), 4-Glcp (approximately 5%), 4-Xylp (approximately 1%), Xylp-(1--> (approximately 2%), Galp-(1--> (approximately 5%), and traces of 4,6-Galp and 3,6-Galp. Hydrolysis with strong acids produced a mixture of short oligosaccharides and an acid-resistant fraction containing greater relative fractions of Manp-(1-->, Araf-(1-->, Xylp-(1-->, and 4-Xylp than the bulk polysaccharide. NMR analysis of oligosaccharides generated by endo-(1-->4)-beta-D-mannanase and acid hydrolysis showed the presence of di-, tri-, and tetrasaccharides of 4-beta-Manp, beta-Glcp-(1-->4)-Man, beta-Glcp-(1-->4)-beta-Manp-(1-->4)-Man, and beta-Manp-(1-->4)-[alpha-Galp-(1-->6)]-Man, consistent with a backbone containing alternating -->4)-beta-Manp-(1--> and -->4)-beta-Glcp-(1--> residues in a approximately 15:1 ratio. Analysis of the sample treated sequentially with endo-(1-->4)-beta-d-mannanase and alpha-D-galactosidase showed that the majority of alpha-Galp-(1--> residues were linked to O-2, O-3, or O-6 of -->4)-beta-Manp-(1--> residues, with approximately 16 -->4)-beta-Manp-(1--> residues between side chains. Our data provide direct evidence of a previously proposed glucomannan backbone, but draw into question previously proposed side-chain structures.

Complexation of vanadium(V) oxyanions with hexopyranose- and mannopyranoseuronic acid-containing polysaccharides: stereochemical considerations

Carbohydrates containing galactopyranosyl and mannopyranosyl units with vicinal cis-diols were treated with NaVO(3) in D(2)O, and complexation was determined by (51)V NMR spectroscopy. Me alpha-Galp, Me beta-Galp (3,4-cis-diols), and Me alpha-Manp (2,3-cis-diol) complexed, but Me beta-Manp barely did so. This low degree of complexation also occurred with a beta-mannan containing alternate (1-->3)- and (1-->4)-linkages and an alginate having beta-ManpA blocks. In contrast, branched alpha-mannans complexed readily, although the (51)V resonances for one with side chains terminated with alpha-Manp-(1-->3)-alpha-Manp-(1--> differed from another with only alpha-Manp-(1-->2)-alpha-Manp-(1--> groups. The anomeric configuration of Me alpha-Galp and Me beta-Galp, each with 3,4-cis-diols remote from C-1, gave rise to three (51)V signals of complexes with similar shifts and proportions. The shifts of a galactomannan with terminal alpha-Galp-(1-->2)-alpha-Manp- were the same as those with alpha-Galp-(1-->6)-beta-Manp- groups, but fewer complexes were formed with the former structure, probably due to greater steric crowding of the vanadate esters. Most of the complexes gave rise to a signal in the delta515 region, consistent with the dimeric trigonal-bipyramidal structure.

Associative phenomena in galactomannan-deacetylated xanthan systems

The interaction between mesquite seed galactomannan (MSG; D-mannose to D-galactose ratio (M/G) approximately 1.1) and deacetylated xanthan (DX) in 5 mM NaCl leading to synergistic gel formation at 25 degrees C was investigated and compared with the far more studied system made of xanthan and locust bean gum (LBG; M/G approximately 3.5). Rheology and differential scanning calorimetry were used to measure temperatures of gel formation and transition enthalpy as a function of polymer composition, while circular dichroism was used to probe the conformation of DX in the LBG-DX system. MSG and DX associate at 25 degrees C with a well defined stoichiometry of 0.6:1.0 (w/w) at low ionic strength favouring the disordered coil state of DX. When LBG was used in place of MSG in water or 5 mM NaCl, two types of mechanisms of interpolymeric association are envisaged.

Real-time monitoring of enzymatic hydrolysis of galactomannans

Enzymatic hydrolysis was monitored in real-time using time dependent static light scattering (TDSLS) for a variety of galactomannans from native Brazilian flora. alpha-Galactosidase, which strips only the (1-6)alpha-D galactose side groups, and beta-mannanase, which hydrolyses only the (1-4)beta-D mannan main chain into oligosaccharides were investigated separately and in combination. The time-dependent signatures matched those describing side-chain stripping for galactosidase, whereas those resulting from the action of mannanase followed the signature typical of random backbone cleavage. Use of both enzymes together required that the TDSLS theory of polymer degradation be extended to the case where random backbone cleavage sites appear as side chains are stripped by the first enzyme. Whereas galactosidase allowed mannanase to access more backbone cleavage sites as time passes, leading to a higher degree of hydrolysis, there was no increase in rate constants. The distribution of random fragments in the case of mannanase digestion alone followed reasonably well the predictions for random cleavage of a single-strand polymer with a restricted number of cleavage sites. The fragment distributions were evaluated by size exclusion chromatography.

Role of galactomannan composition on the binary gel formation with xanthan

The influence of the galactomannan characteristic ratios (M/G) on the temperature of gelation (Tg) and the gel strength of mixtures of galactomannan with xanthan is reported. Two galactomannans were investigated: one highly substituted from the seeds of Mimosa scabrella (M/G = 11), and the other, less substituted, from the endosperm of Schizolobium parahybae, with (M/G = 30) [Ganter JLMS, Zawadzki-Baggio SF, Leitner SC, Sierakowski MR, Reicher F. J Carbohydr Chem 1993;12:753]. The xanthan:galactomannan systems (4:2 g l(-1), in 5 mM NaCl) showed a temperature of gel formation (Tg) of 24 degrees C for that of S. parahybae [Bresolin TMB, Milas M, Rinaudo M and Ganter JLMS. Int J Biol Macromol 1998;23:263] and 20 degrees C for the galactomannan of M. scabrella, determined by viscoelastic measurements and microcalorimetry. A Tg of 40-50 degrees C was found by Shatwell et al. [Shatwell KP, Sutherland IW, Ross-Murphy SB, Dea ICM. Carbohydr Polym 1991;14:29] for locust bean gum-LBG (M/G = 43). Lundin and Hermansson [Lundin L, Hermansson AM. Carbohydr Polym 1995;26:129] reported a difference of 13 degrees C for Tg of two LBG samples with M/G = 3 (40 degrees C) and 5 (53 degrees C), in mixtures with xanthan. It appears that the more substituted galactomannans have lower temperatures of gelation in the presence of xanthan. The mechanism of gelation depends also on the M/G ratio. For the lower values it involves only disordered xanthan chains in contrast to M/G ratios higher than 3. In addition, the presence of the galactomannan from M. scabrella increased slightly the temperature of the conformational change (Tm) of xanthan probably due to the ionic strength contribution of proteins (3.9%) present in the galactomannan. On the other hand, the galactomannans from S. parahybae, with 1.5% of proteins and M. scabrella, with 2.4% of protein, did not show this effect, the Tm of xanthan alone or in a mixture being practically unchanged.

Solution properties of the galactomannans extracted from the seeds of Caesalpinia pulcherrima and Cassia javanica: comparison with locust bean gum

The galactomannans from the seeds of Caesalpinia pulcherrima and Cassia javanica were extracted from the milled seeds in water at room temperature. Both products, as well as a commercial sample of locust bean gum (LBG), were purified by precipitation in isopropyl alcohol. The intrinsic viscosity determined for LBG, [eta] = 15.2 dl/g, was slightly higher than those for the other two galactomannans. The dependence of the specific viscosity at zero shear rate on the coil overlap parameter, C[eta], revealed a similar behaviour for the three galactomannans. A master curve was obtained with a critical concentration, C*, at C*[eta] = 3.3. The slope of the curve in the concentrated regime is higher than the values in the range of 3.9-6.6, obtained for the generalized behaviour of several random coil polysaccharides. Dynamic experiments showed that, at the concentrations studied, the behaviour of the galactomannans was typical of systems with predominant entanglement networks in the region between the terminal and plateau zones of frequency response. The correlation between dynamic and steady shear properties (Cox Merz rule) was satisfactory for the three galactomannans.

Galactomannan from the seeds of Mimosa scabrella: a scale-up process

In view of the wide industrial applications of galactomannans as a thickening agent, those of Mimosa scabrella (bracatinga), a leguminous tree abundant in Southern Brazil, are under investigation. Seeds of bracatinga were processed on a pilot plant scale in order to obtain its galactomannan. The process consisted of successive milling, enzyme inactivation, aqueous extraction, precipitation of polysaccharide, and drying and milling. The product was obtained in 20% yield, with characteristics similar to those obtained on the laboratory scale, namely mannose:galactose ratio (M:G) 1.1:1.0 and intrinsic viscosity. Considering the seed availability in the metropolitan regions of Curitiba, it should be possible to obtain 3000 ton/year of this polysaccharide.

High-field NMR as a technique for the determination of polysaccharide structures

NMR spectroscopy has played a developing role in the study of polysaccharide structures for over 30 years. Many new bacterial polysaccharide repeat unit structures have recently been published as a result of the application of modern NMR techniques. NMR can also be used to elucidate the structures of both regular and heterogeneous polysaccharides from fungal and plant sources, as well as complex glycosaminoglycans of animal origin. In addition to covalent structure, conformation and dynamics of polysaccharides are susceptible to NMR analysis, both in solution and in the solid state. Improvements in NMR technology with potential applications to polysaccharide studies hold promise for the future.