Versatile high resolution oligosaccharide microarrays for plant glycobiology and cell wall research.
Pedersen, H. L., Fangel, J. U., McCleary, B., Ruzanski, C., Rydahl, M. G., Ralet, M. C., Farkas, V., Von Schantz, L., Marcus, S. E., Andersen, M.C. F., Field, R., Ohlin, M., Knox, J. P., Clausen, M. H. & Willats, W. G. T. (2012). Journal of Biological Chemistry, 287(47), 39429-39438.
Microarrays are powerful tools for high throughput analysis, and hundreds or thousands of molecular interactions can be assessed simultaneously using very small amounts of analytes. Nucleotide microarrays are well established in plant research, but carbohydrate microarrays are much less established, and one reason for this is a lack of suitable glycans with which to populate arrays. Polysaccharide microarrays are relatively easy to produce because of the ease of immobilizing large polymers noncovalently onto a variety of microarray surfaces, but they lack analytical resolution because polysaccharides often contain multiple distinct carbohydrate substructures. Microarrays of defined oligosaccharides potentially overcome this problem but are harder to produce because oligosaccharides usually require coupling prior to immobilization. We have assembled a library of well characterized plant oligosaccharides produced either by partial hydrolysis from polysaccharides or by de novo chemical synthesis. Once coupled to protein, these neoglycoconjugates are versatile reagents that can be printed as microarrays onto a variety of slide types and membranes. We show that these microarrays are suitable for the high throughput characterization of the recognition capabilities of monoclonal antibodies, carbohydrate-binding modules, and other oligosaccharide-binding proteins of biological significance and also that they have potential for the characterization of carbohydrate-active enzymes.
Softwood hemicellulose-degrading enzymes from Aspergillus niger: Purification and properties of a β-mannanase.
Ademark, P., Varga, A., Medve, J., Harjunpää, V., Drakenberg, T., Tjerneld, F. & Stålbrand, H. (1998). Journal of Biotechnology, 63(3), 199-210.
The enzymes needed for galactomannan hydrolysis, i.e. β-mannanase, α-galactosidase and β-mannosidase, were produced by the filamentous fungus Aspergillus niger. The β-mannanase was purified to electrophoretic homogeneity in three steps using ammonium sulfate precipitation, anion-exchange chromatography and gel filtration. The purified enzyme had an isoelectric point of 3.7 and a molecular mass of 40 kDa. Ivory nut mannan was degraded mainly to mannobiose and mannotriose when incubated with the β-mannanase. Analysis by 1H NMR spectroscopy during hydrolysis of mannopentaose showed that the enzyme acts by the retaining mechanism. The N-terminus of the purified A. niger β-mannanase was sequenced by Edman degradation, and comparison with Aspergillus aculeatus β-mannanase indicated high identity. The enzyme most probably lacks a cellulose binding domain since it was unable to adsorb on cellulose.
Protein release from galactoglucomannan hydrogels: influence of substitutions and enzymatic hydrolysis by β-mannanase.
Roos, A. A., Edlund, U., Sjoberg, J., Albertsson, A. C. & Stålbrand, H. (2008). Biomacromolecules, 9(8), 2104-2110.
O-Acetyl-galactoglucomannan (AcGGM) is the major soft-wood hemicellulose. Structurally modified AcGGM and hydrogels of AcGGM were prepared. The degree of substitution (DS) of AcGGM was modified enzymatically with α-galactosidase, and chemically with an acrylate derivative, 2-hydroxyethylmethacrylate (HEMA). The hydrolysis of AcGGM with β-mannanase was shown to increase with decreasing DS. AcGGM hydrogels were prepared from chemically modified AcGGM with varying DS of HEMA. Bovine serum albumin (BSA) was encapsulated in hydrogels. A spontaneous burst release of BSA was decreased with increased DS of HEMA. The addition of β-mannanase significantly enhanced the BSA release from hydrogels with a DS of 0.36, reaching a maximum of 95% released BSA after eight hours compared to 60% without enzyme. Thus, both the pendant group composition and the enzyme action are valuable tools in the tailoring of hydrogel release profiles of potential interest for intestine drug delivery.
Mannotriose regulates learning and memory signal transduction in the hippocampus.
Zhang, L., Dai, W., Zhang, X., Gong, Z. & Jin, G. (2013). Neural Regeneration Research, 8(32), 3020-3026.
Rehmannia is a commonly used Chinese herb, which improves learning and memory. However, the crucial components of the signal transduction pathway associated with this effect remain elusive. Primary hippocampal neurons were cultured in vitro, insulted with high-concentration (1 × 10-4 mol/L) corticosterone, and treated with 1 × 10-4 mol/L mannotriose. Thiazolyl blue tetrazolium bromide assay and western blot analysis showed that hippocampal neuron survival rates and protein levels of glucocorticoid receptor, serum and glucocorticoid-regulated protein kinase, and brain-derived neurotrophic factor were all dramatically decreased after high-concentration corticosterone-induced injury. This effect was reversed by mannotriose, to a similar level as RU38486 and donepezil. Our findings indicate that mannotriose could protect hippocampal neurons from high-concentration corticosterone-induced injury. The mechanism by which this occurred was associated with levels of glucocorticoid receptor protein, serum and glucocorticoid-regulated protein kinase, and brain-derived neurotrophic factor.
Operational and storage stability of neutral β-mannanase from Bacillus licheniformis.
Zhang, J., He, M. & He, Z. (2002). Biotechnology Letters, 24(19), 1611-1613.
The stability of neutral β-mannanase from Bacillus licheniformis during operation and storage was investigated. The enzyme activity decreased by 70% with a hydrolysate of glucomannan at 20 g l-1 over 30 min at 25°C. In an enzymatic membrane reactor operated at 50°C after 24 h, the loss of enzyme activities were 23% and 9% in the absence/presence of the substrate. The residual activities of the enzyme were 21% and 90%, respectively, when stored in 30% (v/v) glycerol solution and in solid state at 4°C after one year.
Substrate Specificities of α-Galactosidase from Rice.
Li, S. H., Zhu, M. P. & Li, T. P. (2011). Advanced Materials Research, 183, 447-451.
The α-galactosidase from rice cleaved not only α-D-galactosyl residues from the non-reducing end of substrates such as melibiose, raffinose and stachyose, but also liberated the terminal galactosyl residues attached O-6 position of the reducing-end mannosyl residue in mannobiose and mannotriose. In addition, the enzyme tore off the stubbed galactosyl residues attached inner-mannosyl residues in mannopentaose. It also could catalyze efficient degalactosylation of galactomannans, such as guar gum and locust bean gum.
Purification and characterization of two β-mannanases from Trichoderma reesei.
Stålbrand, H., Siika-aho, M., Tenkanen, M. & Viikari, L. (1993). Journal of Biotechnology, 29(3), 229-242.
Five enzymes with mannanase activity were separated from Trichoderma reesei culture filtrate using analytical isoelectric focusing and subsequently detected with the zymogram technique. The crude enzymes had isoelectric points in the range of 3.6–6.5. Two of the mannanases with pI values of 4.6 and 5.4 were purified using ion-exchange chromatography, affinity chromatography and chromatofocusing. The molecular weights determined with SDS-PAGE were 51 000 (mannanase pI 4.6) and 53 000 (mannanase pI 5.4). The two enzymes had similar properties with respect to pH optimae and pH stabilities. Both mannanases hydrolyzed ivory nut mannan mainly to mannotriose and mannobiose. The specific activities (against locust bean gum) of the purified enzymes were 1860 and 1430 nkat mg-1 for the pI 4.6 and pI 5.4 mannanases, respectively.
Fractionation of extracted hemicellulosic saccharides from Pinus pinaster wood by multistep membrane processing.
González-Muñoz, M. J., Rivas, S., Santos, V. & Parajó, J. C. (2013). Journal of Membrane Science, 428, 281-289.
Hemicelluloses of Pinus pinaster wood were selectively separated from cellulose and lignin by reaction with hot, compressed water (autohydrolysis) under optimized conditions. The reaction liquor contained polymeric or oligomeric hemicellulose saccharides (POHS, accounting jointly for 69.6% of the dissolved wood fraction), followed by monosaccharides (accounting for 20.0% of the non-volatile compounds), and non-saccharide compounds. For concentration, purification and fractionation purposes, liquors from hydrothermal processing were subjected to consecutive steps of diafiltration and concentration using membranes of 10, 5, 3, 1 and 0.3 kDa molar mass cut-off. Samples from selected process streams were characterized by chromatographic and spectrometric methods. The experimental results provided information on the separation and refining effects achieved by the various membrane processing steps, which affect the technological properties of products.
β-Mannanolytic system of Aureobasidium pullulans.
Kremnický, L. & Biely, P. (1997). Archives of Microbiology, 167(6), 350-355.
A xylanolytic yeast strain Aureobasidium pullulans NRRL Y 2311-1, was found to produce all enzymes required for complete degradation of galactomannan and galactoglucomannan. The enzymes differed in function and cellular localization: endo-β-1,4-mannanase was secreted into the culture fluid, β-mannosidase was strictly intracellular, and α-galactosidase and β-glucosidase were found both extracellularly and intracellularly. Among these enzyme components, only extracellular β-mannanase and intracellular β-mannosidase were inducible. The production of β-mannanase and β-mannosidase was 10- to 100-fold higher in galactomannan medium than in medium with one of the other carbon sources. β-mannanase and β-mannosidase were coinduced in glucose-grown cells by galactomannan, galactoglucomannan, and β-1,4-manno-oligosaccharides. The natural inducer of extracellular β-mannanase and intracellular β-mannosidase appeared to be β-1,4-mannobiose. Synthesis of both enzymes was completely repressed by glucose, mannose, or galactose. The synthetic glycoside methyl β-D-mannopyranoside served as a nonmetabolizable inducer of both β-mannosidase and β-mannanase.
The modular architecture of Cellvibrio japonicus mannanases in glycoside hydrolase families 5 and 26 points to differences in their role in mannan degradation.
Hogg, D., Pell, G., Dupree, P., Goubet, F., Martin-Orue, S., Armand, S. & Gilbert, H. (2003). Biochem. J, 371(3), 1027-1043.
β-1,4-Mannanases (mannanases), which hydrolyse mannans and glucomannans, are located in glycoside hydrolase families (GHs) 5 and 26. To investigate whether there are fundamental differences in the molecular architecture and biochemical properties of GH5 and GH26 mannanases, four genes encoding these enzymes were isolated from Cellvibrio japonicus and the encoded glycoside hydrolases were characterized. The four genes, man5A, man5B, man5C and man26B, encode the mannanases Man5A, Man5B, Man5C and Man26B, respectively. Man26B consists of an N-terminal signal peptide linked via an extended serine-rich region to a GH26 catalytic domain. Man5A, Man5B and Man5C contain GH5 catalytic domains and non-catalytic carbohydrate-binding modules (CBMs) belonging to families 2a, 5 and 10; Man5C in addition contains a module defined as X4 of unknown function. The family 10 and 2a CBMs bound to crystalline cellulose and ivory nut crystalline mannan, displaying very similar properties to the corresponding family 10 and 2a CBMs from Cellvibrio cellulases and xylanases. CBM5 bound weakly to these crystalline polysaccharides. The catalytic domains of Man5A, Man5B and Man26B hydrolysed galactomannan and glucomannan, but displayed no activity against crystalline mannan or cellulosic substrates. Although Man5C was less active against glucomannan and galactomannan than the other mannanases, it did attack crystalline ivory nut mannan. All the enzymes exhibited classic endo-activity producing a mixture of oligosaccharides during the initial phase of the reaction, although their mode of action against manno-oligosaccharides and glucomannan indicated differences in the topology of the respective substrate-binding sites. This report points to a different role for GH5 and GH26 mannanases from C. japonicus. We propose that as the GH5 enzymes contain CBMs that bind crystalline polysaccharides, these enzymes are likely to target mannans that are integral to the plant cell wall, while GH26 mannanases, which lack CBMs and rapidly release mannose from polysaccharides and oligosaccharides, target the storage polysaccharide galactomannan and manno-oligosaccharides.
Two-stage hot-water extraction of galactoglucomannans from spruce wood.
Pranovich, A., Holmbom, B. & Willför, S. (2016). Journal of Wood Chemistry and Technology, 36(2), 140-156.
In order to preserve the polymeric structure and the acetylation degree of extracted galactoglucomannans and, at the same time, achieve high yield, ground spruce wood was subjected to a series of sequential two-stage extractions with an Accelerated Solvent Extraction (ASE) apparatus using plain water at 170 deg;C. The total combined extraction time was one hour in all the extractions. The total yield of the dissolved material after 1 h extraction was almost the same, about 25% of the wood, irrespective of the time ratios between the first and the second extractions. The yield of hemicellulose high polymers with the weight average molar mass of 8-10 kDa during the first extraction had a maximum at 20 min extraction time, amounting to about 7% on dry wood basis, and comprising about half of the total extract. Along with the progress of the extraction, the molar mass of the hemicelluloses decreased and hemicellulose-derived low polymers with the weight average molar mass of 6-2 kDa became dominating. The extracted substances were fractionated, mainly according to their molar mass, by sequential precipitation with ethanol, acetone, and methyl tert-butyl ether (MTBE). The hemicelluloses with some amount of pectins comprised 83-90% of the precipitated polymeric material and the content of galactoglucomannans was about 80%.
A comparison between a yeast cell wall extract (Bio-Mos®) and palm kernel expeller as mannan-oligosac-charides sources on the performance and ileal microbial population of broiler chickens.
Navidshad, B., Liang, J. B., Jahromi, M. F., Akhlaghi, A. & Abdullah, N. (2015). Italian Journal of Animal Science, 14(1), 3452.
The present study was conducted to determine the effect of a yeast cell wall extract (Bio-Mos) and palm kernel expeller (PKE) on the performance, nutrient digestibility, and ileal bacteria population of broiler chickens. A total of 60 1-d-old male broiler chicks (Cobb 500) were fed one of the 3 isonitrogenous and isocaloric diet including a control diet, or a control diet supplemented with 2 g/kg Bio-Mos (1-42 d), and for the third group, the control diet at 1-28 d following a diet containing 200 g/kg of an enzymatically-treated PKE at 29-42 d. The weight gains of birds fed the PKE containing diet (96.17 g/d) were less than other groups (109.10 and 104.42 g/d for the Bio-Mos and control diet, respectively) (P<0.05). Dietary inclusion of PKE increased bird’s feed intake (214.45 g/d) and feed conversion ratio (FCR) (2.23) than the Bio-Mos diet (194.87 and 1.79 g/d for feed intake and FCR, respectively) (P<0.05). The PKE diet had lower digestibility coefficients for dry matter (83.37%), ash and crude protein (78.63%) than the PKE free diets (P<0.05). As a ratio of the ileal total bacteria, there were no differences in the ileal population of Lactobacilli and Enterococcus genus or Enterobacteriaceae among the experimental groups (P>0.05), but the birds fed PKE or Bio-Mos containing diets had a lower population of Escherichia colithan the control group (P<0.05). The results showed that PKE potentially has a prebiotic property for chicken; however, a 200 g/kg dietary inclusion rate of PKE is not commercially recommendable because of its negative effects on the nutrients digestibility.
A Novel β-1, 4-mannanase Isolated from Paenibacillus polymyxa KT551.
Hori, K., Kawabata, Y., Nakazawa, Y., Nishizawa, M. & Toeda, K. (2014). Food Science and Technology Research, 20(6), 1261-1265.
A β-1,4-mannanase producing bacterium was isolated from soil collected in Akita Prefecture, Japan. The bacterium was identified as Paenibacillus polymyxa KT551 and was shown to produce a novel β-1,4-mannanase. The novelty of the enzyme was established by its N-terminal amino acid sequence, molecular weight and isoelectric point. The isolated β-1,4-mannanase showed activity against mannotetraose, mannopentaose and mannohexaose to produce mannobiose, mannotriose and mannotetraose. However, the enzyme exhibited no activity against mannobiose and mannotriose. Moreover, the crude enzyme preparation of the bacterium had no or minimal β-mannosidase or α-galactosidase activity. Therefore, the enzyme preparation from P. polymyxa KT551 holds potential for the efficient production of mannooligosaccharides from natural resources of galactomannans.
Biochemical characterization of an acidophilic β-mannanase from Gloeophyllum trabeum CBS900. 73 with significant transglycosylation activity and feed digesting ability.
Wang, C., Zhang, J., Wang, Y., Niu, C., Ma, R., Wang, Y., Bai, Y., Luo, H. & Yao, B. (2016). Food Chemistry, 197, 474-481.
Acidophilic β-mannanases have been attracting much attention due to their excellent activity under extreme acidic conditions and significant industrial applications. In this study, a β-mannanase gene of glycoside hydrolase family 5, man5A, was cloned from Gloeophyllum trabeum CBS900.73, and successfully expressed in Pichia pastoris. Purified recombinant Man5A was acidophilic with a pH optimum of 2.5 and exhibited great pH adaptability and stability (>80% activity over pH 2.0-6.0 and pH 2.0-10.0, respectively). It had a high specific activity (1356 U/mg) against locust bean gum, was able to degrade galactomannan and glucomannan in a classical four-site binding mode, and catalyzed the transglycosylation of mannotetrose to mannooligosaccharides with higher degree of polymerization. Besides, it had great resistance to pepsin and trypsin and digested corn-soybean meal based diet in a comparable way with a commercial β-mannanase under the simulated gastrointestinal conditions of pigs. This acidophilic β-mannanase represents a valuable candidate for wide use in various industries, especially in the feed.
An Aspergillus nidulans GH26 endo-β-mannanase with a novel degradation pattern on highly substituted galactomannans.
von Freiesleben, P., Spodsberg, N., Blicher, T. H., Anderson, L., Jørgensen, H., Stålbrand, H., Meyer, A. S. & Krogh, K. B. (2016). Enzyme and Microbial Technology, 83, 68-77.
The activity and substrate degradation pattern of a novel Aspergillus nidulans GH26 endo-β-mannanase (AnMan26A) was investigated using two galactomannan substrates with varying amounts of galactopyranosyl residues. The AnMan26A was characterized in parallel with the GH26 endomannanase from Podospora anserina (PaMan26A) and three GH5 endomannanases from A. nidulans and Trichoderma reesei (AnMan5A, AnMan5C and TrMan5A). The initial rates and the maximal degree of enzymatically catalyzed conversion of locust bean gum and guar gum galactomannans were determined. The hydrolysis product profile at maximal degree of conversion was determined using DNA sequencer-Assisted Saccharide analysis in High throughput (DASH). This is the first reported use of this method for analyzing galactomannooligosaccharides. AnMan26A and PaMan26A were found to have a novel substrate degradation pattern on the two galactomannan substrates. On the highly substituted guar gum AnMan26A and PaMan26A reached 35-40% as their maximal degree of conversion whereas the three tested GH5 endomannanases only reached 8-10% as their maximal degree of conversion. α-Galactosyl-mannose was identified as the dominant degradation product resulting from AnMan26A and PaMan26A action on guar gum, strongly indicating that these two enzymes can accommodate galactopyranosyl residues in the -1 and in the +1 subsite. The degradation of α-64-63-di-galactosyl-mannopentaose by AnMan26A revealed accommodation of galactopyranosyl residues in the -2, -1 and +1 subsite of the enzyme. Accommodation of galactopyranosyl residues in subsites -2 and +1 has not been observed for other characterized endomannanases to date. Docking analysis of galactomannooligosaccharides in available crystal structures and homology models supported the conclusions drawn from the experimental results. This newly discovered diversity of substrate degradation patterns demonstrates an expanded functionality of fungal endomannanases, than hitherto reported.
A novel thermostable GH5_7 β-mannanase from Bacillus pumilus GBSW19 and its application in manno-oligosaccharides (MOS) production.
Zang, H., Xie, S., Wu, H., Wang, W., Shao, X., Wu, L., Rajer, F. U. & Gao, X. (2015). Enzyme and microbial technology, 78, 1-9.
A novel thermostable mannanase from a newly isolated Bacillus pumilus GBSW19 has been identified, expressed, purified and characterized. The enzyme shows a structure comprising a 28 amino acid signal peptide, a glycoside hydrolase family 5 (GH5) catalytic domain and no carbohydrate-binding module. The recombinant mannanase has molecular weight of 45 kDa with an optimal pH around 6.5 and is stable in the range from pH 5-11. Meanwhile, the optimal temperature is around 65°C, and it retains 50% relative activity at 60°C for 12 h. In addition, the purified enzyme can be activated by several ions and organic solvents and is resistant to detergents. Bpman5 can efficiently convert locus bean gum to mainly M2, M3 and M5, and hydrolyze manno-oligosaccharides with a minimum DP of 3. Further exploration of the optimum condition using HPLC to prepare oligosaccharides from locust bean gum was obtained as 10 mg/ml locust bean gum incubated with 10 U/mg enzyme at 50°C for 24 h. By using this enzyme, locust bean gum can be utilized to generate high value-added oligosaccharides with a DP of 2-6.
High-level expression and characterization of a thermophilic β-mannanase from Aspergillus niger in Pichia pastoris.
Yu, S., Li, Z., Wang, Y., Chen, W., Fu, L., Tang, W., Chen, C., Liu, Y., Zhang, X. & Ma, L. (2015). Biotechnology Letters, 37(9), 1853-1859.
Objectives: A novel, high-level expression, thermostable mannan endo-1,4-β-mannosidase is urgently needed for industrial applications. Results: The mannan endo-1,4-β-mannosidase gene (MAN) from Aspergillus niger CBS 513.88 was optimized based on the codon usage bias in Pichia pastoris and synthesized by overlapping PCR to produce MAN-P. It was expressed in P. pastoris GS115 from a constitutive expression vector pHBM-905 M. MAN-P reached 594 mg/l in shake-flasks after 192 h induction. On production in a 5 l fermenter, the yield of MAN-P reached ~3.5 mg/ml and the enzyme activity was 1612 U/ml. The enzyme exhibited a maximum activity of 3049 U/ml at 80°C and retained 60 % enzyme activity at 80°C for 2 h. The pH optimum was 4.5 and the enzyme was stable over the pH range 1.5-11. Conclusion: The thermostability of MAN-P is higher than other known fungal mannanases and the expression and thermophilic properties make MAN-P useful for industrial applications.
From native malt to pure starch-Development and characterization of a purification procedure for modified starch.
Rittenauer, M., Kolesnik, L., Gastl, M. & Becker, T. (2016). Food Hydrocolloids, 56, 50-57.
Starch characteristics influence the gelatinization process, which is an important prerequisite for the saccharification required in many industrial processes. In order to determine these characteristics in barley malt, an adapted purification procedure allowing to preserve the native starch composition and simultaneously segregating the amylolytic enzymes which were formed during the germination is indispensable. Therefore, this research aimed to develop a method based on a combination of dry milling, micro-sieving and density gradient centrifugation. The impact on the starch characteristics was evaluated for three germinated barley varieties. The purified starches showed starch contents greater than 90% and proteins contents less than 0.4%. Yields ranged from 40.3 to 48.6%, depending on the variety. Considering the starch properties, the amylose/amylopectin ratio was not modified during the purification. The circularity of the granules as well as the ratio of A- and B-type granules remained constant. The particle size distribution of A-granules was not shifted, B-granules with a specific diameter of 5-10 µm were slightly reduced in dependency of the native granule composition. The highest impact could be observed on the amylolytic enzymes, which were completely segregated regardless of their initial value. The standard deviation of repeatability was less than 5%, except for the determination of B-type particle size distribution (7%). The newly developed procedure supplements existing isolation methods of unmalted grains by enabling the purification of germinated barley in a reproducible manner, without altering the native starch properties and by providing pure starch free of amylolytic activity.
An extremely alkaline mannanase from Streptomyces sp. CS428 hydrolyzes galactomannan producing series of mannooligosaccharides.
Pradeep, G. C., Cho, S. S., Choi, Y. H., Choi, Y. S., Jee, J. P., Seong, C. N. & Yoo, J. C. (2016). World Journal of Microbiology and Biotechnology, 32(5), 1-9.
An alkaline-thermostable mannanase from Streptomyces sp. CS428 was produced, purified, and biochemically characterized. The extracellular mannanase (Mn428) was purified to homogeneity with 12.4 fold, specific activity of 2406.7 U/mg, and final recovery of 37.6 %. The purified β-mannanase was found to be a monomeric protein with a molecular mass of approximately 35 kDa as analyzed by SDS-PAGE and zymography. The first N-terminal amino acid sequences of mannanase enzyme were HIRNGNHQLPTG. The optimal temperature and pH for enzyme were 60°C and 12.5, respectively. The mannanase activities were significantly affected by the presence of metal ions, modulators, and detergents. Km and Vmax values of Mn428 were 1.01 ± 3.4 mg/mL and 5029 ± 85 µmol/min mg, respectively when different concentrations (0.6-10 mg/mL) of locust bean gum galactomannan were used as substrate. The substrate specificity of enzyme showed its highest specificity towards galactomannan which was further hydrolyzed to produce mannose, mannobiose, mannotriose, and a series of mannooligosaccharides. Mannooligosaccharides can be further converted to ethanol production, thus the purified β-mannanase isolated from Streptomyces sp. CS428 was found to be attractive for biotechnological applications.
Transglycosylation reactions, a main mechanism of phenolics incorporation in coffee melanoidins: inhibition by Maillard reaction.
Moreira, A. S., Nunes, F. M., Simões, C., Maciel, E., Domingues, P., Domingues, M. R. M. & Coimbra, M. A. (2017). Food Chemistry, 227, 422-431.
Under roasting conditions, polysaccharides depolymerize and also are able to polymerize, forming new polymers through non-enzymatic transglycosylation reactions (TGRs). TGRs can also occur between carbohydrates and aglycones, such as the phenolic compounds present in daily consumed foods like coffee. In this study, glycosidically linked phenolic compounds were quantified in coffee melanoidins, the polymeric nitrogenous brown-colored compounds formed during roasting, defined as end-products of Maillard reaction. One third of the phenolics present were in glycosidically linked form. In addition, the roasting of solid state mixtures mimicking coffee beans composition allowed the conclusion that proteins play a regulatory role in TGRs extension and, consequently, modulate melanoidins composition. Overall, the results obtained showed that TGRs are a main mechanism of phenolics incorporation in melanoidins and are inhibited by amino groups through Maillard reaction.