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Chapter 1: Theory of endo-1, 4-Beta-D-Xylanase Assay Procedure
Chapter 2: Buffers & Reagents
Chapter 3: Assay Procedure
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|Content:||200 Tablets or 1,000 Tablets|
|Stability:||> 10 years under recommended storage conditions|
|Substrate For (Enzyme):||endo-1,4-β-Xylanase|
|Reproducibility (%):||~ 5%|
|Method recognition:||RACI Standard Method|
High purity dyed and crosslinked Xylazyme AX (60 mg tablets) for the measurement of enzyme activity, for research, biochemical enzyme assays and in vitro diagnostic analysis.
For the assay of endo-1,4-β-D-xylanase. Containing AZCL-arabinoxylan (wheat).
Please note the video above shows the protocol for assay of endo-xylanase using xylazyme tablets. The procedure for the assay of endo-1,4-β-Xylanase using Xylazyme AX Tablets is equivalent to this.
Browse all available enzyme tablet tests.
Validation of Methods
(Trichoderma longibrachiatum) E-XYLAA - endo-1,4-β-Xylanase (Aspergillus aculeatus) E-XYAN4 - endo-1,4-β-Xylanase M4 (Aspergillus niger) E-XYRU6 - endo-1,4-β-Xylanase (rumen microorganism) E-XYNAP - endo-1,4-β-Xylanase (Aeromonas punctata) E-XYNBS - endo-1,4-β-Xylanase
(Bacillus stearothermophilus T6) E-XYNACJ - endo-1,4-β-Xylanase (Cellvibrio japonicus) E-XYNBCM - endo-1,4-β-Xylanase (Cellvibrio mixtus) E-XYLNP - endo-1,4-β-Xylanase (Neocallimastix patriciarum) E-XYLATM - endo-1,4-β-Xylanase (Thermotoga maritima) E-BXSR-1KU - β-D-Xylosidase (Selenomonas ruminantium) E-BXSEBP - β-Xylosidase (Bacillus pumilus)
Mangan, D., Cornaggia, C., Liadova, A., McCormack, N., Ivory, R., McKie, V. A., Ormerod, A. & McCleary, D. V. (2017). Carbohydrate Research, 445, 14-22.
endo-1,4-β-Xylanase (EC 22.214.171.124) is employed across a broad range of industries including animal feed, brewing, baking, biofuels, detergents and pulp (paper). Despite its importance, a rapid, reliable, reproducible, automatable assay for this enzyme that is based on the use of a chemically defined substrate has not been described to date. Reported herein is a new enzyme coupled assay procedure, termed the XylX6 assay, that employs a novel substrate, namely 4,6-O-(3-ketobutylidene)-4-nitrophenyl-β-45-O-glucosyl-xylopentaoside. The development of the substrate and associated assay is discussed here and the relationship between the activity values obtained with the XylX6 assay versus traditional reducing sugar assays and its specificity and reproducibility were thoroughly investigated.Hide Abstract
Van den Broek, L. A. M., Lloyd, R. M., Beldman, G., Verdoes, J. C., McCleary, B. V. & Voragen, A. G. J. (2005). Applied Microbiology and Biotechnology, 67(5), 641-647.
Arabinoxylan arabinofuranohydrolase-D3 (AXHd3) from Bifidobacterium adolescentis releases only C3-linked arabinose residues from double-substituted xylose residues. A genomic library of B. adolescentis DSM20083 was screened for the presence of the axhD3 gene. Two plasmids were identified containing part of the axhD3 gene. The nucleotide sequences were combined and three open reading frames (ORFs) were found. The first ORF showed high homology with xylanases belonging to family 8 of the glycoside hydrolases and this gene was designated xylA. The second ORF was the axhD3 gene belonging to glycoside hydrolase family 43. The third (partial) ORF coded for a putative carboxylesterase. The axhD3 gene was cloned and expressed in Escherichia coli. Several substrates were employed in the biochemical characterization of recombinant AXHd3. The enzyme showed the highest activity toward wheat arabinoxylan oligosaccharides. In addition, β-xylanase from Trichoderma sp. was able to degrade soluble wheat arabinoxylan polymer to a higher extent, after pretreatment with recombinant AXHd3. Arabinoxylan oligosaccharides incubated with a combination of recombinant AXHd3 and an α-L-arabinofuranosidase from Aspergillus niger did not result in a higher maximal release of arabinose than incubation with these enzymes separately.Hide Abstract
Optimising the response.
Acamovic, T. & McCleary, B. V. (1996). Feed Mix, 4, 14-19.
A fine balance exists between enzyme activity and the adverse effects associated with feed processing. Accurate estimation of enzyme activity in the feed is a pre-requisite to optimising the response.Hide Abstract
Measurement of endo-1,4-β-D-xylanase.
McCleary, B. V. (1992). “Xylans and Xylanases”, (J. Visser, G. Beldman, M. A. Kusters-van Someron and A. G. J. Voragen, Eds.), Progress in Biotechnology, Vol. 7, Elsevier, Science Publishers B. V., pp. 161-169.
Various procedures for the measurement of xylanase in fermentation broths, commercial enzyme mixtures, bread improver mixtures and feed samples are described. Problems associated with the routine use of reducing-sugar based methods axe highlighted and the advantages and limitations of viscometric and dye-labelled substrate procedures for measurement of trace levels of activity in feed samples are discussed.Hide Abstract
McCleary, B. V. (1991). “Enzymes in Biomass Conversion”, (M. E. Himmel and G. F. Leatham, Eds.), ACS Symposium Series, 460, Chapter 34, pp. 437-449. American Chemical Society, Washington.
Hydrolysis of mannan-type polysaccharides by β-mannanase is dependent on substitution on and within the main-chain as well as the source of the β-mannanase employed. Characterisation of reaction products can be used to define the sub-site binding requirements of the enzymes as well as the fine-structures of the polysaccharides. Action of endo-arabinanase and endo-galactanase on arabinans and arabinogalactans is described. Specific assays for endo-arabinanase and arabinan (in fruit-juice concentrates) are reported.Hide Abstract
Measurement of polysaccharide degrading enzymes using chromogenic and colorimetric substrates.
McCleary, B. V. (1991). Chemistry in Australia, September, 398-401.
Enzymic degradation of carbohydrates is of major significance in the industrial processing of cereals and fruits. In the production of beer, barley is germinated under well defined conditions (malting) to induce maximum enzyme synthesis with minimum respiration of reserve carbohydrates. The grains are dried and then extracted with water under controlled conditions. The amylolytic enzymes synthesized during malting, as well as those present in the original barley, convert the starch reserves to fermentable sugars. Other enzymes act on the cell wall polysaccharides, mixed-linkage β-glucan and arabinoxylan, reducing the viscosity and thus aiding filtration, and reducing the possibility of subsequent precipitation of polymeric material. In baking, β-amylase and α-amylase give controlled degradation of starch to fermentable sugars so as to sustain yeast growth and gas production. Excess quantities of α-amylase in the flour result in excessive degradation of starch during baking which in turn gives a sticky crumb texture and subsequent problems with bread slicing. Juice yield from fruit pulp is significantly improved if cell-wall degrading enzymes are used to destroy the three-dimensional structure and water binding capacity of the pectic polysaccharide components of the cell walls. Problems of routine and reliable assay of carbohydrate degrading enzymes in the presence of high levels of sugar compounds are experienced with such industrial process.Hide Abstract
Microbial succession during wheat bran fermentation and colonisation by human faecal microbiota as a result of niche diversification.
De Paepe, K., Verspreet, J., Courtin, C. M. & Van de Wiele, T. (2020). The ISME Journal, 14(2), 584-596.
The human gut can be viewed as a flow-through system with a short residence time, a high turnover rate and a spatial gradient of physiological conditions. As a consequence, the gut microbiota is exposed to highly fluctuating environmental determinants presented by the host and diet. Here, we assessed the fermentation and colonisation of insoluble wheat bran by faecal microbiota of three individuals at an unprecedented sampling intensity. Time-resolved 16S rRNA gene amplicon sequencing, revealed a dynamic microbial community, characterised by abrupt shifts in composition, delimiting states with a more constant community, giving rise to a succession of bacterial taxa alternately dominating the community over a 72 h timespan. Early stages were dominated by Enterobacteriaceae and Fusobacterium species, growing on the carbohydrate-low, protein rich medium to which wheat bran was supplemented. The onset of wheat bran fermentation, marked by a spike in short chain fatty acid production with an increasing butyrate proportion and an increased endo-1,4-β-xylanase activity, corresponded to donor-dependent proportional increases of Bacteroides ovatus/stercoris, Prevotella copri and Firmicutes species, which were strongly enriched in the bran-attached community. Literature and database searches provided novel insights into the metabolic and growth characteristics underlying the observed succession and colonisation, illustrating the potency of a time-resolved analysis to increase our understanding of gut microbiota dynamics upon dietary modulations.Hide Abstract
Variation in milk production, fat, protein, and lactose responses to exogenous feed enzymes in dairy cows.
Rossow, H. A., Golder, H. M., & Lean, I. J. (2020). Applied Animal Science, 36(3), 292-307.
Objective: Our objectives were to evaluate milk production and constituent responses to changes in the diet for pens of cows over time and whether differences in response were attributable to fibrolytic enzymes and dairy. Materials and Methods: A multiherd trial used 7,507 cows in 8 control and enzyme-treated (750 mL/t of DM feed) replicates (16 pens) on 3 dairies. Feed composition and milk production and constituents by pen (n = 12) were analyzed weekly. Time-series cross-correlation estimates by pen of feed component intakes (kg/d) and milk responses were pooled to produce effect size (ES) estimates. Results and Discussion: We observed differences between treatment and control pens for soluble protein (ES = 0.249) in the same week, acid detergent–insoluble CP (ES = 0.293) and lignin (ES = 0.237) 1 wk before with milk protein percentage, and acid detergent–insoluble CP (ES = 0.276) and lignin (ES = 0.246) 1 wk before with milk protein yield. These differences are consistent with enzymes improving feed digestibility, particularly for protein and fiber fractions. Differences in production responses to intake of feed components among dairies were observed. More significant and larger differences occurred among dairies than for treatments. The dairy that increased milk production most with treatment had an estimated MP excess from the diet, whereas the least responsive had an estimated MP-deficit diet and was the highest producing. Implications and Applications: We provide evidence for variability in enzyme response and that changes in dietary feed components influence production outcomes immediately and up to 3-wk later.Hide Abstract
Effect of Vacuum Steam Treatment of Hard Red Spring Wheat on Flour Quality and Reduction of Escherichia coli O121 and Salmonella Enteritidis PT 30.
Snelling, J., Malekmohammadi, S., Bergholz, T. M., Ohm, J. & Simsek, S. (2020). Journal of Food Protection, 83(5), 836-843.
Recent outbreaks traced to contaminated flour have created a need in the milling industry for a process that reduces pathogens in wheat while maintaining its functional properties. Vacuum steam treatment is a promising technology for treatment of low-moisture foods. Traditional thermal treatment methods can compromise wheat functionality due to high temperatures; thus, maintaining the functional quality of the wheat protein was critical for this research. The objective of this study was to evaluate the effect of vacuum steam treatment of hard red spring (HRS) wheat kernels on final flour quality and the overall efficacy of vacuum stream treatment for reducing pathogens on HRS wheat kernels. HRS wheat samples were treated with steam under vacuum at 65, 70, 75, and 85°C for 4 and 8 min. Significant changes in dough and baked product functionality were observed for treatments at ≥ 70°C. Treatment time had no significant effect on the qualities evaluated. After determining that vacuum steam treatment at 65°C best preserved product quality, HRS wheat was inoculated with Escherichia coli O121 and Salmonella Enteritidis PT 30 and processed at 65°C for 0, 2, 4, 6, or 8 min. The treatments achieved a maximum average reduction of 3.57 ± 0.33 log CFU/g for E. coli O121 and 3.21 ± 0.27 log CFU/g for Salmonella. Vacuum steam treatment could be an effective pathogen inactivation method for the flour milling industry.Hide Abstract
Effects of in-feed enzymes on milk production and components, reproduction, and health in dairy cows.
Golder, H. M., Rossow, H. A. & Lean, I. J. (2019). Journal of Dairy Science, 102(9), 8011-8026.
Our objectives were to characterize responses in the field to a mix of fibrolytic enzymes using large commercial dairy herds and sufficient study power to evaluate milk production and reproductive responses to an enzyme treatment started during the precalving period. We hypothesized that the use of the enzyme treatment would increase milk production when provided to dairy cows precalving and for approximately 200 d of lactation. The study was conducted on 7,507 cows, in 8 replicates and 16 pens, at 3 dairies in the United States. Eight pens were randomly allocated as control pens and received no enzyme, and another 8 pens received enzyme treatment at a dose of 750 mL/t of dry matter feed. Milk production and energy-corrected milk yield were increased with the enzyme treatment by 0.70 and 0.80 kg/d, respectively, across a 5-month period. Milk fat percentage was not significantly increased by enzyme treatment, but milk fat yield was significantly increased by 0.040 kg/d, compared with controls. Milk protein yield increased 0.010 kg/d with enzyme treatment despite a small reduction of 0.020 percentage units in milk protein percentage. We found no evidence of an increase in the ln somatic cell count for the enzyme-treated cows. Body weight overall was not increased for enzyme-treated cows, but we did observe a numerical increase in dry matter intake (0.20 kg/head per day) for enzyme-treated cows. Most production responses to the enzyme treatment were influenced by dairy. Compared with controls, milk yield in enzyme-treated cows was significantly higher by 3.6 kg/d in dairy 2 and numerically higher by 0.60 and 0.20 kg/d in dairies 1 and 3, respectively. Reproduction, health, and risk of removal or death were not significantly influenced by treatment, apart from a reduced time to first breeding. Production responses to the enzyme treatment varied by dairy from substantial to minor increases, but variation among dairies was not evident in differences in dry matter intake or in partitioning of body weight among enzyme-treated and control pens and cows. It appears likely that the increase in production reflected increased digestibility of feed; however, further work is needed to identify factors influencing the variation in production responses to enzymes.Hide Abstract
Growth performance, gastrointestinal weight, microbial metabolites and apparent retention of components in broiler chickens fed up to 11% rice bran in a corn-soybean meal diet without or with a multi-enzyme supplement.
Sanchez, J., Thanabalan, A., Khanal, T., Patterson, R., Slominski, B. A. & Kiarie, E. (2019). Animal Nutrition, 5(1), 41-48.
We investigated the effects of adding up to 11% rice bran (RB) in corn-soybean meal diets fed to broiler chickens without or with a multi-enzyme supplement (MES). The MES supplied xylanase, β-glucanase, invertase, protease, cellulase, α-amylase and mannanase with targeted activity of 2,500, 300, 700, 10,000, 1,200, 24,000, and 20 U/kg of feed, respectively. The study used a two-phase feeding program (starter, d 0 to 24; finisher, d 25 to 35) with RB added at 5% and 11%, respectively creating 4 diets in each phase. Diets were iso-caloric and iso-nitrogenous and contained phytase (500 FTU/kg) and TiO2 as a digestibility marker. Three hundred and sixty d-old male Ross 708 broiler chicks were placed in cages based on BW (15 birds/cage) and allocated to 4 diets (n = 6). Birds had free access to feed and water. Body weight and feed intake were recorded. Excreta samples were collected 3 d prior to the end of each phase for apparent retention (AR) of components. Samples of birds were sacrificed on d 24 and 35 for gut weight and ceca digesta for organic acid content. There was no interaction (P > 0.10) between RB and MES on BWG and FCR in starter or finisher phase. In finisher phase, birds fed MES had better BWG (961 versus 858 g) and FCR (1.69 versus 1.86) than birds fed non-MES diets (P < 0.01). Feeding RB reduced (P = 0.02) BWG in finisher phase resulting in lower d 35 BW. Birds fed RB had higher (P ≤ 0.01) gizzard weight on d 24 and 35 than non-RB birds. An interaction (P ≤ 0.01) between RB and MES on concentrations of propionic and iso-butyric acids in ceca digesta showed that MES reduced these acids in non-RB diet. The AR of gross energy was higher (P < 0.02) for MES versus non-MES birds in starter and finisher phases. In conclusion, independently, RB increased gizzard weight and reduced final BW whereas MES improved growth and energy utilization.Hide Abstract
Partial purification of components in rye water extractables which improve the quality of oat bread.
Pauly, A. & Delcour, J. A. (2018). Journal of Cereal Science, 79, 141-147.
Unlike wheat bread, the dough of which has a visco-elastic network and high gas-holding capacity, oat bread generally has a low volume and a dense structure. We showed earlier that including rye water-extractable components in an oat bread batter recipe increases loaf volume by ca. 30% (Pauly and Delcour, submitted as back-to-back publication). We here report on efforts to identify the active factor(s). Anion exchange chromatography allowed enriching the active factor(s). This and the fact that only a limited volume increase was observed when oat batter was supplemented with boiled rye extract indicate that proteins are likely the most important components responsible for the volume increase. While the most active factor(s) had a pI below 4.5, components with pI values between 4.5 and 8.5 also contributed to oat loaf volume. Alkaline rye components (pI > 8.5) or rye arabinoxylan had no impact. Rye water-extractable components smaller than 6–8 kDa also had a positive impact on loaf volume.Hide Abstract
Impact of water-extractable components from different cereals on the quality of oat bread.
Pauly, A. & Delcour, J. A. (2018). Journal of Cereal Science, 79, 134-140.
Loaf volume and crumb structure of oat bread are not comparable to those of bread from wheat flour. Hydrocolloids, surfactants and/or enzymes are often included in oat batter recipes for quality enhancement reasons. In this study, we examined the impact of water-extractable components from barley, oat, rye and wheat flour on oat bread quality. We speculated that such water extracts contain components which also would enhance the quality of oat bread. As expected, extract protein, non-starch polysaccharide, lipid and enzyme levels varied widely amongst the different cereal flours used. The extracts also varied in foaming properties and extract viscosities. Rye flour contained the highest level of water-extractable components. Inclusion of rye aqueous extract resulted in the largest loaf volume increase and in softer crumb than noted for control oat bread. Rheofermentometer analyses showed that the moment of gas cell opening was delayed when rye extract was added, indicating improved batter gas cell stabilization, while collapse during baking was not affected. The oat bread improving effect of the rye extract is likely due to a combination of the impact of different of its constituents such as enzymes and surface active components.Hide Abstract
Multi-carbohydrase and phytase supplementation improves growth performance and liver insulin receptor sensitivity in broiler chickens fed diets containing full-fat rapeseed.
Józefiak, D., Ptak, A., Kaczmarek, S., Maćkowiak, P., Sassek, M. & Slominski, B. A. (2010). Poultry Science, 89(9), 1939-1946.
The effect of a combination of carbohydrase and phytase enzymes on growth performance, insulin-like growth factor 1 gene expression, insulin status, and insulin receptor sensitivity in broiler chickens fed wheat-soybean meal diets containing 6% (starter) and 12% (grower-finisher) of full-fat rapeseed (canola type; low glucosinolate, low erucic acid) from 1 to 42 d of age was studied. A total of 510 one-day-old male broiler chickens were randomly assigned to 3 dietary treatments, with 17 pens per treatment and 10 birds per pen. The dietary treatments consisted of a control diet and P- and Ca-deficient diets supplemented with either phytase (500 U/kg) or a combination of phytase and a multi-carbohydrase enzyme (Superzyme OM). The diets were pelleted at 78°C and were fed ad libitum throughout the starter (9 d), grower (18 d), and finisher (15 d) phases of the experiment. Over the entire trial, growth performance of birds fed the phytase-supplemented diet did not differ from birds fed the control diet. The use of phytase in combination with a multicarbohydrase enzyme improved (P = 0.007) the feed conversion ratio from 1.90 to 1.84. Insulin liver receptor sensitivity increased by 9.3 and 12.3% (P = 0.004) for the phytase- and the carbohydrase-phytase-supplemented diets, respectively. There was no effect of phytase alone or carbohydrase and phytase supplementation on total plasma cholesterol, high-density lipoprotein cholesterol, and blood glucose levels. However, low-density lipoprotein cholesterol decreased (P = 0.007) for the phytase-carbohydrase treatment. Gene expression of insulin-like growth factor 1 tended to decrease by 32% (P = 0.083) after phytase-carbohydrase supplementation. The combination of carbohydrase and phytase enzymes may serve as an attractive means of facilitating nutrient availability for digestion and thus enhance the feeding value of wheat-soybean meal-based diets containing full-fat rapeseed. However, the extent to which the effects of enzyme addition on insulin receptors are associated with growth performance of broiler chicken requires further research.Hide Abstract
An accurate normalization strategy for RT-qPCR in Hypocrea jecorina (Trichoderma reesei).
Steiger, M. G., Mach, R. L. & Mach-Aigner, A. R. (2010). Journal of Biotechnology, 145(1), 30-37.
Hypocrea jecorina is an important, filamentous fungus due to its effective production of hydrolytic enzymes. Gene expression studies provide deeper insight into environment sensing and cellular response mechanisms. Reverse transcription-quantitative PCR is a gene-specific and powerful tool to measure even minor changes in mRNA composition. An accurate normalization strategy is absolutely necessary for appropriate interpretation of reverse transcription-quantitative PCR results. One frequently applied strategy is the usage of a reference gene. Adequate reference genes for Hypocrea have not been published so far. By using the NormFinder and geNorm softwares, we evaluated the most stable genes amongst six potential reference genes in 34 samples from diverse cultivation conditions. Under those experimental conditions, sar1 encoding for a small GTPase was found to be the most stable gene, whereas act encoding for actin was not amongst the best validated ones. The influence of the reference system on the expression data is demonstrated by analysis of two target genes, encoding for the Xylanase regulator 1 and for Xylanase II. We further validated obtained xylanase 2 transcription rates with the corresponding enzyme activity.Hide Abstract
Transcriptional regulation of xyr1, encoding the main regulator of the xylanolytic and cellulolytic enzyme system in Hypocrea jecorina.
Mach-Aigner, A. R., Pucher, M. E., Steiger, M. G., Bauer, G. E., Preis, S. J. & Mach, R. L. (2008). Applied and Environmental Microbiology, 74(21), 6554-6562.
In Hypocrea jecorina, Xyr1 (xylanase regulator 1) is the main transcription activator of hydrolase-encoding genes, such as xyn1, xyn2, bxl1, cbh1, cbh2, egl1, and bgl1. Even though Xyr1 mediates the induction signal for all these genes derived from various inducing carbon sources and compounds, xyr1 transcription itself is not inducible by any of these substances. However, cultivation on glucose as the carbon source provokes carbon catabolite repression of xyr1 transcription mediated by Cre1. In addition, xyr1 transcription is repressed by the specific transcription factor Ace1. Moreover, Xyr1 is permanently available in the cell, and no de novo synthesis of this factor is needed for a first induction of xyn1 transcription. The constitutive expression of xyr1 leads to a significant elevation/deregulation of the xyn1, xyn2, and bxl1 transcription compared to what is seen for the parental strain. Overall, the corresponding xylanolytic enzyme activities are clearly elevated in a constitutively xyr1-expressing strain, emphasizing this factor as an auspicious target for genetically engineered strain improvement.Hide Abstract
Xylanases from microbial origin induce syrup formation in dough.
De Schryver, P., Sesena, S., Decaigny, B., Van de Wiele, T., Verstraete, W. & Boon, N. (2008). Journal of Cereal Science, 47(1), 18-28.
Syrup formation in refrigerated doughs is a problem since it reduces the doughs’ shelf life. Microbial exogenous xylanases associated with wheat kernels were found to play a role in this syruping phenomenon. Using xylanase-producing microorganisms isolated from wheat kernels, we investigated their potency to induce syruping in dough. Growth of the fungal xylanase producer Fusarium sp. (102 colony forming units (CFU)/g dough) and the bacterial xylanase producer Paenibacillus sp. (104 CFU/g dough) in synthetic media and their respective addition to wheat dough could not bring about a significant amount of syruping. However, when these species were grown on moist wheat kernels and an extract of these kernels containing both the organisms and its xylanases was made and added to dough, intensive syruping was noted. This effect was primarily attributed to the xylanases present in the extract. These findings suggest that the involvement of xylanase-producing microorganisms in the syruping phenomenon is situated prior to harvest. Additional quantitative analyses of microbial biomass present on wheat kernels revealed that the fungi in particular could be correlated to higher microbial exogenous xylanase activities on wheat. Our results indicate that the syruping is linked to fungal xylanase production on the wheat kernels in the field.Hide Abstract
Variability in the release of free and bound hydroxycinnamic acids from diverse malted barley (Hordeum vulgare L.) cultivars during wort production.
Vanbeneden, N., Gils, F., Delvaux, F. & Delvaux, F. R. (2007). Journal of Agricultural and Food Chemistry, 55(26), 11002-11010.
Volatile phenols have long been recognized as important flavor contributors to the aroma of various alcoholic beverages. The two main flavor-active volatile phenols in beer are 4-vinylguaiacol and 4-vinylphenol. They are the decarboxylation products of the precursors ferulic acid and p-coumaric acid, respectively, which are released during the brewing process, mainly from malt. In this study, the variability in the release of free and ester-bound hydroxycinnamic acids from nine malted barley (Hordeum vulgare L.) varieties during wort production was investigated. A large variability between different barley malts and their corresponding worts was observed. Differences were also found between free ferulic acid levels from identical malt varieties originating from different malt houses. During mashing, free hydroxycinnamic acids in wort are both water-extracted and enzymatically released by cinnamoyl esterase activity. Esterase activities clearly differ between different barley malt varieties. Multiple linear regression analysis showed that the release of ferulic acid during mashing did not depend only on the barley malt esterase activity but also on the amount of ester-bound ferulic acid initially present in the wort and on its endoxylanase activity. The study demonstrates the importance of selecting a suitable malt variety as the first means of controlling the final volatile phenol levels in beer.Hide Abstract
Xyr1 receives the lactose induction signal and regulates lactose metabolism in Hypocrea jecorina.
Stricker, A., R., Steiger, M., G. & Mach, R., L. (2007). FEBS Letters, 581(21), 3915-3920.
This study reports the vital regulatory influence of Xyr1 (xylanase regulator 1) on the transcription of hydrolytic enzyme-encoding genes and hydrolase formation on lactose in Hypocrea jecorina. While the transcription of the xyr1 gene itself is achieved by release of carbon catabolite repression, the transcript formation of xyr1 (xylanase 1) is regulated by an additional induction mechanism mediated by lactose. Xyr1 has an important impact on lactose metabolism by directly activating xyr1 (xylose reductase 1) transcription and indirectly influencing transcription of bga1 (β-galactosidase 1). The latter is achieved by regulating the conversion of D-galactose to the inducing carbon source galactitol.Hide Abstract
Impact of wheat flour-associated endoxylanases on arabinoxylan in dough after mixing and resting.
Dornez, E., Gebruers, K., Cuyvers, S., Delcour, J. A. & Courtin, C. M. (2007). Journal of Agricultural and Food Chemistry, 55(17), 7149-7155.
The impact of varying levels of endoxylanase activity in wheat flour on arabinoxylan (AX) in mixed and rested dough was studied using eight industrially milled wheat flour fractions with varying endoxylanase activity levels. Analysis of the levels of reducing end xylose (RX) and solubilized AX (S-AX) formed during mixing and resting and their correlation with the endoxylanase activity in the flour milling fractions showed that solubilization of AX during the mixing phase is mainly due to mechanical forces, while solubilization of AX during resting is caused by endoxylanase activity. Moreover, solubilization of AX during the dough resting phase is more outspoken than that during the mixing phase. Besides endoxylanase activity, there were significant xylosidase and arabinofuranosidase activities during the dough resting phase. The results indicate that wheat flour-associated endoxylanases can alter part of the AX in dough, thereby changing their functionality in bread making and potentially affecting dough and end product properties.Hide Abstract