Characterization of a xylanase from the newly isolated thermophilic Thermomyces lanuginosus CAU44 and its application in bread making

AIMS: A xylanase from the newly isolated thermophilic fungus, Thermomyces lanuginosus CAU44, was characterized and evaluated for its suitability in bread making. METHODS AND RESULTS: Xylanase was purified 3.5-fold to homogeneity with a recovery yield of 32.8%. It appeared as a single protein band on SDS-PAGE gel with a molecular mass of c. 25.6 kDa. The purified xylanase had an optimum pH of 6.2, and it was stable over pH 5.6-10.3. The optimal temperature of xylanase was 75 degrees C and it was stable up to 65 degrees C at pH 6.2. Study was further carried out to investigate the effect of the purified xylanase on the properties of wheat bread and its staling during storage. CONCLUSIONS: The purified xylanase from T. lanuginosus CAU44 was stable up to 65 degrees C and had a broad pH range. The presence of thermostable xylanase during bread making led to an improvement of the specific bread volume and better crumb texture. Besides, addition of xylanase provided an anti-staling effect. SIGNIFICANCE AND IMPACT OF THE STUDY: The xylanase from the newly isolated Thermomyces lanuginosus CAU44 shows great promise as a processing aid in the bread-making industry.     

Production of thermo-alkali-stable xylanase by a novel polyextremophilic Bacillus halodurans TSEV1 in cane molasses medium and its applicability in making whole wheat bread

A high titre of thermo-alkali-stable xylanase was attained in cane molasses medium. When the culture variables for endoxylanase production were optimized [cane molasses 7 %, soluble alkaline extract of wheat bran (SAE-WB) 37 % and ammonium chloride 0.30 %], a 4.5-fold enhancement in xylanase production (69 U ml^?1) was achieved as compared to that in the unoptimized medium (15 U ml^?1). The enzyme titre attained in shake flasks could be sustained in a 7-l laboratory bioreactor. An activity band corresponding to 40 kDa was visualized on SDS-PAGE zymogram analysis. The enzyme has broad range of pH and temperature for activity with optima at 9.0 and 80 °C, and stable between pH 4.0 and 11.0 with 85 % retention of activity. It has T _1/2 of 40 and 15 min at 70 and 80 °C. The enzyme is halotolerant since it displays activity in the presence of salt up to 15 %, and remains 100 % active in the absence of salt. The supplementation of whole wheat dough with xylanase improves antistaling property, reducing sugar content, bread volume with prebiotic xylooligosaccharides in bread. This is the first report on xylanase production in cane molasses medium with SAE-WB as the inducer and its applicability in whole wheat bread making that improves human health.     

Improvement of the quality of wheat bread by addition of glycoside hydrolase family 10 xylanases

Although many xylanases are widely used in the baking industry, only one glycoside hydrolase family 10 (GH 10) xylanase has previously been reported to be effective in baking. In this study, we compared the effectiveness of two GH 10 xylanases, psychrophilic XynA from Glaciecola mesophila and mesophilic EX1 from Trichoderma pseudokoningii, in bread making. The optimal dosages needed to improve wheat flour dough and bread quality were 270-U/kg flour for EX1 and 0.9-U/kg flour for XynA. At their optimal dosage, both XynA and EX1 had significant dough-softening ability, resulting in a 50% reduction in Brabender units. XynA was more effective than EX1 in reducing the time to reach maximum consistency. XynA and EX1 showed similar effects in improving the bread volume (~30% increase). EX1 was more effective in reducing the initial crumb firmness. Although both enzymes exhibited similar anti-staling effects on the bread, based on a decrease in the bread firmness, XynA had a greater effect on reducing the firming rate, and EX1 showed an enhanced reduction in the initial firmness. These results show that these two GH 10 xylanases have unique advantages in improving dough and bread quality and indicate their potential in bread making.     

Changes in the texture and viscoelastic properties of bread containing rice porridge during storage

The objective of this study was to investigate the effects of rice porridge on the texture and viscoelastic properties of bread during storage. Three types of bread, wheat flour bread, 15% rice flour bread, and 15% rice porridge bread, were prepared. After baking and storing the bread for 24 h, 48 h, and 72 h at room temperature, we measured the texture and viscoelastic properties of the bread crumbs by texture profile analysis (TPA) and creep test. The 15% rice porridge bread showed a significantly higher specific volume and maintained softer crumbs than the other two types (p<0.05). It also had a slightly stickier texture than the others. It can be concluded that rice porridge improves the specific volume, texture, and viscoelastic properties of bread crumbs during storage.     

Characterization of a cellulase-free, neutral xylanase from Thermomyces lanuginosus CBS 288.54 and its biobleaching effect on wheat straw pulp

A xylanase purified from the thermophilic fungus Thermomyces lanuginosus CBS 288.54 was characterized and its potential application in wheat straw pulp biobleaching was evaluated. Xylanase was purified 33.6-fold to homogeneity with a recovery yield of 21.5%. It appeared as a single protein band on SDS-PAGE gel with a molecular mass of approx. 26.2 kDa. The purified xylanase had a neutral optimum pH ranging from pH 7.0 to pH 7.5, and it was also stable over pH 6.5-10.0. The optimal temperature of the xylanase was 70-75 degrees C and it was stable up to 65 degrees C. The purified xylanase was found to be not glycosylated. The xylanase was highly specific towards xylan, but did not exhibit other enzyme activity. Apparent Km values of the xylanase for birchwood, beechwood, soluble oat-spelt and insoluble oat-spelt xylans were 4.0, 4.7, 2.0 and 23.4 mg ml-1, respectively. The potential application of the xylanase was further evaluated in biobleaching of wheat straw pulp. The brightness of bleached pulps from the xylanase pretreated wheat straw pulp was 1.8-7.79% ISO higher than that of the control, and showed slightly lower tensile index and breaking length than the control. Although chlorine consumption was reduced by 28.3% during bleaching, the xylanase pretreated pulp (15 U g-1 pulp) still maintained its brightness at the control level. Besides, pretreatment of pulp with the xylanase was also effective at an alkaline pH as high as pH 10.0.     

Isolation and properties of Aspergillus niger IBT-90 xylanase for bakery

Xylanase of low molecular weight (K II) was isolated from the fungus Aspergillus niger IBT-90 cultivated in medium with wheat bran. K II was purified by precipitation with ammonium sulphate (20–80% saturation) and gel filtration on Biogel P-10. This enzyme is most active in hydrolysis of birchwood xylan at 50°C and pH 5.5. Xylanase K II has an ability to degrade 1,4-β-bonds and to debranch substrates. It degrades not only xylans but also cellulose, an important factor for its application in bakery. Ag⁺, Fe³⁺ and NBS are strong inhibitors of the enzyme. DTT and Na⁺ activate xylanase K II by 24 and 13%, respectively. Enzyme K II used as additive to flour improves dough properties, increases the volume of wheat–rye and whole meal bread, and increases the porosity of crumb and the moisture of the final product, consequently extending the shelf life of bread.     

Optimization of xylanase production using inexpensive agro-residues by alkalophilic Bacillus subtilis ASH in solid-state fermentation

Alkalophilic Bacillus subtilis ASH produced high levels of xylanase using easily available inexpensive agricultural waste residues such as wheat bran, wheat straw, rice husk, sawdust, gram bran, groundnut and maize bran in solid-state fermentation (SSF). Among these, wheat bran was found to be best substrate. Xylanase production was highest after 72 h of incubation at 37 °C and at a substrate to moisture ratio of 1:2 (w/v). The inoculum level of 15% resulted in maximum production of xylanase. The enzyme production was stimulated by the addition of nutrients such as yeast extract, peptone and beef extract. In contrast, addition of glucose and xylose repressed the production of xylanase. The extent of repression by glucose (10%, w/v) was 81% and it was concentration-dependent. Supplementation of the medium with 4% xylose caused 59% repression. Under optimized conditions, xylanase production in SSF (8,964 U of xylanase/g dry wheat bran) was about twofold greater than in submerged fermentation. Thus, B. subtilis produced a very high level of xylanase in SSF using inexpensive agro-residues, a level which is much higher than that reported by any other bacterial isolate. Furthermore, the enzyme was produced at room temperature and with tap water without the addition of any mineral salt in SSF, leading to a marked decrease in the cost of xylanase production, which enhances its industrial potential.     

Wheat-yellow pumpkin composite flour: Physico-functional,rheological, antioxidant potential and quality properties of pan and flat bread

The impact of yellow pumpkin powder (YP) substitution (5, 10, and 15%) on wheat flour's physico-functional, pasting, gel texture, and dough rheology was studied. Moreover, the nutritional, organoleptic properties and bioactivity of the composite pan and pita bread were evaluated. An improved water holding capacity was noticed for the blended flour than for control. The pasting parameters were declined significantly (p < 0.05) with increasing YP. Composite flours presented a softer gel texture in the presence of YP. Reduced water absorption, increased dough development time, and lower stability for combined flour dough. The bread with YP depicted increased protein, fat, fiber, and mineral contents, while a reduced volume and specific volume were noticed for pan bread. YP incorporated 5% and did not compromise pan and pita bread's color and overall acceptability. Additionally, composite bread depicted higher total phenolics with enhanced antioxidant activities at the higher substitution of YP.     

High-level of xylanase production by the thermophilic Paecilomyces themophila J18 on wheat straw in solid-state fermentation

The production of extracellular xylanase by a newly isolated thermophilic fungus, Paecilomyces themophila J18, on the lignocellulosic materials was studied in solid-state fermentation (SSF). The strain grew well at 50 degrees C and produced a high-level of xylanase activity using the selected lignocellulosic materials, especially wheat straw. Production of xylanase by P. themophila J18 on wheat straw was enhanced by optimizing the particle size of wheat straw, nitrogen source, initial moisture level, growth temperature and initial pH of the culture medium. Under the optimized conditions, yield as high as 18,580 Ug(-1) of carbon source of xylanase was achieved. No CMCase activity was observed. The xylanase exhibited remarkable stability and retained more than 50% of its original activity at 70 degrees C for 4h at pH 7.0-8.0. Therefore, P. themophila J18 could to be a promising microorganism for thermostable, cellulase-free xylanase production in SSF.     

Polymorphism of omega-gliadins in durum wheat as revealed by the two-step APAGE/SDS-PAGE technique

Polymorphism of omega-gliadins was studied in 243 durum wheats from 27 countries using the two-step one-dimensional APAGE/SDS-PAGE technique. A total of 12 bands of different mobility were observed, and four of them were found to be different from those previously detected by Khelifi et al. (1992) in bread wheat. Fifteen alleles, six coded by the Gli-A1 locus and nine coded by the Gli-B1 locus, were identified, accounting for 19 different electrophoretic patterns. Seven new alleles were detected: two at the Gli-A1 locus and five at the Gli-B1 locus. The polymorphism found at the Gli-A1 and Gli-B1 loci was slightly greater than that found in bread wheat. Allelic differences between both species were higher at the Gli-B1 locus. A comparison of the frequencies of alleles in both species was carried out. The null allele, Gli-A1e, was more common in durum wheat than in bread wheat. The Gli-B1b allele, present in 60% of the bread wheats, was found in only 2% of the durum wheats and Gli-B1e, very common in durum wheat (45%), was rare in bread wheat (4%). The Gli-B1IV allele, common in durum wheat (28%), was not detected in bread wheat.     

Rheological and breadmaking properties of wheat samples infected with<Emphasis Type="Italic">Fusarium spp.</Emphasis>

Rheological and breadmaking properties of untreated and suboptimally stored wheat samples (grain moisture: 20%, temperature: 20°C) and also of wheat which was inoculated withFusarium spp. were investigated. The deoxynivalenol (DON) content of the stored and inoculated wheat samples ranged between 820–12,000 μg/kg. Gluten proteins were isolated with different extraction solutions and the fractions obtained were analysed by means of RP-HPLC. Microextension tests and micro-baking tests were used for the determination of dough properties (maximum resistance (MR) and extensibility (EX)) and bread volume, respectively. In spite of the extremely high DON concentrations of some wheat samples contaminated withFusarium spp. they showed only a slight decrease of the amount of gluten proteins. Extension tests of dough led to a slight decrease of MR, bread volumes stayed almost the same compared with the non-contaminated grain. The contamination of wheat withAspergillus andPenicillium led to a high decrease of gluten proteins, which resulted in an extremely decreased MR of the dough and a very low bread volume.     

Deoxynivalenol contents in foodstuffs of organical and conventional production

Samples of wheat flour, bread, noodles, rice, corn and corn based foods as well as oats and oats based foods of conventional and organical production were analysed for trichothecene toxins. In wheat flour, bread and noodels the median deoxynivalenol (DON) contents were lower in ecological than in conventional products with significant differences for what flour and bread. To estimate toxin uptake of the consumer a corrected mean of DON concentration was calculated, which was lower in wheat flour and bread for ecological than for conventional products. In noodles the corrected mean of organical products was higher than that of conventional ones.     

Effect of dietary carbohydrate source on soluble protein glucose concentration and enzyme activity (aldolase) of European eels (Anguilla anguilla L.)

This study was undertaken to determine the influence of dietary carbohydrate sources: wheat meal, bread meal, soluble corn starch, native potato starch and sorghum meal, on soluble protein, enzyme activity (aldolase) and glucose concentration in muscle and liver of European eels (Anguilla anguilla). There was less soluble protein in both muscle and liver of eels fed 30% wheat meal or bread meal than the other experimental groups. However, eels fed 30% bread meal or soluble corn starch had a higher glucose concentration in muscle and liver than the other experimental groups. High enzyme activity (aldolase) was found in the liver of eels fed 30% wheat meal, bread meal or soluble starch.     

Development of functional foods using psyllium husk and wheat bran fractions: Phytic acid contents

Wheat grain is a rich source of phosphorus which is present mostly as phytic acid and is distributed mainly in the bran and germ fractions. Phytic acid has now been recognized as an important phytochemical having antioxidant properties. This study deals with the determination of total as well as phytic phosphorus contents of psyllium (PS), course (CB) and fine wheat bran (FB) enriched pan bread and Arabic flat bread. The concentration of phytic acid in CB, FB, wheat germ, wholegrain wheat flour (WGF), white wheat flour (WWF), and psyllium were found to be 8.86 mg/g, 8.52 mg/g, 6.05 mg/g, 1.74 mg/g, 0.46 mg/g and 0.02 mg/g, respectively. Most of the phosphorus existed as phytic phosphorus (74.7–90.8%) in FB, CB, germ, and WGF as compared to only 42.6% in WWF. The level of phytic phosphorus in pan bread containing 10% CB, 20% FB (both containing with 5% PS) was found to be 0.63 mg/g and 1.53 mg/g respectively, as compared to only 0.34 mg/g in WWF pan bread, and 0.90 mg/g in WGF pan bread. The phytic phosphorus content in Arabic bread made with WGF and 3% psyllium was 1.32 mg/g as compared to only 0.48 mg/g in WWF Arabic flat bread. The results obtained indicate that the level of phytic phosphorus significantly increased in bread formulations containing CB, FB, and WGF, but no change with psyllium addition was observed. Adding these wheat mill fractions, and psyllium will enable bakeries not only to produce fiber-enriched pan bread and Arabic bread but would also benefit consumers to increase their dietary fiber intakes, and health-promoting phytochemicals coming from wheat bran and germ fractions.     

Can spelt wheat be used as heterotic group for hybrid wheat breeding?

Key message

Spelt wheat is a distinct genetic group to elite bread wheat, but heterosis for yield and protein quality is too low for spelt to be recommended as heterotic group for hybrid breeding in wheat.

Abstract

The feasibility to switch from line to hybrid breeding is currently a hot topic in the wheat community. One limitation seems to be the lack of divergent heterotic groups within wheat adapted to a certain region. Spelt wheat is a hexaploid wheat that can easily be crossed with bread wheat and that forms a divergent genetic group when compared to elite bread wheat. The aim of this study was to investigate the potential of Central European spelt as a heterotic group for Central European bread wheat. We performed two large experimental field studies comprising in total 43 spelt lines, 14 wheat lines, and 273 wheat–spelt hybrids, and determined yield, heading time, plant height, resistance against yellow rust, leaf rust, and powdery mildew, as well as protein content and sedimentation volume. Heterosis of yield was found to be lower than that of hybrids made between elite wheat lines. Moreover, heterosis of the quality trait sedimentation volume was negative. Consequently, spelt wheat does not appear suited to be used as heterotic group in hybrid wheat breeding. Nevertheless, high combining abilities of a few spelt lines with elite bread wheat lines make them interesting resources for pre-breeding in bread wheat. Thereby, the low correlation between line per se performance and combining ability of these spelt lines shows the potential to unravel the breeding value of genetic resources by crossing them to an elite tester.

     

Optimization of fermentation medium for xylanase-producing strain Xw2

To improve the fermentation yield of xylanase by optimizing the fermentation conditions for strain Xw2, a Plackett-Burman design was used to evaluate the effects of eight variables on xylanase production by strain Xw2. The steepest ascent （descent） method was used to approach the optimal response surface experimental area. The optimal fermentation conditions were obtained by central composite design and response surface analysis. The results showed that the composition of the optimal fermentation medium was corn cob ＋ 1.5% wheat bran （1：1）, 0.04% MnSO4, 0.04% K2HPO4. 3H2O, and an inoculum size of 6% in 50 mL liquid volume （pH = 6.0）. The optimal culture conditions were 28oc at 150 r/min for 54.23 h. The results of this study can serve as the basis for the industrial production and application of xylanase.     

Immunochemical Assay for Quality and Immunological Homology of Storage Proteins in Different Closely Related Genera and Species of Wheat

An immunochemical assay using polyclonal and monoclonal antibodies of high-molecular-weight glutenin subunit (HMW-GS) in Triticum aestivum L. was carried out to determine the quality of wheat and to investigate the immunological homology of the storage proteins in cereal endosperms in different closely related wheat genera and species. The results showed that correlation between the antigen-antibody reaction and the wheat quality varied with the type of antibodies used and the quality. The correlation coeffecient was slightly higher when the polyclonal antibodies were used than monoclonal antibodies were used. The correlation coeffecient was high between the antibody binding and the protein content, and wet/dry gluten coment, with Zeleny sedimentation value, while that between antibody binding and bread characters was lower. The highest correlation coeffecient between the polyclonal antibody binding and the protein content in grains, wet and dry gluten contents, bread volume and bread ratio volume was 0. 762 0, 0. 894 2, 0. 887 3, 0.610 3, 0.459 8 and 0.474 4 respectively, while the highest correlation coeffecient between the monoclonal antibody binding and the above parameters was 0. 783 7, 0. 774 5, 0.782 2, 0. 684 1, 0. 687 3 and 0. 598 2 respectively. The immunological homologies between I-IMW-GS 1Dyl0 in common wheat and endosperm storage protein in wheat grains of different genera and species were noticed. The cross-reac-tion among Triticum aestivum L., Secale cereale, T. spelta L., Aegilops squearrosa L. and T. Turgidtan L. was stronger than that among other cereals.     

Statistical optimization of medium components for the production of xylanase byAspergillus niger KK2 in submerged cultivation

Medium composition was optimized for the production of xylanase byAspergillus niger KK2 using statistical experimental designs. Corn steep liquor (CSL) and industrial yeast extract (IYE) were the most important factors affecting xylanase activity. The medium that produced the optimum conditions for the production of xylanase contained 3% rice straw, 1% wheat bran, 6.3% CSL, 0.15% IYE, and 0.5% KH₂PO₄. After 4 days of cultivation under optimized conditions in a 2.5-L stirred tank reactor the activity and productivity of xylanase were 620 IU/mL and 6,458 IU/L.h, respectively. The highest xylanase activity obtained using the optimized medium was 80% greater than the activity obtained using basal medium. The xylanase activity predicted by a polynomial model was 670 IU/ml.     

Major genes for Na+ exclusion, Nax1 and Nax2 (wheat HKT1;4 and HKT1;5), decrease Na+ accumulation in bread wheat leaves under saline and waterlogged conditions

Two major genes for Na(+) exclusion in durum wheat, Nax1 and Nax2, that were previously identified as the Na(+) transporters TmHKT1;4-A2 and TmHKT1;5-A, were transferred into bread wheat in order to increase its capacity to restrict the accumulation of Na(+) in leaves. The genes were crossed from tetraploid durum wheat (Triticum turgidum ssp. durum) into hexaploid bread wheat (Triticum aestivum) by interspecific crossing and marker-assisted selection for hexaploid plants containing one or both genes. Nax1 decreased the leaf blade Na(+) concentration by 50%, Nax2 decreased it by 30%, and both genes together decreased it by 60%. The signature phenotype of Nax1, the retention of Na(+) in leaf sheaths resulting in a high Na(+) sheath:blade ratio, was found in the Nax1 lines. This conferred an extra advantage under a combination of waterlogged and saline conditions. The effect of Nax2 on lowering the Na(+) concentration in bread wheat was surprising as this gene is very similar to the TaHKT1;5-D Na(+) transporter already present in bread wheat, putatively at the Kna1 locus. The results indicate that both Nax genes have the potential to improve the salt tolerance of bread wheat.     

酸性木聚糖酶产生菌的筛选及产酶条件

从１５０株真菌中筛选到８株产木聚糖酶活力在１００Ｕ／ｍＬ以上的菌株,其中活力最高的为黑曲霉（编号１４９）（Ａｓｐｅｒｇｉｌｕｓｎｉｇｅｒ）。该菌株产酶较适培养基为：麸皮半纤维素４％,ＮａＮＯ３１％,麸皮１％,用不加（ＮＨ４）２ＳＯ４和尿素的Ｍａｎｄｅｌｓ氏营养盐液配制。２８℃～３０℃振荡培养６０ｈ,酶活力最高可达３７５．２Ｕ／ｍＬ。该酶最适作用ｐＨ为４６,在ｐＨ３～１１之间基本稳定。该菌株发酵液中含有木聚糖酶（相对活力１００）外还有淀粉酶（１８）,甘露聚糖酶（０９８）,β木糖苷酶（０９４）和纤维素酶（０１７）。