Wheat Bran Concentration Research Articles

Kinetics and thermodynamics of high level β-glucosidase production by mutant derivative of Aspergillus niger under submerged growth conditions

Gamma rays mediated mutagenesis and subsequent selection on 2-deoxy-D-glucose developed a highly catabolite de-repressed and stable β-glucosidase (BGL) hyper-producer mutant of local Aspergillus niger NIBGE, which has high potential for industrial applications. The M6 mutant showed highest constitutive production of BGL (14,900 IU/L) on glucose as compared to control (5,900 IU/L). Wheat bran was the best carbon source and BGL production by parent and mutant strain was 16,200 and 29,500 IU/L, respectively. Effect of inoculum density, pH, temperature and wheat bran concentration on the BGL production was determined in terms of kinetic growth parameters, that is, specific growth rate (m), biomass doubling time (td), product yield coefficient with respect to cell mass (Yp/x) and specific rate of product formation (qp). Optimal conditions for BGL production by parent and mutant strain were same: inoculum level= 0.184 mg cells/mL (10% v/v); optimum temperature= 30°C and pH= 5.0; wheat bran= 3% (w/v). The apparent subunit molecular mass of BGL from both strains was also same (130 kDa). Determination of thermodynamic parameters led to consider that the hyper-production of BGL by the mutant was due to decrease in: activation energy (Ea(p)), change in enthalpy (ΔH*(p)) and Gibbs free energy (ΔG*(p)) for product (BGL) formation. Key words: β-glucosidase, Aspergillus niger, activation energy, enthalpy, Gibbs free energy.

Online Shear Viscosity Measurement of Starchy Melts Enriched in Wheat Bran

Addition of wheat bran to flours modifies their expansion properties after cooking extrusion. This can be attributed to changes in the melt shear viscosity at the die. The effect of wheat bran concentration added to achieve 2 levels of dietary fibers of 12. 6% and 24.4%, and process conditions on the shear viscosity of wheat flour was therefore assessed using an online twin-slit rheometer. The shear viscosity measured at 30 s⁻¹ ranged from 9.5 × 10³ to 53.4 × 10³ Pa s. Regardless of the process conditions and bran concentration, the extruded melts showed a pseudoplastic behavior with a power law index n ranging from 0.05 to 0.27. Increasing the barrel temperature of the extruder from 120 to 180 °C, the water content from 18% to 22% or the screw speed from 400 to 800 rpm significantly decreased the melt shear viscosity at the extruder exit. The addition of bran significantly increased the melt shear viscosity only at the highest bran concentration. The effect was process condition dependant. Mathematical interpretations, based upon observations, of the experimental data were carried out. They can be used to predict the effect of the process conditions on the melt shear viscosity at the die of extruded wheat flour with increasing bran concentration. The viscosity data will be applied in future works to study the expansion properties of extruded wheat flour supplemented with bran. Incorporation of wheat bran, a readily available and low cost by-product, in extruded puffed foods is constrained due to its negative effect on the product texture. Understanding the effect of wheat bran on rheological properties of extruded melts, driving the final product properties, is essential to provide solutions to the food industry and enhance its use.

Effect of particle size and addition level of wheat bran on quality of dry white Chinese noodles

Wheat bran is one of the major dietary fiber sources widely used in the food industry in order to produce fiber-rich foods. The effects of particle size and addition level of wheat bran on the quality of flour and of dry white Chinese noodles (DWCN) were investigated. Results suggested that increasing wheat bran concentration and particle size decreased midline peak value (MPV). However, the MTxW and MPT increased as particle size increased. Peak viscosity, trough, final viscosity, area of viscosity, breakdown, and setback of blends decreased significantly with increasing bran levels from 5% to 20%, but there were no significant differences in the impact of particle size on pasting properties. For the 5% and 10% addition levels, there was no distinct effect in breaking strength of the noodles when bran size was 0.21 mm and 0.53 mm. Hardness, gumminess and chewiness of cooked DWCN showed a downtrend with increasing addition levels and particle size, while adhesiveness showed uptrend. The total score of DWCN showed a downtrend with increasing of addition level and particle size. For the 5% bran level, the scores of cooked DWCN were more than 83 when wheat bran particle size was 0.21 mm and 0.53 mm. By using 5–10% fine bran or using 5% medium bran in wheat flour, it is possible to satisfactorily produce fiber-rich DWCN.

Supplementation of extruded foams with wheat bran: Effect on textural properties

The objective of this study was to investigate the effect of wheat bran concentrations on the mechanical properties determining the texture of extruded carbohydrate matrices. For this wheat flour was extruded under different conditions with an increasing concentration of wheat bran. The mechanical properties were assessed using a threepoint bending test and the cellular structure was determined by micro-computed X-ray tomography. Regardless of the bran concentration, the stress at rupture of the extruded foams was positively correlated with their relative density according to the Gibson-Ashby model. At same relative densities and bran concentration, finer structures with higher density of small cells led to a higher mechanical strength of the foams. Expanded foams with added bran at an intermediate level showed increased mechanical strength. This was attributed to the finer cellular structures obtained.The effect of increasing the bran to a higher concentration on the mechanical properties was depending on the cell wall thickness and bran particle dimensions.

Statistical optimization of xylanase production by Aspergillus niger AN-13 under submerged fermentation using response surface methodology

Response surface methodology (RSM) was performed to evaluate the effects of cultivation time, pH and substrate concentration on production of xylanase by Aspergillus niger AN-13. Agricultural residue wheat bran was used as main substrate under submerged fermentation. Xylanase production was optimized by Box-Behnken design (BBD). Statistical analysis of results showed that, the linear and quadric terms of these three variables had significant effects, and evident interactions existing between pH and substrate concentration were found to contribute to the response at a significant level. Furthermore, Box-Behnken design (BBD) used for the analysis of treatment combinations gave a second-order polynomial regression model, which was in good agreement with experimental results, with R2=0.9959 (P namely cultivation time of 53.3 h, pH of 7.92 and wheat bran concentration of 54.2 g·L-1, the model predicted a xylanase activity of 125.14 U·mL-1. Verification of the optimization showed that xylanase production of 127.12 U·mL-1 was observed under the optimal condition, which had a marked increase compared with a xylanase activity of 4.80 U·mL-1 in experiments according to Box-Behnken design.

Response surface methodology for optimizing the fermentation medium of alpha-galactosidase in solid-state fermentation

Alpha-galactosidase is applied in food and feed industries for hydrolysing raffinose series oligosaccharides (RO) that are the factors primarily responsible for flatulence upon ingestion of soybean-derived products. The objective of the current work was to develop an optimal culture medium for the production of alpha-galactosidase in solid-state fermentation (SSF) by a mutant strain Aspergillus foetidus. Response surface methodology (RSM) was applied to evaluate the effects of variables, namely the concentrations of wheat bran, soybean meal, KH(2)PO(4), MnSO(4).H(2)O and CuSO(4).5H(2)O on alpha-galactosidase production in the solid substrate. A fractional factorial design (FFD) was firstly used to isolate the main factors that affected the production of alpha-galactosidase and the central composite experimental design (CCD) was then adopted to derive a statistical model for optimizing the composition of the fermentation medium. The experimental results showed that the optimum fermentation medium for alpha-galactosidase production by Aspergillus foetidus ZU-G1 was composed of 8.2137 g wheat bran, 1.7843 g soybean meal, 0.001 g MnSO(4).H(2)O and 0.001 g CuSO(4).5H(2)O in 10 g dry matter fermentation medium. After incubating 96 h in the optimum fermentation medium, alpha-galactosidase activity was predicted to be 2210.76 U g(-1) dry matter in 250 ml shake flask. In the present study, alpha-galactosidase activity reached 2207.19 U g(-1) dry matter. Optimization of the solid substrate was a very important measure to increase enzyme activity and realize industrial production of alpha-galactosidase. The process of alpha-galactosidase production in laboratory scale may have the potential to scale-up.

Production of xylanases by immobilized Aspergillus sp. using lignocellulosic waste.

In shake flasks immobilized Aspergillus terreus and Aspergillus niger produced 29 IU/ml, 26.7 IU/ml xylanases at 10 mg/ml, 14 mg/ml wheat bran concentration after 48 and 60 h of incubation at 37 °C respectively. In repeated batch fermentation of immobilized Aspergillus sp. the same biocatalyst could be used for three successive cycles.

Optimization of xylanase production by a hyperxylanolytic mutant strain of Fusarium oxysporum

Cultural conditions for xylanase production by a hyperxylanolytic mutant strain (NTG-19) of Fusarium oxysporum were optimized in shake flask cultures. The mutant secretes high levels of xylanase on birchwood xylan as well as on agricultural residues. Among different agricultural residues and inorganic/organic nitrogen sources tested, wheat bran and peptone produced the highest titres of xylanase. The optimum concentration of wheat bran (4%, w/v) produced a titre of 46·2 IU/ml in 96 h. Optimum pH and temperature for xylanase production by F. oxysporum NTG-19 were pH 3·0–3·5 and 30°C, respectively. Addition of Tween-80 and olive oil to the medium significantly improved the enzyme yields. When the mutant was grown in a controlled fermentor, the xylanase yield was enhanced by about 50%, (65 IU/ml). Optimum pH and temperature for xylanase activity was 6·0 and 55°C. The enzyme was most stable up to 50°C, stability decreased above 55°C, but 40% activity was retained at 80°C for 2 h.