Extraction And Purification Of Endo-1,4-β-xylanase From Wheat Malt And Its Degradation Effect On Arabinoxylan Derived From Plant

Arabinoxylan(AX)is rich in wheat malt.The molecular weight(Mw)and structure of AX and their enzymatic degradation products have a profound effect on beer properties,such as viscosity,turbidity,and filtration rate.AX has great benefits to human health due to their anti-tumor properties and potential roles in the immune system.Endo-1,4-β-xylanase is a key enzyme for degradation of AX,and altering the properties of AX,such as solubility,viscosity,and turbidity.In this study,extraction,purification and degradation effect on the Arabinoxylan derived from plant of an wheat malt endo-1,4-β-xylanase was described.The main results are listed as following:(1)After ammonium sulfate precipitation(ASI),anion exchange chromatography,hydrophobic chromatography(HICIII),and gel filtration chromatography,a Mw of 27.8 kDa endo-1,4-β-xylanase with a single band on SDS-PAGE was obtained(E-WMA),which had a purification fold of 12.08,a specific activity of 4.47 u/mg,and a recovery rate of 1.45%.(2)It was found that the SDS-PAGE band of 14.0 kDa Mw also contain the sequence matched to the endo-1,4-β-xylanase,which indicated that wheat malt may contian a 14.0 kDa endo-1,4-β-xylanase.(3)After the degradation of ASI to wheat malt-based wort(the crude enzyme after ammonium sulfate)at 40 oC,compared to control,turbidity was decreased obviously,30 min,90 min,120 min decreased by 7.16%,38.01%,and 22.22% respectively.WEAX was increased.The content of 1.85×10~3 Da Mw had the most significant changes.Transform WUAX into WEAX of 1.85×10~3 Da was the preferred major role less than 30 min,degrade 1.85×10~3 Da WEAX was the preferred major role above 30 min.(4)It was found that ASI reduced the final wort filtration time after adding ASI to wheat malt-based wort at the beginning of mashing process.Wort viscosity had no significant change.ASI can reduce wort turbidity by 30.36% ~ 50.00%.Transforming WUAX into 1.92×10~3 Da WEAX was the preferred major role of ASI with adding less than 0.9 mg/mL.Besides,degrade 1.92×10~3 Da WEAX was the preferred major role of ASI with adding more than 0.9 mg/m L.(5)HICIII(the enzyme after hydrophobic chromatography)can transform corncob WUAX into WEAX,and the main product Mw was 1.54×106 Da.HICIII had obvious degradation effect for bagasse WEAX,it can transform WUAX into WEAX,and degrade WEAX from 1.20×106 Da to 2.81×104 Da and 2.18×10~3 Da.(6)E-WMA had degradation effect on WEAX of low,medium,high viscosity,and the most significant degradation was the high viscosity.The concentration of three WEAX were 2 mg/m L,and the viscosity of high viscosity WEAX was 2.42 mPa·s.After enzymic degrading of high viscosity WEAX,the viscosity was decreased by 9.92%,the proportion of the 2.07×106 Da of WEAX was degraded into 3.37×105 Da.E-WMA also had degradation effect on low viscosity WEAX and medium viscosity WEAX with a viscosity of 1.77 mPa·s and 2.09 mPa·s,and the viscosity of WEAX decreased by 5.65% and 8.13% respectively.Moreover,E-WMA can transform WUAX into WEAX,where the viscosity of WEAX decreased by 1.89%.Also,the degradation made the Mw of converted WEAX decrease by 20.77%.