Effect Of Arabinoxylan Arabinofuranohydrolase On Filterability Of Jiangsu Barley Malt

Jiangsu Province is one of the main malting barley grown areas in China, Dan’er is oneof the dominant cultivars. However, the filterability defect of its barley malt compared withimported ones, like a Canadian cultivar of Metcalfe with superior malt filterability. In thisdissertation, differential metabolic proteins between Dan’er and Metcalfe barley malts withdistinct filterability were studied by comparative proteomics, and then differentialarabinoxylan arabinofuranohydrolase I (AXAH-I) was selected to investigate the impact formalt filterability.The most differential metabolic proteins were focused on material metabolism-relatedand pathogenesis-related proteins. Standard abundance ratio of AXAH-I as one of theobviously differential proteins between Dan’er and Metcalfe went beyond2, and AXAHactivities of Dan’er malt was only about60.5%of that of Metcalfe.AXAH-I was purified from Daner barley malt by ammonium sulfate precipitation,HiTrap16/10SP FF, HiPrep16/10Q FF ion exchange chromatography, and HiPrep16/60Sephacryl S-100HR gel filtration chromatography. The purified protein was identified bySDS-PAGE and tandem mass spectrometry (MS/MS). The secondary structure of the AXAH-Iwas measured by circular dichroism (CD) method, and α-helix was found to be the majorcontent of the secondary structure. The specific activity of the purified AXAH-I was111.11mU mg-1, the activity increased by99.21folds and the final recovery rate of the total activitywas12.00%. The optimum pH of the purified AXAH-I was4.5, and it was relatively stableunder pH4.0~6.0. The optimum temperature was55℃, and it was relatively stable at thetempateture of30~55℃. Mn2+had significant activating effect on the activity of AXAH-I,while Cu2+and Fe2+had the most significant inhibitory effect. The parameter of enzymekinetics (Km) was0.46mg mL-1.The filterability of malt was significantly improved with addition of the purifiedAXAH-I into mashing process of Dan’er malt. When6mU g-1of AXAH-I was added, thefiltration rate of wort increased by34.2%. Wort viscosity decreased by5.5%while wortturbidity increased by32.5%. The contents of PAX and the ratio of A/X decreased by6.7%and31.0%, respectively. Orthogonal analysis with three factors (AXAH-I, β-amlyse andenzymes preparations) in two levels were tested. When enzyme preparations (0.4mg g-1),β-ayme (40.0U g-1) and AXAH-I (6.0mU g-1) were added, the filtration rate of wortincreased by81.4%, while wort turbidity and wort viscosity decreased by48.5%and7.3%.