Screening Of Producing β-glucanase Strain And Evaluation Of Its Malting Characterization

Gansu is one of the three major producing areas of the domestic malting barley and malt，distributed in cold regions which elevation is above1900m. The effect of climatic conditions andgeographical location caused high content of glucan and protein for local barley, the endospermcell of malt produced dissolving insufficiently, high content of finished malt glucan，high Viscosity,slow filtration, all which lead to the uncertainty for beer brewing. In orde r to solve these problemsrelating to the barley industry development, this thesis was focused on the purpose of the screeningof malting microbiology, using separation and screening tryed to obtain a microbial strains havinghigh yield ofβ-glucanase from different vegetative cover and raw barley surface, and implying thestrain in the malting process, by its measuring growth characteristics in the given material maltingenvironmention, and enzyme activity characteristics and their impact on malt quality,comprehensively evaluating the malting performance of this strain to determine whether the strainwounld be used as malting starter strains to provide a scientific basis and reference.The main research results are as follows:1.In this study,10strains were isolated from different vegetation cover using initial selectivemethod and activity quantitative assay, which were able to break down the β-glucan, then evaluatedthe malting performance throungh microbial malting test. The results showed that: strain M-28inoculated in the malting process could effectively increase malt β-glucanase and xylanase activity,reduce malt glucan content. throngth description of the colony morphology and microscopicmorphological observation, strains M-28was preliminary identificated as Mucor petrinsularis.2. Implying liquid-state and solid-state fermentation experiments of productingβ-glucanase totreat Strain M-28, using single-factor test design and response surface experimention design tooptimize the conditions of enzyme production. Finally, the optimum condition of productingβ-glucanase activity in the liquid–state were fermentation temperature30℃, fermentation time81h, the inoculum concentration7.2%, initial pH value6.0, under the conditions, the level of strainsproducing β-glucanase activity came up to15.8775U/mL. the optimize condition ofproducingβ-glucanase activity in the solid-state were the best mixing ratio of the medium flour andwheat bran was1:2, solid to liquid ratio was1.0:1.2, fermentation temperature26℃,fermentation time4d, inoculum concentrance13%, under these conditions, the β-glucanase activitythe strains produced could come up to51.7283U/mL. 3. To perform the three main factors about microbiology affecting malting by single factor test,based on the significant difference between the trends in various indicators, as well as the level ofanalysis to determine the best malting process conditions: the spore germination time6h,inoculation time was the end for the first steeping, inoculum concentrance of105cells/mL, inaccordance with the optimum conditions to take the the malting test. the results showed that: in themalting process of adding M-28, the malt leaching rate increased by7.8%, the Chur Bach valueincreased by10%, agreements wort β-glucan content decreased by45%, the filtration rate increasedby7.3%, showing that the strain M-28as the starter culture played an importent role in promotingmalt dissolution during microbial malting process.5. During the microbial malting process adding M-28, the trend of the solubility of relatedenzymes were measured, the results showed that malting process adding strain M-28of barleyβ-glucanase, xylanase and amylase activitylate in the malting than controlling malting process, andamylase in germination late remains a persistent tendency to increase enzyme activity, two maltingprocess the process of change in the overall level of protease activity in line. Visible inoculatedmicroorganisms in the microbial malting process exogenous e nzyme affect the malt enzymes,promote the improvement of the overall level of enzymes, effectively improve the solubility ofmalt.