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Most Saccharomyces spp. cannot degrade or ferment dextrin, which is the second most abundant carbohydrate in wort for commercial beer production. Dextrin-degrading brewer’s bottom and top yeasts expressing the glucoamylase gene (GAM1) from Debaryomyces occidentalis were developed to produce low-carbohydrate (calorie) beers. GAM1 was constitutively expressed in brewer’s yeasts using a rDNA-integration system that contained yeast CUP1 gene coding for copper resistance as a selective marker. The recombinants secreted active glucoamylase, displaying both α-1,4- and α-1,6-debranching activities, that degraded dextrin and isomaltose and consequently grew using them as sole carbon source. One of the recombinant strains expressing GAM1 hydrolyzed 96 % of 2 % (w/v) dextrin and 98 % of 2 % (w/v) isomaltose within 5 days of growth. Growth, substrate assimilation, and enzyme activity of these strains were characterized.  相似文献   
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用GC,IR,NMR,GC-MS及高碘酸氧化,Smith降解,甲基化分析,部分酸水解等方法确定了一个新的碱提水溶小皮伞多糖的一级结构:分子主链α-D-(1→2)Man,支链α-(1→4),α-(a→6)Glc,且均连在主链的0─6上。  相似文献   
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It is becoming increasingly likely that rodents will drive future disease epidemics with the continued expansion of cities worldwide. Though transmission risk is a growing concern, relatively little is known about pathogens carried by urban rats. Here, we assess whether the diversity and prevalence of Bartonella bacteria differ according to the (co)occurrence of rat hosts across New Orleans, LA (NO), where both Norway (Rattus norvegicus) and roof rats (Rattus rattus) are found, relative to New York City (NYC) which only harbors Norway rats. We detected human pathogenic Bartonella species in both NYC and New Orleans rodents. We found that Norway rats in New Orleans harbored a more diverse assemblage of Bartonella than Norway rats in NYC and that Norway rats harbored a more diverse and distinct assemblage of Bartonella compared to roof rats in New Orleans. Additionally, Norway rats were more likely to be infected with Bartonella than roof rats in New Orleans. Flea infestation appears to be an important predictor of Bartonella infection in Norway rats across both cities. These findings illustrate that pathogen infections can be heterogeneous in urban rodents and indicate that further study of host species interactions could clarify variation in spillover risk across cities.  相似文献   
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无花果蛋白酶通过8%戊二醛活化载体,共价结合到聚苯乙烯阴离子交换树脂GM201上,固定化作用在pH7.7,酶浓度0.8mg/g树脂,4℃下进行6h。得到的固定化酶表观K_m值(酪蛋白,1.11×10~(-4)mol/L)小于溶液酶K_m值(1.96×10~(-4)mol/L);固定化酶活性在pH6~8保持稳定,溶液酶最适pH为7.2;固定化酶最适温度由溶液酶的50~60℃移至37℃;固定化酶25℃保持7d,重复水解酪蛋白7次后,保留83.3%活性。固定化酶对酪蛋白水解度达47.5%,对大豆球蛋白达11.6%。  相似文献   
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Brucella cell surface protein (BCSP31) is potentially useful for diagnosing brucellosis. We aimed to establish a monoclonal antibody (MAb) against Brucella melitensis BCSP31 and to investigate its distribution in diagnosis. Soluble recombinant BCSP31 was successfully expressed and purified. Two MAbs (1F1 and 1E5) against B. melitensis BCSP31, effective in detecting both recombinant and cellular proteins, were obtained and characterized. The MAbs did not react with Escherichia coli, Staphylococcus aureus, Bacillus subtilis, Mycobacterium tuberculosis, or Bacillus aeruginosus, but strongly reacted with BCSP31 and B. melitensis by ELISA and Western blot analysis. We also tested different Brucella species and brucellosis using the prepared anti-BCSP31 MAbs. BCSP31 and anti-BCSP31 MAbs may play important roles in future research in diagnosing brucellosis.  相似文献   
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