大曲来源淀粉利用型乳酸菌的筛选及其淀粉利用特性

Starch utilization characteristics of lactic acid bacteria isolated from Daqu

【背景】乳酸菌是面包、馒头等发酵食品中的重要功能微生物,对改善质地和风味均具有重要作用。淀粉利用能力高的乳酸菌,因其能够在生面粉中更好地定殖而具有重要的应用价值。【目的】筛选获得淀粉水解型乳酸菌并研究其淀粉利用特性。【方法】以浓香型白酒大曲为筛选源,采用淀粉基质碳源对大曲中乳酸菌进行定向富集,结合淀粉发酵能力筛选高淀粉利用能力菌株,并对筛选得到的优良菌株展开淀粉酶表达及其酶活力研究。【结果】以贮存3‒6个月的大曲为优秀筛选源,以生面糊传代富集方法可较快筛选出具有良好淀粉利用能力的乳杆菌,主要物种为植物乳杆菌和类食品乳杆菌。对其中一株具有淀粉利用能力的类食品乳杆菌LBM12001的淀粉水解特征和淀粉酶活力展开研究,该菌株淀粉水解能力达10 g/L,并且其在面糊中具有良好的定殖能力;酶活力测定表明,其α-淀粉酶和麦芽糖淀粉酶为胞外酶;麦芽糖淀粉酶水解淀粉的最适pH值为3.5,比酶活为1240 U/mg。【结论】建立起从我国传统白酒发酵大曲中高效筛选淀粉水解型乳酸菌的富集筛选方法,以及菌株的水解能力评价方法,获得的胞外麦芽糖淀粉酶分泌型乳杆菌在酸面团、馒头等需进行生面粉发酵食品的生产中具有重要应用前景。

[Background]Lactic acid bacteria(LAB)are important microorganisms which affect the texture and flavor of fermentation foods such as sourdough and steamed bun.Amylolytic LAB have enormous application possibilities owing to their ability to colonize in flour.[Objective]To screen amylolytic LAB and study their starch utilization characteristics.[Methods]The medium with starch as carbon source was used to enrich target strains from Daqu for strong aromatic Chinese spirit,followed by testing the starch hydrolysis ablility.Then,expression level of amylase in the yielded strain and the enzyme activity were determined.[Results]Daqu which had been stored for 3‒6 months was optmal for screening the bactia.Amylolytic LAB can be quickly screened out by subculture with batter.The yielded strains were dominated by Lactobacillus plantarum and Lactobacillus paralimentarius.The starch utilization characteristics and amylase activity in the amylolytic L.paralimentarius LBM12001 were analyzed.The findings showed that it can hydrolyze starch at 10 g/L and well colonize in batter.Theα-amylase and maltogenic amylase were extracellular enzymes.The specific enzyme activity of maltogenic amylase reached 1240 U/mg at pH 3.5.[Conclusion]We developed a method to enrich about screen amylolytic LAB from Daqu for traditional Chinese spirit and a method for evaluating the starch hydrolysis ability,and screened out the extracellular maltogenic amylase-secreting strain which had great potential in the production of sourdough,steamed bun,and other fermentation foods.