耐高温产淀粉酶芽孢杆菌在烟叶烘烤中降解淀粉的应用研究

为降低烤后烟叶的淀粉含量，本研究对分离自烟叶，具有高效降解烟叶淀粉功能的两株细菌菌株进行了种类鉴定、发酵条件优化及烟叶烘烤应用效果研究。结果表明，菌株YTK1为解淀粉芽孢杆菌（Bacillus amyloliquefaciens），菌株B5221为枯草芽孢杆菌（B.subtilis）。两株芽孢杆菌都可以耐受60℃高温生长且长势良好，均主要产α-淀粉酶，具有较强的淀粉水解能力。菌株YTK1和B5221经发酵条件优化后，产胞外淀粉酶能力比优化前分别提高了338.52%和316.28%。将菌株YTK1和B5221制备的菌悬液均匀喷施于待烤烟叶进行密集式烘烤，烤后烟叶化学成分发生较大的变化，与对照相比，菌株YTK1处理后的中、上部烟叶淀粉分别下降了34.35%和32.66%，总糖分别增加了23.20%和16.51%，还原糖分别增加了16.69%和15.38%；菌株B5221处理后的中、上部烟叶淀粉分别下降了31.68%和30.46%，总糖分别增加了19.31%和14.25%，还原糖分别增加了12.36%和11.71%；总氮和蛋白质含量与相应的对照（CK）比略有降低，氯和钾含量变化不明显。本研究筛选获得的功能菌株将为降低烟叶淀粉含量、改善烟草品质开辟新的途径。 

Effects of amylase producing thermophilic Bacillus strains on starch degradation in tobacco during flue-curing

In order to reduce content of starch in flue-cured tobacco, functional microorganisms with efficient starch degradation were screened from tobacco leaves. Species identification, optimization of fermentation conditions and application possibility in tobacco flue-curing of the isolates were performed. Results showed that two strains YTK1 and B5221 belonged to B. amyloliquefaciens and B. subtilis respectively. They could withstand 60℃ with strong ability of starch hydrolysis. Two Bacillus strains mainly produced alpha-amylase. After optimized fermentation, cell growth and activity of amylase were significantly changed. The extracellular amylase activity of strains YTK1 and B5221 increased by 338.52% and 316.28%, respectively. The bacterial suspension of YTK1 and B5221 was evenly sprayed on cured tobacco leaves. The chemical composition of tobacco leaves after curing was greatly changed. Compared with control, the content of starch in middle and upper tobacco leaves by spraying strain YTK1 was decreased by 34.35% and 32.66%, the content of total sugar increased by 23.20% and 16.51%, the content of reducing sugar in tobacco leaves increased by 16.69% and 15.38% respectively. In sprayed treatments by strain B5221, the content of starch in middle and upper tobacco leaves was decreased by 31.68% and 30.46%, the content of total sugar increased by 19.31% and 14.25%, the content of reducing sugar increased by 12.36% and 11.71%, respectively. The contents of total nitrogen and protein were decreased slightly compared with the control (CK). The contents of chlorine and kalium showed no obvious change. The functional strains with efficient degradation of starch obtained in this study will provide strong scientific basis for tobacco quality improvement.