烟叶淀粉和蛋白质降解复合菌剂研究

Study on Compound Bacterial Agent for Degradation of Starch and Protein in Tobacco Leaves

目的:为有效降解烟叶淀粉和蛋白质,提高烟叶可用性、品质和安全性。方法:对两株分别具有蛋白质和淀粉降解能力的菌株BS1、BS3进行发酵条件的优化及复合菌剂的制备,并对复合菌剂的应用效果进行了评价。结果:菌株BS1的最适发酵条件为:10 g/L可溶性淀粉作为碳源、10 g/L蛋白胨作为氮源、CaCl2作为无机盐,在37℃、pH7、转速为230 rpm/min的条件下发酵24 h,BS1的蛋白酶活性为78.18 U/mL;菌株BS3的最适发酵条件为:10 g/L可溶性淀粉作为碳源、10 g/L酵母粉作为氮源及5 g/L的KNO3作为无机盐,在37℃、pH7、转速为230 rpm/min的条件下发酵24 h,测得BS3淀粉酶活为133.93 U/mL。复合菌剂的最佳配方为:载体为水合硅酸,与发酵液比例为1:5;分散剂为2.00%的六偏磷酸钠;湿润剂为1.00%的烷基糖苷;稳定剂为1.00%的甘油。复合菌剂处理48 h并烘烤后,烟叶淀粉和蛋白质含量分别降低了26.41%和17.14%,还原糖和钾离子含量明显升高,糖碱比、钾氯比升高,烟碱含量降低;烟叶颜色、色度及成熟度更好,叶片油润感强,香气质增加,杂气和刺激性减少。结论:通过发酵条件的优化,提高了BS1和BS3的淀粉酶和蛋白酶活性,制备的复合菌剂有效降低了烟叶的蛋白质和淀粉含量,提升了烤后烟叶的品质,具有较好的应用前景。Objective: To effectively degrade the starch and protein of tobacco leaves and improve the availability, quality and safety of tobacco leaves. Methods: In this study, two strains BS1 and BS3 with protein and starch degradation ability were optimized for fermentation conditions and preparation of complex bacterial agent, and the application effect of the complex bacterial agent was evaluated. Results: The optimal fermentation conditions for strain BS1 are: 10 g/L soluble starch as a carbon source, 10 g/L peptone as a nitrogen source, and CaCl2 as an inorganic salt. The protease activity of BS1 was 78.18 U/mL after 24 hours of fermentation at 37˚C, pH7, and rotation speed of 230 rpm/min. The optimal fermentation conditions for strain BS3 are: 10 g/L soluble starch as a carbon source, 10 g/L yeast extract as a nitrogen source, and 5 g/L KNO3 as an inorganic salt. Fermentation is carried out at 37˚C, pH7, and speed of 230 rpm/min for 24 hours, and the amylase activity of BS3 is measured to be 133.93 U/mL. The optimal formula for the compound bacteria agent is the carrier is hydrated silica, with a ratio of 1:5 to the fermentation broth;the dispersant is 2.00% sodium hexametaphosphate;the wetting agent is 1.00% alkyl glucoside;the stabilizer is 1.00% glycerol. After 48 hours of treatment with compound bacteria agents and baking, the starch and protein content of tobacco leaves decreased by 26.41% and 17.14%, respectively. The content of reducing sugars and potassium ions significantly increased, while the sugar alkali ratio and potassium chloride ratio increased, and the nicotine content decreased. The color, chromaticity, and maturity of tobacco leaves are better, the leaves have a strong oiliness, the aroma quality increases, and the impurities and irritancy decrease. Conclusion: By optimizing the fermentation conditions, the amylase and protease activities of BS1 and BS3 were improved. The prepared compound bacteria agent effectively reduced the protein and starch content of tobacco leaves, improved the quality of cured tobacco leaves, and had good application prospects.