【作者】 谢丽源；

【导师】 贺稚非；

【作者基本信息】 西南农业大学 ， 微生物学， 2003， 硕士

【摘要】 本试验以黄瓜汁为基质，通过添加2％的葡萄糖、0.5％的蛋白胨制成基础培养基，对5株乳酸菌进行了发酵性能研究。选取其中两株菌作为发酵菌种，以发酵过程中的pH值，活菌数为指标，对其菌种配比、培养基成分、培养条件、富集方法、冻干保护剂等进行了系统研究，旨在为直投型的乳酸菌发酵剂生产提供依据。研究结果表明： 1．通过研究五株菌发酵产酸特性，选取A菌株和D菌株两株菌作为发酵菌种。当双菌混合培养时，表现出了良好的互生发酵特性。且当双菌配比为1：1时，产酸能力和活菌数均高于其它组合。 2．通过单因子试验，筛选了用作发酵剂制作的最佳碳源为葡萄糖，最佳氮源为蛋白胨，生长促进因子为番茄汁。由正交试验确定了发酵培养基的最佳配方为2％葡萄糖、1％蛋白胨、5％番茄汁、10％磷酸盐、0.1％吐温80。 3．研究表明：在接种量3％，培养温度30℃，初始pH6.6，装液量40mL(100mL三角瓶)，振荡频率120r／min条件下培养，培养14h后补充营养物质继续培养，到20h时可使乳酸菌活菌数达到7.24×10~9cfu／mL。 4．在摇床恒温培养20h后，菌数达到最大值，即可进行离心收获菌体。离心条件设计为4000r／min，15min；4000r／min，30min；6000r／min，15min；6000r／min，30min；结果表明：4000r／min转速下离心30min，可以得到相对较好的菌体富 2003届硕士学位论文：活性干燥乳酸菌发酵剂的研究集效果。 5．以 10％的脱脂乳为冻于悬浮基质，对蔗糖、血清蛋白、甘油、海藻酸钠四种保护剂的保护效果进行了研究。结果表明：四种保护剂对菌体都有一定程度的保护效果，其中甘油的保护效果最佳，冻干后菌体的存活率最高。 6．在真空冷冻干燥机中将添加保护剂的菌悬液冷冻至－30C以下，于真空度为 60mm汞柱下冷冻干燥，2832h后，即可得到每克含活菌数为 3．4 XIO“个的高活力的乳酸菌粉末状发酵剂。 7．将冻干发酵剂成品进行应用特性研究，结果表明：发酵剂在保存期间菌数呈下降趋势。真空包装条件下菌数明显高于常压包装。－18t和 4oC保存效果优于常温，刁8C的保存效果略优于4C，但h者差别不大。从生产应用考虑，采用真空包装，在4C下贮藏，2个月对菌数影响不太大。 8．研究表明：冻干发酵剂的接种量可比普通液体发酵剂接种量小 100倍左右。冻干发酵剂需经过较长一段时间的延迟期才迅速产酸，但产酸总量与液体发酵剂相当，用冻干发酵剂制得的泡黄瓜风味与色泽与液体发酵剂无明显差别。更多还原

【Abstract】 A primary medium which was on the basis of cucumber juice was prepared by adding 2% glucose, 0.5% peptone. The fermentative ability of five lactic acid bacteria was studied, which affirmed two strains as the primary fermentative species. Taking pH value and living cell count as indexes in the process of fermentation, the experiment had studied strain ratios, cultural medium components, cultivation conditions, enrichment methods and cryoprotectant. The purpose is to provide experimental basis for direct-to-vat culture starters. The results indicated:1. Two strains (A and D) showed good mutual fermentation character and when the ratio of the two strains’ amount was 1:1, acid content and living cell count were higher than other strain ratio.2. Fermentation experiment indicated: the optimum carbon source was glucose, the optimum nitrogen source was peptone, growth factor was tomato juice. According to orthogonal experiment, the optimal medium contained the following ingredients: 2% glucose, 1% peotone, 5%tomato juice, 10% phosphate and 1% Tween 80.3. Seed volume was 3%, the incubation temperature was 30 C, Na2CO3 was used to control initial pH at 6.6, cultural fluid amount is 40mL, shaking culture with rotating speed 120 rotation per minute was used, after 14 hours’ culture, nutrient substance was added to the medium and the cell population got to 7.24 + 109cfu/mL, after 20 hours’ culture.Master Degree Dissertation: Study on High Effective Lyophilized Lactic Acid Starter Culture Concentrates4. After 20 hours’ culture, lactic acid bacteria cells were harvested by centrifugation. Results indicated that the best effect could be obtained at 4 C with 4000 r/min for 30 min .5. Using 10% nonfat dried-milk as suspended substrate, the function of four protectors including sucrose, serum protein, glycerin and trehalose were studied. Results suggested that all of them had some effects on promoting cell count and glycerin was the best one.6. The cell suspension in 10% nonfat dried milk containing the suitable protector might be lyophilized into the lactic acid bacteria powder with high viability (the number of viable cell 3.4 + 1010cfu/g).7. The RP-F bags containing the dry starter concentrated were sealed under vacuum, stored at 4 C for 60 days. Culture starter had little effect on cell count.8. By culture starter quality test, we studied the culture starter application feature. Compared with tradition fluid culture starter, the seed volume of freeze-drying culture starter reduced 100 times. Freeze-drying culture starter produced quickly acid through long lag phase, but acid-produced amount was as well as liquid culture starter’s . The pickle by freeze-drying culture had good in color, smell and taste.更多还原