低温乳酸菌复合系的构建、培养条件优化及在玉米干秸杆微贮中的应用

目的]研究筛选得到的低温乳酸菌复合菌系(LAC-1)的最佳培养条件及应用于玉米干秸杆微贮的效果.方法]通过连续限制性培养的方法,以pH为指标进行低温乳酸菌复合系的筛选;利用单因素试验、Box-Benhnken试验设计和响应面的分析方法对低温乳酸菌复合系的培养条件进行优化.结果]筛选获得培养液pH下降迅速、变化稳定及接种干玉米秸杆后可降低发酵体系pH、提高发酵饲料感官品质的低温乳酸菌复合菌系LAC-1.培养时间对LAC-1的pH降低速度影响最大,温度次之,接种量影响最小；响应面分析LAC-1最佳的培养条件为培养温度9.5℃、接种量3.3％和培养时间139 h.经过优化,LAC-1培养过程中pH下降到4.0的时间比优化前缩短48 h,乳酸菌数提高了20.5％.LAC-1接种于干玉米秸秆发酵5d时,秸秆发酵体系pH降至4.1；与对照相比,秸秆发酵饲料可散发出甜酸香味,外观质地松散、色泽鲜亮,可溶性碳水化合物含量降低了46.3％,霉菌、恶臭醋酸杆菌和酵母菌数量显著降低,乳酸菌数量提高了33.3％.结论]接种LAC-1可促进干玉米秸秆低温微贮进程,提高饲料品质.

Construction and optimization the culture conditions for the micro storage of corn straw by lactic acid bacteria community at low temperature

Objective] To optimize the culture conditions of lactic acid bacteria community (LAC-1) screened at low temperature, and investigate the micro storage effects of cornstalk inoculated with LAC-1. Methods] The LAC-1 was screened by continuous restricted cultivation, using system pH as the only indicator. The single factor experiment, Box-Behnken design and response surface methodology were used to optimize the culture conditions of LAC-1. Results] A community which could decrease pH rapidly was screened and named as LAC-1. LAC-1 could keep the pH and fermentation system stable, which could improve the sensory quality of fermented silage. Results showed that the pH reduction speed of LAC-1 was greatly influenced in this order: culture time, temperature and inoculated quantity. The optimal culture parameters were: culture temperature at 9.5 °C, inoculated quantity at 3.3% and culture time at 139 h. Under the optimal conditions, the fermentation time was shortened by 48 h and the number of lactic acid bacteria was increased by 20.5%. When the dry cornstalk was inoculated with LAC-1 by 5 days, the system pH fell to 4.1. The silage smelled sweet, flavor and sour, the texture was loose in appearance and bright in color. The following determination indicated the content of water-soluble carbohydrate was declined by 46.3% and the number of lactic acid bacteria was improved by 33.3%. Conclusion] The application of LAC-1 could promote the conversion of dry cornstalk into micro storage and improve the quality of silage.