德氏乳杆菌保加利亚亚种自发突变抗噬菌体菌株的选育及其特性

Selection and characterization of spontaneous phage-resistant strains of Lactobacillus delbrueckii subsp.bulgaricus

利用德氏乳杆菌L.bulgaricus KLDS08021为宿主菌,采用次级感染的方法筛选自发突变的抗噬菌体菌株,将筛选出的有抗性的7株菌株进行RAPD-PCR鉴定,然后进行EOP、遗传稳定性、溶源性检测,并对其中的2株抗性菌BIM1、BIM7及野生株进行发酵性能测定。结果显示,7株菌RAPD-PCR电泳图谱一致,均来自宿主菌,是遗传性稳定的非溶源性菌;无论噬菌体是否存在2株抗性菌BIM1、BIM7其发酵活菌数、产酸能力都比野生株高,且制作的发酵乳黏度与硬度也比野生菌株强,适于作为酸奶发酵菌株。

Lactobacillus delbrueckii subsp.bulgaricus KLDS08021 was used as original strain. The bacteriophage-resistant mutants were isolated by secondary culture. Random amplification of polymorphic DNA （RAPD-PCR） was used to confirm strain identity among seven phage-resistant strains and their parent strain. Characteristics related to their phage-resistance capacities, EOP, phage- resistance stability, lysogeny were determined. The yogurt fermentation properties of mutants were also studied for two strains of mutants （BIM1, BIM7）. The study show that the phage-resistant strains were isolated from original strains and were stable and non-lysogen. The fermentation characteristic（viable count, acidifying） and texture characteristic （consistency, firmness） were superior to the origin strain regardless of the absence or presence of phage, so the two strains of mutants could be used for yogurt industrial production.