耐酸耐氧双歧杆菌突变株的选育与冷冻浓缩发酵剂的制备

Breeding of oxygen-and acid-resistant Bifidobacterium and preparation of freezing concentrated starter

应用紫外线、^60Co辐照育种，选育出1株耐酸、耐氧的长双歧杆菌突变株GKSW1101。该菌株在pH4．5的液体培养基中，37．5℃培养24h，活菌数达到4．2×10^8cfu／mL。采用加碱中和保持培养液pH6．0～6．5进行发酵，在4℃、6000r／min离心15min收集菌体，添加脱脂奶粉、甘油、蔗糖，L-半胱氨酸盐酸盐为冷冻保护剂，-25％冷冻保藏，制备成双歧杆菌冷冻浓缩发酵剂，活菌数达到2．4×10^10cfu／g，-25％贮存3个月后，活菌存活率为50％。

An acid- and oxygen- resistant Bifidobacterium longum mutant strain GKSW1101 was obtained by UV and ^60Co treatment. The cell density of mutant strain reached 4.2× 10^8 cfu/ml when it was cultured in pH 4.5 liquid medium for 24 h at 37.5 ℃. The strain GKSW1101 was used for the production of freezing concentrated starters. During fermentation, 6 mol/L NaOH was used to regulate the pH of medium, which was ranged between 6.0 and 6.5. After fermentation, the cells were collected by centrifugation at 6000 r/min and 4℃ for 15 min. Then, the skimmed milk powder, glycerol, sucrose and L-cysteine hydrochloride were added as protective additives for the freezing storage of strain GKSW1101 at -25 ℃. As freezing concentrated starter. After being stored at -25℃ for 3 months, the living cell count of the starter kept at 2.4× 10^10 cfu/g and the survival rate was 50%