开菲尔粒中乳酸菌的筛选与发酵特性

Screening and Fermentation Characteristics of Antimicrobial Lactic Acid Bacteria Isolated from Kefir Grains

以大肠杆菌ATCC25922和金黄色葡萄球菌ATCC25923为抑菌对象筛选开菲尔粒中具有抑菌功能的乳酸菌,将该乳酸菌株发酵上清液制成冻干粉,未纯化的抗菌肽质量浓度大于6.250 mg/mL时,对大肠杆菌ATCC25922和金黄色葡萄球菌ATCC25923抑菌效果显著,利用16S rDNA方法,鉴定该菌株为干酪乳杆菌。以该菌株制备发酵剂,添加量2、3、4 g/100 mL发酵全脂乳,4℃冷藏保存30 d,结果表明,发酵剂添加量越多,酸乳pH值越低,滴定酸度、硬度、黏度和持水率越高,脱水收缩率越低;发酵剂添加量3 g/100 mL和4 g/100 mL酸乳的感官评分无明显差异,且均高于发酵剂添加量2 g/100 mL酸乳。

Escherichia coli ATCC25922 and Staphylococcus aureus ATCC25923 were used as test strains for screening of antimicrobial lactic acid bacteria from kefir grains.The fermentation supernatant of the selected isolate was processed into a freeze-dried powder.When used at a concentration greater than 6.250 mg/mL,the unpurified antimicrobial peptides had a strong bacteriostatic effect.The strain was identified as Lactobacillus casei by 16S rDNA gene sequencing.Raw whole milk was fermented by inoculating this strain at 2,3 or 4 g/100 mL,and stored at 4℃for 30 days.The pH and syneresis of fermented milk decreased with increasing inoculum size,whereas the titratable acidity,hardness,viscosity and water-holding capacity increased.The fermented milks with inoculum amounts of 3 and 4 g/100 mL did not significantly differ in sensory evaluation scores,both higher than that inoculated at 2 g/100 mL.