| Summary: | 碩士 === 國立臺灣大學 === 農業化學研究所 === 89 === Four strains, I5-12, H5-1, A6-9 and A6-14 with high titratable acid producing ability were isolated from infant feces. In acid tolerance test, survival of I5-12, A6-9 and A6-14 strains were about 106 CFU/mL after 2 hours of incubation at pH 2.5. In bile tolerance test, A6-14 strain showed a delay of growth of 27.48 minutes to obtain OD660＝0.3 as compared with growth in control culture. In addition, oxgall changed intrinsic resistance of most strains to gentamicin, kanamycin and streptomycin.
The identification result of A6-14 is Lactobacillus paracasei subsp. paracasei that named L. para. subsp. paracasei NTU101. The highest lactic acid concentration was 17.54 g/L and conversion yield was 88% in MRS static incubation at 30℃ for 48 hours. L. para. subsp. paracasei NTU101 grew well in milk and soymilk. Supplementation with glucose and yeast extract increased the growth and lactic acid production of L. para. subsp. paracasei NTU101.
In application, 25% milk and 75% soymilk supplemented with different amount of Lycium chinense Miller solution was fermented by a mix culture in 1:2 (v/v) ratio of L. para. subsp. paracasei NTU101 and Bifidobacterium longum CCRC 11847. In sensory evaluation, the mean scores of overall acceptability of 25% milk and 75% soymilk supplemented with 5% Lycium chinense Miller solution is significantly higher than other samples. For the product, syneresis didn’t occur apparently and its cell count maintains 109 CFU/mL after 14 days’ storage period at 4℃.
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