Acid tolerant mutants of Bifidobacterium animalis subsp. lactis with improved stability in fruit juice

Maria Saarela (Corresponding Author), Hanna-Leena Alakomi, Jaana Mättö, A.-M. Ahonen, S. Tynkkynen

Research output: Contribution to journalArticleScientificpeer-review

24 Citations (Scopus)


The potential of UV mutagenesis combined with a specific selection step to generate more acid-resistant Bifidobacterium animalis subsp. lactis Bb-12 strains with improved viability in low pH food matrices was investigated in this study. A total of 144 Bb-12 UV-mutants were initially characterised. After prolonged storage in apple juice (pH 3.5) and various pheno- and genotypic tests (acid and bile tolerance, substrate utilisation, antibiotic susceptibility, aerotolerance, RAPD) two mutants (2.20 and 2.56) were chosen for further studies including cell surface morphology, stability of various traits after repeated inoculations, and performance in a fermenter and during down-stream processing. 2.20 and 2.56 showed over two Log-values better viability in pH 3.5 juice compared to Bb-12. Alterations in cell surface structures of 2.20 and 2.56 were detected with AFM, whereas other studied traits remained unchanged.

In conclusion, UV mutagenesis and subsequent incubation in acidic medium enabled improving the stability of B. animalis subsp. lactis in low pH juice. Acid tolerance testing (HCl, pH 2.5, 2 h) results did not predict long-term stability of the strains in acidic food matrix (apple juice pH 3.5).

Original languageEnglish
Pages (from-to)1012-1018
Number of pages7
JournalLWT - Food Science and Technology
Issue number4
Publication statusPublished - 2010
MoE publication typeA1 Journal article-refereed


  • Bifidobacterium
  • UV mutagenesis
  • acid tolerance
  • fruit juice
  • stability

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