Development of Tyrosine Decarboxylase-Negative Strains of Lactobacillus curvatus by Classical Strain Improvement
| Autor: | Kim I. Sørensen, Ana Rute Neves, Patrick M. F. Derkx, Per Strøman |
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| Rok vydání: | 2018 |
| Předmět: |
0301 basic medicine
030106 microbiology Mutant Tyramine Microbiology law.invention 03 medical and health sciences chemistry.chemical_compound law Tyrosine Gene chemistry.chemical_classification biology food and beverages Tyrosine Decarboxylase biology.organism_classification Tyrosine decarboxylase Amino acid Meat Products Lactobacillus chemistry Biochemistry Fermentation Recombinant DNA Food Microbiology Bacteria Food Science |
| Zdroj: | Journal of food protection. 81(4) |
| ISSN: | 1944-9097 |
| Popis: | Biogenic amines have been widely studied because of their potential toxicity in fermented foods. Several lactic acid bacteria have the potential to decarboxylate the amino acid tyrosine to tyramine. In this work, we identified two strains of Lactobacillus curvatus, Lbc1 and Lbc2, endowed with the ability to produce tyramine, a metabolic feature that limits their application in starter cultures for fermented meat. To overcome this limitation, we set out to eliminate tyramine production from L. curvatus strains by using classical strain improvement. About 4,000 mutant isolates of both strains were screened using a colorimetric method, and then potential tyrosine decarboxylase-negative mutants were selected. Firm identification of loss-of-function mutants was performed by analytical determination of tyrosine and tyramine in cultivation medium. Of the 8,000 mutants screened, only one mutant of Lbc1 and two mutants of Lbc2 had completely lost the potential to produce tyramine. Subsequently, one tyrosine decarboxylase-negative mutant of both Lbc1 and Lbc2 was characterized in more detail. DNA sequencing of the Lbc1 mutant tdcA gene disclosed two missense mutations in the promoter distal part of the coding sequence. These two mutations result in two amino acid changes in the encoded tyrosine decarboxylase, Pro87Thr and Ser130Leu, presumably inactivating the enzyme activity. The DNA sequence of the other characterized mutant, derived from strain Lbc2, showed that insertion of a 6-bp fragment at nucleotide position 1348 in the tdc gene is presumably the factor leading to loss of activity. With the successful elimination of the undesirable tyramine-producing phenotype without the use of recombinant DNA technology, these developed L. curvatus mutant strains can be safely used in the dairy industry or in the manufacture of various food products. |
| Databáze: | OpenAIRE |
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