Lactobacillus paracasei: an evaluation of the flavour diversification potential of the species through genomics, metabolomics and applications
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Date
2017
Authors
Stefanovic, Ewelina
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Publisher
University College Cork
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Abstract
Strains of Lactobacillus paracasei are commonly isolated from numerous and diverse niches, such as dairy products, plant materials and reproductive and gastrointestinal tracts of humans and animals. In cheese, strains of L. paracasei belong predominantly to the non-starter microbiota, which is often considered to be immensely important for the development of flavour. In this project, the genetic and phenotypic diversity of L. paracasei strains and their application as adjunct cultures to support the development of flavour compounds was assessed. The bank of 310 strains investigated in this study consisted of isolates originating from cheese, yoghurt and sourdough. After genomic profiling, 99 strains were selected for future examination. The phenotypic characterisation included in vitro assessment of the key proteolytic enzyme activities, the most important factor contributing to the flavour compound development. The activities of the examined enzymes significantly differed among the analysed strains. Ten strains showing different enzyme activities were selected to compare their ability for flavour compounds production in two cheese model systems. The volatile profiles of the strains differed in both model systems, and according to the all generated results, three strains (DPC2071, DPC4206 and DPC4536) were selected as adjunct cultures for Cheddar cheese manufacture. The cheese analysis showed that although some differences existed, they were minimal and cheeses were of similar flavour characteristics. Finally, to identify and characterise specific genes that may contribute to the overall differentiation of the selected strains, genome sequencing and assembly and comparative genome analysis were performed on the three strains used in the cheese production, and a considerable level of genetic heterogeneity was observed.
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Keywords
Lactobacillus paracasei , Genomics , Flavour potential , Metabolomics
Citation
Stefanovic, E. 2017. Lactobacillus paracasei: an evaluation of the flavour diversification potential of the species through genomics, metabolomics and applications. PhD Thesis, University College Cork.