Dataset Information

Phenotypic Diversity of Lactobacillus casei Group Isolates as a Selection Criterion for Use as Secondary Adjunct Starters.

ABSTRACT: Autochthonous lactic acid bacteria (LAB) play a key role in the development of cheese flavor. As the pasteurization treatment on raw milk causes the elimination of LAB, secondary starter cultures are used in cheese manufacture to obtain cheeses with improved and standardized flavors. In this work, strains of the L. casei group isolated from traditional Italian cheeses were screened for their phenotypic features of technological interest for use as secondary starters. Their milk acidifying performance and the production of volatile compounds when grown in milk were evaluated. Simultaneously, the acetoin metabolic pathway presence was screened in the strains and assessed for its transcriptional activation. The results showed that the analyzed strains, despite belonging to taxonomically-related species, vary greatly according to the measured phenotypes. Four strains among the fourteen screened could be potentially used as adjunct cultures for cheese-making processes. The strain that showed the highest production of acetoin upregulated the aspartate pathway. An increased knowledge of volatile compounds' production and acidifying properties of LAB strains isolated from traditional dairy products might guide the selection of strains for industrial applications.

SUBMITTER: Levante A

PROVIDER: S-EPMC7022476 | biostudies-literature | 2020 Jan

REPOSITORIES: biostudies-literature

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Phenotypic Diversity of <i>Lactobacillus casei</i> Group Isolates as a Selection Criterion for Use as Secondary Adjunct Starters.

Levante Alessia A Bancalari Elena E Tambassi Martina M Lazzi Camilla C Neviani Erasmo E Gatti Monica M

Microorganisms 20200117 1

Autochthonous lactic acid bacteria (LAB) play a key role in the development of cheese flavor. As the pasteurization treatment on raw milk causes the elimination of LAB, secondary starter cultures are used in cheese manufacture to obtain cheeses with improved and standardized flavors. In this work, strains of the <i>L. casei</i> group isolated from traditional Italian cheeses were screened for their phenotypic features of technological interest for use as secondary starters. Their milk acidifying ...[more]

PMID: 31963444

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Project description:Lactobacillus casei, Lactobacillus paracasei, and Lactobacillus rhamnosus are phenotypically and genotypically closely related, and together comprise the L. casei group. Although the strains of this group are commercially valuable as probiotics, the taxonomic status and nomenclature of the L. casei group have long been contentious because of the difficulties in identifying these three species by using the most frequently used genotypic methodology of 16S rRNA gene sequencing. Long used as the gold standard for species classification, DNA-DNA hybridization is laborious, requires expert skills, and is difficult to use routinely in laboratories. Currently, genome-based comparisons, including average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH), are commonly applied to bacterial taxonomy as alternatives to the gold standard method for the demarcating phylogenetic relationships. To establish quick and accurate methods for identifying strains in the L. casei group at the species and subspecies levels, we developed species- and subspecies-specific identification methods based on housekeeping gene sequences and whole-cell matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) spectral pattern analysis. By phylogenetic analysis based on concatenated housekeeping gene sequences (dnaJ, dnaK, mutL, pheS, and yycH), 53 strains were separated into four clusters corresponding to the four species: L. casei, L. paracasei and L. rhamnosus, and Lactobacillus chiayiensis sp. nov. A multiplex minisequencing assay using single nucleotide polymorphism (SNP)-specific primers based on the dnaK gene sequences and species-specific primers based on the mutL gene sequences provided high resolution that enabled the strains at the species level to be identified as L. casei, L. paracasei, and L. rhamnosus. By MALDI-TOF MS analysis coupled with an internal database and ClinProTools software, species- and subspecies-level L. casei group strains were identified based on reliable scores and species- and subspecies-specific MS peaks. The L. paracasei strains were distinguished clearly at the subspecies level based on subspecies-specific MS peaks. This article describes the rapid and accurate methods used for identification and classification of strains in the L. casei group based on housekeeping gene sequences and MALDI-TOF MS analysis as well as the novel speciation of this group including L. chiayiensis sp. nov. and 'Lactobacillus zeae' by genome-based methods.

Dataset Information

Phenotypic Diversity of Lactobacillus casei Group Isolates as a Selection Criterion for Use as Secondary Adjunct Starters.

Publications

Phenotypic Diversity of <i>Lactobacillus casei</i> Group Isolates as a Selection Criterion for Use as Secondary Adjunct Starters.

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