Large Genetic Intraspecific Diversity of Autochthonous Lactic Acid Bacteria and Yeasts Isolated from PDO Tuscan Bread Sourdough

Michela Palla,Manuela Giovannetti,Monica Agnolucci,Caterina Cristani

doi:10.3390/app10031043

Michela Palla, Manuela Giovannetti + Show 2 more

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https://doi.org/10.3390/app10031043

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Journal: Applied Sciences	Publication Date: Feb 4, 2020
Citations: 11	License type: CC BY 4.0

Affiliation: University of Pisa

Abstract

The diverse metabolites, positively affecting the nutritional, organoleptic and technological traits of leavened baked goods, are produced by different sourdough lactic acid bacteria (LAB) and yeast strains, as the result of their genetic intraspecific diversity. Therefore, the molecular and functional strain-level characterization of sourdough microbiota is crucial to valorize traditional or origin protected baked end-products, develop innovative starter cultures and design functional cereal-based foods. To this aim, the genetic intraspecific diversity of 96 Lactobacillus sanfranciscensis, 65 Kazachstania humilis and three Saccharomyces cerevisiae characterizing Protected Designation of Origin (PDO) Tuscan bread sourdough, was investigated, using P4, P7 and M13 random amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR), (GTG)5 repetitive element sequence-based (rep)-PCR and inter-delta region analyses, respectively. Regarding LAB, the combination of P4, P7 and M13 RAPD-PCR analyses revealed a huge degree of intraspecific variability, discriminating 43 biotypes out of 96 isolates of L. sanfranciscensis. (GTG)5 rep-PCR showed a discriminatory index of 0.95, grouping the 65 K. humilis isolated from PDO Tuscan bread sourdough in 9 biotypes. The high polymorphism among both LAB and yeast isolates of PDO Tuscan bread sourdough outlines a highly complex microbial community structure, whose relative composition and specific physiological characteristics could be responsible for the peculiar organoleptic, rheological, nutritional and potentially nutraceutical features of PDO Tuscan bread.

Highlights

Sourdough is a mixture of cereal flour and water, fermented by a complex biological ecosystem, consisting of different genera, species and strains of lactic acid bacteria (LAB) and yeasts, which interact among themselves, often establishing stable associations
Considering that a high genetic intraspecific diversity of sourdough microbial communities may provide differential functional features affecting nutritional, organoleptic and technological properties of leavened baked goods, here, for the first time, we investigated the molecular diversity of Protected Designation of Origin (PDO) Tuscan bread sourdough microbiota at the strain level
RAPD-PCR profiles, obtained using three single reactions with P4, P7 and M13 primers, were combined to create a dendrogram, which grouped the isolates into two main clusters with a similarity level of 79%, and clustered L. sanfranciscensis IMA

Summary

Introduction

Sourdough is a mixture of cereal flour and water, fermented by a complex biological ecosystem, consisting of different genera, species and strains of lactic acid bacteria (LAB) and yeasts, which interact among themselves, often establishing stable associations. The molecular and functional strain-level characterization of sourdough microbiota is crucial to give value to traditional or origin protected baked end-products, to develop innovative starter cultures and to design functional cereal-based foods. To this aim, molecular tools for the intraspecific characterization of sourdough microbiota are fundamental, though there is no universally applicable typing method to discriminate among isolates from the same ecological niche, harbouring different microbial communities well adapted to the environment and often closely related among them [4]

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