Isolation and Characterization of Lactic Acid Bacteria and Yeasts from Typical Bulgarian Sourdoughs

Mariana Petkova,Petya Stefanova,Angel Angelov,Velitchka Gotcheva

doi:10.3390/microorganisms9071346

Mariana Petkova, Petya Stefanova + Show 2 more

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https://doi.org/10.3390/microorganisms9071346

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Abstract

Traditional sourdoughs in Bulgaria were almost extinct during the centralized food production system. However, a rapidly developing trend of sourdough revival in the country is setting the demand for increased production and use of commercial starter cultures. The selection of strains for such cultures is based on geographical specificity and beneficial technological properties. In this connection, the aim of this study was to isolate, identify and characterize lactic acid bacteria (LAB) and yeasts from typical Bulgarian sourdoughs for the selection of strains for commercial sourdough starter cultures. Twelve samples of typical Bulgarian sourdoughs were collected from different geographical locations. All samples were analyzed for pH, total titratable acidity and dry matter content. Enumeration of LAB and yeast was also carried out. Molecular identification by 16S rDNA sequence analysis was performed for 167 LAB isolates, and 106 yeast strains were identified by ITS1-5.8S-ITS2 rRNA gene partial sequence analysis. The LAB strains were characterized according to their amylolytic and proteolytic activity and acidification capacity, and 11 strains were selected for further testing of their antimicrobial properties. The strains with the most pronounced antibacterial and antifungal activity are listed as recommended candidates for the development of starter cultures for sourdoughs or other food products.

Highlights

Bread and bakery products made with sourdoughs are becoming increasingly popular in the European market
Samples of a total of 12 typical Bulgarian sourdoughs, all produced without the addition of commercial yeast, were collected from 5 bakeries and 1 household in Bulgaria
Twelve samples of typical Bulgarian sourdoughs produced without the addition of commercial yeast were collected from different locations in Bulgaria and subjected to physico-chemical and microbial characterization

Summary

Introduction

Bread and bakery products made with sourdoughs are becoming increasingly popular in the European market. As the mixed microbial cultures in the sourdoughs are formed spontaneously, the stability of the mature doughs depends on a number of factors: (1) the microflora of the flour and other ingredients used, as well as the environment; (2) the metabolic activity in the dough—production of amylolytic and proteolytic enzymes by the microorganisms, and other physiological characteristics; (3) chemical composition and enzymatic activity of the flour; and (4) technological process parameters (flour/water ratio, fermentation and storage temperature, pH and redox potential, number of backsloppings, use of starter cultures and/or baker’s yeast, etc.) [9,10,11,12,13,14]. As a result of the heterogeneity of these factors, mature sourdoughs differ in the diversity of microbial species and metabolic activities [15,16,17,18,19]

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