Selection of cereal-sourced lactic acid bacteria as candidate starters for the baking industry.

Vesna Milanović,Roberta Foligni,Federica Cardinali,Luca Belleggia,Andrea Osimani,Lucia Aquilanti,Francesca Clementi,Cristiana Garofalo,Massimo Mozzon,Antonietta Maoloni,Leonidas Matsakas

doi:10.1371/journal.pone.0236190

Abstract

The quality of sourdough bread mainly depends on metabolic activities of lactic acid bacteria (LAB). The exopolysaccharides (EPS) produced by LAB affect positively the technological and nutritional properties of the bread, while phytases improve the bioavailability of the minerals by reducing its phytate content. In the present study, a pool of 152 cereal-sourced LAB were screened for production of phytases and EPS for potential use as sourdough starter cultures for the baking industry. There was large heterogeneity in the phytase activity observed among the screened isolates, with 95% showing the ability to degrade sodium phytate on plates containing Sourdough Simulation Medium (SSM). The isolates Lactobacillus brevis LD65 and Lactobacillus plantarum PB241 showed the highest enzymatic activity, while the isolates ascribed to Weissella confusa were characterized by low or no phytase activity. Only 18% of the screened LAB produced EPS, which were distinguished as ropy or mucoid phenotypes on SSM supplemented with sucrose. Almost all the EPS producers carried one or more genes (epsD/E and/or epsA) involved in the production of heteropolysaccharides (HePS), whereas the isolates ascribed to Leuconostoc citreum and W. confusa carried genes involved in the production of both HePS and homopolysaccharides (HoPS). Monosaccharide composition analysis of the EPS produced by a selected subset of isolates revealed that all the HePS included glucose, mannose, and galactose, though at different ratios. Furthermore, a few isolates ascribed to L. citreum and W. confusa and carrying the gtf gene produced β-glucans after fermentation in an ad hoc formulated barley flour medium. Based on the overall results collected, a subset of candidate sourdough starter cultures for the baking industry was selected, including Lb. brevis LD66 and L. citreum PB220, which showed high phytase activity and positive EPS production.

Highlights

Cereal-based foods are an essential part of the daily diet worldwide, representing an important source of energy, carbohydrates and fiber, as well as proteins, minerals and micronutrients to a lesser extent [1]
Though 16S rRNA gene sequencing is recognized as one of the most efficient molecular techniques for the establishment of taxonomic relationships between prokaryota, it is not suitable for the discrimination of some closely related species, as those belonging to the Lactobacillus casei, Lactobacillus plantarum, Lactobacillus buchneri, and Lactobacillus sakei groups, which are characterized by a high-level similarity ( 99%) in the 16S rRNA gene sequences
This implies that advanced methods, including whole genome sequencing or multilocus sequence typing (MLST), can be applied to differentiate these microorganisms [40]

Summary

Introduction

Cereal-based foods are an essential part of the daily diet worldwide, representing an important source of energy, carbohydrates and fiber, as well as proteins, minerals (e.g., zinc and magnesium) and micronutrients (e.g., vitamins B and E) to a lesser extent [1]. The increasing consumer demand for cereal-based foods with improved nutritional and health

Methods

Results

Conclusion