Selection of raw cow’s milk thermophilic lactic acid bacteria obtained from southwest Parana, Brazil, with potential use as autochthonous starter

Simone Beux,João Francisco Marchi,Carla Todescatto,Edimir Andrade Pereira

doi:10.1590/1981-6723.17019

Abstract

Abstract This work aimed to isolate and identify Streptococcus and Lactobacillus species from raw cow’s milk obtained from Southwest Paraná - Brazil. We used randomly amplified polymorphic DNA (RAPD)-PCR to identify and type 58Streptococcus and 48 Lactobacillus isolates, of which 04 Streptococcus thermophilus and 02 Streptpcoccus macedonicus were confirmed by species-specific PCR and by sequencing of the 16S ribosomal RNA of 02Streptococcus lutetiensis/infantarius, 10 Lactobacillus fermentum, 03 Lactobacillus delbrueickii subspecies bulgaricus, 01 Lactobacillus rhamnosus/casei and 02 Lactobacillus helveticus. The results indicated predominance of Streptococcus thermophillus and Lactobacillus fermentum. Streptococcus thermophilus and Lactobacillus delbrueickii subspecies bulgaricus strains were tested on the basis of their acidification kinetics. Considerable variation between the Streptococcus thermophilus was observed for the maximum rate of acidification (Vm), with a maximum of -4.5 and minimum of -4.2 pH milliunits min-1. The Lactobacillus delbrueickii subspecies bulgaricus showed values between -8.4 and -7.1 pH milliunits min-1. These results suggest that strains characterized as having a high acidifying capacity, could be used as starters in cheesemaking. The ferments presented an excellent performance in the acidification process, generating adequate curves, characteristics of a starter culture.

Highlights

The lactic acid bacteria (LAB) are found as autochthonous microflora in raw milk (Rodríguez et al, 2000)
The cultures were maintained at -40 °C in 0.25 mL of M17 or MRS broths, supplemented with freezing mix (20 mM MgSO4 and 80% glycerol) and 0.5 mL of reconstituted powdered milk, denominated the Stock Culture 1 (SC1), and numbered from S01 to S150 for Streptococcus, and from L01 to L141 for Lactobacillus species
The strains, S120 and S141, in cluster 2 were confirmed by genetic sequencing as S. lutetiensis/infantarius, and 70.7% of the isolates obtained from the raw milk were identified as S. thermophilus

Summary

Introduction

The lactic acid bacteria (LAB) are found as autochthonous microflora in raw milk (Rodríguez et al, 2000). Bulgaricus or lactis) have long been used as starter cultures in the production of fermented milks and various Swiss and Italian cheeses (Iyer et al, 2010; Rizzello & De Angelis, 2011). The acidification rate during the fermentation period can be described from the pH curves and the following kinetic parameters are calculated by: the maximum acidification rate (Vm= dpH/dt), expressed as pH milliunits min-1, which is the maximum slope of the acidification curve; and the time (Tm), expressed as minutes, at which Vm occurred (Zanatta & Basso, 1992). Actions that can contribute to the development and enhancement of the dairy chain are important and should be considered

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Conclusion