Influence of culture media, pH and temperature on growth and bacteriocin production of bacteriocinogenic lactic acid bacteria

En Yang,Jinping Yan,Yueming Jiang,Craig Doucette,Sherry Fillmore,Bradley Walker,Lihua Fan

doi:10.1186/s13568-018-0536-0

Abstract

There has been continued interest in bacteriocins research from an applied perspective as bacteriocins have potential to be used as natural preservative. Four bacteriocinogenic lactic acid bacteria (LAB) strains of Lactobacillus curvatus (Arla-10), Enterococcus faecium (JFR-1), Lactobacillus paracasei subsp. paracasei (JFR-5) and Streptococcus thermophilus (TSB-8) were previously isolated and identified in our lab. The objective of this study was to determine the optimal growth conditions for both LAB growth and bacteriocins production. In this study, various growth conditions including culture media (MRS and BHI), initial pH of culture media (4.5, 5.5, 6.2, 7.4 and 8.5), and incubation temperatures (20, 37 and 44 °C) were investigated for LAB growth measured as optical density (OD), bacteriocin activity determined as arbitrary unit and viability of LAB expressed as log CFU ml−1. Growth curves of the bacteriocinogenic LAB were generated using a Bioscreen C. Our results indicated that Arla-10, JFR-1, and JFR-5 strains grew well on both MRS and BHI media at growth temperature tested whereas TSB-8 strain, unable to grow at 20 °C. LAB growth was significantly affected by the initial pH of culture media (p < 0.001) and the optimal pH was found ranging from 6.2 to 8.5. Bacteriocin activity was significantly different in MRS versus BHI (p < 0.001), and the optimal condition for LAB to produce bacteriocins was determined in MRS broth, pH 6.2 at 37 °C. This study provides useful information on potential application of bacteriocinogenic LAB in food fermentation processes.

Highlights

Lactic acid bacteria (LAB) are a diverse group of gram positive, catalase negative, oxidase negative, and microaerophilic organisms (Carr et al 2002)
The results showed that culture medium and pH played an important role in bacteriocin production
Lactic acid bacteria are generally recognized as safe bacteria in fermented foods like dairy products, processed vegetables and play an important role in preservation

Summary

Introduction

Lactic acid bacteria (LAB) are a diverse group of gram positive, catalase negative, oxidase negative, and microaerophilic organisms (Carr et al 2002). They are generally recognized as safe bacteria (GRAS status) and play an important role in food and feed fermentation and preservation, either as the natural microflora or as starter cultures under controlled conditions (Daeschel 1989). Mataragas et al (2003) reported that the highest bacteriocin production is determined at temperatures and pH lower than that of the optimal cell growth. Because high bacteriocin production may or may not occur at optimal growth conditions and high cell mass (Todorov and Dicks 2009; Masuda et al 2016), this necessitates study on the relationship between bacterial growth conditions and bacteriocin production (Leroy and De Vuyst 2002)

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Methods

Conclusion