Influence of Media Heat Sterilization Process on Growth Performance of Representative Strains of the Genus Lactobacillus

Martin Senz,Claudia Keil,Martin Hageböck,Sophie Palinski,Maximilian Schmacht,Bettina Cämmerer

doi:10.3390/fermentation5010020

Abstract

Lactic acid bacteria (LAB) are widely applied microorganisms in food, feed, and beverage applications, where they can provide essential functionality for product modification, increase product shelf life, or act as beneficial organisms after consumption. Among these, strains of the genus Lactobacillus are often used as starters, probiotics, or biopreservatives. For all these types of bacterial preparations, a transportable shelf-stable form of concentrated bacteria, preserving their intrinsic properties, is essential for commercial distribution. Former studies revealed a relationship between the culture medium, cellular morphology, and the robustness of Lactobacillus acidophilus NCFM (name derived from North Carolina Food Microbiology) cultures. Due to these insights, a multitude of Lactobacillus strains representative of the genus were screened regarding their sensitivity to thermal medium pretreatment possibly accompanied by the alteration of their chemical composition, such as the formation of Maillard reaction products (MRPs). This study reveals a quite diverse and different growth behavior of those strains in the form of altered or non-altered cell concentrations and the size distributions of the populations, whereby five strains of the L. delbrueckii group in particular showed increased cell concentrations combined with decreased mean cell volumes. The results are of both scientific and industrial relevance, as they highlight the necessity to consider and understand the effects of media sterilization for the applied production strain.

Highlights

Lactobacillus is one of the most important genera of lactic acid bacteria (LAB) used in diverse food and agricultural applications, for example, as starter cultures, probiotics, or biopreservatives [1,2,3].To ensure the functionality of the bacteria, an appropriate viability is a prerequisite
The application of reducing sugars like D -glucose as the carbon source in the presence of amino-rich components inevitably leads to the generation of Maillard reaction products (MRPs) and to changes in the physicochemical media characteristics when sterilizing them by heat treatment [25]
For bifidobacteria and selected LAB, the addition of growth components glycated via Maillard reaction was obviously beneficial for growth performance [28]

Summary

Introduction

Lactobacillus is one of the most important genera of lactic acid bacteria (LAB) used in diverse food and agricultural applications, for example, as starter cultures, probiotics, or biopreservatives [1,2,3]. To ensure the functionality of the bacteria, an appropriate viability is a prerequisite. This is even more important keeping in mind that lactobacilli have relatively high nutritional demands and that many species lost the ability to synthesize diverse amino acids, cofactors, and vitamins during their evolutionary adaption to their natural habitats, which are often the human or animal gastrointestinal. Intense scientific research is conducted using strains of the genus Lactobacillus in fields such as wine fermentation [8], sourdough fermentation [3,9], or cocoa bean fermentation [10]. From an industrial point of view, suppliers of lactobacilli are requested to provide highly concentrated cultures with adequate properties; the latter defined amongst others by good metabolic activity as well as high robustness against stress occurring during and after processing

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