Abstract
Phenotypic and genotypic evidence indicates that many LAB strains can grow in presence of oxygen and can shift from fermentative to aerobic and/or respiratory metabolism. The aerobic and respiratory growth of several LAB species have been studied, allowing the selection of strains showing improved biomass production, long-term survival, and resistance under oxygen and stress conditions. The aim of this work was to observe the adaptation of two Lactobacillus gasseri strains, described in a previous work, to aerobic (air injection) and respiratory (air injection plus hemin and menaquionone) conditions obtained in a batch bioreactor. One strain showed the higher biomass production and oxygen consumption as well as the lower acidification in respiratory condition. Instead, the other one grew better in aerobic condition, even though the higher resistance to cold-starvation stress was registered in respiratory condition. In silico analysis revealed notable differences between AL3 and AL5 genomes and that of the type strain. This work contributes to understanding the adaptation response of lactobacilli to aerobic and respiratory metabolism. We demonstrated that the supposed activation of respiratory metabolism may provide several modifications to cell physiology. These features may be relevant in some technological and health-promoting applications, including starter and probiotic formulations.
Highlights
The fermentative metabolism of lactic acid bacteria (LAB) has been intensively studied because of its technological implications in the food industry
For the first time, the ability of Lactobacillus gasseri strains to shift towards aerobic and/or respiratory metabolism was investigated during growth in a bioreactor and the effect of different conditions (AE, RS, AN) on growth performance and starvation stress tolerance was evaluated
In RS cultivation, AL3 showed increased biomass production, reduced acidification, and higher oxygen consumption. These results suggest the activation of a respiratory metabolism
Summary
The fermentative metabolism of lactic acid bacteria (LAB) has been intensively studied because of its technological implications in the food industry. Aerobic and respiratory metabolism have been widely investigated in some strains of Lactobacillus reuteri and Lactobacillus spicheri [4], in the Lactobacillus casei group [5,6], and in the Lactobacillus plantarum group [7,8,9,10]. Some of these studies led to the selection of strains that improved the features of foods when used like adjunct cultures [11,12]. Only the probiotic Lb. johnsonii NCC 533 has been studied to help provide a more global understanding of the molecular responses to the presence of oxygen [16,17]
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