Adaptation of Lactobacillus plantarum IMDO 130201, a Wheat Sourdough Isolate, to Growth in Wheat Sourdough Simulation Medium at Different pH Values through Differential Gene Expression

Abstract

Sourdough is a very competitive and challenging environment for microorganisms. Usually, a stable microbiota composed of lactic acid bacteria (LAB) and yeasts dominates this ecosystem. Although sourdough is rich in carbohydrates, thus providing an ideal environment for microorganisms to grow, its low pH presents a particular challenge. The nature of the adaptation to this low pH was investigated for Lactobacillus plantarum IMDO 130201, an isolate from a laboratory wheat sourdough fermentation. Batch fermentations were carried out in wheat sourdough simulation medium, and total RNA was isolated from mid-exponential-growth-phase cultures, followed by differential gene expression analysis using a LAB functional gene microarray. At low pH values, an increased expression of genes involved in peptide and amino acid metabolism was found as well as that of genes involved in plantaricin production and lipoteichoic acid biosynthesis. The results highlight cellular mechanisms that allow L. plantarum to function at a low environmental pH.Lactic acid bacteria (LAB) are known to be able to survive in acid environments (4,25,34). Important mechanisms to resist acid conditions include intracellular proton removal through H ϩ -ATPase activity, alterations in cell membrane composition, and amino acid conversions (3,21,26). Lactobacillus plantarum, a facultative heterofermentative LAB species, is mostly associated with plant materials (16) and is hence present in many types of food fermentations, including sauerkraut and other vegetable fermentations, cocoa bean fermentations, and sourdough fermentations (1, 2, 8, 9, 27). As a result, strains of L. plantarum have developed a large degree of metabolic flexibility to deal with these challenging environments (5,29,30).In a sourdough environment, for example, two metabolic characteristics provide a competitive advantage to bacterial strains, i.e., the use of maltose as an energy source and the ability to convert arginine into ornithine via citrulline by means of the arginine deiminase (ADI) pathway. Indeed, maltose is taken up by a H ϩ -maltose symport system, resulting in a higher uptake at a lower pH, and is intracellularly converted into glucose and glucose-1-phosphate by the enzyme maltose phosphorylase (11,12,14,19). This enzyme uses inorganic phosphate and therefore represents an energy saving, as no ATP has to be expended for carbohydrate phosphorylation (14, 15). Furthermore, the ADI pathway generates two moles of ammonia, contributing to survival in acid stress conditions, and one mole of ATP per mole of arginine. The final product of the ADI pathway, ornithine, is a desirable product during sourdough fermentation, as it is the precursor of 2-acetyl-1-pyrroline, which gives freshly baked bread crust its characteristic flavor (7,17).Because of the presence of L. plantarum in many fermented food ecosystems and other environmental and human niches, the genome sequences of L. plantarum WCFS1 (a human saliva isolate [20]) and L. plantarum JDM1 (a human intestinal tract isolate [43...

Sourdough microbial community dynamics: An analysis during French organic bread-making processes

“…Thus, the origin of the flour may make a difference although the number of LAB in rye sourdough is assumed to be similar to that in wheat sourdough (Ercolini, 2013;Ercolini et al, 2013;Weckx et al, 2010). Alternatively, external factors such as temperature fluctuations could change microbial counts between breadmaking runs (Kurtzman and Robnett, 2003;Meroth et al, 2003a;Vogelmann and Hertel, 2011;Vrancken et al, 2011b). Finally, the microbial composition of the community may affect the microbial counts, as suggested by the low counts of yeasts in presence of T. delbrueckii observed for Bakery 1 and also in a Belgium sourdough (Scheirlinck et al, 2007).…”

Dynamic Stresses of Lactic Acid Bacteria Associated to Fermentation Processes

“…At the same time, the low pH values implied a poor expression of the genes involved in carbohydrate degradation in L. plantarum IMDO 130201. The bacterium was directed toward survival at low pH by amino acid conversions rather than by relying on growth [112]. The same behavior was identified in L. sanfranciscensis LSCE1 response to pH 3.6 [15].…”

“…Another example of the influence of the process on LAB metabolism has been widely described [112]. These Authors monitored the evolution of the gene expression of L. plantarum IMDO 130201 during a sourdough process.…”

Enhancement of bacteriocin production and antimicrobial activity of Pediococcus acidilactici HA-6111-2

“…2.3-fold) than the control, while maintaining the maximum production value (6400 AU ml -1 ), without altering the maximum specifi c growth rate and the maximum reached value (Table 1). This increase in bacteriocin production may occur as a response to exposure to sub-lethal pressure conditions, as it has been previously reported that bacteriocin production is stimulated by various stress conditions (NEYSENS & DE VUYST, 2005;ZAMFIR & GROSU-TUDOR, 2009;VRANCKEN et al, 2011). Nevertheless, the enhancement of the bacteriocin production due to cells exposure to low pressure treatments needs to be further investigated.…”

“…It has been observed that production of bacteriocins is infl uenced by the bacterial growth phase (GARCIA et al, 2016), medium composition (HALAMI & CHANDRASHEKAR, 2005), and culture conditions (MATARAGAS et al, 2003). In addition, bacteriocin production can be induced by exogenous factors (NEYSENS & DE VUYST, 2005;ZAMFIR & GROSU-TUDOR, 2009;VRANCKEN et al, 2011) or exhibit auto-induction (HAKIM et al, 2007). Presently, little information is available about the effect of such exogenous factors, including low pressures, on the bacteriocin production.…”