Adaptation and tolerance of bacteria against acetic acid

Abstract

Acetic acid is a weak organic acid exerting a toxic effect to most microorganisms at concentrations as low as 0.5 wt%. This toxic effect results mostly from acetic acid dissociation inside microbial cells, causing a decrease of intracellular pH and metabolic disturbance by the anion, among other deleterious effects. These microbial inhibition mechanisms enable acetic acid to be used as a preservative, although its usefulness is limited by the emergence of highly tolerant spoilage strains. Several biotechnological processes are also inhibited by the accumulation of acetic acid in the growth medium including production of bioethanol from lignocellulosics, wine making, and microbe-based production of acetic acid itself. To design better preservation strategies based on acetic acid and to improve the robustness of industrial biotechnological processes limited by this acid's toxicity, it is essential to deepen the understanding of the underlying toxicity mechanisms. In this sense, adaptive responses that improve tolerance to acetic acid have been well studied in Escherichia coli and Saccharomyces cerevisiae. Strains highly tolerant to acetic acid, either isolated from natural environments or specifically engineered for this effect, represent a unique reservoir of information that could increase our understanding of acetic acid tolerance and contribute to the design of additional tolerance mechanisms. In this article, the mechanisms underlying the acetic acid tolerance exhibited by several bacterial strains are reviewed, with emphasis on the knowledge gathered in acetic acid bacteria and E. coli. A comparison of how these bacterial adaptive responses to acetic acid stress fit to those described in the yeast Saccharomyces cerevisiae is also performed. A systematic comparison of the similarities and dissimilarities of the ways by which different microbial systems surpass the deleterious effects of acetic acid toxicity has not been performed so far, although such exchange of knowledge can open the door to the design of novel approaches aiming the development of acetic acid-tolerant strains with increased industrial robustness in a synthetic biology perspective.

The CgHaa1-Regulon Mediates Response and Tolerance to Acetic Acid Stress in the Human Pathogen Candida glabrata

“…In conditions of eubiosis, the amount of acetic acid is estimated to range between 1 and 4 mM, while in conditions of dysbiosis, the concentration can increase to > 100 mM (Chaudry et al 2004). In the acidic environment of the vaginal tract (pH ∼3.5–4.2) (O’Hanlon et al 2013; Owen and Katz 1999) acetic acid (pKa 4.7) will be predominately in its undissociated form (RCOOH), which has a well described antifungal effect (Piper et al 2001; Mira et al 2010c; Trckek et al 2015). Undissociated acetic acid molecules can permeate the microbial plasma membrane simply by passive diffusion, dissociating in the near-neutral cytosol, and leading to the accumulation of protons and acetate.…”

“…Undissociated acetic acid molecules can permeate the microbial plasma membrane simply by passive diffusion, dissociating in the near-neutral cytosol, and leading to the accumulation of protons and acetate. The internal acidification and the accumulation of acetate has been shown to cause multiple deleterious effects in yeast cells, including increase in turgor pressure, oxidative stress, reduced activity of metabolic enzymes, and dissipation of the electrochemical gradient maintained across the plasma membrane, an essential feature for secondary transport (Mira et al 2010c; Mollapour et al 2008; Piper et al 2001; Trckek et al 2015)…”

Lactobacillus pentosus CECT 4023 T co‐utilizes glucose and xylose to produce lactic acid from wheat straw hydrolysate: Anaerobiosis as a key factor

“…Acetic acid begins to affect cell growth even at concentrations as low as 5 g L −1 both in Gram‐positive and Gram‐negative bacteria . As mentioned, when acetic acid crosses the membrane and decreases intracellular pH, transmembrane gradient is affected and energy is used to maintain that pH gradient instead of growing .…”

“…37 Acetic acid begins to affect cell growth even at concentrations as low as 5 g L −1 both in Gram-positive and Gramnegative bacteria. 38 As mentioned, when acetic acid crosses the membrane and decreases intracellular pH, transmembrane gradient is affected and energy is used to maintain that pH gradient instead of growing. 39 However, it has been reported that some Lactobacillus plantarum and L. pentosus strains were able to grow at high concentrations of this acid, even at 12.14 g L −1 .…”

Comparative Genomics of Acetobacterpasteurianus Ab3, an Acetic Acid Producing Strain Isolated from Chinese Traditional Rice Vinegar Meiguichu

“…pasteurianus Ab3 are high acetic acid yield and resistance. Bacteria have evolved different mechanisms to cope with the deleterious effects imposed by acetic acid [43]. The mechanisms of acetic acid resistance can be roughly classified into two groups: (1) mechanisms that aim to reduce the concentration of acetic acid through catabolism and (2) mechanisms that aim to hinder the entry of acetic acid into the cell and/or suppress the deleterious effects of internal acid accumulation.…”