In this study, yeast and acetic acid bacteria strains were adopted to enhance the ethanol-type fermentation resulting to a volatile fatty acids yield of 30.22 g/L, and improve acetic acid production to 25.88 g/L, with food wastes as substrate. In contrast, only 12.81 g/L acetic acid can be obtained in the absence of strains. The parameters such as pH, oxidation reduction potential and volatile fatty acids were tested and the microbial diversity of different strains and activity of hydrolytic ferment were investigated to reveal the mechanism. The optimum pH and oxidation reduction potential for the acetic acid production were determined to be at 3.0-3.5 and -500 mV, respectively. Yeast can convert organic matters into ethanol, which is used by acetic acid bacteria to convert the organic wastes into acetic acid. The acetic acid thus obtained from food wastes micro-aerobic fermentation liquid could be extracted by distillation to get high-pure acetic acid.

Microbial cell factories with the ability to maintain high productivity in the presence of weak organic acids, such as acetic acid, are required in many industrial processes. For example, fermentation media derived from lignocellulosic biomass are rich in acetic acid and other weak acids. The rate of diffusional entry of acetic acid is one parameter determining the ability of microorganisms to tolerance the acid. The present study demonstrates that the rate of acetic acid diffusion in S. cerevisiae is strongly affected by the alcohols ethanol and n-butanol. Ethanol of 40 g/L and n-butanol of 8 g/L both caused a 65% increase in the rate of acetic acid diffusion, and higher alcohol concentrations caused even greater increases. Molecular dynamics simulations of membrane dynamics in the presence of alcohols demonstrated that the partitioning of alcohols to the head group region of the lipid bilayer causes a considerable increase in the membrane area, together with reduced membrane thickness and lipid order. These changes in physiochemical membrane properties lead to an increased number of water molecules in the membrane interior, providing biophysical mechanisms for the alcohol-induced increase in acetic acid diffusion rate. n-butanol affected S. cerevisiae and the cell membrane properties at lower concentrations than ethanol, due to greater and deeper partitioning in the membrane. This study demonstrates that the rate of acetic acid diffusion can be strongly affected by compounds that partition into the cell membrane, and highlights the need for considering interaction effects between compounds in the design of microbial processes.

Indole-3-acetic acid (IAA) is the most common plant hormone of the auxin class and regulates various plant growth processes. The present study investigated IAA production by the basidiomycetous yeast Rhodosporidiobolus fluvialis DMKU-CP293 using the one-factor-at-a-time (OFAT) method and response surface methodology (RSM). IAA production was optimized in shake-flask culture using a cost-effective medium containing 4.5% crude glycerol, 2% CSL and 0.55% feed-grade L-tryptophan. The optimized medium resulted in a 3.3-fold improvement in IAA production and a 3.6-fold reduction in cost compared with those obtained with a non-optimized medium. Production was then scaled up to a 15-L bioreactor and to a pilot-scale (100-L) bioreactor based on the constant impeller tip speed (Vtip) strategy. By doing so, IAA was successfully produced at a concentration of 3569.32 mg/L at the pilot scale. To the best of our knowledge, this is the first report of pilot-scale IAA production by microorganisms. In addition, we evaluated the effect of crude IAA on weed growth. The results showed that weed (Cyperus rotundus L.) growth could be inhibited by 50 mg/L of crude IAA. IAA therefore has the potential to be developed as a herbicidal bioproduct to replace the chemical herbicides that have been banned in various countries, including Thailand.

Lignocellulosic raw material plays a crucial role in the development of sustainable processes for the production of fuels and chemicals. Weak acids such as acetic acid and formic acid are troublesome inhibitors restricting efficient microbial conversion of the biomass to desired products. To improve our understanding of weak acid inhibition and to identify engineering strategies to reduce acetic acid toxicity, the highly acetic-acid-tolerant yeast Zygosaccharomyces bailii was studied. The impact of acetic acid membrane permeability on acetic acid tolerance in Z. bailii was investigated with particular focus on how the previously demonstrated high sphingolipid content in the plasma membrane influences acetic acid tolerance and membrane permeability. Through molecular dynamics simulations, we concluded that membranes with a high content of sphingolipids are thicker and more dense, increasing the free energy barrier for the permeation of acetic acid through the membrane. Z. bailii cultured with the drug myriocin, known to decrease cellular sphingo-lipid levels, exhibited significant growth inhibition in the presence of acetic acid, while growth in medium without acetic acid was unaffected by the myriocin addition. Furthermore, following an acetic acid pulse, the intracellular pH decreased more in myriocin-treated cells than in control cells. This indicates a higher inflow rate of acetic acid and confirms that the reduction in growth of cells cultured with myriocin in the medium with acetic acid was due to an increase in membrane permeability, thereby demonstrating the importance of a high fraction of sphingolipids in the membrane of Z. bailii to facilitate acetic acid resistance; a property potentially transferable to desired production organisms suffering from weak acid stress.

The decision to consume or reject a food based on the degree of acidity is critical for animal survival. However, the gustatory receptors that detect sour compounds and influence feeding behavior have been elusive. Here, using the fly, Drosophila melanogaster, we reveal that a member of the ionotropic receptor family, IR7a, is essential for rejecting foods laced with high levels of acetic acid. IR7a is dispensable for repulsion of other acidic compounds, indicating that the gustatory sensation of acids occurs through a repertoire rather than a single receptor. The fly's main taste organ, the labellum, is decorated with bristles that house dendrites of gustatory receptor neurons (GRNs). IR7a is expressed in a subset of bitter GRNs rather than GRNs dedicated to sour taste. Our findings indicate that flies taste acids through a repertoire of receptors, enabling them to discriminate foods on the basis of acid composition rather than just pH.

Herein, the concentrations of formic acid, acetic acid, and ammonia in samples of indoor air for 47 new houses were measured two weeks after completion. The houses were fabricated with light-gauge steel structures. The measurements were performed in living rooms and bedrooms without furniture and outdoors. Air samples were analyzed using ion chromatography. The mean values were 28 (living room), 30 (bedroom), and 20 μg m-3 (outdoor air) for formic acid; 166 (living room), 151 (bedroom), and 51 μg m-3 (outdoor air) for acetic acid; and 73 (living room), 76 (bedroom), and 21 μg m-3 (outdoor air) for ammonia. The total values of the three substances accounted for 39.4-40.7% of the sum of chemical compound values. The analyzed compounds were indicated by two principal components (PC), PC1 (30.1%) and PC2 (9%), with 39.1% total variance. Formic acid, acetic acid, and ammonia were positively aligned with PC1 and negatively aligned with PC2. Factors such as room temperature, aldehydes, and phthalates were positively aligned with PC1 and negatively aligned with PC2. Furthermore, concentrations of formic acid, acetic acid, and ammonia were significantly and positively correlated with room temperature (p < 0.05).

Effective measures are needed to prevent the spread and infectivity of SARS-CoV-2 that causes COVID-19. Chemical inactivation may help to prevent the spread and transmission of this and other viruses. Hence, we tested the SARS-CoV-2 antiviral activity of acetic acid, the main component of vinegar, in vitro. Inactivation and binding assays suggest that acetic acid is virucidal. We found that 6% acetic acid, a concentration typically found in white distilled vinegar, effectively inactivated SARS-CoV-2 after 15-min incubation with a complete loss of replication of competent virus as measured by TCID50. Transmission electron microscopy further demonstrated that 6% acetic acid disrupts SARS-CoV-2 virion structure. In addition, 6% acetic acid significantly inhibits and disrupts the binding of SARS-CoV-2 spike protein binding to ACE2, the primary SARS-CoV-2 cell receptor, after contact with spike protein for 5, 10, 30 and 60 minutes incubation. Taken together, our findings demonstrate that acetic acid possesses inactivating activity against SARS-CoV-2 and may represent a safe alternative to commonly used chemical disinfectants to effectively control the spread of SARS-CoV-2.

Accumulation of acetic acid indicates an imbalance of the process due to a disturbed composition of the microorganisms. Hence, monitoring the acetic acid concentration is an important parameter to control the biogas process. Here, we describe the generation and validation of a fluorescence-based whole cell sensor for the detection of acetic acid based on the yeast Saccharomyces cerevisiae. Acetic acid induces the transcription of a subset of genes. The 5´-regulatory sequences (5´ URS) of these genes were cloned into a multicopy plasmid to drive the expression of a red fluorescent reporter gene. The 5´ URS of YGP1, encoding a cell wall-related glycoprotein, led to a 20-fold increase of fluorescence upon addition of 30 mM acetic acid to the media. We show that the system allows estimating the approximate concentration of acetic acid in condensation samples from a biogas plant. To avoid plasmid loss and increase the long-term stability of the sensor, we integrated the reporter construct into the yeast genome and tested the suitability of spores for long-term storage of sensor cells. Lowering the reporter gene's copy number resulted in a significant drop of the fluorescence, which can be compensated by applying a yeast pheromone-based signal amplification system.

In pea, the auxins 4-chloroindole-3-acetic acid (4-Cl-IAA) and indole-3-acetic acid (IAA) occur naturally; however, only 4-Cl-IAA stimulates pericarp growth and gibberellin (GA) biosynthesis, and inhibits the ethylene response in deseeded ovaries (pericarps), mimicking the presence of seeds. Expression of ovary ethylene biosynthesis genes was regulated similarly in most cases by the presence of 4-Cl-IAA or seeds. PsACS1 [which encodes an enzyme that synthesizes 1-aminocyclopropane-1-carboxylic acid (ACC)] transcript abundance was high in pericarp tissue adjacent to developing seeds following pollination. ACC accumulation in 4-Cl-IAA-treated deseeded pericarps was driven by high PsASC1 expression (1800-fold). 4-Cl-IAA, but not IAA, also suppressed the pericarp transcript levels of PsACS4. 4-Cl-IAA increased PsACO1 and decreased PsACO2 and PsACO3 expression (enzymes that convert ACC to ethylene) but did not change ACO enzyme activity. Increased ethylene was countered by a 4-Cl-IAA-specific decrease in ethylene responsiveness potentially via modulation of pericarp ethylene receptor and signaling gene expression. This pattern did not occur in IAA-treated pericarps. Overall, the effect of 4-Cl-IAA and IAA on ethylene biosynthesis gene expression generally explains the ethylene evolution patterns, and their effects on GA biosynthesis and ethylene signaling gene expression explain the tissue response patterns in young pea ovaries.

Plant growth-promoting bacteria have several abilities to promote plant growth and development. One of these skills is the synthesis of indole-3-acetic acid (IAA), which mainly promotes root and shoot development. The bacteria Bacillus subtilis and Azospirillum brasilense have been widely used in agriculture with this function. However, little is known about whether the joint inoculation of these bacteria can reduce plant development by the excess of IAA produced as a result of the joint inoculation. The objective of the present study was to verify the effect of IAA on the inoculation of B. subtilis and A. brasilense in three tomato genotypes. The Micro-Tom genotype without mutation for IAA synthesis, Entire, has high sensitivity to IAA, and the diageotropic genotype (dgt) has low sensitivity to IAA. The results show that the plant parameter most sensitive to microbial inoculation is the number of roots. No treatment increased the shoot dry mass parameters for the Micro-Tom genotype and dgt, root dry mass for the Micro-Tom genotype, plant height for the Micro-Tom and Entire genotypes, root area and root volume for the genotype dgt. The Azm treatment reduced plant height compared to the control in the dgt, the BS + Azw and BS + Azm treatments in the Micro-Tom genotype and the Azw + Azm treatment in the dgt genotype reduced the plant diameter compared to the control. BS and BS + Azw reduced the number of roots in the Micro-Tom. The results strongly support that the mixture of B. subtilis and A. brasilense can reduce some parameters of plant development; however, this effect is possibly an interference in the mode of action of growth promotion of each isolate and is not related to an excess of IAA produced by the bacteria.

Phenotypic plasticity is the ability of a single genotype of an organism to exhibit variable phenotypes in response to fluctuating environments. It plays a crucial role in their evolutionary success. In natural environments, the importance of interactions between microalgae and other microorganisms is generally well appreciated, but the effects of these interactions on algal phenotypic plasticity has not been investigated. In this study, it revealed that indole-3-acetic acid (IAA), the most common naturally occurring plant hormone, can exert stimulatory at low concentrations and inhibitory effects at high concentrations on the growth of the green alga Desmodesmus. The morphological characteristics of Desmodesmus changed drastically under exposure to IAA compared with the algae in the control environment. The proportion of Desmodesmus unicells in monocultures increased with the IAA concentration, and these unicells exhibited less possibility of sedimentation than large cells. Furthermore, we discovered that lipid droplets accumulated in algal cells grown at a high IAA concentration. Results also demonstrated that the presence of algal competitor further stimulated inducible morphological changes in Desmodesmus populations. The relative abundance of competitors influenced the proportion of induced morphological changes. The results indicate that phenotypic plasticity in microalgae can be a response to fluctuating environments, in which algae optimize the cost-benefit ratio.

The external application of acetic acid has recently been reported to enhance survival of drought in plants such as Arabidopsis, rapeseed, maize, rice, and wheat, but the effects of acetic acid application on increased drought tolerance in woody plants such as a tropical crop "cassava" remain elusive. A molecular understanding of acetic acid-induced drought avoidance in cassava will contribute to the development of technology that can be used to enhance drought tolerance, without resorting to transgenic technology or advancements in cassava cultivation. In the present study, morphological, physiological, and molecular responses to drought were analyzed in cassava after treatment with acetic acid. Results indicated that the acetic acid-treated cassava plants had a higher level of drought avoidance than water-treated, control plants. Specifically, higher leaf relative water content, and chlorophyll and carotenoid levels were observed as soils dried out during the drought treatment. Leaf temperatures in acetic acid-treated cassava plants were higher relative to leaves on plants pretreated with water and an increase of ABA content was observed in leaves of acetic acid-treated plants, suggesting that stomatal conductance and the transpiration rate in leaves of acetic acid-treated plants decreased to maintain relative water contents and to avoid drought. Transcriptome analysis revealed that acetic acid treatment increased the expression of ABA signaling-related genes, such as OPEN STOMATA 1 (OST1) and protein phosphatase 2C; as well as the drought response and tolerance-related genes, such as the outer membrane tryptophan-rich sensory protein (TSPO), and the heat shock proteins. Collectively, the external application of acetic acid enhances drought avoidance in cassava through the upregulation of ABA signaling pathway genes and several stress responses- and tolerance-related genes. These data support the idea that adjustments of the acetic acid application to plants is useful to enhance drought tolerance, to minimize the growth inhibition in the agricultural field.

Acetic acid can cause cellular injury. We previously reported that acetic acid induces cancer cell-selective death in rat gastric cells. However, the mechanism is unclear. Generally, cancer cells are more sensitive to reactive oxygen species than normal cells. Accordingly, in this study, we investigated the involvement of oxidative stress in cancer cell-selective death by acetic acid using normal gastric mucosal cells and cancerous gastric mucosal cells. The cancer cell-selective death was induced at the concentration of 2-5 µM acetic acid. Cancerous gastric mucosal cells had increased expression of monocarboxylic transporter 1 and high uptake of acetic acid, compared to normal gastric mucosal cells. The exposure of cancerous gastric mucosal cells to acetic acid enhanced production of reactive oxygen species and expression of monocarboxylic transporter 1, and induced apoptosis. In contrast, acetic acid showed minor effects in normal gastric mucosal cells. These results indicate that acetic acid induced cancer cell-selective death in gastric cells through a mechanism involving oxidative stress.

Acetic acid bacteria have unique metabolic characteristics that suit them for a variety of biotechnological applications. They possess an arsenal of membrane-bound dehydrogenases in the periplasmic space that are capable of regiospecific and enantioselective partial oxidations of sugars, alcohols, and polyols. The resulting products are deposited directly into the medium where they are easily recovered for use as pharmaceutical precursors, industrial chemicals, food additives, and consumer products. Expression of extracytoplasmic enzymes to augment the oxidative capabilities of acetic acid bacteria is desired but is challenging due to the already crowded inner membrane. To this end, an original surface display system was developed to express recombinant enzymes at the outer membrane of the model acetic acid bacterium Gluconobacter oxydans. Outer membrane porin F (OprF) was used to deliver alkaline phosphatase (PhoA) to the cell surface. Constitutive high-strength p264 and moderate-strength p452 promoters were used to direct expression of the surface display system. This system was demonstrated for biocatalysis in whole-cell assays with the p264 promoter having a twofold increase in PhoA activity compared to the p452 promoter. Proteolytic cleavage of PhoA from the cell surface confirmed proper delivery to the outer membrane. Furthermore, a linker library was constructed to optimize surface display. A rigid (EAAAK)1 linker led to the greatest improvement, increasing PhoA activity by 69%. This surface display system could be used both to extend the capabilities of acetic acid bacteria in current biotechnological processes, and to broaden the potential of these microbes in the production of value-added products.

While the pathogenesis of acetic acid (AA)-induced colitis is unclear, reactive oxygen species are considered to have a significant effect. The aim of the present study was to elucidate the therapeutic potential of dexpanthenol (Dxp) on the amelioration of colitis in rats. Group I (n=8; control group) was intrarectally administered 1 ml saline solution (0.9%); group II [n=8; AA] was administered 4% AA into the colon via the rectum as a single dose for three consecutive days; group III (n=8; AA + Dxp) was administered AA at the same dosage as group II from day 4, and a single dose of Dxp was administered intraperitoneally; and group IV (n=8; Dxp) was administered Dxp similarly to Group III. Oxidative stress and colonic damage were assessed via biochemical and histologic examination methods. AA treatment led to an increase in oxidative parameters and a decrease in antioxidant systems. Histopathological examination showed that AA treatment caused tissue injury and increased caspase-3 activity in the distal colon and triggered apoptosis. Dxp treatment caused biochemical and histopathological improvements, indicating that Dxp may have an anti-oxidant effect in colitis; therefore, Dxp may be a potential therapeutic agent for the amelioration of IBD.

The polycystic kidney disease (PKD) 1L3-PKD2L1 channel is a candidate sour taste receptor expressed in mammalian taste receptor cells. Various acids are reported to activate PKD channels after the removal of the acid stimuli, but little information is available on the activation of these channels by acetic acid. It was difficult to analyze the PKD channel activation by acetic acid using Ca2+ imaging experiments because this acid induces a transient and nonspecific response in cultured cells. Here, we developed a novel method to evaluate PKD channel activation by acetic acid. Nonspecific responses were observed only over a short period after the application of acetic acid. In contrast, PKD channel activation evoked by acetic acid as well as citric acid was detected even at a later time point. This method revealed that PKD1L3-PKD2L1 channel activation by acetic acid was pH-dependent and occurred when the ambient pH was <3.1.

Mentha longifolia L (Wild Mint or Habak) (ML) is used in traditional medicine in treatment of many gastrointestinal disorders.

A simple, mild and synthetically useful method for the desulfurization of cyclic thioureas and related compounds, existing as thiol-thione tautomeric mixtures, by hydrogen peroxide in acetic acid is proposed. The effect of substituting different solvents for the acetic acid was investigated.

The present study was undertaken to investigate the effect of lactic acid (LA), acetic acid, (AA) and trisodium phosphate (TSP) spray on the microbiological population of beef carcass surfaces slaughtered in a traditional abattoir in Zagazig, Egypt. Higher microbial populations were determined on the shoulder than on the thigh surfaces, and meat sampling by tissue excision technique yielded significantly higher (P < 0.01) microbial count than swabbing method. The application of LA (2%), AA (2%), and TSP (12%) sprays for 30 seconds significantly (P < 0.01) reduced the microbial population counts on the beef surfaces by 0.9 to 2.2 logs. A complete inhibition of enterococci growth was achieved by LA and AA sprays. In general, LA and AA sprays were more efficient as antimicrobial agents than the TSP spray. Among the studied organisms, enterococci were the most reducible bacteria by LA and AA, followed by Enterobacteriaceae and coliforms, while Staphylococcus aureus being the least. This study also indicated that microbial populations determined on the shoulder were higher than on the thigh surfaces, and meat sampling by tissue excision technique yielded significantly higher (P < 0.01) microbial count than swabbing method.

Acetic acid bacteria (AAB) are industrial microorganisms used for vinegar fermentation. Herein, we investigated the distribution and genome structures of mitomycin C-inducible temperate phages in AAB. Transmission electron microscopy analysis revealed phage-like particles in 15 out of a total 177 acetic acid bacterial strains, all of which showed morphology similar to myoviridae-type phage. The complete genome sequences of the six phages derived from three strains each of Acetobacter and Komagataeibacter strains were determined, harboring a genome size ranging from 34,100 to 53,798 bp. A phage AP1 from A. pasteurianus NBRC 109446 was predicted as an active phage based on the genomic information, and actually had the ability to infect its phiAP1-cured strain. The attachment sites for phiAP1 were located in the 3'-end region of the tRNAser gene. We also developed a chromosome-integrative vector, p2096int, based on the integrase function of phiAP1, and it was successfully integrated into the attachment site of the phiAP1-cured strain, which may be used as a valuable tool for the genetic engineering. Overall, this study showed the distribution of mitomycin C-inducible temperate phages in AAB, and identified the active temperate phage o f A. pasteurianus.