Identification of acetic-acid tolerance of Saccharomyces cerevisiae strains by microsatellite markers

The aim of this paper is to use the microsatellites to evaluate acid-tolerance in Saccharomyces(S.) cerevisiae. Microsatellites have been widely used as the molecular marker to classify and identify S. cerevisiae strains, analyze genetic relationships among strains, and reveal genetic diversity of S. cerevisiae populations. In this paper, 25 key microsatellites of S. cerevisiae from 44 industrial yeast strains are investigated in the medium withconcentration gradients of acetic acid. Based on the analysis of correlations between the key microsatellite loci repeat numbers and acid-tolerance of the strains, the allele size of 4P14 a and 10P13 is positively related to acid-tolerance(p ? 0.05), the allele size of AT-X, 4P1 a and 10P8 are significantly negatively related to acid-tolerance(p ? 0.01). The above results provide informations on the molecular biodiversity of S. cerevisiae strains and can be a theoretical guidance for molecular marker assisted selection.

Pseudomonas fluorescens-like bacteria from the stomach:A microbiological and molecular study

AIM:To characterize oxidase-and urease-producing bacterial isolates,grown aerobically,that originated from antral biopsies of patients suffering from acid peptic diseases.METHODS:A total of 258 antral biopsy specimens were subjected to isolation of bacteria followed by tests for oxidase and urease production,acid tolerance and aerobic growth.The selected isolates were further characterized by molecular techniques viz.amplifications for 16S rRNA using universal eubacterial and HSP60 gene specific primers.The amplicons were subjected to restriction analysis and partial sequencing.A phylogenetic tree was generated using unweighted pair group method with arithmetic mean(UPGMA) from evolutionary distance computed with bootstrap test of phylogeny.Assessment of acidity tolerance of bacteria isolated from antrum was performed using hydrochloric acid from 10-7 mol/L to 10-1 mol/L.RESULTS:Of the 258 antral biopsy specimens collected from patients,179(69.4%) were positive for urease production by rapid urease test and 31%(80/258) yielded typical Helicobacter pylori(H.pylori) after 5-7 d of incubation under a microaerophilic environment.A total of 240(93%) antral biopsies yielded homogeneous semi-translucent and small colonies after overnight incubation.The partial 16S rRNA sequences revealed that the isolates had 99% similarity with Pseudomonas species.A phylogenetic tree on the basis of 16S rRNA sequences denoted that JQ927226 and JQ927227 were likely to be related to Pseudomonas fluorescens(P.fluorescens).On the basis ofHSP60 sequences applied to the UPGMA phylogenetic tree,it was observed that isolated strains in an aerobic environment were likely to be P.fluorescens,and HSP60 sequences had more discriminatory potential rather than 16S rRNA sequences.Interestingly,this bacterium was acid tolerant for hours at low pH.Further,a total of 250(96.9%) genomic DNA samples of 258 biopsy specimens and DNA from 240 bacterial isolates were positive for the 613 bp amplicons by targeting P.fluorescens-specific conserved putative outer membrane protein gene sequences.CONCLUSION:This study indicates that bacterial isolates from antral biopsies grown aerobically were P.fluorescens,and thus acid-tolerant bacteria other than H.pylori can also colonize the stomach and may be implicated in pathogenesis/protection.

Factors Affecting Sensitivity of Variable Charge Soils to Acid Rain

The sensitivity of a large number of variable charge soils to acid rain was evaluated through examiningpH-H_2SO_4 input curves. Two derivative parameters, the consumption of hydrogen ions by the soil and theacidtolerant limit as defined as the quantity of sulfuric acid required to bring the soil to PH 3.5 in a 0.00lmolLi￣(-1) Ca(NO_3)_2 solution, were used. The sensitivity of variable charge soils was higher than that of constantcharge soils, due to the predominance of kaolinite in clay mineralogical composition. Among these soils thesensitivity was generally of the order lateritic red soil >red soil >latosol. For a given type of soil within thesame region the sensitivity was affected by parent material, due to differences in clay minerals and texture.The sensitivity of surface soil may be lower or higher than that of subsoil, depending on whether organicmatter or texture plays the dominant role in determining the buffering capacity. Paddy soils consnmedmore acid within lower range of acid input when compared with upland soils, due to the presence of moreexchangeable bases, but consumed less acid within higher acid input range, caused by the decrease in claycontent.

Effect of Acid Species on <i>Cryptococcus</i>sp. T1 and Construction of Its Bioreactor System for Continuous Neutralization of Acidic Media

Generally, the tolerance of yeasts to acid is stronger than that of bacteria. In addition, some of the yeasts are able to neutralize acidic media, which is called acid-neutralizing yeast. An acid-neutralizing yeast, Cryptococcus sp. strain T1, was previously isolated from Lake Tazawa in Japan. Here we investigated the effect of several types of acid on the neutralizing ability of strain T1, and we improved an existing bioreactor model to effectively neutralize acidic water. First we carried out a neutralizing test with strain T1 using casamino acid solution adjusted to pH 3.0 - 5.0 with each inorganic or organic acid. The solutions adjusted to pH 3.0 with nitric acid, phosphoric acid, sulfuric acid, and citric acid were neutralized by strain T1. The pH 3.0 solutions with lactic acid, formic acid, and acetic acid were not neutralized. These results demonstrated that some types of organic acid avoid neutralization by strain T1, and we hypothesized that this might be due to the sterilizing function of non-dissociative organic acid. We then constructed a bioreactor system with a column filled with T1-immobilized alginate beads. The previous research identified a problem in this bioreactor system: the high level of ammonium ions (NH+4) in the neutralized water might pollute water environments, and aluminum ions (Al3+) included in acidic water prevent the neutralization. Here, we used zeolite to get rid of the NH+4 and Al3+, and the addition of a zeolite reactor enabled the bioreactor system to neutralize the acidic water with a decrease of NH+4 in the water.

Characterization of Yeasts Capable of Neutralizing Acidic Media from Natural Neutral Environments

Acid-tolerant yeasts often inhabit extremely acidic environments: mine drain-ages, hot springs, and even fermented foods. Some of them also possess the ability to neutralize acidic media. However, the examples of these yeasts that are already known were isolated from acidic environments. In this study, the isolation of acid-tolerant yeasts from natural neutral aquatic environments and the identification of yeasts able to neutralize an acidic medium (acid-neutralizing yeast) in Japan were carried out. Various kinds of acid-tolerant and acid-neutralizing yeasts were obtained. In a neutralizing test using an acidic casamino acid solution adjusted to a pH of 4.0 with sulfuric acid, the obtained acid-neutralizing yeasts elevated the pH to approximately 7.0, and their neutralizing abilities were similar to those of previously reported yeasts that had been isolated from acidic environments. These results showed that acid-tolerant yeasts and acid-neutralizing yeasts exist widely in neutral environments, and little difference was found in the neutralizing abilities of yeasts obtained from neutral environments in comparison to those obtained from acidic environments.

Thermoresistant, Ethanol-Resistant and Acid-Resistant Properties of Acetic Acid Bacteria Isolated from Fermented Mango Alcohol

Vinegar production is seriously affected by the sensitivity of acetic acid bacteria (AAB) to high temperature, high ethanol concentrations, and high acetic acid concentrations. The aim of this study was to investigate the thermo-ethanol-acid tolerance characters of five AAB strains (VMA1, VMA5, VMA7, VMAM, VMAO) previously isolated from fermented mango alcohol and belonging to Gluconoacetobacter genera. As result, the five AAB strains exhibited good growth and acid production at temperatures up to 45°C;they could tolerate and produce acetic acid at ethanol concentrations up to 20% (v/v). In addition, the studied strains showed growth at acetic acid concentrations up to 4.5% (w/v). Strains VMA7 and VMAO showed the highest resistance properties: they demonstrated acid production at 50°C and VMAO could even grow at 60°C;they tolerated and produced acetic acid at 25% (v/v) ethanol concentration;they showed resistance to acetic acid concentrations up to 6% (w/v). Considering all these properties, the use of these strains would seriously contribute to improving the quality of the vinegar produced and help to reduce the cooling water feeds in vinegar production especially in hot countries in the context of global warming.

New perspectives in free nitrous acid (FNA) uses for sustainable wastewater management

The biocidal effects of free nitrous acid (FNA) have found applications in multiple units in an urban wastewater system, including sewer networks, wastewater treatment processes, and sludge treatment processes. However, these applications are associated with chemical costs as both nitrite and acid are needed to produce FNA at the required levels. The recent discovery of novel acid-tolerant ammonia oxidizers offers the possibility to produce FNA from domestic wastewater, enabling the development of next-generation FNA-based technologies capable of achieving self-sustaining FNA production. In this study, we focus on the concept of in situ FNA generation facilitated by acid-tolerant ammonia oxidizers and highlight the multiple benefits it creates, after a brief review of the historical development of FNA-based technologies. We will discuss how wastewater systems can be made more energy-efficient and sustainable by leveraging the potential of acid-tolerant ammonia oxidizers.