Final Acetic Acid Concentration Research Articles

The Impact of Chitosan on the Chemical Composition of Wines Fermented with Schizosaccharomyces pombe and Saccharomyces cerevisiae.

This study investigates the influence of the antimicrobial agent chitosan on a selected Schizosaccharomyces pombe strain during the alcoholic fermentation of ultra-pasteurized grape juice with a high concentration of malic acid. It also studies a selected Saccharomyces cerevisiae strain as a control. The study examines several parameters relating to wine quality, including volatile and non-volatile compounds. The principal aim of the study is to test the influence of chitosan on the final chemical composition of the wine during alcoholic fermentation, and to compare the two studied fermentative yeasts between them. The results show that chitosan influences the final concentration of acetic acid, ethanol, glycerol, acetaldehyde, pyruvic acid, α-ketoglutarate, higher alcohols, acetate esters, ethyl esters, and fatty acids, depending on the yeast species.

A study on acetification process to produce olive vinegar from oil mill wastewaters

In this study, two different acetification procedures to produce olive vinegar (OV) from oil mill wastewaters (OMW) were assayed. Specifically, (i) alcoholic-acetous double fermentation with addition of Saccharomyces cerevisiae starter was compared with (ii) spontaneous acetification, without addition of any starter. Within few days from their production, the OMWs were diluted with distilled water (40:60, v/v) and supplemented with sucrose (100 g L−1) and yeast nutrients (0.5 g L−1). Both the procedures gave a satisfactory acidification, leaving a final acetic acid concentration of around 4% on average. Significant amount of residual sugars, especially fructose, was found in the OV by spontaneous acetification. Therefore, in relation to the consumed sugars, spontaneous acetification has been more performing in terms of acetic acid formation; in addition, the acetogenesis appeared to occur bypassing the alcoholic fermentation. Finally, both spontaneous and starter-driven OVs were permanently clear, with a vinous red color and without any abnormal smell.

Two-stage oxygen supply strategy based on energy metabolism analysis for improving acetic acid production by Acetobacter pasteurianus.

Oxygen acts as the electron acceptor to oxidize ethanol by acetic acid bacteria during acetic acid fermentation. In this study, the energy release rate from ethanol and glucose under different aerate rate were compared, and the relationship between energy metabolism and acetic acid fermentation was analyzed. The results imply that proper oxygen supply can maintain the reasonable energy metabolism and cell tolerance to improve the acetic acid fermentation. Further, the transcriptions of genes that involve in the ethanol oxidation, TCA cycle, ATP synthesis and tolerance protein expression were analyzed to outline the effect of oxygen supply on cell metabolism of Acetobacter pasteurianus. Under the direction of energy metabolism framework a rational two-stage oxygen supply strategy was established to release the power consumption and substrates volatilization during acetic acid fermentation. As a result, the acetic acid production rate of 1.86g/L/h was obtained, which were 20.78% higher than that of 0.1vvm one-stage aerate rate. And the final acetic acid concentration and the stoichiometric yield were 88.5g/L and 94.1%, respectively, which were 84.6g/L and 89.5% for 0.15vvm one-stage aerate rate.

Comparative functional properties of kafirin and zein viscoelastic masses formed by simple coacervation at different acetic acid and protein concentrations

Kafirin and zein could be used in making wheat-free leavened dough-based products if their functionality can be modified to more closely resemble gluten. Recently, stable viscoelastic masses were produced from isolated kafirin and total zein by dissolution of the prolamins in glacial acetic acid, followed by simple coacervation with rapid water addition. The methodology was, however, not compatible with food systems, as the final acid concentration was too high (33%). This work revealed that coacervation with reduction in the final acetic acid concentration down to 0.1% still enabled formation of kafirin and zein viscoelastic masses, with functionality retained on storage at 4 °C for an extended period; indicating an irreversible molecular change with dissolution in glacial acetic acid. Kafirin masses were much firmer than zein masses but both were softer than gluten. However, kafirin displayed a similarly elastic high component to gluten, whereas zein exhibited more viscous flow characteristics. This was probably due to the presence of more disulphide bonds in kafirin than zein. A model to explain this behaviour is proposed. Regarding the effect of prolamin concentration in glacial acetic acid, a minimum, between 5 and 10% was necessary for viscoelastic mass formation at low final acetic acid concentration (5%).

Aroma profile of pilot plant-scale produced fruit vinegar using a thermotolerant Acetobacter pasteurianus strain isolated from Moroccan cactus

In this study, new thermotolerant Acetobacter pasteurianus CV01 strain recently isolated from local product of Morocco has been investigated for its ability to perform efficient acetous fermentation at a large-scale. Firstly, the thermotolerance basis bioconversion of CV01 strain was compared to other mesophilic and thermotolerant acetic acid bacteria. Subsequently, CV01 strain was assessed for its ability to produce and tolerate high amount of acetic acid at optimal and thermal stress conditions in lab-scale bioreactor. It was found that the studied strain exhibited thermotolerant properties compared to reference strains and could withstand the increase in temperature during acetous fermentation in fermenter. Furthermore, gas chromatography-mass spectrometry (GC-MS) was used on the samples prepared with solid phase microextraction (SPME) to determine the volatile compounds of the pilot plant produced apple vinegar based on developed start-up and semi-continuous fermentation protocol. The operation strategy in the 500-L pilot plant scale acetator allowed achieving 7.3% (w/v) of final acetic acid concentration recording high yield and acetification rate. The aroma profile of experimentally produced vinegar was found different from that of the commercial reference one. According to the literature, the results obtained show that major volatile compounds found in pilot-plant produced apple vinegar are related to good aromatic note descriptors which could have a positive impact on the organoleptic quality of industrial vinegar. Consequently, it can be concluded that CV01 Acetobacter strain is well suited for large-scale production of high quality fruit vinegar.

Effect of acetic acid in recycling water on ethanol production for cassava in an integrated ethanol-methane fermentation process.

Recently, the integrated ethanol-methane fermentation process has been studied to prevent wastewater pollution. However, when the anaerobic digestion reaction runs poorly, acetic acid will accumulate in the recycling water. In this paper, we studied the effect of low concentration of acetic acid (≤25 mM) on ethanol fermentation at different initial pH values (4.2, 5.2 or 6.2). At an initial pH of 4.2, ethanol yields increased by 3.0% and glycerol yields decreased by 33.6% as the acetic acid concentration was increased from 0 to 25 mM. Raising the concentration of acetic acid to 25 mM increased the buffering capacity of the medium without obvious effects on biomass production in the cassava medium. Acetic acid was metabolized by Saccharomyces cerevisiae for the reason that the final concentration of acetic acid was 38.17% lower than initial concentration at pH 5.2 when 25 mM acetic acid was added. These results confirmed that a low concentration of acetic acid in the process stimulated ethanol fermentation. Thus, reducing the acetic acid concentration to a controlled low level is more advantageous than completely removing it.

Co-culturing a novel Bacillus strain with Clostridium tyrobutyricum ATCC 25755 to produce butyric acid from sucrose

BackgroundCurrently, the most promising microorganism used for the bio-production of butyric acid is Clostridium tyrobutyricum ATCC 25755T; however, it is unable to use sucrose as a sole carbon source. Consequently, a newly isolated strain, Bacillus sp. SGP1, that was found to produce a levansucrase enzyme, which hydrolyzes sucrose into fructose and glucose, was used in a co-culture with this strain, permitting C. tyrobutyricum ATCC 25755T to ferment sucrose to butyric acid.ResultsB. sp. SGP1 alone did not show any butyric acid production and the main metabolite produced was lactic acid. This allowed C. tyrobutyricum ATCC 25755T to utilize the monosaccharides resulting from the activity of levansucrase together with the lactic acid produced by B. sp. SGP1 to generate butyric acid, which was the main fermentative product within the co-culture. Furthermore, the final acetic acid concentration in the co-culture was significantly lower when compared with pure C. tyrobutyricum ATCC 25755T cultures grown on glucose. In fed-batch fermentations, the optimum conditions for the production of butyric acid were around pH 5.50 and a temperature of 37°C. Under these conditions, the final butyrate concentration was 34.2±1.8 g/L with yields of 0.35±0.03 g butyrate/g sucrose and maximum productivity of 0.3±0.04 g/L/h.ConclusionsUsing this co-culture, sucrose can be utilized as a carbon source for butyric acid production at a relatively high yield. In addition, this co-culture offers also the benefit of a greater selectivity, with butyric acid constituting 92.8% of the acids when the fermentation was terminated.

Transforming Waste Cheese-Whey into Acetic Acid through a Continuous Membrane-Integrated Hybrid Process

Experimental investigations were conducted on fermentative production of acetic acid from waste cheese-whey in a multistage membrane-integrated hybrid process. Traditional fermentation allowed cheese-whey, a cheap and waste material, to be used as carbon source where judicious combinations of cross-flow membrane filtration at the micro, ultra, and nano regimes permitted efficient downstream separation and purification of the product. The provision of separation and recycling of microbial cells and unconverted carbon source allowed fermentation under high cell density with effective use of a carbon source. Continuous separation and removal of the acid product helped to remove product inhibition to a large extent. All these provisions in this novel design resulted in high productivity (4.06 g L–1 h–1), substrate to product yield (0.96 g g–1), purity (94.6%), and final acetic acid concentration of 96.9 g L–1 at 303 K temperature, 150 rpm of agitator speed under non-neutralizing conditions, and at a dilution ...

Formation of kafirin microparticles by phase separation from an organic acid and their characterisation

Protein microparticles (microspheres) have numerous food and pharmaceutical applications. However, generally preparation of prolamin protein microparticles involves aqueous ethanol as a solvent. An ethanol-free method of making microparticles from kafirin with a novel structure was devised. Glacial acetic acid or other organic acids were used as kafirin solvent and the microparticles formed by phase separation on addition of water. The kafirin microparticles were characterised by light microscopy, scanning electron microscopy and transmission electron microscopy and their size distribution was measured. The kafirin microparticles prepared by phase separation from organic acid were spherical or irregular shaped, between 1 and 10 μm in diameter, with rough, porous outer surfaces and many internal holes or vacuoles. The holes seem to be the footprint of air bubbles which were entrapped during microparticle preparation. With an increase in the final concentration of acetic acid, the structure of the microparticles changed from porous spheres to an open matrix, with a concomitant change in kafirin secondary structure from α-helical to β-sheet, indicative of protein aggregation. These highly vacuolated and open matrix type microparticles appear to have potential as encapsulating agents and support structures.

Influence of fermentation oxygen partial pressure on semicontinuous acetification for wine vinegar production

This paper describes semicontinuous acetic acid fermentations for wine vinegar production carried out with different aerating gas compositions ranging from 21% (air) to 63% oxygen content and using low aeration (3.7 h−1, vvm), in order to study the influence of the oxygen partial pressure on the aerating gas supplied to the reactor in this industrial biotransformation process. The acetification process was conducted in 6- to 100-l reactors. The overall acetic acid productivity increased from 0.72 g l−1 h−1 with air to 1.35 g l−1 h−1 when oxygen-rich (36%) air was used. The same behaviour was observed for the maximum acetification rate, and therefore the total process time was reduced in proportion to the increase in productivity, from 65 h using air to 35 h using an aerating gas mixture containing 36% oxygen. The yield of the process was high, 96–99%; the final concentration of acetic acid reached was 116–118 g l−1; and the substrate yield coefficient based on ethanol metabolised was higher using oxygen-rich air than with air. It was not feasible to carry out semicontinuous acetification cycles with an oxygen content higher than 40%, and when the oxygen content was 63%, the process stopped during the first cycle with very little acetic acid production. Moreover, an inverse relationship between the acetic acid formation rate profile in the course of the acetification process and the amount of dissolved acetaldehyde in the fermentation broth formed by the acetic bacteria was observed.

Influence of fermentation temperature on semi-continuous acetification for wine vinegar production

This paper describes semi-continuous acetic acid fermentations for wine vinegar production performed isothermally and using temperature gradients in order to determine the influence of temperature on this industrial biotransformation. Acetifications were conduced in 6- to 100-l reactors. Overall process productivity improved about 15–20% using a temperature gradient. An initial temperature of 32 °C was employed until the product concentration reached 90–95 g/l/h. Thereafter, the temperature was gradually reduced to 30 °C until the end of the production cycle. Under these operating conditions, the 100-l acetator yielded an overall productivity of 1.84±0.03 g/l/h, a maximum acetification rate of 2.10±0.02 g/l/h, a 94.3±0.4% process yield, and a final acetic acid concentration of 116.0±0.9 g/l.

Calcium magnesium acetate (CMA) production from whey permeate: process and economic analysis

About 28 billion lbs of liquid whey produced from cheese manufacture are being wasted in the US. An anaerobic fermentation process is developed to produce calcium magnesium acetate (CMA) from whey permeate. CMA can be used to replace salt as a noncorrosive road deicer. A co-culture consisting of homolactic and homoacetic bacteria was used to convert whey lactose to lactate and then to acetate in continuous, immobilized cell bioreactors. The acetate yield from lactose was ∼ 95% ( w/ w), and the final concentration of acetic acid obtained from this homofermentative process was 4%. The acetic acid produced from fermentation can be readily recovered by solvent extraction with a tertiary amine and reacted with dolomitic lime (CA/MgO) to form a concentrated (>25%) CMA solution. This CMA solution can then be dried to form the granular CMA deicer. About 40 tons CMA can be produced from a plant processing 1.5 million lbs whey permeate per day, at a cost of $215/ton. The total capital investment is estimated at ∼ 7 million dollars, with a return rate of less than 1.5 years at the current market price of $600/ton.

Production of acetic acid by a repeated batch culture with cell recycle ofAcetobacter aceti

A comparison of volumetric production rates of acetic acid inAcetobacter aceti M23 was conducted for repeated batch (RB), cell-recycling repeated batch (CRB) and continuous (C) cultures. Best result was obtained with CRB culture. The magnification of productivity was 1.7 (to RB culture) and 3.3 (to C culture) for aiming final acetic acid concentration of 60 g/l and 42 g/l, respectively.

Isolation of a Strain of Clostridium thermoaceticum Capable of Growth and Acetic Acid Production at pH 4.5

Using a series of pH controlled batch fermentations operated in a fed-batch mode and adaptation and selection techniques where pH and acetic acid provided the selective pressures, we isolated a culture of Clostridium thermoaceticum that can grow and produce acetic acid at pH 4.5. At pH 4.5 the fastest mass doubling time was 36 h, and the highest acetic acid concentration reached was 4.5 g/liter. Generally, as the pH was decreased from 6.0 and the initial acetic acid concentration increased, the mass doubling time increased, and the final acetic acid concentration decreased. These observations can be explained in terms of inhibition by the free acetic acid concentration at a given pH, relative to the total acetic acid concentration (free acid plus acetate ion). We have thus reached one of the criteria determined by us to be required for an economically viable fermentation acetic acid process, i.e., pH 4.5. A second requirement for a mass doubling time of about 7 h (0.1/h dilution rate) can probably be reached by selection in continuous culture. The final requirement for an acetic acid concentration of 50 g/liter will be the most difficult to achieve in view of the organism's sensitivity to low concentrations of free acetic acid.

Production of acetic acid and other volatile compounds by Leucoostoc citrovorum and Leuconostoc dextranicum.

Single-strain milk cultures of Leuconostoc dextranicum are capable of reducing added acetaldehyde, propionaldehyde, and butanone to the corresponding alcohols at 30 C. L. dextranicum and L. citrovorum reduced propionaldehyde to n-propanol quantitatively in 30 hr, and the reduction of this compound paralleled culture growth. Under unagitated conditions, these organisms produced large amounts of acetic acid and ethyl alcohol. The yield of acetic acid increased when cultures were agitated during growth. This increase in acetic acid production was accompanied by a 20- to 70-fold decrease in ethyl alcohol. The addition of acetaldehyde to the fermentation caused a reduction in the final concentration of acetic acid.

Production of Acetic Acid and Other Volatile Compounds by Leuconostoc citrovorum and Leuconostoc dextranicum1

Single-strain milk cultures of Leuconostoc dextranicum are capable of reducing added acetaldehyde, propionaldehyde, and butanone to the corresponding alcohols at 30 C. L. dextranicum and L. citrovorum reduced propionaldehyde to n-propanol quantitatively in 30 hr, and the reduction of this compound paralleled culture growth. Under unagitated conditions, these organisms produced large amounts of acetic acid and ethyl alcohol. The yield of acetic acid increased when cultures were agitated during growth. This increase in acetic acid production was accompanied by a 20- to 70-fold decrease in ethyl alcohol. The addition of acetaldehyde to the fermentation caused a reduction in the final concentration of acetic acid.

Growth Response of Lactobacillus brevis to Aeration and Organic Catalysts

Under stationary and anaerobic conditions, greater cell yields of Lactobacillus brevis were obtained from autoclaved than from filter-sterilized glucose media. Fructose, tentatively identified as a product generated by the heating process, served as an excellent catalyst for inducing growth. The addition of micromolar quantities of pentoses or potential pentose precursors to the filter-sterilized medium was equally effective in stimulating growth. These organic catalysts were not essential for growth under aerobic conditions. Upon agitation, similar cell yields were obtained from the autoclaved and filter-sterilized media. The micromolar quantities of lactic acid produced per micromole of carbohydrate fermented appeared to be similar under aerobic and static conditions of incubation. The final concentration of acetic acid increased as the result of agitation. This increase in volatile acidity was accompanied by a significant decrease in ethyl alcohol production. The cell yield was increased nearly 50% under aerobic conditions.

Growth Response of Lactobacillus brevis to Aeration and Organic Catalysts1

Under stationary and anaerobic conditions, greater cell yields of Lactobacillus brevis were obtained from autoclaved than from filter-sterilized glucose media. Fructose, tentatively identified as a product generated by the heating process, served as an excellent catalyst for inducing growth. The addition of micromolar quantities of pentoses or potential pentose precursors to the filter-sterilized medium was equally effective in stimulating growth. These organic catalysts were not essential for growth under aerobic conditions. Upon agitation, similar cell yields were obtained from the autoclaved and filter-sterilized media. The micromolar quantities of lactic acid produced per micromole of carbohydrate fermented appeared to be similar under aerobic and static conditions of incubation. The final concentration of acetic acid increased as the result of agitation. This increase in volatile acidity was accompanied by a significant decrease in ethyl alcohol production. The cell yield was increased nearly 50% under aerobic conditions.