Acetic Acid Production by an Electrodialysis Fermentation Method with a Computerized Control System

In acetic acid fermentation by Acetobacter aceti, the acetic acid produced inhibits the production of acetic acid by this microorganism. To alleviate this inhibitory effect, we developed an electrodialysis fermentation method such that acetic acid is continuously removed from the broth. The fermentation unit has a computerized system for the control of the pH and the concentration of ethanol in the fermentation broth. The electrodialysis fermentation system resulted in improved cell growth and higher productivity over an extended period; the productivity exceeded that from non-pH-controlled fermentation. During electrodialysis fermentation in our system, 97.6 g of acetic acid was produced from 86.0 g of ethanol; the amount of acetic acid was about 2.4 times greater than that produced by non-pH-controlled fermentation (40.1 g of acetic acid produced from 33.8 g of ethanol). Maximum productivity of electrodialysis fermentation in our system was 2.13 g/h, a rate which was 1.35 times higher than that of non-pH-controlled fermentation (1.58 g/h).     

Production and recovery of propionic and acetic acids in electrodialysis culture of Propionibacterium shermanii

The simultaneous production and recovery of propionic and acetic acids in cultures of Propionibacterium shermanii were examined while maintaining the concentrations of these acids in the fermentation broth at low values with electrodialysis to alleviate end product inhibition. By this method, maximum cell concentration increased 1.36 fold and the average productivities of propionic and acetic acids increased 1.4 fold and 1.31 fold, respectively, compared to cultures without electrodialysis. The mass ratio of propionic and acetic acids recovered was the same as that for the acids produced by fermentation. The inhibitory effect of propionic acid was more significant on the growth of cells than on the production of propionic acid. Some kinetic equations are presented for simulating the dry cell concentration in the fermentor and the concentrations of propionic and acetic acids in the permeate solution of an electrodialysis culture.     

Influence of operating parameters on concentration and purification of L-lactic acid using electrodialysis

An experimental investigation was presented to determine the optimum configuration of influential parameters (concentrate volume, flow rate, temperature, initial lactate concentration, voltage, and impurities) for the best performance. AMX-CMX ion-exchange membranes were used in all experiments. Temperature was found to possess an important role in the increase of lactate recovery, and it was not increased to high values due to membrane destruction. When the higher voltage was applied to electrodialyzer, the better performance of electrodialysis was observed due to enhancement of the driving force. It was found that, to achieve an optimum operating condition, feed volume, concentrate volume, flow rate, temperature, initial lactate concentration in concentrate, and voltage should be 2 L, 1 L, 0.8 L/min, 32°C, 1 g/L, and 15.0 V, respectively. Under these optimized conditions, 97% of lactate was successfully recovered from the fermentation broth, where the lactate flux and energy cost were 7.2 ± 0.6 moles/m²/h and 0.25 kWh/kg, respectively. The results of experiments indicate that the lactic acid in the fermentation broth can be economically purified by electrodialysis.     

Rheological properties of chromosomal and plasmid DNA during alkaline lysis reaction

The experimental apparatus for the simultaneous L-lactic acid fermentation by Rhizopus oryzae immobilized in calcium alginate beads and product separation process was set up in which a three-phase fluidized-bed bioreactor was used as a fermentor and an external electrodialyzer as a separator, and a pump was applied to recycle the fermentation broth between the bioreactor and the separator. The L-lactic acid produced in the fermentor was separated in the separator, product inhibition was alleviated without any addition of alkali or alkali salts and the product purification process could be simplified. The specific productivity and the yield in electrodialysis fermentation (ED-F) process operated in continuous feeding mode were almost the same as that in CaCO₃-buffered fermentation process. A mathematical model of L-lactic acid production in ED-F process was also suggested, in which the model equations for the bioreactor and the electrodialyzer were combined to describe the simultaneous fermentation and product separation. The model predictions were in good agreement with the experimental data.     

Recovery of ammonium lactate and removal of hardness from fermentation broth by nanofiltration

Nanofiltration (NF) was investigated as an alternative to desalting electrodialysis (ED) and ion exchange for the recovery of ammonium lactate from fermentation broth. Three commercial NF membranes, NF45, NF70, and NTR-729HF, were characterized with 50 mM NaCl, MgSO(4), and glucose solutions. NF45 membrane was selected because it showed the lowest rejection of monovalent ion, the highest rejection of divalent ion, and the highest rejection of nonpolar molecule. Effects of the operating pressure were investigated in a range of 100-400 psig, on the flux, lactate recovery, and glucose and magnesium removal from a real fermentation broth containing about 1.0 M of ammonium lactate. The flux and recovery rate increased linearly with the pressure. However, lactate rejection also increased with the pressure, lowering the recovery yield. More magnesium ions and glucose were rejected as the pressure was increased, and at 400 psig, for example, magnesium ion was almost completely rejected, highlighting the chance of obviating the necessity of ion exchange to remove hardness, by using NF instead of desalting ED. Membrane fouling was not so severe as expected, considering the complex nature and a rather high concentration of the fermentation broth treated.     

Application of bipolar electrodialysis on recovery of free lactic acid after simultaneous saccharification and fermentation of cassava starch

The efficiency of bipolar electrodialysis (BED) for the recovery of lactic acid from fermentation broth was evaluated. Three systems of BED (bipolar-anion, bipolar-cation and bipolar-anion-cation) at fixed voltage (20 V) were compared using a model solution of ammonium lactate (100 g l(-1)). Results showed that bipolar-anion (BED-anion) was the most beneficial in terms of lactate flux, current efficiency, energy consumption and recovery ratio. Consequently, BED-anion was used to purify lactic acid from fermentation broth which had been pre-treated with mono-polar electrodialysis (MED). The final lactic acid concentration and lactate flux obtained were 144 g l(-1) and 393 g m(-2) h(-1), respectively. Using the two-step process (MED and BED-anion) the concentration of fermentation broth was increased by 33% and the total energy consumption was 2.76 kW h kg(-1).     

Enhanced hyaluronic acid production of Streptococcus zooepidemicus by an intermittent alkaline-stress strategy

Aims: Enhanced hyaluronic acid (HA) production of Streptococcus zooepidemicus by redirecting carbon flux through an intermittent alkaline‐stress strategy. Methods and Results: pH value was kept at 7·0 for the first 6 h, and then intermittently switched to 8·5 for 1 h and back to 7·0 for 1 h until the end of fermentation at 16 h (one pH switch cycle every 2 h). With this intermittent alkaline‐stress strategy, HA production was increased to 6·5 ± 0·2 g l^?1 from 5·0 ± 0·1 g l^?1 of the control, in which pH was always kept at 7·0. In addition, biomass and lactic acid concentration decreased by 24% and 14%, respectively, while acetic acid concentration increased by 10% under intermittent alkaline stress. The redirection of carbon flux from lactic acid to acetic acid was further supported by the decreased lactate dehydrogenase activity and the increased acetate kinase activity. As indicated by the increased NADH oxidase (NOX) activity, intermittent alkaline‐stress induced a more oxidative intracellular environment which would facilitate HA synthesis. Conclusions: Overproduction of HA was realized by redirecting carbon flux through the proposed intermittent alkaline‐stress strategy. Significance and Impact of the Study: This study clearly demonstrated the importance of metabolic‐pathway‐analysis based fermentation strategy in industrial processes and provided an alternative optimization approach for high viscosity fermentation.     

Novel Method of Lactic Acid Production by Electrodialysis Fermentation

In lactic acid fermentation by Lactobacillus delbrueckii, the produced lactic acid affected the lactic acid productivity. Therefore, for the purpose of alleviating this inhibitory effect, an electrodialysis fermentation method which can continuously remove produced lactic acid from the fermentation broth was applied to this fermentation process. As a result, the continuation of fermentation activity was obtained, and the productivity was three times higher than in non-pH-controlled fermentation. In electrodialysis fermentation, the amount of produced lactic acid was 82.2 g/liter, which was about 5.5 times greater than that produced in non-pH-controlled fermentation. It was concluded that these good results were obtained on account of alleviating the lactic acid inhibitory effect by electrodialysis fermentation. However, the fouling of anion-exchange membranes by cells was observed in electrodialysis fermentation.     

电渗析发酵法生产乳酸的研究

在乳酸发酵过程中,所生成的乳酸对进一步发酵有抑制作用。采用电渗析法从发酵液中及时地分离出产物乳酸,使乳酸的生产量提高到86.4g/L,是不控制pH值发酵时的4倍多。结果表明:电渗析法能有效地消除产物乳酸的抑制作用,提高了乳酸生产率,且简化了提取工艺。     

Recovery of lactic acid from fermentation broth by the two-stage process of nanofiltration and water-splitting electrodialysis

A two-stage process of nanofiltration and water-splitting electrodialysis was investigated for lactic acid recovery from fermentation broth. In this process, sodium lactate is isolated from fermentation broth in the first stage of nanofiltration by using an NTR-729HF membrane, and then is converted to lactic acid in the second stage by water-splitting electrodialysis. To determine the optimal operating conditions for nanofiltration, the effects of pressure, lactate concentration, pH and known added impurities were studied. Lactate rejection was less than 5%, magnesium rejection approximated 45%, and calcium rejection was at 40%. In subsequent water-splitting electrodialysis, both the sodium lactate conversion to lactic acid and sodium hydroxide recovery, were about 95%, with a power requirement of 0.9∼1.0 kWh per kg of lactate.     

Production of acetic acid by Clostridium thermoaceticum in electrodialysis culture using a fermenter equipped with an electrodialyser

Electrodialysis culture of Clostridium thermoaceticum increased the yield of acetate by its continuous removal. In normal batch cultures without pH control the yield was 4.2 g acetic acid/800 ml, while in pH-controlled culture it was 16.8 g/800 ml. Although electrodialysis cultures gave almost the same yield (15.4 g/800 ml) as that in pH-controlled cultures, sparging CO₂ into the broth in electrodialysis culture increased the amount of acetic acid to 22.3 g/800 ml. CO₂ sparging into normal cultures with or without pH control did not significantly increase the amount of acetate produced but yields, in terms of amounts of glucose consumed, were higher than without sparging. The theoretical yield was almost obtained in pH-controlled, electrodialysis cultures with CO₂ sparging.The authors are with the Department of Applied Microbial Technology, Kumamoto Institute of Technology, Ikeda 4-22-1, Kumamoto 860, Japan     

In situ separation of lactic acid from fermentation broth using ion exchange resins

Lactic acid fermentation is an end product inhibited reaction. In situ separation of lactic acid from fermentation broth using ion exchange resins was investigated and compared with conventional fermentation system. Amberlite resin (IRA-400, Cl⁻) was used to separate lactic acid from fermentation broth and pH was controlled online with an automatic pH controller. The effect of process variables on lactic acid production by Lactobacillus casei in whey permeate was studied. The maximum productivity was obtained at pH = 6.1, T = 37 °C and impeller speed = 200 rpm. The maximum concentration of lactic acid at optimum condition was found to be 37.4 g/L after 38 h of fermentation using in situ separation system. The productivity of in situ separation system was five times increased in comparison with conventional system.     

The influence of thermal treatment and operational conditions on xanthan produced by X. arboricola pv pruni strain 106

The influence of thermal treatment and operational conditions (pH and stirrer speed) used in the process of xanthan production by Xanthomonas arboricola pv pruni strain 106 were evaluated through yield of xanthan, aqueous solution and fermentation broth viscosity, sodium content, pyruvate and acetyl content and molar mass. Different conditions used during the fermentation affected the xanthan characteristics. Thermal treatment decreased the final yield and pyruvate and acetyl content, and increased the xanthan aqueous solution and fermentation broth viscosities, as well as molar mass. In this study the best combination of yield and viscosity was obtained with the use of pH 7 and 400 rpm during fermentation and post-fermentation thermal treatment. Aggregation of xanthan molecules promoted by heating and detected through an increase of molar mass was apparently affected by the sodium content. As a result, a correlation between molar mass and xanthan solution viscosity could be observed.     

Selective extraction of acetic acid from the fermentation broth produced by Mannheimia succiniciproducens

Acetic acid is by-product from fermentation processes for producing succinic acid using Mannheimia succiniciproducens . To obtain pure succinic acid from the final fermentation broth, acetic acid was selectively removed based on the different extractability of succinic acid and acetic acid with pH using tri-n-octylamine (TOA) as extractant. When successive batch extractions were performed using 0.25 mol TOA kg(-1) dissolved in 1-octanol at pH 5, the mol ratio of succinic acid to acetic acid before extraction was 4.9 and the final ratio after the fourth batch was 9.4.     

Downstream separation and purification of bio-based alpha-ketoglutaric acid from post-fermentation broth using a multi-stage membrane process

In this study, a multi-stage membrane process, assisted by vacuum evaporation and crystallization, for recovery of bio-based alpha-ketoglutaric acid from the actual post-fermentation broth was designed and investigated. In the first part of this study, pre-treatment of crude fermentation broth (centrifugation-ultrafiltration-nanofiltration) was carried out to remove biomass, proteins, sugars, part of inorganic ions and color compounds. The commercial ceramic UF membrane (15 kDa) and nanofiltration ceramic membrane (200 Da or 450 Da) were applied. Electrodialysis with a bipolar membrane was proposed for separation of ionic compounds and simultaneous electro-acidification to the acid form. During bipolar membrane electrodialysis carried out under acidic conditions, it was possible to remove close to 90 % of alpha-ketoglutaric acid. Moreover, the migration of other acids present in the fermentation broth (lactic and acetic) was significantly limited. The calculated specific energy consumption was low and equal to 0.6 kW h/kg. The final purification using crystallization assisted vacuum evaporation allowed obtaining alpha-ketoglutaric acid in solid form. Analysis of the final product showed that the proposed method of alpha-ketoglutaric acid recovery gives the acid of high purity equal to 94.8 %. Furthermore, the presented results have practical relevance and may in future be the basis for the development of separation technologies of alpha-ketoglutaric acid from the fermentation broth on industrial scale.     

Development of a beverage from red grape juice fermented with the Kombucha consortium

Kombucha is a health-promoting fermented beverage traditionally made by fermenting a sweetened tea with a symbiotic culture of yeast species and acetic acid bacteria. The aim of this work was to develop a beverage using red grape juice as an alternative substrate. Grape juice contains various nutrient elements and phytochemicals, such as polyphenols, which possess a wide range of biological activities. We investigated the chemical characteristics and sensory and antimicrobial activities of the fermented grape juice Kombucha beverage. The pH decreased from 3.95 to 2.9 during the fermentation process and remained fairly constant thereafter, and the acetic acid bacteria and yeast counts in the broth increased up to 6 days of fermentation and subsequently decreased. Phenolic and anthocyanin contents and the antioxidant activity of the fermented beverage were higher after fermentation, with the maximum increase observed on the sixth day of fermentation when values were approximately 2.47- and 1.59-fold higher than pre-fermentation values, respectively, as assessed by 2,2-diphenyl-1-picrylhydrazyl and 2,2′-azino-bis (3-ethylbenzothiazoline-6- sulfonic acid) radical scavenging assays. Fourier transform infrared spectroscopy was used for the qualitative analysis of the grape juice before and after fermentation. Distinct peak variations in the spectral region between 2500 and 1650 cm^?1 were observed, which matched the appearance of organic acids and changes in phenolic compounds. Fermented juice Kombucha showed antibacterial activity toward all tested bacteria, which can be primarily ascribed to the increased production of acetic acid, but also to the biosynthesis of other metabolites, during the fermentation process. The 6-day fermented juice was the most appreciated by the taste panel based on the overall quality evaluation; with prolongation of fermentation the fermented juice acquired a distinct sour flavor.     

Stimulation of the rate of l-lactate fermentation using Lactococcus lactis IO-1 by periodic electrodialysis

Lactic acid fermentation in glucose medium with periodic electrodialysis by Lactococcus lactis IO-1 was examined. The fermentation time was reduced considerably, compared with the time required for ordinary built-in electrodialysis fermentation with a microfilter module (ED-MF). Fermentation with an initial glucose concentration of 80 g/l was completed within 18 h, about 50% of the time required with an ED-MF. The maximum productivity of this novel system was about two-fold that of the ordinary ED-MF system even when the lactate concentration in broth was higher than in the ED-MF. The H₂ gas produced from the ED-MF made the culture redox potential (CRP) lower than in the novel system. Online culture redox potential was monitored and higher CRP indicated a higher fermentation rate.     

Recovery of succinic acid from fermentation broth

Succinic acid is of high interest as bio-feedstock for the chemical industry. It is a precursor for a variety of many other chemicals, e.g. 1,4-butandiol, tetrahydrofuran, biodegradable polymers and fumaric acid. Besides optimized production strains and fermentation processes it is indispensable to develop cost-saving and energy-effective downstream processes to compete with the current petrochemical production process. Various methods such as precipitation, sorption and ion exchange, electrodialysis, and liquid–liquid extraction have been investigated for the recovery of succinic acid from fermentation broth and are reviewed critically here.     

Production of Alkaline Protease from Acetic Acid

The use of acetic acid as a carbon source in alkaline protease fermentation was examined. Acetic acid was a good carbon source and yielded a great deal of alkaline protease.

Acetic acid has advantages over ordinary carbon sources such as starch and glucose in that it can be supplied to culturing liquid as much as needed to perform the fermentation efficiently, that it has a function to control the pH of culturing liquid at a constant level and that it was obtained at lower price.

The maximum proteolytic activity attained was 1.6 × 10⁴ units/ml (11.4 mg-enzyme/ml).     

Effects of pH and acetic acid on homoacetic fermentation of lactate by Clostridium formicoaceticum

Clostridium formicoaceticum homofermentatively converts lactate to acetate at 37 degrees C and pH 6.6-9.6. However, this fermentation is strongly inhibited by acetic acid at acidic pH. The specific growth rate of this organism decreased from a maximum at pH 7.6 to zero at pH 6.6. This inhibition effect was found to be attributed to both H(+) and undissociated acetic acid. At pH values below 7.6, the H(+) inhibited the fermentation following non-competitive inhibition kinetics. The acetic acid inhibition was found to be stronger at a lower medium pH. At pH 6.45-6.8, cell growth was found to be primarily limited by a maximum undissociated acetic acid concentration of 0.358 g/L (6mM). This indicates that the undissociated acid, not the dissociated acid, is the major acid inhibitor. At pH 7.6 or higher, this organism could tolerate acetate concentrations of higher than 0.8M, but salt (Na(+)) became a strong inhibitor at concentrations of higher than 0.4M. Acetic acid inhibition also can be represented by noncompetitive inhibition kinetics. A mathematical model for this homoacetic fermentation was also developed. This model can be used to simulate batch fermentation at any pH between 6.9 and 7.6.