Electrodialysis Fermentation Research Articles

Hydrogen fermentation of organic wastewater with high ammonium concentration via electrodialysis system

An advanced electrodialysis fermentation system was set up to remove ammonium during hydrogen fermentation. When the voltage was increased from 0 to 6 V, the average ammonium removal rate was improved from 8.7 to 31.1 mg/L/h at an initial ammonium concentration of 3000 mg/L. A model based on the Nernst-Plank equation and porous media properties of ion exchange membranes was successfully implemented to predict the ammonium removal performance. When such a system was fed with synthetic wastewater at an ammonium concentration of 3000 mg/L for hydrogen fermentation, a significant increase in specific hydrogen yield was observed in the experiment group at 4 V. Specific hydrogen yield was 225.0 mL/g glucose, this value is 47.9% higher than the control. Moreover, ammonium concentration in experiment group was reduced to 701.6 mg/L at 72 h when voltage was set at 4 V, which is 63.7% lower than that in 0 V experiment group.

Production of lactic acid by continuous electrodialysis fermentation with a glucose concentration controller

In this study, the system of electrodialysis fermentation (EDF) was improved by a glucose concentration controller (GC controller) which could control glucose concentration stable and low in fermentation broth. Under the control of the GC controller, there were little inhibitory effects of the end product and substrate on bacteria so as to result in high activity of bacteria and, further, in high productivity of lactic acid. Moreover, the low glucose concentration in the fermentation broth brought about little glucose leakage to the recovery solution and hence high yield of lactic acid. Compared with the EDFs carried out in the previous studies, the continuous EDF with a glucose concentration controller (CEDF with GC controller) was higher in productivity, yield and conversion ratio of lactic acid, indicating that it was a system more efficient to produce lactic acid.

Development of a continuous electrodialysis fermentation system for production of lactic acid by Lactobacillus rhamnosus

Experimental devices for stimulating productivity of lactic acid fermentation were installed and a level meter was used to control the volume of fermentation broth. Experiments were carried out by means of continuous EDF with feed medium. It was verified that 175 g/L of glucose concentrations in the feed medium was the best value. In this case, the continuous EDF lasted for above 350 h and was stable for above 200 h. The maximum productivity, yield and conversion ratio were 8.18 g/L h, 68.8% and 71%, respectively. Compared with other EDFs, the continuous EDF with a level meter had the highest productivity and produced 2637 g of lactic acid from 4000 g of glucose. The amount of lactic acid produced was, due to the longest fermentation time and the highest productivity, about 19.5 times greater than that of the conventional EDF and was about 9.7 times greater than that of the intermittent EDF. The glucose, however, began to be excessive in fermentation broth after 200 h, resulting in a decrease of lactic acid production.

Production of l-lactic acid by electrodialysis fermentation (EDF)

An efficient process for producing l-lactic acid using an, EDF method is described. The results showed that intermittent EDF with continuous medium feed was the best one among the experiment methods employed. Comparing with the conventional EDF, intermittent EDF (seven on–off) with continuous medium feed indicated that the maximum value of o.d. 660 was not increased, but productivity was 1.5 times higher. The yield increased by above 30% and glucose transport decreased to 1/10 (from 0.46 to 0.05).

L-lactic acid production using immobilized Rhizopus oryzae in a three-phase fluidized-bed with simultaneous product separation by electrodialysis

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.

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 H 2 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.

Reduction in the length of the lag phase of l-lactate fermentation by the use of inocula from electrodialysis seed cultures

The effect of an inoculum grown in electrodialysis fermentation (ED-F) on the length of the lag phase of l-lactate production fermentation was investigated. No lag time was observed in the production fermentation using the inoculum grown in ED-F, while a clear lag time was observed in a production fermentation using an inoculum cultured for 24 h by a conventional seed culture (without ED-F). It is claimed that the lag time reduction is due to the removal of the inhibitory effects of lactate produced during the seed stage. It is shown that the adoption of ED-F for the production of inoculum should reduce variability in inoculum quality.

Factors affecting lactic acid production rate in the built-in electrodialysis fermentation, an approach to high speed batch culture

To avoid cells adhering to the ion-exchange membrane and damage of the cells in electrodialysis fermentation (ED-F), ED-F with a microfiltration (MF) module, was used in lactate fermentation. In this system, after 38 h of cultivation, the dry cell weight (2.89 g/ l) and the number of viable cells (4.8 × 10 9/ml) were about 1.8 and 1.6 times more than those of the control fermentation, respectively. Lactate dehydrogenase activity in this system was maintained at a high level, resulting in reduction of fermentation time to complete batch culture within 38 h. From these results, ED-F with an MF module enabled high speed batch culture.

Built-in electrodialysis batch culture, a new approach to release of end product inhibition

Electrodialysis fermentation (ED-F) was carried out to study the kinetic analysis of the release of end product inhibition in l-lactate fermentation. The l-lactate was continuously extracted by a dialyzer as it was being produced, and removed from the culture system so that the l-lactate concentration in the broth was maintained at a level as low as about 10 g/ l. In spite of such a low concentration, however, the release of end product inhibition was not as great as the release level expected from the lactate concentration in the broth. In a culture with a low initial sugar concentration of 50 g/ l, the fermentation rate was not stimulated by electrodialysis, while the fermentation rate for ED-F at a high initial sugar concentration of 85 g/ l was stimulated, resulting in a reduction of the fermentation time. The reason for this contradiction was explained by computer simulation. It was assumed that the fermentation rate was regulated by the lactate concentration in the culture system, which has a concentration gradient across the cell membrane. The lactate gradient is greater in the early and the middle stages of batch culture, so the effect of dialysis did not develop at low initial sugar concentrations. The lactate gradient gradually became smaller as the fermentation proceeded, thus permitting the effect of dialysis to develop at high initial sugar concentrations. The kinetic analysis using computer simulation, and the fact that the lactate concentration calculated with kinetic data from ED-F agreed well with the lactate concentration observed, supported this assumption.

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).

Lactic acid production by electrodialysis fermentation using immobilized growing cells

Lactic acid production by electrodialysis fermentation using immobilized growing cells

通電透析発酵法のＬ‐リジン発酵への応用

Aspartate kinase of Brevibacterium flavum QL-5 is inhibited by L-lysine plus L-threonine. Ele-ctrodialysis fermentation was applied to L-lysine production to reduce this inhibition. After 72 hr, the amount of L-lysine produced by electrodialysis fermentation was 57.2 g, which was 1.2 times greater than that by non-electrodialysis fermenta-tion (46.9 g), and similar to that by diffusion dialysis fermentation (57.0g). In electrodialysis fermentation, the L-lysine concentration in dialyz-ing solution was only 0.2%, while that in the fermentation broth was about 2%. It was sug-gested that production of L-lysine was limited by transport of L-lysine across the hollow fiber wall. L-Lysine monohydrochloride was added to the cul-ture broth at various culture stage, but the produc-tion of L-lysine was not influenced by the L-lysine added. Therefore, it was considered that the inhibition by L-lysine plus L-threonine in L-lysine production by Brevibacterium flavum QL-5 was not alleviated even when the L-lysine concentration in the fermentation broth was maintained at low by electrodialysis fermentation or diffusion dialysis 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.