Immobilized Cells Of Zymomonas Mobilis Research Articles

High-sodium maltobionate production by immobilized Zymomonas mobilis cells in polyurethane

The purpose of this study was the production of maltobionic acid, in the form of sodium maltobionate, by Z. mobilis cells immobilized in polyurethane. The in situ immobilized system (0.125-0.35mm) was composed of 7g polyol, 3.5g isocyanate, 0.02g silicone, and 7g Z. mobilis cell, at the concentration of 210g/L. The bioconversion of maltose to sodium maltobionate was performed with different cell concentrations (7.0-9.0 gimobilized/Lreaction_medium), temperature (30.54-47.46°C), pH (5.55-7.25), and substrate concentration (0.7-1.3mol/L). The stability of the immobilized system was evaluated for 24h bioconversion cycles and storage of 6months. The maximum concentration of sodium maltobionate was 648.61mmol/L in 34.34h process (8.5 gdry_cell/Lreaction_medium) at 39°C and pH 6.30. The immobilized system showed stability for 19 successive operational cycles of 24h bioconversion and 6months of storage, at 4°C or 22°C.

Correction to: High lactobionic acid production by immobilized Zymomonas mobilis cells: a great step for large-scale process.

In the original publication, table captions were incorrectly published. The correct captions are given here.

High lactobionic acid production by immobilized Zymomonas mobilis cells: a great step for large-scale process.

Lactobionic acid and sorbitol are produced from lactose and fructose in reactions catalyzed by glucose-fructose oxidoreductase and glucono-δ-lactonase, periplasmic enzymes present in Zymomonas mobilis cells. Considering the previously established laboratory-scale process parameters, the bioproduction of lactobionic acid was explored to enable the transfer of this technology to the productive sector. Aspects such as pH, temperature, reuse and storage conditions of Ca-alginate immobilized Z. mobilis cells, and large-scale bioconversion were assessed. Greatest catalyst performance was observed between pH range of 6.4 and 6.8 and from 39 to 43°C. The immobilized biocatalyst was reused for twenty three 24-h batches preserving the enzymatic activity. The activity was maintained during biocatalyst storage for up to 120days. Statistically similar results, approximately 510mmol/L of lactobionic acid, were attained in bioconversion of 0.2 and 3.0L, indicating the potential of this technique of lactobionic acid production to be scaled up to the industrial level.

Production of organic acids by periplasmic enzymes present in free and immobilized cells of Zymomonas mobilis

In this work the periplasmic enzymatic complex glucose-fructose oxidoreductase (GFOR)/glucono-δ-lactonase (GL) of permeabilized free or immobilized cells of Zymomonas mobilis was evaluated for the bioconversion of mixtures of fructose and different aldoses into organic acids. For all tested pairs of substrates with permeabilized free-cells, the best enzymatic activities were obtained in reactions with pH around 6.4 and temperatures ranging from 39 to 45 °C. Decreasing enzyme/substrate affinities were observed when fructose was in the mixture with glucose, maltose, galactose, and lactose, in this order. In bioconversion runs with 0.7 mol l(-1) of fructose and with aldose, with permeabilized free-cells of Z. mobilis, maximal concentrations of the respective aldonic acids of 0.64, 0.57, 0.51, and 0.51 mol l(-1) were achieved, with conversion yields of 95, 88, 78, and 78 %, respectively. Due to the important applications of lactobionic acid, the formation of this substance by the enzymatic GFOR/GL complex in Ca-alginate-immobilized cells was assessed. The highest GFOR/GL activities were found at pH 7.0-8.0 and temperatures of 47-50 °C. However, when a 24 h bioconversion run was carried out, it was observed that a combination of pH 6.4 and temperature of 47 °C led to the best results. In this case, despite the fact that Ca-alginate acts as a barrier for the diffusion of substrates and products, maximal lactobionic acid concentration, conversion yields and specific productivity similar to those obtained with permeabilized free-cells were achieved.

The production of sorbitol by permeabilized and immobilized cells of Z. mobilis in sucrose

The production of sorbitol by permeabilized and immobilized cells of Zymomonas mobilis in Luffa cylindrica was investigated in sucrose medium. A full 2³ factorial design was used to verify the influence of each factor and its interactions. The cell permeabilization showed a significant and negative effect upon the production of sorbitol, while the time of cultivation and the immobilization process were significant and positive. The results demonstrated that the cell immobilization and the time of cultivation of 36 h presented higher production of sorbitol.

Coupling of an electrodialysis unit to a hollow fiber bioreactor for separation of gluconic acid from sorbitol produced by Zymomonas mobilis permeabilized cells

The objective of this study was to evaluate the coupling of an electrodialysis unit to a reactor in which gluconic acid and sorbitol were produced by permeabilized and immobilized Zymomonas mobilis cells. The experimental results have shown that electrodialysis unit coupled to the bioreactor allowed an efficient removal of gluconic acid from the reaction medium, as well as an improvement in the stability of the enzyme. It was not observed any reduction in the reaction rate, even after 60 h of operation. On the other hand, when NaOH was applied to neutralize the gluconic acid produced, it was verified a reduction of 80% in the reaction rate in the same period. These results lead to the hypothesis that the enzyme stability is associated to gluconate accumulation in the reaction medium.

5177012 Biosensor containing immobilized zymomonas mobilis cells for measuring glucose, fructose and sucrose: Hak-Sung Kim, Je-Kyun Park, Seoul, Republic Of Korea assigned to Korea Advanced Institute of Science & Technology

5177012 Biosensor containing immobilized zymomonas mobilis cells for measuring glucose, fructose and sucrose: Hak-Sung Kim, Je-Kyun Park, Seoul, Republic Of Korea assigned to Korea Advanced Institute of Science & Technology

Continuous ethanol production at high glucose concentrations by a passively immobilized Zymomonas mobilis system

The effect of high glucose concentrations on continuous ethanol production by passively immobilized Zymomonas mobilis cells has been studied. High effluent ethanol concentrations always led to low productivities. The maximum ethanol concentration attained was 92.8 g/l (98% glucose conversion) at a dilution rate of 0.14 h-1 with 200 g/l glucose medium. The observed enhancement of cell immobilization in the fibrous support at high glucose concentrations in the feed input seems to be related to the formation of bacterial filaments.

Ethanol production from sucrose by immobilizedZymomonas mobilis cells in polyurethane foam

The possibility of using polyurethane foam as a support for the immobilization ofZymomonas mobilis cells to carry out sucrose conversion to ethanol was investigated. Sucrose hydrolysis efficiencies of 90% and higher, volumetric reactor productivity of 20 gL−1h−1 and final ethanol concentration of 6.3% (v/v) at a dilution rate of 0.4 h−1 show the good performance of polyurethane foams for whole cell immobilization.

Effects of ethanol concentration on immobilized Zymomonas mobilis for continuous production of ethanol

The effects of ethanol concentration on the ethanol productivity and activity of immobilized Zymomonas mobilis cells during continuous fermentation of glucose has been studied at various ethanol concentrations. On changing the inlet ethanol concentration, Po, from 0.0 kg/m 3 to any other level, 8 h were required to fully experience the effects of a change in Po, whereas 8 h to 2 days, depending on Po, were required to reach the steady state on switching back to the ethanol free medium. The volumetric ethanol productivity decreased from 92.5 to 0.0 kg/m 3·h as the ethanol concentration in the bioreactor was changed from 46.3 to 126 kg/m 3. The activity of the immobilized cells recovered up to 63% in 2 days even after exposing the cells to 126 kg/m 3 of ethanol.

A study on the ethanol production by immobilized cells ofZymomonas mobilis

Cells ofZymomonas mobilis immobilized in Ca-alginate matrix were used for ethanol production under various conditions. Immobilized cells showed broad optimum pH profile and their operational optimum temperature shifted from 30‡C to 40‡C upon immobilization. As reportedlyZ. mobilis did get the substrate inhibition by glucose, but at high concentration level of glucose the reduction of activity for ethanol production was less severe than that for yeast. The used beads of the immobilizedZ. mobilis were reactivated by incubating them in the activation medium. The increase in cell number and the enhancement of the specific activity per each cell are considered the two major factors responsible for the overall activation. A packed-bed reactor with the feed glucose concentration of 20% (W/V) gave an ethanol productivity as high as 33.0 g/l.hr at the flow rate of 58.5 ml/hr. A comparison between the experimental results from the real packed-bed reactor and the simulation results of an ideal case showed a two-fold inferior performance by the real reactor and this is at least partly attributed to the CO2 gas effect.