Aerobic chromate reduction by chromium-resistant bacteria isolated from serpentine soil

A group of 34 chromium-resistant bacteria were isolated from naturally occurring chromium percolated serpentine soil of Andaman (India). These isolates displayed different degrees of chromate reduction under aerobic conditions. One of the 34 isolates identified as Bacillus sphaericus was tolerant to 800 mg l⁻¹ Cr(VI) and reduced >80% Cr(VI) during growth. In Vogel Bonner broth, B. sphaericus cells (10¹⁰ cells ml⁻¹) reduced 62% of 20 mg l⁻¹ of Cr(VI) in 48 h with concomitant discoloring of yellow medium to white one. Reduction of chromate was pronounced by the addition of glucose and yeast extract as electron donors. In the presence of 4.0 g l⁻¹ of glucose, 20 mg l⁻¹ of Cr(VI) was reduced to 2.45 mg l⁻¹ after 96 h of incubation. Optimum pH and temperature for reduction were 6.0 and 25 °C, respectively. Increase in cell density and initial Cr(VI) concentration increased chromate reduction but was inhibited by metal ions like, Ni²⁺, Co²⁺, Cd²⁺ and Pb²⁺. Experiments with cell-free extracts indicated that the soluble fraction of the cell was responsible for aerobic reduction of Cr(VI) by this organism.     

Simultaneous production of anthocyanin and triterpenoids in suspension cultures of Perilla frutescens

When cultivated in Murashige & Skoog medium supplemented with 0.2 mg l⁻¹ 2,4-dichlorophenoxy acetic acid and 0.5 mg l⁻¹ 6-benzyladenine, Perilla frutescens cells in suspension culture grew rapidly reaching about 13.6 g dry wt l⁻¹ after 12 days. The cell line produced both anthocyanin 0.9 g l⁻¹ and triterpenoids: 16 mg l⁻¹ oleanolic acid (OA), 25 mg l⁻¹ ursolic acid (UA) and 14 mg l⁻¹ tormentic acid (TA). When P. frutescens cells of 7-day-old cultures were exposed to a yeast elicitor at 0.5–5% (v/v) for 7 days, it was found that anthocyanin content peaked at 10.2% of dry weight with yeast elicitor at 1% (v/v) whereas the maximum production of oleanolic acid and ursolic acid in cultures treated with 2% (v/v) yeast elicitor was 19 and 27 mg l⁻¹, a 46 and 24% increase over the control, respectively. This is the first report of simultaneous production of both anthocyanin and triterpenoids in a single culture system.     

Optimization of bio-indigo production by recombinant E. coli harboring fmo gene

A bacterial flavin-containing monooxygenase (FMO) gene was cloned from Methylophaga aminisulfidivorans MP^T, and a plasmid pBlue 2.0 was constructed to express the bacterial fmo gene in E. coli. To increase the production of bio-indigo, upstream sequence size of fmo gene was optimized and response surface methodology was used. The pBlue 1.7 plasmid (1686 bp) was prepared by the deletion of upstream sequence of pBlue 2.0. The recombinant E. coli harboring the pBlue 1.7 plasmid produced 662 mg l⁻¹ of bio-indigo in tryptophan medium after 24 h of cultivation in flask. The production of bio-indigo was optimized using a response surface methodology with a 2ⁿ central composite design. The optimal combination of media constituents for the maximum production of bio-indigo was determined as tryptophan 2.4 g l⁻¹, yeast extract 4.5 g l⁻¹ and sodium chloride 11.4 g l⁻¹. In addition, the optimum culture temperature and pH were 30 °C and pH 7.0, respectively. Under the optimized conditions mentioned above, the recombinant E. coli harboring pBlue 1.7 plasmid produced 920 mg of bio-indigo per liter in optimum tryptophan medium after 24 h of cultivation in fermentor. The combination of truncated insert sizes and culture optimization resulted in a 575% increase in the production of bio-indigo.     

Effects of feed sugar concentration on continuous ethanol fermentation of cheese whey powder solution (CWP)

Cheese whey powder (CWP) solution with different CWP or sugar concentrations was fermented to ethanol in a continuous fermenter using pure culture of Kluyveromyces marxianus (DSMZ 7239). Sugar concentration of the feed CWP solution varied between 55 and 200 g l⁻¹ while the hydraulic residence time (HRT) was kept constant at 54 h. Ethanol formation, sugar utilization and biomass formation were investigated as functions of the feed sugar concentration. Percent sugar utilization and biomass concentrations decreased and the effluent sugar concentration increased with increasing feed sugar concentrations especially for the feed sugar contents above 100 g l⁻¹. Ethanol concentration and productivity (DP) increased with increasing feed sugar up to 100 g l⁻¹ and then decreased with further increases in the feed sugar content. The highest ethanol concentration (3.7%, v v⁻¹) and productivity (0.54 gE l⁻¹ h⁻¹) were obtained with the feed sugar content of 100 g l⁻¹ or 125 g l⁻¹. The ethanol yield coefficient (Y_P/S) was also maximum (0.49 gE gS⁻¹) when the feed sugar was between 100 and 125 g l⁻¹. The growth yield coefficient (Y_X/S) decreased steadily from 0.123 to 0.063 gX gS⁻¹ when the feed sugar increased from 55 to 200 g l⁻¹ due to adverse effects of high sugar contents on yeast growth. The optimal feed sugar concentration maximizing the ethanol productivity and sugar utilization was between 100 and 125 g l⁻¹ under the specified experimental conditions.     

Phenol inhibition of biological nutrient removal in a four-step sequencing batch reactor

Nutrient removal from synthetic wastewater was investigated using a four-step sequencing batch reactor (SBR) at different phenol (C₆H₅OH) concentrations in order to determine the inhibition effects of phenol on biological nutrient removal. The nutrient removal process consisted of anaerobic, oxic, anoxic, and oxic phases with hydraulic residence times (HRT) of 1 h/3 h/1 h/1 h and a settling phase of 3/4 h. Solids retention time (SRT) was kept constant at 10 days in all experiments. Initial phenol concentrations were varied between 0 and 600 mg l⁻¹ at seven different levels. The effects of phenol on COD, NH₄-N, and PO₄-P removals and effluent nutrient levels were investigated. Phenol was almost completely degraded up to 400 mg l⁻¹ phenol concentration resulting in almost negligible inhibition effects on COD, NH₄-N, and PO₄-P removals. Nutrient removals were adversely affected by phenol at concentrations above 400 mg l⁻¹. Above 95% COD, 90% NH₄-N and 65% PO₄-P removal was obtained for phenol concentrations below 400 mg l⁻¹. The sludge volume index (SVI) was almost constant around 45 ml g⁻¹ for phenol concentrations below 400 mg l⁻¹ but increased to 90 ml g⁻¹ at a phenol level of 600 mg l⁻¹.     

Carbon exchange and water use efficiency of a growing, irrigated olive orchard

We measured eddy covariance fluxes of CO₂ and H₂O over a flat irrigated olive orchard during growth, in different periods from Leaf Area Index (LAI) of 0.3–1.9; measurements of soil respiration were also collected. The daily net ecosystem exchange flux (F_NEE) was practically zero at LAI around 0.4 or when the orchard intercepted 11% of the incoming daily radiation; at the end of the experiment, with LAI of 1.9 (and the fraction of intercepted daily radiation close to 0.5), F_NEE was around 10 g CO₂ m⁻² day⁻¹. The night-time ecosystem respiration (R_eco), calculated from eddy fluxes in well-mixed night conditions, show a clear but non-linear dependence with LAI; it ranged from 0.05 to 0.15 mg CO₂ m⁻² s⁻¹ (in average), being the lower limit ideally close to the heterotrophic soil respiration at the site. The gross primary production flux (F_GPP) was linearly related to LAI within the LAI range of this experiment (with 11 g CO₂ m⁻² day⁻¹ increments per unit of LAI) and to the fraction of intercepted radiation. The maximum rates of F_GPP (0.75 mg CO₂ m⁻² s⁻¹) were obtained in the summer mornings of 2002, at LAI close to 1.9. F_GPP was strongly modulated by vapour pressure deficit (VPD) through the canopy conductance, even in absence of water stress. Hence, especially in the summer, the maximum rates of carbon assimilation are reached always before noon. The daily course of F_GPP shows a two-phase pattern, first related to irradiance and then to canopy conductance. The water use efficiency (WUE) was, in average, 3.8, 6.3 and 7 g CO₂ L⁻¹ in 1999, 2001 and 2002, respectively, with maxima always in the early morning. Hourly WUE was strongly related to VPD (WUE = −10.25 + 22.52 × VPD^−0.34). Our results suggest that drip irrigated orchards in general, and olive in particular, deserve specific carbon exchange and carbon budget studies and cannot be easily included in other biomes.     

Effect of oxygen supply on cell growth and saponin production in bioreactor cultures of Panax ginseng

The effects of oxygen supply within the range 20.8–50% (using pure oxygen and air), on cell cultures of Panax ginseng were investigated in a balloon-type bubble bioreactor (5 L capacity, containing 4 L Murashige and Skoog medium, supplemented with 7.0 mg L⁻¹ indolebutyric acid, 0.5 mg L⁻¹ kinetin and 30 g L⁻¹ sucrose). A 40% oxygen supply was found to be optimal for the production of both cell mass and saponin yielding values of 12.8 g (DW) L⁻¹, 4.5 mg (g DW)⁻¹ on day 25, respectively. Low (20.8%, 30%) and high (50%) oxygen concentration supplies were unfavorable to cell growth and saponin accumulation. The results indicate that oxygen supplementation to bioreactor-based ginseng cultures was beneficial for biomass accumulation and saponin production.     

A study in UF-membrane reactor on activity and stability of nitrile hydratase from Microbacterium imperiale CBS 498-74 resting cells for propionamide production

The bioconversion of propionitrile to propionamide was catalysed by nitrile hydratase (NHase) using resting cells of Microbacterium imperiale CBS 498-74 (formerly, Brevibacterium imperiale). This microorganism, cultivated in a shake flask, at 28 °C, presented a specific NHase activity of 34.4 U mg_DCW⁻¹ (dry cell weight). The kinetic parameters, K_m and V_max, tested in 50 mM sodium phosphate buffer, pH 7.0, in the propionitrile bioconversion was evaluated in batch reactor at 10 °C and resulted 21.6 mM and 11.04 μmol min⁻¹ mg_DCW⁻¹, respectively. The measured apparent activation energy, 25.54 kJ mol⁻¹, indicated a partial control by mass transport, more likely through the cell wall.

UF-membrane reactors were used for kinetic characterisation of the NHase catalysed reaction. The time dependence of enzyme deactivation on reaction temperature (from 5 to 25 °C), on substrate concentrations (from 100 to 800 mM), and on resting cell loading (from 1.5 to 200 μg  ml⁻¹) indicated: lower diffusional control (E_a=37.73 kJ mol⁻¹); and NHase irreversible damage caused by high substrate concentration. Finally, it is noteworthy that in an integral reactor continuously operating for 30 h, at 10 °C, 100% conversion of propionitrile (200 mM) was attained using 200 μg  ml⁻¹ of resting cells, with a maximum volumetric productivity of 0.5 g l⁻¹ h⁻¹.     

Bioreactor operation for transgenic Nicotiana tabacum cell cultures and continuous production of recombinant human granulocyte-macrophage colony-stimulating factor by perfusion culture

The production of hGM-CSF was investigated in both a flask and a 5-l bioreactor, using transgenic Nicotiana tabacum suspension cells. While the maximum cell density and secreted hGM-CSF in the flask were 15.4 g l⁻¹ and 6.5 μg l⁻¹, respectively, those in the bioreactor were 15.6 g l⁻¹ and 7.6 μg l⁻¹. No detectable growth inhibition, shorter production of hGM-CSF and reduced cell viability in the batch bioreactor were observed under the specific conditions used compared with the flask culture. To improve the productivity, a perfusion culture was carried out in the bioreactor, with three different perfusion rates (0.5, 1.0 and 2.0 day⁻¹). In all cases, the hGM-CSF in the medium was significantly increased during the overall culture period (16 days), with maximum values 3.0-, 9.4- and 6.0-fold higher than those obtained in the batch cultures, respectively, even though the intracellular hGM-CSF content was not significantly varied by the perfusion rate. In terms of the total amount of hGM-CSF secreted, 205.5, 1073.2 and 1246.3 μg accumulated in the perfusate within 16 days at the perfusion rates of 0.5, 1.0 and 2.0 day⁻¹, respectively. It was concluded that the beneficial effect of perfusion on the production of hGM-CSF originated from the reduced proteolytic degradation due to the lower protease activity caused by the perfusion. Additionally, the cell growth and physiology in the perfusion culture were somewhat negatively affected by the increased perfusion rate, although the dry cell density steadily increased, and as a result, 19.4, 22.4 and 22.9 g l⁻¹ of maximum cells were obtained with perfusion rates of 0.5, 1.0 and 2.0 day⁻¹, respectively. This work highlighted the importance of proteolytic degradation in plant cell cultures for the production of secretory proteins and the feasibility of perfusion strategies for the continuous production of foreign proteins by the prevention of protein loss due to proteolytic enzymes.     

Decolorization of reactive dyes by mixed cultures isolated from textile effluent under anaerobic conditions

In the present study mixed cultures that could grew in the molasses media were isolated from textile dye effluent and its decolorization activity was studied in a batch system under anaerobic conditions, in order to determine the optimal conditions required for the highest decolorization activity. The optimum pH value for decolorization was determined as 8 for all the dyes tested. In the experiment with pH 8 dye decolorizations by mixed cultures were investigated at about 96.2–1031.3 mg l⁻¹ initial dye concentrations. The highest dye removal rates of mixed cultures were 94.9% for Reactive Red RB, 91.0% for Reactive Black B and 63.6% for Remazol Blue at 953.2, 864.9 and 1031.3 mg l⁻¹ initial dye concentrations respectively within 24 h incubation period. When the Reactive Red RB was used, approximately 82–98% total color removal was obtained at between 96.2 and 953.2 mg l⁻¹ initial dye concentrations after 12 h of incubation at 35 °C. These results show that our enriched mixed cultures have the potential to serve as an excellent biomass for the use in reactive dye removal from wastewaters under anaerobic conditions.     

The response of an emergent sedge Bolboschoenus medianus to salinity and nutrients

The potential for nutrient load (30, 100 and 350 g N m⁻² per year) to alter plant performance under saline conditions (control, 4.5, 9 and 13 dS m⁻¹) was examined in the sedge Bolboschoenus medianus. Relative growth rates (RGR) across nutrient loadings ranged from 30.2 to 41.8 mg g⁻¹ per day in controls and were reduced to 20.9–28.5 mg g⁻¹ per day by salinities of 13 dS m⁻¹. Whilst higher nutrient loads generally increased RGR, the response was smaller at higher salinities. Responses to salinity and nutrient load were specific. Nutrient load increased the RGR via increases in the leaf area ratio (LAR). The LAR ranged from 1.9 to 2.1 m² kg⁻¹ across salinity treatments at 30 g N m⁻² per year, and increased to 2.5–2.8 m² kg⁻¹ at 350 g N m⁻² per year. Salinity reduced the RGR via a reduction in the net assimilation rate (NAR). The NAR in control plants ranged from 14.7 to 16 g m⁻² per day across nutrient loadings and decreased to 11–12 g m⁻² per day at 13 dS m⁻¹. Carbon isotope discrimination of leaves decreased by 2–3‰ in response to 13 dS m⁻¹ at the lower nutrient loadings. A prominent response of B. medianus to salinity was a change in biomass allocation from culms to tubers. In contrast, the response to nutrient load was characterised by a shift in biomass allocation from roots to leaves.     

Determination of kinetic constants of hybrid textile wastewater treatment system

The present study is related to treatment of textile wastewater in microaerophilic–aerobic hybrid reactor. The study showed the effectiveness of biological treatment of wastewater involving appropriate microorganism and suitable reactors. COD and color were reduced to 82–94%, and 99% respectively for textile wastewater. The reactor was operated at highest loading of 16.4 g COD g l⁻¹ d⁻¹ and obtained 80% COD and 72% color removal. Biokinetic models were applied to data obtained from experimental studies in continuously operated hybrid reactor. Treatment efficiencies of the reactor were investigated at different hydraulic retention times (2.3–9.1 d) and organic loading rates (2.6–16.4 g COD l⁻¹ d⁻¹). Second-order and a Stover–Kincannon models were best fitted to the hybrid column reactor. The second-order substrate removal rate constant (k_2(S)) was found as 41.44 d⁻¹ for hybrid reactor. Applying the modified Stover–Kincannon model to the hybrid reactor, the maximum removal rate constant (U_max) and saturation value constant (K_B) were found to be 212 g l⁻¹ d⁻¹ and 22.89 g l⁻¹ d⁻¹, respectively.     

Stopped-flow system with ozonizer for the estimation of low biochemical oxygen demand in environmental samples

The stopped-flow system with an ozonizer was developed to estimate low biochemical oxygen demand (BOD) in rivers. Rivers contain many biopersistent organic compounds such as humic acid, lignin, and gum arabic. Free radicals generated by self-decomposition of ozone were used as powerful oxidants to split organic compounds. Ozonysis of the samples was carried out by 42.4 g N⁻¹ m⁻³ ozone for 3 min at pH 7.0. Artificial wastewater (AWW) solutions were employed as standard solutions for the calibrations of the BOD sensor. At a BOD of 1 mg l⁻¹, the sensor response after ozonation was 1.6-fold higher than that before ozonation. The response time of the BOD sensor was only 5 min, being independent of the concentrations, and the lower detection limit was 0.5 mg l⁻¹ BOD. The degradations of lignin and tannic acid by ozonation were 54.1 and 42.3%, respectively. In the biosensor responses by ozonation, lignin, gum arabic, and surfactant increased by double or more compared with previous responses. BOD in rivers was estimated using the stopped-flow system. Environmental samples pretreated with ozone gave high responses to the biosensor that were similar to those of the conventional BOD₅ method. Accordingly, a good correlation between the sensor and the conventional BOD₅ was obtained (r = 0.989). The system has to evolve the highly sensitive BOD determination.     

Production of cyclodextrin by poly-lysine fused Bacillus macerans cyclodextrin glycosyltransferase immobilized on cation exchanger

Bacillus macerans cyclodextrin glycosyltransferase (CGTase) fused with 10 lysine residues at its C-terminus (CGTK10ase) was immobilized onto a cation exchanger by ionic interaction and used to produce -cyclodextrin (CD) from soluble starch. Poly-lysine fused immobilization increased the V_m of the immobilized CGTase by 40% without a change in K_m. The activation energies of thermal deactivation (E_a) were 41.4, 28.1, and 25.9 kcal mol⁻¹, respectively, for soluble wild-type (WT) CGTase, soluble CGTK10ase, and immobilized CGTK10ase, suggesting destabilization of CGTase by poly-lysine fusion and immobilization onto a cation exchanger. Maximum -CD productivity of 539.4 g l⁻¹ h⁻¹ was obtained with 2% soluble starch solution which was constantly fed at a flow rate of 4.0 ml min⁻¹ (D = 240 h⁻¹) in a continuous operation mode of a packed-bed reactor. The operational half-life of the packed-bed enzyme reactor was estimated 12 days at 25 °C and pH 6.0.     

Asparaginase production by a recombinant Pichia pastoris strain harbouring Saccharomyces cerevisiae ASP3 gene

The therapeutic enzyme asparaginase, which is used for the treatment of acute lymphoblastic leukaemia, is industrially produced by the bacteria Escherichia coli or Erwinia crysanthemi. In spite of its effectiveness as a therapeutic agent, the drug causes severe immunological reactions. As asparaginase is also produced by the yeast Saccharomyces cerevisiae, this microorganism could be considered for the production of the enzyme, providing an alternative antitumoral agent. In this study the ASP3 gene, that codes for the periplasmic, nitrogen regulated, asparaginase II from S. cerevisiae, was cloned and expressed in the methylotrophic yeast Pichia pastoris, under the control of the AOX1 gene promoter. Similarly to S. cerevisiae the heterologous enzyme was addressed to the P. pastoris cell periplasmic space. Enzyme yield per dry cell mass reached 800 U g⁻¹, which was seven fold higher than that obtained using a nitrogen de-repressed ure2 dal80 S. cerevisiae strain. High cell density cultures performed with P. pastoris harbouring the ASP3 gene using a 2 l instrumented bioreactor, where biomass concentration reached 107 g l⁻¹, resulted in a dramatic increase in volumetric yield (85,600 U l⁻¹) and global volumetric productivity (1083 U l⁻¹ h⁻¹).     

Oxygen limitation improves glycerol production by Candida krusei in a bioreactor

An oxygen limitation strategy based on dynamic enzyme activity was applied to improve glycerol accumulation and decrease the residual sugar level in a fermentation of Candida krusei in a bioreactor. By applying oxygen limitation at 88 h when the activities of two glycerol synthetic enzymes cytosolic glycerol-3-phosphate dehydrogenase (ctGPD) and glycerol-3-phosphatase (GPP) were low and the activity of mitochondrial glycerol-3-phosphate dehydrogenase (mtGPD) which catalyzes the glycerol dissimilation was high, the glycerol dissimilation was efficiently reduced. The final glycerol concentration reached 51.8 g l⁻¹ at 96 h and 54.9 g l⁻¹ at 116 h, which was 18 and 60% higher than the control (without oxygen limitation), respectively. The residual sugar was consumed completely while it was 11.2 g l⁻¹ at the end of fermentation in the control. Under oxygen limitation, ethanol production was detected at a final concentration of 3.6 g l⁻¹. This work suggests a metabolic flux shift by oxygen limitation in the bioreactor.     

Effect of iron concentration on hydrogen fermentation

The effect of the iron concentration in the external environment on hydrogen production was studied using sucrose solution and the mixed microorganisms from a soybean-meal silo. The iron concentration ranged from 0 to 4000 mgFeCl₂ l⁻¹. The temperature was maintained at 37°C. The maximum specific hydrogen production rate was found to be 24.0 mlg⁻¹ VSSh⁻¹ at 4000 mgFeCl₂ l⁻¹. The specific production rate of butyrate increased with increasing iron concentration from 0 to 20 mgFeCl₂ l⁻¹, and decreased with increasing iron concentration from 20 to 4000 mgFeCl₂ l⁻¹. The maximum specific production rates of ethanol (682 mgg⁻¹ VSSh⁻¹) and butanol (47.0 mgg⁻¹ VSSh⁻¹) were obtained at iron concentrations of 5 and 3 mgFeCl₂ l⁻¹, respectively. The maximum hydrogen production yield of 131.9 mlg⁻¹ sucrose was obtained at the iron concentration of 800 mgFeCl₂ l⁻¹. The maximum yields of acetate (389.3 mgg⁻¹ sucrose), propionate (37.8 mgg⁻¹ sucrose), and butyrate (196.5 mg g⁻¹ sucros) were obtained at iron concentrations of 3, 200 and 200 mgFeCl₂ l⁻¹, respectively. The sucrose degradation efficiencies were close to 1.0 when iron concentrations were between 200 and 800 mgFeCl₂ l⁻¹. The maximum biomass production yield was 0.283 gVSSg⁻¹ sucrose at an iron concentration of 3000 mgFeCl₂ l⁻¹.     

Continuous ethanol production and evaluation of yeast cell lysis and viability loss under very high gravity medium conditions

A combined bioreactor system, composed of a stirred tank and a three-stage tubular bioreactor in series and with a total working volume of 3260 ml, was established. Continuous ethanol production was carried out using Saccharomyces cerevisiae and a very high gravity (VHG) medium containing 280 g l⁻¹ glucose. An average ethanol concentration of 124.6 g l⁻¹ or 15.8% (v) was produced when the bioreactor system was operated at a dilution rate of 0.012 h⁻¹. The yield of ethanol to glucose consumed was calculated to be 0.484 or 94.7% of its theoretical value of 0.511 when ethanol entrapped in the exhaust gas was incorporated. Meanwhile, quasi-steady states and non-steady oscillations were observed for residual glucose, ethanol and biomass concentrations for all of these bioreactors during their operations. Models that can be used to predict yeast cell lysis and viability loss were developed.     

Batch and continuous fermentation of succinic acid from wood hydrolysate by Mannheimia succiniciproducens MBEL55E

Batch and continuous cultures of Mannheimia succiniciproducens MBEL55E were carried out in a complex medium containing a NaOH-treated wood hydrolysate for the production of succinic acid. The wood hydrolysate based medium was treated with NaOH before sterilization to reduce the formation of inhibitory compounds. M. succiniciproducens MBEL55E utilized xylose as well as glucose in the wood hydrolysate based medium as a carbon source for the succinic acid production. In batch cultures, the final succinic acid concentration of 11.73 g l⁻¹ was obtained from the pre-treated wood hydrolysate based medium, resulting in a succinic acid yield of 56% and a succinic acid productivity of 1.17 g l⁻¹ h⁻¹, while the corresponding continuous cultures gave the succinic acid yield and productivity of 55% and 3.19 g l⁻¹ h⁻¹, respectively. These results suggest that succinic acid can be produced economically and efficiently by the fermentation of M. succiniciproducens MBEL55E from an inexpensive biomass-based wood hydrolysate.