Production of lipolytic enzymes in batch cultures of Ophiostoma piceae

After an extensive fungal screening, an Ophiostoma piceae strain was selected for its ability to produce high concentrations of lipase and esterase to remove pitch components of wood pulp. Optimal conditions for growth and enzyme production were established first in shaken flasks. A medium containing rapeseed oil and mycological peptone resulted in a lipase activity of 736 U dm^?3 and an esterase activity of 1569 U dm^?3. When fermentation runs were implemented using the same medium under controlled conditions in 2‐dm³ fermenters, the lipase and esterase activities were increased to 1005 and 4006 U dm^?3 respectively. Further scale‐up was carried out in two stages to 20 dm³ and 72 dm³ (pilot‐scale) stirred tank reactors. The results proved that the cultures could be scaled‐up successfully from shaken flasks to pilot‐scale with increases of 47% and 146% in lipase and esterase activities respectively. © 2001 Society of Chemical Industry     

Design of different bioreactor configurations: application to ligninolytic enzyme production in semi‐solid‐state cultivation

The production of ligninolytic enzymes by Phanerochaete chrysosporium BKM‐F‐1767 (ATCC 24725) in laboratory‐scale bioreactors was studied. The cultivations were carried out in semi‐solid‐state conditions, employing corncob as carrier, which functioned both as a place of attachment and as a source of nutrients. Several bioreactor configurations were investigated in order to determine the most suitable one for ligninolytic enzyme production: a 1‐dm³‐static‐bed bioreactor, a 1‐dm³‐static‐bed bioreactor with air diffusers into the bed, a 0.5‐dm³‐static‐bed bioreactor with air diffusers into the bed and a tray bioreactor. Although the static‐bed configurations produced maximum individual lignin peroxidase (LiP) activities about 400 U dm⁻³ (1.0‐dm³ bioreactor) and about 700 U dm⁻³ (0.5‐dm³ bioreactor), manganese‐dependent peroxidase (MnP) was not detected throughout the cultures. Nevertheless, the tray configuration led to maximum individual MnP and LiP activities of about 200 U dm⁻³ and 300 U dm⁻³, respectively. Therefore, this configuration is the most adequate of the different bioreactor configurations tested in the present work, since the ligninolytic complex formed by MnP and LiP is more efficient for its application to bio‐processing systems. In addition, the results indicated the influence of the oxygen in ligninolytic enzyme production. © 2001 Society of Chemical Industry     

Production and characterization of laccase and manganese peroxidase from the ligninolytic fungus Fomes sclerodermeus

Fomes sclerodermeus was grown on semi‐defined media based on yeast extract, peptone and glucose (YPG). The fungus produced a minimum basal level of laccase activity irrespective of culture medium. The highest laccase production (20 U cm^?3) was obtained in cultures supplemented with CuSO₄. Manganese peroxidase (MnP) could only be detected when MnSO₄ was added to the medium. None of the aromatic compounds tested stimulated further laccase or MnP production. Laccase and MnP stimulated by Cu²⁺ or Mn²⁺ respectively were purified. Two different laccase isoenzymes with the same molecular mass (67 kDa) and N‐linked carbohydrate content (3%) and a slight difference in their pI values (3.41 and 3.48) were characterized. In addition, two different MnP isoenzymes with the same molecular mass (47 kDa) and N‐linked carbohydrate content (4%) and different pI values (3.35 and 3.45) were characterized. Both enzymes showed good stability at 25 °C and over a wide range of pH. Both laccases oxidize ABTS (2,2′‐azino‐bis(3‐ethylbenzthiazoline‐6‐sulfonic acid) more efficiently than 2,6‐dimethoxyphenol (DMP) with similar efficiency values (K_cat/K_m) while the MnP I, the major peroxidase isoenzyme in the studied conditions, oxidizes the Mn²⁺ and Mn‐mediated activity on DMP more efficiently than MnP II. Copyright © 2006 Society of Chemical Industry     

Optimum culture medium composition for rhamnolipid production by pseudomonas aeruginosa AT10 using a novel multi‐objective optimization method

BACKGROUND: Rhamnolipid is a biosurfactant that finds wide applications in pharmaceuticals and beauty products. Pseudomonas aeruginosa is a producer of rhamnolipids, and the process can be implemented under laboratory‐scale conditions. Rhamnolipid concentration depends on medium composition namely, carbon source concentration, nitrogen source concentration, phosphate content and iron content. In this work, existing data⁷ were used to develop an artificial neural network‐based response surface model (ANN RSM) for rhamnolipid production by pseudomonas aeruginosa AT10. This ANN RSM model is integrated with non‐dominated sorting differential evolution (DE) to identify the optimum medium composition for this process. RESULTS: Different strategies for optimization of culture medium composition for this process were evaluated, and the best determined to be an ANN model combined with DE involving a combination of Naïve and Slow and ε‐constrained techniques. The optimal culture medium is determined to have carbon source concentration of 49.86 g dm^?3, nitrogen source concentration of 4.99 g dm^?3, phosphate content of 1.42 g dm^?3, and iron content of 17.12 g dm^?3. The maximum rhamnolipid activity was found to be 18.07 g dm^?3, which compares favorably with that previously reported (18.66 g dm^?3), and is in fact closer to the experimentally determined value of 16.50 g dm^?3. CONCLUSION: This method has distinct advantages over methods using statistical regression models, and can be used for optimization of other multi‐objective biosurfactant production processes. © 2012 Society of Chemical Industry     

Utilization of response surface methodology to optimize the culture media for the production of rhamnolipids by Pseudomonas aeruginosa AT10

Pseudomonas aeruginosa AT10 produced a mixture of surface‐active rhamnolipids when cultivated on mineral medium with waste free fatty acids as carbon source. The development of the production process to an industrial scale included the design of the culture medium. A 2⁴ full factorial, central composite rotational design and response surface modelling method (RSM) was used to enhance rhamnolipid production by Pseudomonas aeruginosa AT10. The components that are critical for the process medium were the carbon source, the nitrogen source (NaNO₃), the phosphate content (K₂ HPO₄/KH₂PO₄ 2:1) and the iron content (FeSO₄·7H₂O). Two responses were measured, biomass and rhamnolipid production. The maximum biomass obtained was 12.06 g dm^?3 DCW, when the medium contained 50 g dm^?3 carbon source, 9 g dm^?3 NaNO₃, 7 g dm^?3 phosphate and 13.7 mg dm^?3 FeSO₄·7H₂O. The maximum concentration of rhamnolipid, 18.7 g dm^?3, was attained in medium that contained 50 g dm^?3 carbon source, 4.6 g dm^?3 NaNO₃, 1 g dm^?3 phosphate and 7.4 mg dm^?3 FeSO₄·7H₂O. © 2002 Society of Chemical Industry     

High‐level production of recombinant His‐tagged rhamnulose 1‐phosphate aldolase in Escherichia coli

An expression system based on Escherichia coli and the T5 promoter allowed the overproduction of a his‐tagged rhamnulose‐1‐phosphate aldolase (RhuA; EC 4.1.2.19), an enzyme with applications in the production of deoxyazasugars and deoxysugars compounds. Shake flask and bioreactor cultivation with E coli M15 (pQErham) were performed under different media and inducing conditions for RhuA expression. A Defined Medium (DM) with glucose as carbon source gave a high volumetric and enzyme productivity (3460 AU dm^?3 and 288 AU dm^?3 h^?1 respectively) compared with Luria–Bertoni (LB) medium (2292 AU dm^? 3 and 255 AU dm^?3 h^?1). The minimum quantity of (isopropyl‐β‐D ‐thiogalactoside) IPTG for optimal induction was estimated in 18–20 µmol IPTG gDCW^?1. The highest volumetric production of RhuA (8333 AU dm^?3) was obtained when IPTG was added in the late log‐phase. No significant differences were found in specific RhuA activity for induction temperatures of 30 and 37 °C. An effective two‐step purification process comprising affinity chromatography and gel permeation has been developed (overall recovery 66.5%). These studies provide the basis for the further development of an integrated process for recombinant RhuA production suitable for biotransformation applications. Copyright © 2003 Society of Chemical Industry     

Scale-Up studies of non-aerated fed-batch fermentation of dextransucrase and the industrial synthesis of dextran using the enzymatic route

High activities of the enzyme dextransucrase were repeatedly produced using slowly agitated non-aerated fed-batch fermentations of Leuconostoc mesenteroides B-512(F). Activities in excess of 24.0 U cm^?3 were obtained consistently in a 16 dm³ laboratory fermenter using a 6 dm³ initial work volume. Yeast extract type was identified to be one of the important factors influencing the enzyme yield. Studies on aerating the medium with different gases indicated that the presence of carbon dioxide in the medium favoured high enzyme production. Agitation rates did not appear to have significant effects on either cell growth or enzyme production. One type of antifoam (silicone antifoam) was observed to affect enzyme production but not the cell growth. Scale-up of the non-aerated process was carried out up to a 1000 dm³ scale with enzyme broths containing up to 21.0 U cm^?3 being produced. Two batches of the enzyme that were produced at the large scale were used for the first time to synthesize dextran at a 50000 dm³ industrial scale. The dextran yields were up to 95.5% of the conventional industrial yields and were achieved in much shorter reaction time intervals.     

Effects of cationic polymer on start‐up and granulation in upflow anaerobic sludge blanket reactors

The upflow anaerobic sludge blanket (UASB) has been used successfully to treat a variety of industrial wastewaters. It offers a high degree of organics removal, low sludge production and low energy consumption, along with energy production in the form of biogas. However, two major drawbacks are its long start‐up period and deficiency of active biogranules for proper functioning of the process. In this study, the influence of a coagulant polymer on start‐up, sludge granulation and the associated reactor performance was evaluated in four laboratory‐scale UASB reactors. A control reactor (R1) was operated without added polymer, while the other three reactors, designated R2, R3 and R4, were operated with polymer concentrations of 5 mg dm^?3, 10 mg dm^?3 and 20 mg dm^?3, respectively. Adding the polymer at a concentration of 20 mg dm^?3 markedly reduced the start‐up time. The time required to reach stable treatment at an organic loading rate (OLR) of 4.8 g COD dm^?3 d^?1 was reduced by more than 36% (R4) as compared with both R1 and R3, and by 46% as compared with R2. R4 was able to handle an OLR of 16 g COD dm^?3 d^?1 after 93 days of operation, while R1, R2 and R3 achieved the same loading rate only after 116, 116 and 109 days respectively. Compared with the control reactor, the start‐up time of R4 was shortened by about 20% at this OLR. Granule characterization indicated that the granules developed in R4 with 20 mg dm^?3 polymer exhibited the best settleability and methanogenic activity at all OLRs. The organic loading capacities of the reactors were also increased by the addition of polymer. The maximum organic loading of the control reactor (R1) without added polymer was 19.2 g COD dm^?3 d^?1, while the three polymer‐assisted reactors attained a marked increase in organic loading of 25.6 g COD dm^?3 d^?1. Adding the cationic polymer could result in shortening of start‐up time and enhancement of granulation, which may in turn lead to improvement in the efficiency of organics removal and loading capacity of the UASB system. Copyright © 2004 Society of Chemical Industry     

Fermentation optimization for the production of lovastatin by Aspergillus terreus: use of response surface methodology

A Box–Behnken experimental design was used to investigate the effects of five factors—ie oxygen content in the gas phase; concentrations of C, N and P; and fermentation time—on the concentrations of biomass and lovastatin produced in batch cultures of Aspergillus terreus. The values of the various factors in the experiment ranged widely, as follows: 20–80% (v/v) oxygen in the aeration gas; 8–48 g dm^?3 C‐concentration; 0.2–0.6 g dm^?3 N‐concentration; 0.5–2.5 g dm^?3 phosphate‐concentration; and 7–11 days fermentation time. No previous work has used statistical analysis in documenting the interactions between oxygen supply and nutrient concentrations in lovastatin production. The Box–Behnken design identified the oxygen content in the gas phase as the principal factor influencing the production of lovastatin. Both a limitation and excess of oxygen reduced lovastatin titers. A medium containing 48 g dm^?3 C supplied as lactose, 0.46 g dm^?3 N supplied as soybean meal, and 0.79 g dm^?3 phosphate supplied as KH₂PO₄, was shown to support high titers (～230 mg dm^?3) of lovastatin in a 7‐day fermentation in oxygen‐rich conditions (80% v/v oxygen in the aeration gas). Under these conditions, the culture medium had excess carbon but limiting amounts of nitrogen. The optimized fermentation conditions raised the lovastatin titer by four‐fold compared with the worst‐case scenario within the range of factors investigated. Copyright © 2004 Society of Chemical Industry     

Lipolytic enzyme production in batch and fed‐batch cultures of Ophiostoma piceae and Fusarium oxysporum

Lipase and esterase production by Ophiostoma piceae and Fusarium oxysporum were enhanced and extended by developing a fed‐batch process in stirred tank reactors. Fed‐batch strategy improved lipolytic enzyme production from Ophiostoma piceae in both 2 and 20 dm³ stirred tank reactors. However, fed‐batch fermentation of Fusarium oxysporum in the 2 dm³ reactor was more effective than both batch and fed‐batch fermentations in the 20 dm³ reactor. When a medium composed of only carbon and nitrogen source was intermittently fed to the cultures, the maximum specific lipase activity was improved by more than 80% and 35% in Ophiostoma piceae and Fusarium oxysporum cultures respectively. The maximum specific esterase activity was improved by 20% and 15% in Ophiostoma piceae and Fusarium oxysporum cultures respectively. The duration of production for both fungi extended from 144 to 216 h compared with a batch culture under the same condition. © 2000 Society of Chemical Industry     

Production of fructose and ethanol from media with high sucrose concentrations by a mutant of Saccharomyces cerevisiae

The production of enriched fructose syrups and ethanol from a synthetic medium with high sucrose concentrations was studied in a batch process using Saccharomyces cerevisiae ATCC 36858. The results showed that the fructose yield was above 92% of theoretical values in synthetic media with sucrose concentrations between 180 g dm^?3 and 726 g dm^?3. Ethanol yield was about 82% in media with sucrose concentrations up to 451 g dm^?3. A product containing 178 g dm^?3 fructose, which represents 97% of the total sugar content, and 79 g dm^?3 ethanol was obtained using a medium with 360 g dm^?3 sucrose. The fructose fraction in the carbohydrates content in the produced syrups decreased with increases in the initial sucrose concentration. In a medium with initial sucrose concentration of 574 g dm^?3, the fructose content in the produced broth was 59% of the total carbohydrates. Glycerol and fructo‐oligosaccharides were also produced in this process. The produced fructo‐oligosaccharides started to be consumed when the concentration of sucrose in the media was less than 30% of its initial value. Complete hydrolysis of these sugars was noticed in media with sucrose concentrations below 451 g dm^?3. These findings will be useful in the production of ethanol and high fructose syrups using sucrose‐based raw materials with high concentrations of this carbohydrate. © 2001 Society of Chemical Industry     

Formaldehyde biodegradation and its inhibitory effect on nitrification

The simultaneous removal of formaldehyde and ammonium in aerobic cultures and the inhibitory effect of formaldehyde on ammonium oxidation were investigated. The influence of a co‐substrate, methanol, on formaldehyde biodegradation and on the nitrification process was also evaluated. Formaldehyde was completely removed at all concentrations tested (30–3890 mg dm^?3) in assays with that compound as the single carbon source and in the presence of methanol as co‐substrate. An initial formaldehyde biodegradation rate of 4.6 g CH₂O g^?1 VSS d^?1 was obtained for 2000 mg CH₂O dm^?3 as single carbon source compared with a rate of 7.3 g CH₂O g^?1 VSS d^?1 when methanol was added. Formaldehyde was inhibitory to the nitrification process at initial concentrations higher than 350 mg dm^?3. Increasing the initial formaldehyde concentration or adding a co‐substrate such as methanol resulted in a longer lag phase before ammonium oxidation and caused a decrease in the degree of nitrification. Nitrification was completely inhibited at initial formaldehyde concentrations higher than 1500 mg dm^?3. Copyright © 2004 Society of Chemical Industry     

Influence of growth medium composition on the lipolytic enzyme activity of Ophiostoma piliferum (CartapipTM)

Production of esterases (carboxyl esterase EC 3.1.1.1) and lipases (glycerol ester hydrolase EC 3.1.1.3) by Ophiostoma piliferum (Cartapip^TM), a fungus commercialized to decrease fatty acyl esters in wood, is described. The influence of various combinations of carbon and nitrogen sources, in the growth medium, was examined. Medium containing yeast extract as a nitrogen source and olive oil as a carbon source was found to be optimal for extracellular esterase (221 U dm⁻³) and lipase (152 U dm ⁻³) activities. Further increases in those enzyme activities were achieved by decreasing medium pH from 6.5 to 5.5 (esterase 508 U dm⁻³; lipase 415 U dm ⁻³) and increasing medium calcium content from 8 m mol dm⁻³ to 160 m mol dm⁻³ (esterase 4084 U dm⁻³; lipase 508 U dm ⁻³) © 1999 Society of Chemical Industry     

Production of the enzyme dihydrofolate reductase by methotrexate-resistant bacteria isolated from soil

Six bacterial cultures isolated from soil were capable of growing in the presence of methotrexate (MTX). Two strains, PFR-1 and 3, developed resistance to 500 μg cm^?3 MTX in the medium and produced elevated levels of the enzyme dihydrofolate reductase (EC 1.5.1.3): 2580 and 2702 U dm^?3 compared to the sensitive parent strains (28 and 35 U dm^?3). Isolate PFR-3 showed maximum enzyme production (4950 U dm^?3, specific activity 12.56 U mg^?1 in flasks and 5737 U dm^?3, specific activity 14.80 U mg^?1 in 5-dm³ fermenter) during exponential phase of growth (6 h) at 37°C and pH 7.0.     

Laccase improvement in submerged cultivation: induced production and kinetic modelling

Improvement of laccase production by Trametes versicolor was made by employing different operational strategies. In the cell growth medium, various glucose concentrations were compared for improving laccase production. A clear and significant stimulation of enzyme production under carbon limitation was obtained. Copper, 2,5‐xylidine, and a phenolic mixture were also used as laccase inducers. A cooperative effect between the inducers on laccase production was identified. Mixtures of inducers produced higher laccase activities, reaching values of 5500 U dm^?3. Further productivity enhancement can be obtained using the inducers along with the carbon limitation strategy. It is shown that low laccase concentrations are obtained by a primary metabolism of T versicolor, and that phenolic compounds and carbon limitation induce a secondary metabolism, providing higher laccase concentrations. A mathematical model for laccase production based on a direct experimental measure of biomass, along with substrate consumption and enzymatic activity over time is proposed for non‐homogeneous fermentations of T versicolor. Copyright © 2005 Society of Chemical Industry     

Optimisation of the biological treatment of hypersaline wastewater from Dunaliella salina carotenogenesis

The reutilisation of Dunaliella salina carotenogenesis medium, after microalgal biomass separation by centrifugation, was assessed. The wastewater had an NaCl concentration between 174 g dm^?3 and 254 g dm^?3 and an average total organic matter concentration of 1540 mg dm^?3 ash‐free dry weight, of which 41% (w/v) was glycerol. The biological treatment was established at laboratory scale and batch operations used halophilic bacteria from the wastewater itself. The wastewater was supplemented with NH₄⁺,PO₄^3?, K⁺ and Mg²⁺ ions to enhance growth. The effect of each ion added per se was initially investigated and a response surface methodology (RSM) used to identify the optimal conditions for maximisation of glycerol removal from the wastewater, which was considered to be the main objective. Addition of NH₄⁺ ions alone achieved 79% glycerol removal compared with only 59% in the absence of supplement, after 8 days incubation. The combined addition of ions ([NaCl] = 214 g dm^?3, [Mg²⁺] = 114 mg dm^?3, [K⁺] = 131 mg dm^?3, [NH₄⁺] = 113 mg dm^?3, [PO₄^3?] = 40 mg dm^?3) increased glycerol removal from the wastewater such that, after 2 days incubation, no residual glycerol was apparent in cultures. These ion combinations enabled the halophilic bacteria to efficiently remove glycerol from the wastewater and consequently reduce organic matter. This treated wastewater should be appropriate for reutilisation as a carotenogenesis medium for β‐carotene production from D salina. © 2001 Society of Chemical Industry     

Removal of aqueous phenolic compounds from a model system by oxidative polymerization with turnip (Brassica napus L var purple top white globe) peroxidase

Turnip roots, which are readily available in Mexico, are a good source of peroxidase, and because of their kinetic and biochemical properties have a high potential as an economic alternative to horseradish peroxidase (HRP). The efficiency of using turnip peroxidase (TP) to remove several different phenolic compounds as water‐insoluble polymers from synthetic wastewater was investigated. The phenol derivatives studied included phenol, 2‐chlorophenol, 3‐chlorophenol, o‐cresol, m‐cresol, 2,4‐dichlorophenol and bisphenol‐A. The effect of pH, substrate concentration, amount of enzyme activity, reaction time and added polyethylene glycol (PEG) was investigated in order to optimize reaction conditions. A removal efficiency ≥85% was achieved for 0.5 mmol dm^?3 phenol derivatives at pH values between 4 and 8, after a contact time of 3 h at 25 °C with 1.28 U dm^?3 of TP and 0.8 mmol dm^?3 H₂O₂. Addition of PEG (100–200 mg dm^?3) significantly reduced the reaction time required (to 10 min) to obtain >95% removal efficiency and up to 230% increase in remaining TP activity. A relatively low enzyme activity (0.228 U dm^?3) was required to remove >95% of three phenolic solutions in the presence of 100–200 mg dm^?3 PEG. TP showed efficient and fast removal of aromatic compounds from synthetic wastewaters in the presence of hydrogen peroxide and PEG. These results demonstrate that TP has good potential for the treatment of phenolic‐contaminated solutions. © 2002 Society of Chemical Industry     

Production of L-aminoacylase by fermentation of Pseudomonas sp. BA2

The growth and enzymatic production of Pseudomonas sp. BA2 a new L -aminoacylase-producing microorganism, were studied in a bench-top fermenter. Multiple fermentations were carried out in order to determine the optical pH and temperature values. The influence of the substrate concentration on both growth and L aminoacylase activity was also investigated. The maximum growth rate and the greatest yield of enzyme were obtained when the fermentation was carried out at pH 7·5, 25°C and DOT ≥ 50%. N-Acetyl-DL -alanine, at a concentration 20 g dm^?3, was used as the sole carbon and nitrogen source. The fermentation process provided a maximum biomass concentration of 3·36 g dry weight dm^?3. The highest L -aminoacylase production (11429 U g^?1 dry weight) was obtained after 39 h of cultivation. The results were a significant improvement over those previously reported.     

Biodiesel production from Stichococcus strains at laboratory scale

BACKGROUND: This paper reports the results of an experimental campaign of autotrophic cultures of Stichococcus strains aiming at selecting the most promising strain for biofuel production. The strain selected—S. bacillaris 158/11—was cultivated in 1 L lab‐scale bubble column photobioreactors under fed‐batch and semi‐continuous conditions. A Bold basal medium supplemented with NaNO₃ as nitrogen source was adopted. Tests were carried out at 23 °C, 140 µE m^?2 s^?1, and air flow rate ranging between 0.4 and 4 vvm. Cultures were characterized in terms of pH, concentration of total nitrogen, total organic carbon, total inorganic carbon, biomass, lipid fraction and methyl‐ester distribution of transesterified lipids. RESULTS: S. bacillaris 158/11 proved to be the best strain to produce biodiesel. Methyl‐ester distribution was characterized by a large fraction of methyl palmitate, methyl linolenate, methyl linoleate, and methyl oleate along with phytol. The process photosynthetic efficiency—fraction of available light stored as chemical energy ‐ was about 1.5%. Specific biomass productivity was ～60 mg_DM L^?1 day^?1 under the semi‐continuous conditions tested. Total lipid productivity was 14 mg L^?1 day^?1 at a dilution rate of 0.050 L day^?1. CONCLUSION: S. bacillaris 158/11 is a potential strain for massive microalgae cultures for biofuel production. Higher biomass/total‐lipid productivity could be obtained in sunlight. Copyright © 2011 Society of Chemical Industry     

Effects of supplementation of succinic acid on the production and molecular weight distribution of exopolysaccharides by Antrodia camphorata in batch cultures

The effects of organic acid supplementation on both yields and molecular weight distributions of exopolysaccharide (EPS) of Antrodia camphorata were investigated in shaker flasks and air‐lift bioreactors. In the shaker flask study, five out of six organic acid‐supplemented cultures showed negative effects on cell growth, the exception being pyruvic acid‐supplemented culture; lower number average molecular weights (Mn) of EPS were obtained in all the supplemented cultures. EPS production was enhanced by 31% due to the addition of succinic acid. Optimum product yield was obtained between 2.0 and 3.0 g dm^?3 succinic acid; however, the specific production of EPS increased monotonically as succinic acid concentration was increased from 0 to 5 g dm^?3. Enhancement of EPS yield by 28% and a higher Mn of EPS (around 310 kDa) due to the addition of succinic acid were also demonstrated in an air‐lift bioreactor. In addition, a novel fermentation process resistant to EPS degradation is proposed, based on the inhibition of β‐glucanase activity by the supplementation with succinic acid. Copyright © 2004 Society of Chemical Industry