Agitated Fermentation Research Articles

Force-Induced Alignment of Nanofibrillated Bacterial Cellulose for the Enhancement of Cellulose Composite Macrofibers.

Bacterial cellulose, as an important renewable bioresource, exhibits excellent mechanical properties along with intrinsic biodegradability. It is expected to replace non-degradable plastics and reduce severe environmental pollution. In this study, using dry jet-wet spinning and stretching methods, we fabricate cellulose composite macrofibers using nanofibrillated bacterial cellulose (BCNFs) which were obtained by agitated fermentation. Ionic liquid (IL) was used as a solvent to perform wet spinning. In this process, force-induced alignment of BCNFs was applied to enhance the mechanical properties of the macrofibers. The results of scanning electron microscopy revealed the well-aligned structure of BCNF along the fiber axis. The fiber prepared with an extrusion rate of 30 m min-1 and a stretching ratio of 46% exhibited a strength of 174 MPa and a Young's modulus of 13.7 GPa. In addition, we investigated the co-spinning of carboxymethyl cellulose-containing BCNF with chitosan using IL as a "container", which indicated the compatibility of BCNFs with other polysaccharides. Recycling of the ionic liquid was also verified to validate the sustainability of our strategy. This study provides a scalable method to fabricate bacterial cellulose composite fibers, which can be applied in the textile or biomaterial industries with further functionalization.

In situ development of bacterial cellulose/hydroxyapatite nanocomposite membrane based on two different fermentation strategies: characterization and cytotoxicity evaluation

Bacterial cellulose (BC) has garnered attention among biomaterial scientists for its unique physicochemical features and biocompatibility; however, the lack of bioactivity has limited its biomedical applications. Thus, this study describes the in situ preparation of BC/hydroxyapatite (HA) nanocomposite membranes using static and agitated fermentation to enhance the bioactivity of BC. The incorporation of HA increased BC production from 2.31 g/L without HA to 4.10 and 3.26 g/L under static and agitated fermentation, respectively, although the SEM observation indicates the formation of a fibrous structure in BC mesh under both fermentations. It was also observed that the content of HA nanoparticles in BC obtained from agitated fermentation was higher than that obtained from static fermentation. In addition, the average fiber diameter was increased from 56 ± 17 nm for agitated nanocomposites (BC/HA-A) to 145 ± 48 nm for static BC/HA nanocomposites (BC/HA-S) and 122 ± 26 nm for BC. In conclusion, the in situ formation of BC/HA nanocomposite under agitated fermentation appears more convenient in term of BC yield, HA content and distribution, and cytotoxicity against fibroblast cells (BJ1). This strategy will inspire new ways to prepare BC-based materials for medical applications.

Optimization for the production of a polyketone 3S,4S-DMD from Panus lecomtei (Agaricomycetes) by submerged fermentation

ABSTRACT 3,4-Dihydroxy-2,2-dimethyl-chroman derivatives have diverse physiological properties. A polyketone (3S,4S)-3,4-Dihydroxy-6-methoxy-2,2-dimethylchromom (3S,4S-DMD) with antibacterial activity was isolated from the solid culture of rare edible fungus Panus lecomtei. However, the yield of 3S,4S-DMD in solid culture of P. lecomtei is very low and the production period are too long. In this work, efficient accumulation of 3S,4S-DMD in P. lecomtei by submerged fermentation is studied. The key fermentation factors of P. lecomtei for 3S,4S-DMD production were optimised by single-factor experiment successively, and then a Box-Behnken design (BBD) experiment was carried out to further enhance 3S,4S-DMD production. A maximum 3S,4S-DMD yield of 196.3 mg/L was obtained at 25.78 g/L glucose, 1.67 g/L MgSO4 · 7H2O, 40°C and 197 r/min, respectively, which increased by 1.3-fold in comparison with that in the non-optimised fermentation conditions. Furthermore, an enhanced yield of 3S,4S-DMD (261.6 mg/L) was obtained in 5-L agitated fermenter. The 3S,4S-DMD productivity in flask and fermenter reached to 7.26 and 8.07 mg/g per day, respectively, which considerably increased by over 121-fold in comparison with that in the solid fermentation (0.06 mg/g per day). This study presents a potential method for the production of 3S,4S-DMD by submerged fermentation.

Bacterial Cellulose: Production, Characterization, and Application as Antimicrobial Agent.

Bacterial cellulose (BC) is recognized as a multifaceted, versatile biomaterial with abundant applications. Groups of microorganisms such as bacteria are accountable for BC synthesis through static or agitated fermentation processes in the presence of competent media. In comparison to static cultivation, agitated cultivation provides the maximum yield of the BC. A pure cellulose BC can positively interact with hydrophilic or hydrophobic biopolymers while being used in the biomedical domain. From the last two decades, the reinforcement of biopolymer-based biocomposites and its applicability with BC have increased in the research field. The harmony of hydrophobic biopolymers can be reduced due to the high moisture content of BC in comparison to hydrophilic biopolymers. Mechanical properties are the important parameters not only in producing green composite but also in dealing with tissue engineering, medical implants, and biofilm. The wide requisition of BC in medical as well as industrial fields has warranted the scaling up of the production of BC with added economy. This review provides a detailed overview of the production and properties of BC and several parameters affecting the production of BC and its biocomposites, elucidating their antimicrobial and antibiofilm efficacy with an insight to highlight their therapeutic potential.

Biological production of citric acid in submerged culture of Aspergillus niger using cassava pulp wastes

Utilization of cassava pulp wastes for citric acid production was investigated using Aspergillus niger in a submerged culture. A series of experiments were designed on various fermentation parameters to establish the optimal conditions for citric acid production from cassava pulp. This study revealed that production parameters such as cassava pulp concentration, initial pH, incubation temperature, agitation, and nitrogen source and fermentation period had effect on the amount of citric acid produced from cassava pulp. Citric acid concentration increased as the concentration of cassava pulp increases up to 20% with maximum citric acid concentration of 14.9 ± 0.413 g/l after 120 hours of fermentation. pH 5.5 was the optimum with maximum citric acid concentration of 16.8 ± 0.23 g/l after 120 hours of fermentation. Incubation temperature at 300 C was the optimum, with citric acid concentration of 19.15 ± 0.43 g/l. Increased in agitation speed from 100 to 225 rpm gave the maximum citric acid concentration of 25.2 ± 0.32 g/l after 120 hours of fermentation. Soybean meal supplementation was the best maximum citric acid concentration of 28.2 ± 0.51 g/l. Evaluating the effect of different concentration of soybean meal shows that 0.3 % supplementation was the optimum with maximum concentration of 31.2 ±0.35g/l from cassava pulp after 120 hours of fermentation. The result suggested that citric acid can be accumulated using cassava pulp by Aspergillus niger in submerged culture during fermentation. Cassava pulp if well harnessed can be used for large scale citric acid production.

Co-culture fermentation on the production of bacterial cellulose nanocomposite produced by Komagataeibacter hansenii

Bacterial cellulose (BC11Uncommon abbreviation used: BC – Bacterial Cellulose) is a biomaterial produced by various strains of microorganisms. BC has improved strength and unique structural properties as compared to plant cellulose, thus has many usages in the food and pharmaceutical industries. In our previous study, a novel co-culture agitated fermentation of Komagataeibacter hansenii, a BC producer, with Aureobasidium pullulans, a producer of pullulan polysaccharide, had been demonstrated where the BC produced exhibited improved mechanical properties. Therefore, this study is undertaken to analyze BC production under different medium composition using response surface methodology (RSM) in shake-flasks and benchtop bioreactors. A verified local high point provided 22.4% higher BC production and 4.5- to 6- folds higher elastic moduli in shake-flasks and bioreactors compared to the baseline media. Overall, the study had revealed the potential of the co-culturing method to enhance BC production while maintaining the desired mechanical properties of BC produced in shake-flasks and larger scale bioreactors.

Physical structure variations of bacterial cellulose produced by different Komagataeibacter xylinus strains and carbon sources in static and agitated conditions

The morphology, crystallinity, crystallite size, and production yield of bacterial cellulose (BC) produced with six different carbon sources (glucose, fructose, lactose, maltitol, sucralose, and xylitol) in static and agitated fermentation conditions by five strains of Komagataeibacter xylinus (KX, TISTR 086, 428, 975, and 1011) which are locally available, were studied. In static condition, the BC pellicle was formed as a membrane sheet at the medium surface exposed to air, while in agitated condition, the spherical or asterisk-like shape BC particles were obtained in the culture media. The XRD and FT-IR analyses found no significant differences in the cellulose crystallinity, crystallite size or polymorphic distribution within the carbon sources. However, changes in crystallinity and mass fraction of the Iα allomorph were observed in BC produced from the different bacterial strains and incubation conditions. The BC samples produced by the same bacterial strain with the varying culture conditions showed the alteration of physical properties more clearly than the BC samples prepared by the opposite situation. These findings suggested that the strains of bacteria and fermentation conditions strongly affected on the physical structures of BC.

Effects of physical and chemical structures of bacterial cellulose on its enhancement to paper physical properties

Bacterial cellulose (BC) was used to reinforce paper sheets made from non-woody fibers, e.g. sugarcane bagasse. BC produced from static and agitated fermentation methods was mixed with bleached sugarcane bagasse pulp (BSBP) to produce composite paper sheets. BC from static culture had a higher degree of polymerization, crystallinity, and crystallite width. Adding BC at a low ratio (<1% of the dry weight of the sheets) can effectively improve the mechanical properties of BSBP paper sheets. Adding static BC improved the tensile index of BC-BSBP composite sheets up to 25%. Furthermore, BC was also chemically modified or cationized by reacting with (3-chloro-2-hydroxypropyl)trimethylammonium chloride. The results demonstrated that the cationization reaction had to be maintained at a low level (DS < 0.005) for effective improvement in mechanical properties of the BC-BSBP composite sheets. The improvements in tensile index were up to 10 and 32%, compared to the unmodified BC-reinforced sheets and sheets without BC, respectively. The low addition and low cationization levels suggest an economical prospect for static BC being used in the paper-based material industries to improve the qualities of non-woody fiber products.

Optimization of hydrolysis conditions for minimizing ammonia accumulation in two-stage biogas production process using kitchen waste for sustainable process development

Accumulation of ammonia produced by deamination of proteins during anaerobic digestion of kitchen waste for biogas production is a critical issue since ammonia is a potential inhibitor of biomethanation process. This work deals with optimization of hydrolysis for minimum ammonia accumulation by controlling the physico-chemical conditions viz. temperature, pH and aeration. The hydrolysis experiments were carried out using kitchen waste slurry (5% w/v) in an agitated fermenter of 1.5L working volume. The study was conducted based on statistically designed experimental sets, to find out the optimum conditions required for maximizing ammonia removal during kitchen waste digestion. Preliminary screening experiments were carried out based on a full factorial design to get key information regarding the system performance and to further, extend into the Box-Behnken design for process optimization. The developed model had R2 of 0.9677 and 0.9406 for % total and free ammoniacal nitrogen removal respectively. The results suggested minimized ammoniacal nitrogen accumulation during hydrolysis (net removal up to 75%) with 3589±469mg/L soluble COD and 1419±136mg/L TVFA concentration at pH 7.2 to 7.5, temperature 43–48°C, Aeration 0.19–0.22 vvm. This leads to reduction in ammonia accumulation up to 66% operated under optimized hydrolysis conditions compared to other operating condition in methanogenic phase. Operating the biogas digesters under these optimum conditions may help to overcome the problem of ammoniacal nitrogen accumulation during anaerobic digestion of kitchen waste for biogas production.

EFFECT OF FERMENTATION PARAMETERS ON BIO-ALCOHOLS PRODUCTION FROM GLYCEROL USING IMMOBILIZED Clostridium pasteurianum: AN OPTIMIZATION STUDY

This article addresses the issue of effect of fermentation parameters for conversion of glycerol (in both pure and crude form) into three value-added products, namely, ethanol, butanol, and 1,3-propanediol (1,3-PDO), by immobilized Clostridium pasteurianum and thereby addresses the statistical optimization of this process. The analysis of effect of different process parameters such as agitation rate, fermentation temperature, medium pH, and initial glycerol concentration indicated that medium pH was the most critical factor for total alcohols production in case of pure glycerol as fermentation substrate. On the other hand, initial glycerol concentration was the most significant factor for fermentation with crude glycerol. An interesting observation was that the optimized set of fermentation parameters was found to be independent of the type of glycerol (either pure or crude) used. At optimum conditions of agitation rate (200 rpm), initial glycerol concentration (25 g/L), fermentation temperature (30°C), and medium pH (7.0), the total alcohols production was almost equal in anaerobic shake flasks and 2-L bioreactor. This essentially means that at optimum process parameters, the scale of operation does not affect the output of the process. The immobilized cells could be reused for multiple cycles for both pure and crude glycerol fermentation.

Two-Staged Temperature and Agitation Strategy for the Production of Transglutaminase from a Streptomyces sp. Isolated from Brazilian Soils

Transglutaminase catalyzes the cross-linking reaction between a glutamine residue and a free amine residue of proteins leading to the formation of protein aggregates. In this research, the effects of temperature, agitation, and aeration on the production of transglutaminase in a bench reactor by a newly isolated Streptomyces sp. from Brazilian soils were investigated using a factorial experimental design. The parameters evaluated influenced the enzyme production, and the data showed that the best conditions to enhance cell growth were different from those leading to enhanced transglutaminase production. Thus, a temperature and agitation shift strategy was adopted to increase transglutaminase productivity. The temperature and agitation were first set at 34 °C and 350 rpm, respectively, and after 24 h decreasing to 26 °C and 150 rpm until the end of fermentation. The transglutaminase activity obtained was 2.18 U/mL after 42 h of fermentation, which was twice than that obtained using a constant temperature and agitation fermentation strategy.

Improving the Fermentation Production of the Individual Key Triterpene Ganoderic Acid Me by the Medicinal Fungus Ganoderma lucidum in Submerged Culture

Enhanced ganoderic acid Me (GA-Me, an important anti-tumor triterpene) yield was attained with the medicinal fungus Ganoderma lucidum using response surface methodology (RSM). Interactions were studied with three variables, viz. glucose, peptone and culture time using a Central Composite Design (CCD). The CCD contains a total of 20 experiments with the first 14 experiments organized in a fractional factorial design, with the experimental trails from 15 to 20 involving the replications of the central points. A polynomial model, describing the relationships between the yield of GA-Me and the three factors in a second-order equation, was developed. The model predicted the maximum GA-Me yield of 11.9 mg·L−1 for glucose, peptone, culture time values of 44.4 g·L−1, 5.0 g·L−1, 437.1 h, respectively, and a maximum GA-Me yield of 12.4 mg·L−1 was obtained in the validation experiment, which represented a 129.6% increase in titre compared to that of the non-optimized conditions. In addition, 11.4 mg·L−1 of GA-Me was obtained in a 30-L agitated fermenter under the optimized conditions, suggesting the submerged culture conditions optimized in the present study were also suitable for GA-Me production on a large scale.

Enhancement of ribitol production during fermentation of Trichosporonoides oedocephalis ATCC 16958 by optimizing the medium and altering agitation strategies

To maximize the productivity of ribitol, which is an important starting material for the production of one expensive rare sugar, L-ribose, the effects of culture medium and agitation speed on cell growth as well as on the productivity of ribitol were thoroughly investigated in a 7 L fermentor. The maximum volumetric productivity, 0.322 g/L/h of ribitol, were obtained at an initial glucose concentration of 200 g/L in a batch culture. Based on the optimum glucose concentration, the ribitol yield conversed from glucose was up to 0.193 g/g when 1% yeast extract was used as a nitrogen source. When the agitation speed was maintained at 200 rpm, the ribitol concentration of 38.60 g/L was collected after 120 h of cultivation time. Additionally, the scheme of two-phase agitation and glucose infusion was employed. To begin, in the first 24 h of fermentation, a high agitation rate at 350 rpm and the initial glucose concentration of 50 g/L were applied, and the biomass concentration of 25.50 g/L was achieved at 36 h of incubation; whereas this value was observed until 60 h in the former batch fermentation methods. Then, in the second phase, with the agitation speed reduced to 150 rpm and the infusion amount of glucose controlled at 150 g/L, the yield of ribitol reached to 65.00 g/L in two-phase agitation fermentation and was 1.68 fold of that obtained in one-stage batch fermentation. To our knowledge, this study first demonstrates its significant effectiveness in improving ribitol production with the application of Trichosporonoides oedocephalis ATCC 16958.

Biosynthesis of spherical Fe3O4/bacterial cellulose nanocomposites as adsorbents for heavy metal ions

In this paper, spherical Fe3O4/bacterial cellulose (BC) nanocomposites as adsorbents for heavy metal ions were biosynthesized from Gluconacetobacter xylinum by agitation fermentation. A pH controlling embedding method as a new approach was applied to biosynthesize spherical Fe3O4/BC nanocomposites. Scanning electron microscopy (SEM) images indicated that the Fe3O4 nanoparticles were enwrapped homogeneously in the spherical BC. The spherical Fe3O4/BC nanocomposites with 33wt% ferrous loading had 41emu/g of the saturated magnetization (σs) and 27Oe of the related coercivity. The adsorption and elution capacities of the spheres for Pb2+, Mn2+, and Cr3+ were evaluated. The results indicated that the spherical Fe3O4/BC nanocomposites had high adsorption capacities and were recyclable after the elution of heavy metal ions. Compared with conventional preparation procedure for cellulose spheres, spherical Fe3O4/BC nanocomposites can be readily prepared without sophisticated steps and have high adsorption and elution capacities.

Enhanced production of bacterial cellulose by using a biofilm reactor and its material property analysis

Bacterial cellulose has been used in the food industry for applications such as low-calorie desserts, salads, and fabricated foods. It has also been used in the paper manufacturing industry to enhance paper strength, the electronics industry in acoustic diaphragms for audio speakers, the pharmaceutical industry as filtration membranes, and in the medical field as wound dressing and artificial skin material. In this study, different types of plastic composite support (PCS) were implemented separately within a fermentation medium in order to enhance bacterial cellulose (BC) production by Acetobacter xylinum. The optimal composition of nutritious compounds in PCS was chosen based on the amount of BC produced. The selected PCS was implemented within a bioreactor to examine the effects on BC production in a batch fermentation. The produced BC was analyzed using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA). Among thirteen types of PCS, the type SFYR+ was selected as solid support for BC production by A. xylinum in a batch biofilm reactor due to its high nitrogen content, moderate nitrogen leaching rate, and sufficient biomass attached on PCS. The PCS biofilm reactor yielded BC production (7.05 g/L) that was 2.5-fold greater than the control (2.82 g/L). The XRD results indicated that the PCS-grown BC exhibited higher crystallinity (93%) and similar crystal size (5.2 nm) to the control. FESEM results showed the attachment of A. xylinum on PCS, producing an interweaving BC product. TGA results demonstrated that PCS-grown BC had about 95% water retention ability, which was lower than BC produced within suspended-cell reactor. PCS-grown BC also exhibited higher Tmax compared to the control. Finally, DMA results showed that BC from the PCS biofilm reactor increased its mechanical property values, i.e., stress at break and Young's modulus when compared to the control BC. The results clearly demonstrated that implementation of PCS within agitated fermentation enhanced BC production and improved its mechanical properties and thermal stability.

Fed-batch fermentation for hyperproduction of polysaccharide and ergosterol by medicinal mushroom Agaricus brasiliensis

A process for simultaneous efficient production of bioactive polysaccharide and ergosterol by fed-batch fermentation of medicinal mushroom Agaricus brasiliensis was developed. Effects of carbon source and initial sugar concentration on the production of extracellular polysaccharide (EPS) and ergosterol were studied at first. Sucrose was suitable for EPS production although the cells could not grow well. Glucose was beneficial for the cell growth and production of ergosterol. When the initial glucose concentration exceeded 40 g/l, the ergosterol accumulation was decreased slightly. A repeated fed-batch fermentation strategy with glucose as carbon source, which feeding of glucose was commenced to 15 g/l from 72 to 120 h at 24 h intervals when the total glucose concentration of the broth was below 15 g/l in 7 l stirred bioreactor, was developed successfully to increase simultaneously EPS and ergosterol production. The maximum EPS and ergosterol production were 1.67 ± 0.08 g/l and 2.50 ± 0.04 mg/100 mg DW on 144 h, respectively, which were 26.9% and 17.2% higher than those by batch fermentation in the same cultivation conditions. It was the first reported to product simultaneously EPS and ergosterol in agitated fermentation of A. brasiliensis.

Inverted hollow spinning cone as a device for controlling foam and hold-up in pilot scale gassed agitated fermentation vessels

The effectiveness of an inverted hollow spinning cone (IHSC) for controlling foam and liquid hold-up is demonstrated in pilot scale equipment for a currently commercially exploited recombinant Bacillus fermentation with the characteristically challenging foaming and hold-up issues of this genus. The cone rotates on the existing agitator shaft at the normal production operating level. A series of 9 trials were conducted in 550-l pilot scale fermenters: 2 fermentations without foam control agent (FCA) addition, 4 controls with FCA addition on demand, and three with the cone as the sole method of level control. Batches running without FCA addition or the use of an IHSC lost 52 ± 15 kg of broth through the exhaust system. Batches with FCA addition on demand or the IHSC ended with a statistically indistinguishable filling of 308 ± 6 kg and 319 ± 13 kg , respectively. Process performance in terms of enzyme titre was not affected. Such encouraging results indicate great potential savings in both fermentation and recovery costs since FCA addition can be completely avoided. A full-scale production evaluation is justified.

Fed-batch fermentation of Ganoderma lucidum for hyperproduction of polysaccharide and ganoderic acid

A process for simultaneous efficient production of bioactive ganoderic acid (GA) and Ganoderma polysaccharide by fed-batch fermentation of Ganoderma lucidum was developed. Effects of carbon source and initial sugar concentration on the production of GA and polysaccharide were studied at first. Sucrose as a carbon source was suitable for the extracellular polysaccharide (EPS) production although the cells could not grow well. Lactose was beneficial for the cell growth and production of GA and intracellular polysaccharide (IPS). When the initial lactose concentration exceeded 35 g/l, the GA accumulation was decreased. The GA production was remarkably improved by pulse feeding of lactose, when its residual concentration was between 10 and 5 g/l. The fed-batch fermentation process in shake flasks could be successfully reproduced in stirred bioreactors (STR) with dissolved oxygen (DO) controlled between 20 and 35% of air saturation during fermentation. The maximum cell density reached 21.89±0.35 and 20.95±0.01 g DW/l in STR and flasks, respectively. The production of EPS reached 0.87±0.05 (STR) and 0.75±0.05 g/l (flask), and the total production of IPS reached 2.49±0.07 (STR) and 2.40±0.05 g/l (flask). The total production of GA reached 367.1±17.4 and 297.9±13.7 mg/l for STR and flask, respectively, and their corresponding productivity was 29.6±0.5 and 14.3±0.1 mg/l per day. Not only the cell density but also the content, production and productivity of GA and IPS obtained in this work are the highest reported in agitated fermentation of G. lucidum.

Solid-substrate fermentation of soybeans with Rhizopus spp.: Comparison of discontinuous rotation with stationary bed fermentation

Tempe is a soybean food obtained by stationary solid-substrate fermentation using moulds (mainly Rhizopus spp.) as starter organism. Traditionally, tempe is fermented in static layer trays or wrapped packages. Due to heat and mass transfer limitations, gradients of temperature and gas atmosphere will result. Agitated fermentation can help to level heat and mass gradients, yielding better homogeneity. This type of process will not result in traditional tempe, but in individually fermented soybeans that could be processed into food ingredients. This report deals with the comparative effect of stationary versus agitated solid-substrate fermentation of soybeans on some chemical indices of substrate modification. For agitated solid-substrate fermentation, a 450- l size rotary-drum bioreactor was designed and constructed. Of two Rhizopus spp. tested, R. microsporus tolerated agitation quite well, as judged by changes of pH, amino nitrogen, ammonia, and soluble dry matter. The other species, R. oligosporus was strongly affected by agitation. This resulted in less pH increase (difference approx. 1.5 units), lower amino nitrogen levels (30–50% of levels in static fermentation), and lower levels of water-soluble non-lipid dry matter (30–50% of levels in static fermentation) with R. oligosporus agitated fermentation of soybeans controlled at 30 and 37°C, compared to static fermentation at temperatures ranging between 25–35 and 30–40°C, respectively.

Enhancing xanthan fermentations by different modes of glucose feeding

This paper is the fourth in a series aimed at improving the understanding and operation of conventional agitated fermenters for the production of the commercially important gum, Xanthan. In the first, reproducible fermentations were established and this protocol was used in studies of different agitator types and of bulk mixing and dissolved oxygen concentration in the next two. Here, building on the previous work, the influence of different glucose feeding strategies on Xanthan production in a 20-L agitated fermenter under equivalent conditions of agitation and dissolved oxygen is reported. The biological performances in three types of fed-batch cultures (a two-step glucose addition, multiple glucose-pulse feeding and continuous feeding of glucose) are compared to two batch fermentations with different initial glucose concentrations. The work confirmed that improved performance cannot be achieved by increasing the initial glucose concentration above 50 g/L nor by a single 10 g/L pulse addition (initial glucose concentration of 40 g/L) while significant nitrogen is still present. On the other hand, the simple pulse and continuous feeding strategies, after nitrogen has been essentially exhausted and under conditions of nonlimiting dissolved oxygen and similar bulk mixing, can result in a greatly enhanced performance compared to batch fermentations. Using the final Xanthan gum concentration, the yield on glucose and the overall productivity as performance indices, values of 62 g/L, 0.82 g of Xanthan/g of glucose, and 0.72 g/(L.h), respectively, were obtained compared to literature values for conventional stirred bioreactors of 15-30 g/L, 0.27-0.86 g of Xanthan/g of glucose, and 0. 12-0.43 g/(L.h).