Sulfated exopolysaccharide production by the halophilic cyanobacterium Aphanocapsa halophytia

Aphanocapsa halophytia MN-11 isolated from a hypersaline environment was found to produce large quantities of exopolysaccharide. We describe here production of exopolysaccharide and the characterization of its properties. The effects of medium composition, particularly NaCl concentration, were tested. Maximum exopolysaccharide production was obtained with nitrogen and phosphorus concentrations in the medium exceeding 100 and 40 mg · L^-1 respectively. In addition, when 30 g · L^-1 NaCl was added to the medium, exopolysaccharide could be recovered from the medium supernatant. Exopolysaccharide from this strain was made up of at least six mono-oses and did not contain uronic derivatives or osamines. Proteins represented about 10% of total weight and, interestingly, 12% (wt/wt) sulfated residues, which is unusual for photosynthetic prokaryotes.     

Increased production of extracellular polysaccharide by Porphyridium cruentum immobilized in foam sheets

Large‐size plate bioreactors were used to compare the production of extracellular polysaccharide by the red microalga Porphyridium cruentum when grown in suspension and in a foam sheet. A well‐defined illuminated area and unidirectional light propagation allowed us to generate information that is better quantified when expressed in terms of illuminated area. This is essential for meaningful comparison of data, especially considering that for a well‐designed and managed bioreactor, the culture production rates are believed to be light limited. At the same level of illumination, the culture immobilized in foam showed double the production rate of extracellular polysaccharide compared with the culture in suspension. The saturation level of biomass density per unit of illuminated area was eight times higher for the immobilized culture compared with the culture in suspension. Despite the increased biomass density for the immobilized culture, an increase in the light level above the optimum found for the culture in suspension reduced the extracellular polysaccharide production, suggesting that the photoinhibition light level was surpassed.     

Hydrogen production by an immobilized cyanobacterium,Lyngbya sp.

The mesophilic, alkaliphilic, filamentous, and nonheterocystous fresh water cyanobacterium, Lyngbya sp. strain no. 108, was immobilized on calcium alginate gel. The optimum immobilizing conditions for hydrogen evolution were: 4% (w/v) alginate; 0.05 M CaCl₂; and 0.11 mg dry microbial cells/ml gel. The pH, temperature, and light intensity were 9.0, 30°C, and 1,000 1x, respectively. The optimum conditions for growth of immobilized cells were pH 9.5, 27°C, and 1,000 1x. Immobilized cells produced 25% more hydrogen than did free cells. The cells were incubated in a reaction mixture for hydrogen evolution and recultivated for 5 days in nitrogen-limited medium. These incubation and reactivation steps were repeated 3 times, after which, the cell yield and the amount of hydrogen evolution were 2.6- and 3.4-fold higher, respectively.     

Sustained ammonia production by immobilized filaments of the nitrogen-fixing cyanobacterium Anabaena 27893

Summary Whole filaments of the N₂-fixing cyanobacterium Anabaena ATCC 27893 have been immobilized by entrapment in calcium alginate gel beads. In a continuous flow fluidized bed reactor sustained photosynthesis, N₂-fixation, and ammonia production have been achieved over a 130 hour period, the longest tested.     

Continuous antibiotic production by an immobilized cyanobacterium in a seaweed-type bioreactor

The filamentous cyanobacterium,Scytonema sp. TISTR 8208, which produces a cyclic peptide antibiotic, was cultivated for 20 d in a seaweed-type bioreactor containing anchored polyurethan foam strips. Cells immobilized onto the foam strips produced the antibiotic for only several days, and the secreted antibiotic disappeared very rapidly from the medium. Cells accumulated the antibiotic intracellularly in a growth-related manner, and secreted it in the stationary phase. Since the antibiotic has a stable physico-chemical nature, the cells seem to take it up and metabolize it. When continuous cultivation was attempted, stable production of the antibiotic was maintained in the bioreactor for 16 d at a dilution rate of 0.01 h^–1. Three times more antibiotic was produced in the continuous culture than in the batch culture by the 16th day.     

Partial characterization of an extracellular polysaccharide produced by the moderately halophilic bacterium Halomonas xianhensis SUR308

A moderately halophilic bacterium, Halomonas xianhensis SUR308 (Genbank Accession No. KJ933394) was isolated from a multi-pond solar saltern at Surala, Ganjam district, Odisha, India. The isolate produced a significant amount (7.87 g l^?1) of extracellular polysaccharides (EPS) when grown in malt extract–yeast extract medium supplemented with 2.5% NaCl, 0.5% casein hydrolysate and 3% glucose. The EPS was isolated and purified following the conventional method of precipitation and dialysis. Chromatographic analysis (paper, GC and GC-MS) of the hydrolyzed EPS confirmed its heteropolymeric nature and showed that it is composed mainly of glucose (45.74 mol%), galactose (33.67 mol %) and mannose (17.83 mol%). Fourier-transform infrared spectroscopy indicated the presence of methylene and carboxyl groups as characteristic functional groups. In addition, its proton nuclear magnetic resonance spectrum revealed functional groups specific for extracellular polysaccharides. X-ray diffraction analysis revealed the amorphous nature (CI_xrd, 0.56) of the EPS. It was thermostable up to 250°C and displayed pseudoplastic rheology and remarkable stability against pH and salts. These unique properties of the EPS produced by H. xianhensis indicate its potential to act as an agent for detoxification, emulsification and diverse biological activities.     

Two-stage system for hydrogen production by immobilized cyanobacterium Gloeocapsa alpicola CALU 743

Previous studies showed that cell suspensions of unicellular nondiazotrophic cyanobacterium G. alpicola grown under nitrate-limiting conditions intensively produces H2 via fermentation of endogenous glycogen with hydrogen yield more then 90% of theoretical maximum (3.8 mol H2 per mol glucose). H2 production is realized by a Hox hydrogenase on the stages of NAD(P)H generation. Exploiting this property, the two-stage cyclic system for sustained hydrogen production was developed using a photobioreactor (PhBR) with G. alpicola immobilized on glass fiber TR-0.3. Immobilization of the cells on the matrix occurred during growth directly in PhBR operated in continuous mode; the density of culture immobilized achieved 37 g Chl alpha cm(-2). The first stage of the cycle was the photosynthetic incubations of G. alpicola in the flow of the culture medium, which contained limiting concentrations of nitrate for efficient glycogen accumulation and activation of hydrogenase. The second stage was the fermentation of glycogen, with H2 production realized in darkness with continuous Ar sparging and without medium flow. Standardization of optimal parameters for both stages provided a stable cyclic regime of the system: photosynthesis (24 hours)-fermentation (24 hours). The total amount of H2 evolved in one cycle was 957.6 mL L(-1)(matrix), and the overage rate of H2 production during the cycle (48 hours) was about 20 mL h(-1) L(-1)(matrix). Ten consequent cycles was carried out in this regime with reproducible H2 production, although PhBR with the same sample of immobilized culture was operated over a period of more then three months.     

Chemical and rheological properties of an extracellular polysaccharide produced by the cyanobacterium Anabaena sp. ATCC 33047

The cyanobacterium (blue-green alga) Anabaena sp. ATCC 33047 produces an exopolysaccharide (EPS) during the stationary growth phase in batch culture. Chemical analysis of EPS revealed a heteropolysaccharidic nature, with xylose, glucose, galactose, and mannose the main neutral sugars found. The infrared (IR) spectrum of EPS showed absorption bands of carboxylate groups. The average molecular mass of the polymer was 1.35 MDa. Aqueous dispersions at EPS concentrations ranging from 0.2% to 0.6% (w/w) showed marked shear-thinning properties (power-law behavior). Linear dynamic viscoelastic properties showed that the elastic component was always higher than the viscous component. Viscous and viscoelastic properties demonstrated the absence of conformational changes within the concentration range studied. Stress-growth experiments revealed that 0.4% and 0.6% (w/w) EPS dispersions showed thixotropic properties. A detailed comparison of the linear dynamic viscoelasticity, transient flow, and decreasing shear rate flow curve properties was made for 0.4% (w/w) dispersions of xanthan gum (XG), Alkemir 110 (AG), and EPS. Viscoelastic spectra demonstrated that the EPS dispersion turned out to be more "fluidlike" than the AG and XG dispersions. The flow indexes indicated that the EPS dispersion was less shear-sensitive than that of XG, showing essentially the same viscosity, that is, >50 s(-1). The fact that viscosities of EPS and AG dispersions were not substantially different within the shear-rate range covered must be emphasized, in relation to EPS potential applications. The rheological behavior of EPS dispersions indicates the formation of an intermediate structure between a random-coil polysaccharide and a weak gel.     

Physiological approach to extracellular polysaccharide production by Lactobacillus rhamnosus strain C83

Extracellular polysaccharide production was studied by growing strain C83 of Lactobacillus rhamnosus in a chemically defined medium containing various carbon sources (glucose, fructose, mannose or maltose) at different concentrations. Mannose or a combination of glucose + fructose were by far the most efficient carbon sources. An optimization of growth medium composition led to an improvement in both growth and EPS production. When the strain was cultured at a lower temperature the EPS production increased. A temperature shift, at the end of the exponential growth phase, did not enhance the EPS production. The EPS synthesis by strain C83 was growth-related. The isolated slime had a sugar composition, as shown by three different methods, of glucose and galactose with a ratio of 1 : 1.     

Antibiotic production by the immobilized cyanobacterium,Scytonema sp. TISTR 8208, in a seaweed-type photobioreactor

A photobioreactor was constructed using either anchored polyurethane foam strips (1 × 1 × 40 cm, PU-strips) fixed on a stainless-steel ring to prevent flotation, or free-floating polyurethane foam blocks (1 × 1 × 1 cm, PU-blocks) as biomass supporting materials (BSM). The cyanobacterium,Scytonema sp. TISTR 8208, which produces an antibiotic, was immobilized onto PU-strips or -blocks. The free-floating PU-blocks could immobilize only about 70% of the total cells, while the anchored PU-strips could immobilize as much as 97%. PU-strips were chosen as the BSM and we named this type of reactor, seaweed-type bioreactor (STB). Optimal physical conditions for antibiotic production were determined in the STB. Inoculum density was 0.4 g l^–1 and cells were sparged with air containing 5% CO₂ circulated at the gas flow rate of 250 ml min^–1 and illuminated at a light intensity of 200 mol photon m^–2 s^–1. The production of antibiotic could be increased 3-fold.Author for correspondence     

Influence of nutrient ratios on the in vitro extracellular polysaccharide production by marine diatoms from the Adriatic Sea

Three different species of marine diatoms, Nitzschia closterium (Ehr) Smith, Chaetoceros sp. (Ehr) and Skeletonema costatum (Grev) Cleve, were isolated from the Adriatic sea and studied in vitro for the production of extracellular carbohydrates. Variations of the nitrogen (N)/phosphorus (P)/silicon (Si) ratios in the growth medium affect the accumulation and release of carbohydrates. In the N.closterium cultures at high N/P ratio, the rate of extracellular polysaccharide release was higher both in rapidly growing cells (2.14 g per 10⁶ cells day^-1 and in stationary phase (1.0 g per 10⁶ cells day^-1) compared to S.costatum and Chaetoceros sp. Instead, at low N/P ratios, S.costatum and Chaetoceros sp. produced large amounts of extracellular polysaccharides during the logarithmic phase, compared to N.closterium, with values of 10 g per 10⁶ cells day^-1 for S.costatum and 2.8 g per 10⁶ cells day^-1 for Chaetoceros sp., respectively; in particular, only S.costatum was able to produce extracellular carbohydrates (1.2 g per 10⁶ cells day^-1) during the stationary phase of growth. Under Si limitation, any of the three diatom species produce extracellular polysaccharides both in the logarithmic and stationary phase of growth. The potential ecological significance of these findings is discussed.      

Combined effect of temperature and light intensity on growth and extracellular polymeric substance production by the cyanobacterium Arthrospira platensis

The effects of light intensity and temperature on Arthrospira platensis growth and production of extracellular polymeric substances (EPS) in batch culture were evaluated using a three-level, full-factorial design and response surface methodology. Three levels were tested for each parameter (temperature: 30, 35, 40°C; light intensity: 50, 115, 180 μmol photons m⁻² s⁻¹). Both growth and EPS production are influenced mainly by the temperature factor but the interaction term temperature*light intensity also had a significant effect. In addition, conditions optimising EPS production are different from those optimising growth. The highest growth rate (0.414 ± 0.003 day⁻¹) was found at the lowest temperature (30°C) and highest light intensity (180 μmol photons m⁻² s⁻¹) tested, no optima were detectable within the given test range. Obviously, optima for growth must be at a temperature lower than 30°C and a light intensity higher than 180 μmol photons m⁻² s⁻¹. For EPS production, light intensity had a positive linear effect (optimum obviously higher than 180 μmol photons m⁻² s⁻¹), but for the temperature parameter a maximum effect was detectable at 35°C.     

Effect of aeration rates on production of extracellular polysaccharide, EPS-R, by marine bacteriumHahella chejuensis

The production of an extracellular polysaccharide, EPS-R, from the marine bacteriumHahella chejuensis was investigated at various aeration rates in a batch culture. Higher aeration rate resulted in enhanced EPS production and increased the viscosity of the culture broth. At an aeration rate of 1.5 vvm, EPS-R (12.2 g/L) was obtained with a yield (Y _P/S) of 0.6 from the STN medium after 72h of cultivation. TheH. chejuensis cells changed their rod morphology to a short-rod form in the stationary growth phase.     

Inhibitory metabolites production by the cyanobacterium Fischerella muscicola

Broad-spectrum inhibitory metabolites were produced by a benthic cyanobacterium Fischerella muscicola (UTEX 1829) in batch culture. These metabolites inhibited the growth of eukaryotic algae, cyanobacteria and eubacteria. The effect of culture age on the production and leakage of these inhibitory metabolites from the cyanobacterium was studied. Confirmation of the presence of an allelochemical, possibly fischerellin was achieved using high performance liquid chromatography (HPLC). The cyanobacterium produced inhibitory metabolites intracellularly at all stages of its growth cycle.     

Effects of agitator configuration and rotational speed on the production of extracellular polysaccharide by Xanthomonas cucurbitae PCSIR B-52

A strain of Xanthomonas cucurbitae PCSIR B-52, efficiently produced extracellular polysaccharide using partially deproteinized low-acid cheese whey without hydrolysis. The effects of the agitator configuration and rotational speed on the viscosity of the fermented broth and the productivity of extracellular polysaccharide based on bacterial growth were evaluated in a batch process. Agitation was performed by a six-bladed disc turbine impeller and by a similar agitator, equipped with six vertically attached stabilizing fins. Comparatively, the magnitude of the decrease in the DO tension resulting from increased viscosity of the broth was less with the stabilizing-fin agitator due to increased system damping. A drastic increase in the mechanical agitation speed after 30-h fermentation, however, increased the broth viscosity and the accumulation of polysaccharide. Moreover, the volume of the macromixing region decreased with increasing rotational speed of agitator.     

Enhanced production of the polysaccharide arabinogalactan using immobilized cultures of Tinospora cordifolia by elicitation and in situ adsorption

Immobilized callus cultures of Tinospora cordifolia (Willd) Miers ex Hooks and Thoms were investigated to find out the combined effect of elicitation, cell permeabilization with chitosan and in situ product recovery by polymeric neutral resin-like Diaion HP 20. In this study, callus cultures of T. cordifolia were immobilized using sodium alginate and calcium chloride and the beads were cultured in Murashige and Skoog's basal medium along with benzyl adenine (BA), 2,4-dichlorophenoxy acetic acid (2,4-D) and 3% sucrose. The immobilized cultures, when subjected to elicitation and cell permeabilization with chitosan and in situ removal of the secondary metabolites by addition of resin, showed a 10-fold increase in production of arabinogalactan (0.490% dry weight) as compared to respective controls devoid of resin and chitosan. This indicates that in situ adsorption may have reduced the feedback inhibition caused by accumulation of secondary metabolites in the media, while the dual effect of elicitation and cell permeabilization by chitosan may have released the intracellular (secreted) berberine and the polysaccharide arabinogalactan, respectively.     

Utilization of unhydrolyzed cheese whey for the production of extracellular polysaccharide by Xanthomonas cucurbitae PCSIR B-52

A strain of Xanthomonas cucurbitae PCSIR B-52 produced extracellular polysaccharide using partially deproteinized cheese whey without hydrolysis. A synthetic lactose-salt medium was also utilized to determine the optiomum level of lactose desirable for successfull fermentation. The amount of extracellular polysaccharide was maximised at 7.8 gl⁻¹ in the presence of 40 gl⁻¹ lactose. The bacterium efficiently consumed cheese whey, particularly in the presence of corn steep liquor and penicillin waste mycelium in shaken flasks. The polysaccharide, bacterial cell mass and viscosity gradients were improved as a result of efficient oxygen transfer in a mechanically agitated fermentor. A depletion in dissolved oxygen tension resulted during the exponential growth phase. The fermentation pattern of extracellular polysaccharide was also studied by repeated batch process.