Production of red pigment by submerged culture of Paecilomyces sinclairii

AIMS: From a survey of submerged culture of edible mushrooms, a high pigment-producing fungus Paecilomyces sinclairii was selected and its optimal culture conditions investigated. METHODS AND RESULTS: The optimal culture conditions for pigment production were as follows: inoculum age, 3 d; temperature, 25 degrees C; initial pH, 6.0; carbon source, 1.5% (w/v) soluble starch; nitrogen source, 1.5% (w/v) meat peptone. Although addition of 10 mmol l(-1) CaCl2 to the culture medium slightly increased pigment production, most of the bio-elements examined had no notable or detrimental effect on pigment production. CONCLUSIONS: Under the optimal conditions obtained in the flask culture tested, a ninefold increase in pigment production (4.4 g l(-1)) was achieved using a 5(-l) batch fermenter. Paecilomyces sinclairii secreted water-soluble red pigment into the culture medium. The pigment colour was strongly dependent on the pH of the solution: red at pH 3-4, violet at pH 5-9 and pink at pH 10-12. SIGNIFICANCE AND IMPACT OF THE STUDY: The high concentration of pigment (4.4 g l(-1)) produced by P. sinclairii demonstrates the possibility of commercial production of pigment by this strain, considering its relatively high production yield and light stability.     

Effect of aeration and agitation on the production of mycelial biomass and exopolysaccharides in an enthomopathogenic fungus Paecilomyces sinclairii

AIMS: The objective of the present study was to investigate the influence of aeration rate and agitation intensity on the production of mycelial biomass and exopolysaccharide (EPS) in Paecilomyces sinclairii. METHODS AND RESULTS: The P. sinclairii was cultivated under various aeration and agitation conditions in a 5 l stirred-tank bioreactor. The highest mycelial biomass (30.5 g l-1) and EPS production (11.5 g l-1) were obtained at a high aeration rate (3.5 v.v.m.) and at a high agitation speed (250 rev min-1). The apparent viscosities (6000-8000 cP) of fermentation broth increased rapidly towards the end of fermentations at high aeration and agitation conditions. CONCLUSIONS: The high level of dissolved oxygen achieved at a high aeration rate (3.5 v.v.m.) associated with higher hyphal density eventually resulted in enhanced EPS production. Agitation intensity was also proved to be a critical factor influencing on both the mycelial biomass and EPS production: high agitation speeds up to 250 rev min-1 were preferred to the yields of biomass and EPS production. SIGNIFICANCE AND IMPACT OF THE STUDY: The critical effects of aeration and agitation in the culture process of P. sinclairii were found, which is widely applicable to other kinds of basidiomycetes or ascomycetes in their submerged culture processes.     

Optimization of submerged culture requirements for the production of mycelial growth and exopolysaccharide by Cordyceps jiangxiensis JXPJ 0109

AIMS: The objective of the present study was to investigate the optimal culture requirements for mycelial growth and exopolysaccharide production by Cordyceps jiangxiensis JXPJ 0109 in submerged culture. METHODS AND RESULTS: The effects of medium ingredients (i.e. carbon and nitrogen sources, and growth factor) and other culture requirements (i.e. initial pH, temperature, etc.) on the production of mycelia and exopolysaccharide were observed using a one-factor-at-a-time method. More suitable culture requirements for mycelial growth and exopolysaccharide production were proved to be maltose, glycerol, tryptone, soya bean steep powder, yeast extract, medium capacity 200 ml in a 500-ml flask, agitation rate 180 rev min(-1), seed age 4-8 days, inoculum size 2.5-7.5% (v/v), etc. The optimal temperatures and initial pHs for mycelial growth and exopolysaccharide production were at 26 degrees C and pH 5 and at 28 degrees C and pH 7, respectively, and corresponding optimal culture age were observed to be 8 and 10 days respectively. According to the primary results of the one-factor-at-a-time experiments, the optimal medium for the mycelial growth and exopolysaccharide production were obtained using an orthogonal layout method to optimize further. Herein the effects of medium ingredients on the mycelial growth of C. jiangxiensis JXPJ 0109 were in the order of yeast extract > tryptone > maltose > CaCl2 > glycerol > MgSO4 > KH2PO4 and the optimal concentration of each composition was 15 g maltose (food-grade), 10 g glycerol, 10 g tryptone, 10 g yeast extract, 1 g KH2PO4, 0.2 g MgSO4, and 0.5 g CaCl2 in 1 l of distilled water, while the order of effects of those components on exopolysaccharide production was yeast extract > maltose > tryptone > glycerol > KH2PO4 > CaCl2 > MgSO4, corresponding to the optimal concentration of medium was as follows: 20 g maltose (food-grade), 8 g glycerol, 5 g tryptone, 10 g yeast extract, 1 g KH2PO4, and 0.5 g CaCl2 in 1 l of distilled water. CONCLUSIONS: Under the optimal culture requirements, the maximum exopolysaccharide production reached 3.5 g l(-1) after 10 days of fermentation, while the maximum production of mycelial growth achieved 14.5 g l(-1) after 8 days of fermentation. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first report on the submerged culture requirements for mycelial growth and exopolysaccharide in C. jiangxiensis, and this two-step optimization strategy in this study can be widely applied to other microbial fermentation processes.     

A comparative study on the production of exopolysaccharides between two entomopathogenic fungi Cordyceps militaris and Cordyceps sinensis in submerged mycelial cultures

AIMS: The present study comparatively investigates the optimal culture conditions for the production of exopolysaccharides (EPS) and cordycepin during submerged mycelial culture of two entomopathogenic fungi Cordyceps militaris and Cordyceps sinensis. METHODS AND RESULTS: Fermentations were performed in flasks and in 5-l stirred-tank fermenters. In the case of C. militaris, the highest mycelial biomass (22.9 g l(-1)) and EPS production (5 g l(-1)) were achieved in a medium of 40 g l(-1) sucrose, 5 g l(-1) corn steep powder at 30 degrees C, and an initial pH 8.0. The optimum culture conditions for C. sinensis was shown to be (in g l(-1)) 20 sucrose, 25 corn steep powder, 0.78 CaCl2, 1.73 MgSO4.7H2O at 20 degrees C, and an initial pH 4.0, where the maximum mycelial biomass and EPS were 20.9 and 4.1 g l(-1) respectively. Cordycepin, another bioactive metabolite, was excreted at low levels during the early fermentation period (maximum 38.8 mg l(-1) in C. militaris; 18.2 mg l(-1) in C. sinensis). CONCLUSIONS: The two fungi showed different nutritional and environmental requirements in their submerged cultures. Overall, the concentrations of mycelial biomass, EPS and cordycepin achieved in submerged culture of C. militaris were higher than those of C. sinensis. SIGNIFICANCE AND IMPACT OF THE STUDY: C. militaris and C. sinensis are representative insect-born fungi which have been longstanding and widely used as traditional medicines in eastern Asia. Comparative studies between two fungi are currently not available and this is the first report on the optimum medium composition for submerged culture of C. sinensis.     

Optimization of submerged culture condition for the production of mycelial biomass and exopolysaccharides by Agrocybe cylindracea

The optimization of submerged culture conditions and nutritional requirements was studied for the production of exopolysaccharide (EPS) from Agrocybe cylindracea ASI-9002 using the statistically based experimental design in a shake flask culture. Both maximum mycelial biomass and EPS were observed at 25 degrees C. The optimal initial pH for the production of mycelial biomass and EPS were found to be pH 4.0 and pH 6.0, respectively. Subsequently, optimum concentration of each medium component was determined using the orthogonal matrix method. The optimal combination of the media constituents for mycelial growth was as follows: maltose 80 g/l, Martone A-1 6 g/l, MgSO4 x 7H2O 1.4 g/l, and CaCl2 1.1 g/l; for EPS production: maltose 60 g/l, Martone A-1 6 g/l, MgSO4 x 7H2O 0.9 g/l, and CaCl2 1.1 g/l. Under the optimal culture condition, the maximum EPS concentration achieved in a 5-l stirred-tank bioreactor indicated 3.0 g/l, which is about three times higher than that at the basal medium.     

Optimization of physical parameters for exo-biopolymer production in submerged mycelial cultures of two entomopathogenic fungi Paecilomyces japonica and Paecilomyces tenuipes

AIMS: In the present study, two different optimization techniques were used to determine the suitable operating parameters for exo-biopolymer production in submerged mycelial cultures of two entomopathogenic fungi Paecilomyces japonica and Paecilomyces tenuipes. METHODS AND RESULTS: First, the rotating simplex method, a nonstatistical optimization technique, was employed to obtain the best combination of physical parameters (viz. pH, agitation intensity, aeration rate) for maximum exo-biopolymer production by P. japonica in a batch bioreactor. The optimal combination was determined to be a pH of 8.06, an aeration of 3 vvm, without any impeller agitation, producing a 17-time increase in exopolymer production (34.5 g l(-1)) when compared with that achieved in unoptimized flask cultures. Second, the uniform design method, a statistical optimization technique, was employed to determine the best operating parameters for submerged culture of P. tenuipes. The optimal combination for mycelial growth was determined to be a pH of 4.88, an aeration of 2 vvm and an agitation of 350 rpm, while a pH of 4, an aeration of 2 vvm and an agitation of 150 rpm was best for exo-biopolymer production. CONCLUSIONS: The exo-biopolymer production in P. japonica optimized by the rotating simplex method was strikingly improved (max. 34.5 g l(-1)), and the exo-biopolymer production in P. tenuipes optimized by the uniform design method was also significantly increased (max. 3.4 g l(-1)). SIGNIFICANCE AND IMPACT OF THE STUDY: The successful application of these two different optimization techniques in this study implies that these methods are worthy of applying to other fermentation systems for the production of bioactive mycelial biomass and exo-biopolymers in liquid culture of higher fungi.     

Laccase production by Monotospora sp., an endophytic fungus in Cynodon dactylon

The effects of the carbon and nitrogen sources, initial pH and incubation temperature on laccase production by the endophytic fungus Monotospora sp. were evaluated. The optimal temperature and initial pH for laccase production by Monotospora sp. in submerged culture were found to be 30 degrees C and 8.5, respectively. Maltose (2 g l(-1)) and ammonium tartrate (10 g l(-1)) were the most suitable carbon and nitrogen source for laccase production. Under optimal culture medium, the maximum laccase activity was determined to be 13.55 U ml(-1), which was approximately four times higher than that in basal medium. This is the first report on laccase production by an endophytic fungus.     

Effect of carbon source and aeration rate on broth rheology and fungal morphology during red pigment production by Paecilomyces sinclairii in a batch bioreactor

The influence of carbon source and aeration rate on fermentation broth rheology, mycelial morphology and red pigment production of Paecilomyces sinclairii was investigated in a 5-l stirred-tank bioreactor. The characteristics of P. sinclairii grown on starch and on sucrose medium were comparatively studied: the specific growth rate in sucrose medium (0.04 h(-1)) was higher than that in starch medium, whereas the specific production rate of red pigments (0.04 gg(-1)d(-1)) was favorable in starch medium. P. sinclairii grown in sucrose medium were highly branched and showed longer hyphal lengths than that in starch medium. The consistency index (K) in sucrose medium was markedly higher than that in starch medium due to higher cell mass, while the higher values of flow behavior index (n) were indicated at the late stationary phase in starch medium. The aeration rate was varied within the ranges from 0.5 to 3.5 vvm while running the fermentation at mild agitation of 150 rpm using sucrose as the carbon source. The maximum biomass concentration of P. sinclairii was about 33 gl(-1) with an aeration rate of 1.5 vvm, whereas the maximum yield of red pigment production (4.73 gl(-1)) was achieved with 3.5 vvm. The highly branched cell morphology appeared at 1.5 vvm and the highly vacuolated cell morphology was observed in a high aeration rate (3.5 vvm). There was no significant variance in rheological parameters (K and n) between culture broths from different aeration conditions.     

Optimization of submerged culture conditions for the mycelial growth and exo-biopolymer production by Cordyceps militaris

AIMS: The objective of the present study was to determine the optimal culture conditions for exo-biopolymer production by Cordyceps militaris in shake flask culture. METHODS AND RESULTS: The optimal temperature and initial pH for both mycelial growth and exo-biopolymer production by Cordyceps militaris in shake flask culture were found to be 20 degrees C and 6.0, respectively. Sucrose (40 g x l(-1)) and corn steep powder (10 g x l(-1)) were the most suitable carbon and nitrogen source for both mycelial growth and exo-biopolymer production. CONCLUSION: Under optimal culture conditions, the maximum exo-biopolymer concentration in a 5-l jar fermenter indicated 10.3 g x l(-1), which was approximately three times higher than that in shake flask culture. SIGNIFICANCE AND IMPACT OF THE STUDY: This process can have a significant impact on the industrial scale when sucrose and corn steep powder were used as carbon and nitrogen source.     

Optimization of submerged culture process for the production of mycelial biomass and exo-polysaccharides by Cordyceps militaris C738

AIMS: The objective of the present study was to determine the optimal culture conditions for mycelial biomass and exo-polysaccharide (EPS) by Cordyceps militaris C738 in submerged culture. METHODS AND RESULTS: The optimal temperatures for mycelial biomass and EPS production were 20 degrees C and 25 degrees C, respectively, and corresponding optimal initial pHs were found to be 9 and 6, respectively. The suggested medium composition for EPS production was as follows: 6% (w/v) sucrose, 1% (w/v) polypeptone, and 0.05% (w/v) K2HPO4. The influence of pH on the fermentation broth rheology, morphology and EPS production of C. militaris C738 was carried out in a 5-l stirred-tank fermenter. The morphological properties were comparatively characterized by pellet roughness and compactness by use of image analyser between the culture conditions with and without pH control. The roughness and compactness of the pellets indicated higher values at pH-stat culture (pH 6.0), suggesting that larger and more compact pellets were desirable for polysaccharide production (0.91 g g(-1) cell d(-1). CONCLUSIONS: Under the optimized culture conditions (with pH control at 6), the maximum concentration of biomass and EPS were 12.7 g l(-1) and 7.3 g l(-1), respectively, in a 5-l stirred-tank fermenter. SIGNIFICANCE AND IMPACT OF THE STUDY: The critical effect of pH on fungal morphology and rheology presented in this study can be widely applied to other mushroom fermentation processes.     

Exopolysaccharide production and mycelial growth in an air-lift bioreactor using Fomitopsis pinicola

For effective exopolysaccharide production and mycelial growth by a liquid culture of Fomitopsis pinicola in an air-lift bioreactor, the culture temperature, pH, carbon source, nitrogen source, and mineral source were initially investigated in a flask. The optimal temperature and pH for mycelial growth and exopolysaccharide production were 25degrees C and 6.0, respectively. Among the various carbon sources tested, glucose was found to be the most suitable carbon source. In particular, the maximum mycelial growth and exopolysaccharide production were achieved in 4% glucose. The best nitrogen sources were yeast extract and malt extract. The optimal concentrations of yeast extract and malt extract were 0.5 and 0.1%, respectively. K2HPO4 and MgSO4 x 7H2O were found to be the best mineral sources for mycelial growth and exopolysaccharide production. In order to investigate the effect of aeration on mycelial growth and exopolysaccharide production in an air-lift bioreactor, various aerations were tested for 8 days. The maximum mycelial growth and exopolysaccharide production were 7.9 g/l and 2.6 g/l, respectively, at 1.5 vvm of aeration. In addition, a batch culture in an air-lift bioreactor was carried out for 11 days under the optimal conditions. The maximum mycelial growth was 10.4 g/l, which was approximately 1.7-fold higher than that of basal medium. The exopolysaccharide production was increased with increased culture time. The maximum concentration of exopolysaccharide was 4.4 g/l, which was about 3.3-fold higher than that of basal medium. These results indicate that exopolysaccharide production increased in parallel with the growth of mycelium, and also show that product formation is associated with mycelial growth. The developed model in an air-lift bioreactor showed good agreement with experimental data and simulated results on mycelial growth and exopolysaccharide production in the culture of F pinicola.     

Utilization of chicory roots for microbial endoinulinase production

AIMS: The optimal culture conditions for endoinulinase production using chicory roots were studied in shake-flask culture. METHODS AND RESULTS: Much higher enzyme production was achieved with Xanthomonas sp. (15 U ml(-1)) than with Pseudomonas sp. (3 U ml(-1)). Optimized culture conditions of Xanthomonas sp. for endoinulinase production in flask culture were: chicory powder, 5 g l(-1); temperature, 37 degrees C; pH, 7.0; agitation speed, 100 rev min(-1). CONCLUSION: Maximum bacterial growth and enzyme production were 6.2 g l(-1) and 20 U ml(-1) under optimal conditions, respectively. SIGNIFICANCE AND IMPACT OF THE STUDY: Chicory roots could be used as a fermentation substrate for the production of enndoinulinase.     

Production of an exopolysaccharide bioflocculant by Sorangium cellulosum

AIMS: To isolate a new exopolysaccharide bioflocculant produced by the myxobacterium Sorangium cellulosum NUST06, and to characterize its chemical composition and expolysaccharide production relative to carbon source. METHODS AND RESULTS: Exopolysaccharide levels and biomass production by S. cellulosum NUST06 were analysed relative to carbon source. Glucose in the medium at a level of 3 g l(-1) completely inhibited cell growth and exopolysaccharide production, but low concentrations of glucose (1-2 g l(-1)) could stimulate cell utilization of starch. The chemical composition and flocculating activity of the NUST06 exopolysaccharide was investigated. The flocculant comprised 38.3% proteins and 58.5% carbohydrates, of which glucose, mannose and glucuronic acid were present at 51.3%, 39.2% and 10.5%, respectively. The flocculating activity of the NUST06 flocculant depended strongly on cations. CONCLUSIONS: It is feasible to produce an exopolysaccharide bioflocculant by the strain NUST06 in a mineral salts medium using starch as a carbon source. SIGNIFICANCE AND IMPACT OF THE STUDY: This strain may be advantageous for commercial bioflocculant production and may enrich existing knowledge of myxobacteria.     

Optimization of exopolysaccharide production from Armillaria mellea in submerged cultures

Aims: To study the optimization of submerged culture conditions for exopolysaccharide (EPS) production by Armillaria mellea in shake‐flask cultures and also to evaluate the performance of an optimized culture medium in a 5‐l stirred tank fermenter. Methods and Results: Shake flask cultures for EPS optimal nutritional production contained having the following composition (in g l^?1): glucose 40, yeast extract 3, KH₂PO₄ 4 and MgSO₄ 2 at an optimal temperature of 22°C and an initial of pH 4·0. The optimal culture medium was then cultivated in a 5‐l stirred tank fermenter at 1 vvm (volume of aeration per volume of bioreactor per min) aeration rate, 150 rev min^?1 agitation speed, controlled pH 4·0 and 22°C. In the optimal culture medium, the maximum EPS production in a 5‐l stirred tank fermenter was 588 mg l^?1, c. twice as great as that in the basal medium. The maximum productivity for EPS (Q_p) and product yield (Y_P/S) were 42·02 mg l^?1 d^?1 and 26·89 mg g^?1, respectively. Conclusions: The optimal culture conditions we proposed in this study enhanced the EPS production of A. mellea from submerged cultures. Significance and Impact of the Study: The optimal culturing conditions we have found will be a suitable starting point for a scale‐up of the fermentation process, helping to develop the production of related medicines and health foods from A. mellea.     

Optimization for the production of exopolysaccharide from Fomes fomentarius in submerged culture and its antitumor effect in vitro

A medicinal mushroom Fomes fomentarius, was isolated from the fruiting body of a wild F. fomentarius and identified by ITS-5.8S rDNA sequencing analysis. Then, the optimization of submerged culture conditions and nutritional requirements of mycelial biomass and exopolysaccharide (EPS) production from F. fomentarius was studied using orthogonal matrix method. Under the optimal culture condition, the maximum EPS concentration reached 3.64 g l(-1), which is about four times higher than that at the basal medium. Furthermore, the EPS from F. fomentarius has a direct antiproliferative effect in vitro on SGC-7901 huaman gastric cancer cells in a dose- and time-dependent manner. Moreover, it was about three times that EPS at noncytocxity concentration of 0.25 mg ml(-1) could sensitize doxorubicin(Dox)-induced growth inhibition of SGC-7901 cells after 24h treatment.     

Nutritional requirements of mycelial growth of Cordyceps sinensis in submerged culture

AIMS: The nutritional requirements for mycelial growth of Cordyceps sinensis in semi-synthetic liquid media were investigated. The results provide a basis for further physiological study and industrial fermentation of the fungus. METHODS AND RESULTS: Nutritional requirements, including 17 carbohydrates, 16 nitrogen compounds, nine vitamins, four macro-elements, four trace-elements and eight ratios of carbon to nitrogen, were studied for their effects on the mycelial growth in submerged cultures of C. sinensis by using one-factor-at-a-time and orthogonal matrix methods. Among these variables, sucrose, peptone, folic acid, calcium, zinc and a carbon to nitrogen ratio 12 : 1 were identified as the requirements for the optimum mycelial growth. The concentrations of sucrose, peptone and yeast extract were optimized and the effects of medium composition on mycelial growth were found to be in the order sucrose > yeast extract > peptone. The optimal concentration for mycelial growth was determined as 50 g l(-1) sucrose, 10 g l(-1) peptone and 3 g l(-1) yeast extract. CONCLUSIONS: Under optimal culture conditions, over 22 g l(-1) of mycelial biomass could be obtained after 40 days in submerged cultures. SIGNIFICANCE AND IMPACT OF THE STUDY: Cordyceps sinensis, one of the most valued medicinal fungi, is shown to grow in axenic culture. This is the first report on nutritional requirements and design of a simplified semi-synthetic medium for mycelial growth of this psychrophilic species, which grows slowly below 20 degrees C. The results of this study will facilitate research on mass production of the fungus under defined culture conditions.     

Production of <Emphasis Type="Italic">Pleurotus sajor-caju</Emphasis> strain PS-2001 biomass in submerged culture

Mushrooms or fruiting bodies of many basidiomycetes are commonly produced in solid-state fermentation, generally after 20-60 days of growth. However, it is also possible to produce biomass from these fungi, in submerged fermentation in shorter time. This work was aimed at evaluating biomass production with the basidiomycete Pleurotus sajor-caju, in a submerged process and to determine the proportion of chemical components of this biomass. Initially, an optimization of the culture medium was done to produce a faster growth of microbial mass by changing the concentrations of ammonium sulfate, soy protein and yeast extract. Using the optimized culture medium, values of approximately 5.5 g L(-1) of biomass in a medium with 10 g L(-1) of glucose were attained. When the optimized culture medium was tested in a 5-L stirred tank bioreactor, using 10 g L(-1) of glucose or sucrose as carbon source, values of 8.18 and 5.94 g L(-1) of biomass concentration were obtained, respectively. In the medium with glucose, high yields (0.82 g g(-1)) and productivity of 0.085 g L(-1) h(-1) were obtained. The exopolysaccharide content (1.58 g dry matter L(-1)) in the culture was higher in the fermentation with sucrose. The nutritional composition of the biomass obtained in the submerged fermentation was similar to that of the fruiting body in terms of quantities of total carbohydrates, ash and calories, but total fat and protein were higher.     

Production and molecular characteristics of four groups of exopolysaccharides from submerged culture of Phellinus gilvus

AIMS: The objective of the present study was to determine the optimal culture conditions for the production of four groups of exopolysaccharides (EPSs) in Phellinus gilvus by submerged culture and to investigate their molecular properties by multi-angle laser-light scattering (MALLS) analysis. METHODS AND RESULTS: The optimal temperature and initial pH for the production of both mycelial biomass and EPSs in P. gilvus by submerged flask cultures were found to be 30 degrees C and pH 9.0, respectively. Glucose and corn steep powder were the most suitable carbon and nitrogen source for both mycelial biomass and EPS production. Optimal medium composition was determined to be glucose 30 g l-1, corn steep powder 5 g l-1, MgSO4 1.23 g l-1, KH2PO4 0.68 g l-1, and K2HPO4 0.87 g l-1. Four groups of EPSs (Fr-I, II, III, and IV) were obtained from the culture filtrates by gel filtration chromatography on Sepharose CL-4B and characterized by size exclusion chromatography (SEC) coupled with MALLS. The weight average molar mass (Mw) of Fr-I, Fr-II, Fr-III and Fr-IV were determined to be 8.628 x 106 (+/-129 420), 1.045 x 106 (+/-19 855), 61.09 x 104 (+/-1244), and 33.55 x 104 (+/-134) g mol-1, respectively. CONCLUSIONS: Under optimal culture conditions, the maximum EPS production in a 5-l stirred fermenter indicated 5.3 g l-1 after 11 days of fermentation. The SEC/MALLS analysis revealed that Fr-I, which has extremely high molecular weight, was presumably an aggregate of complex polysaccharides forming a compact globular shape; whereas Fr-II was nearly spherical, Fr-III and Fr-IV were rod-like chains in an aqueous solution. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first report on the production of high amounts of EPSs from liquid-culture of the basidiomycete, P. gilvus. The SEC/MALLS approach used in this study could be useful in providing greater insight into the characterization of the mushroom polysaccharides without carrying out elaborate fractionation procedures prior to analysis.     

Beta-glucan production by Botryosphaeria rhodina in different bench-top bioreactors

AIMS: Evaluation of the technical feasibility of transferring beta-glucan production by Botryosphaeria rhodina DABAC-P82 from shaken flasks to bench-top bioreactors. METHODS AND RESULTS: Three different bioreactors were used: 3 l stirred tank reactor (STR-1) equipped with two different six-blade turbines; STR as above but equipped with a three-blade marine propeller plus draft-tube (STR-2); 2 l air-lift column reactor (ALR) equipped with an external loop. STR-1, tested at three different stirrer speeds (300, 500 and 700 rev min(-1)) appeared to be less suitable for beta-glucan production by the fungus, being maximum production (19.4 g l(-1)), productivity (0.42 g l(-1) h(-1)) and yield (0.48 g g(-1) of glucose consumed) markedly lower than those obtained in shaken culture (29.7 g l(-1), 1.23 g l(-1) h(-1) and 0.61 g g(-1), respectively). Better performances were obtained with both STR-2 and ALR. With the latter, in particular, the increase of production was accompanied by reduced fermentation time (25.7 g l(-1) after only 22 h); productivity and yield were highest (1.17 g l(-1) h(-1) and 0.62 g g(-1) of glucose consumed, respectively). CONCLUSION: Using an air-lift reactor with external loop, the scaling up from shaken flasks to bench-top bioreactor of the beta-glucan production by B. rhodina DABAC-P82 is technically feasible. SIGNIFICANCE AND IMPACT OF THE STUDY: Although culture conditions are still to be optimized, the results obtained using the ARL are highly promising.     

Optimization of Nutritional Factors for Exopolysaccharide Production by Submerged Cultivation of the Medicinal Mushroom Oudemansiella radicata

Summary Effects of nutritional factors on exopolysaccharide production by submerged cultivation of the medicinal mushroom Oudemansiella radicata were investigated in shake flasks. Sucrose and peptone were optimal carbon and nitrogen sources for cell growth and exopolysaccharide production. The exopolysaccharide production was increased with an increase in initial sucrose concentration within the range of 10–40 g l⁻¹ and initial peptone concentration within the range of 1–3 g l⁻¹. To enhance further exopolysaccharide production, the effect of carbon/nitrogen ratios was studied using central composite design (CCD) and response surface analysis. The maximum exopolysaccharide production of 2.67 ± 0.15 g l⁻¹ was achieved in medium with optimized carbon and nitrogen sources, i.e. 39.3 g sucrose l⁻¹ and 3.16 g peptone l⁻¹ in the same cultivation conditions. The information obtained is helpful for the hyperproduction of exopolysaccharide by submerged cultivation of O. radicata on a large scale.