Exopolysaccharide and Kestose Production by Lactobacillus sanfranciscensis LTH2590

The effect was investigated of sucrose concentration on sucrose metabolism and on the formation of exopolysaccharide (EPS) by Lactobacillus sanfranciscensis LTH2590 in pH-controlled fermentations with sucrose concentrations ranging from 20 to 160 g liter⁻¹. The EPS production increased and the relative sucrose hydrolysis activity decreased by increasing the sucrose concentration in the medium. The carbon recovery decreased from 95% at a sucrose concentration of 30 g liter⁻¹ to 58% at a sucrose concentration of 160 g liter⁻¹ because of the production of an unknown metabolite by L. sanfranciscensis. This metabolite was characterized as a fructo-oligosaccharide. The oligosaccharide produced by L. sanfranciscensis was purified and characterized as a trisaccharide with a glucose/fructose ratio of 1:2. The comparison of the retention time of this oligosaccharide and that of pure oligosaccharide standards using two different chromatography methods revealed that the oligosaccharide produced by L. sanfranciscensis LTH2590 is 1-kestose. Kestose production increased concomitantly with the initial sucrose concentration in the medium.     

Production of a Novel Extracellular Polysaccharide by Lactobacillus sake 0-1 and Characterization of the Polysaccharide

A novel exopolysaccharide (EPS) produced by Lactobacillus sake 0-1 (CBS 532.92) has been isolated and characterized. When the strain was grown on glucose, the produced EPS contained glucose and rhamnose in a molar ratio of 3:2 and the average molecular mass distribution (M(infm)) was determined at 6 x 10(sup6) Da. At a concentration of 1%, the 0-1 EPS had better viscosifying properties than xanthan gum when measured over a range of shear rates from 0 to 300 s(sup-1), while shear-thinning properties were comparable. Rheological data and anion-exchange chromatography suggested the presence of a negatively charged group in the EPS. Physiological parameters for optimal production of EPS were determined in batch fermentation experiments. Maximum EPS production was 1.40 g (middot) liter(sup-1), which was obtained when L. sake 0-1 had been grown anaerobically at 20(deg)C and pH 5.8. When cultured at lower temperatures, the EPS production per gram of biomass increased from 600 mg at 20(deg)C to 700 mg at 10(deg)C but the growth rate in the exponential phase decreased from 0.16 to 0.03 g (middot) liter(sup-1) (middot) h(sup-1). EPS production started in the early growth phase and stopped when the culture reached the stationary phase. Growing the 0-1 strain on different energy sources such as glucose, galactose, mannose, fructose, lactose, and sucrose did not alter the composition of the EPS produced.     

In situ production of exopolysaccharides during Sourdough fermentation by cereal and intestinal isolates of lactic acid bacteria

EPS formed by lactobacilli in situ during sourdough fermentation may replace hydrocolloids currently used as texturizing, antistaling, or prebiotic additives in bread production. In this study, a screening of >100 strains of cereal-associated and intestinal lactic acid bacteria was performed for the production of exopolysaccharides (EPS) from sucrose. Fifteen strains produced fructan, and four strains produced glucan. It was remarkable that formation of glucan and fructan was most frequently found in intestinal isolates and strains of the species Lactobacillus reuteri, Lactobacillus pontis, and Lactobacillus frumenti from type II sourdoughs. By the use of PCR primers derived from conserved amino acid sequences of bacterial levansucrase genes, it was shown that 6 of the 15 fructan-producing lactobacilli and none of 20 glucan producers or EPS-negative strains carried a levansucrase gene. In sourdough fermentations, it was determined whether those strains producing EPS in MRS medium modified as described by Stolz et al. (37) and containing 100 g of sucrose liter(-1) as the sole source of carbon also produce the same EPS from sucrose during sourdough fermentation in the presence of 12% sucrose. For all six EPS-producing strains evaluated in sourdough fermentations, in situ production of EPS at levels ranging from 0.5 to 2 g/kg of flour was demonstrated. Production of EPS from sucrose is a metabolic activity that is widespread among sourdough lactic acid bacteria. Thus, the use of these organisms in bread production may allow the replacement of additives.     

Production of exopolysaccharide by Lactobacillus rhamnosus R and analysis of its enzymatic degradation during prolonged fermentation

The potential of Lactobacillus rhamnosus R for producing exopolysaccharide (EPS) when grown on basal minimum medium supplemented with glucose or lactose was investigated. EPS production by L. rhamnosus R is partially growth associated and about 500 mg of EPS per liter was synthesized with both sugars. The product yield coefficient (Y(EPS/S)) was 3.15 (0.0315 g of EPS [g of lactose](-1)) and 2.88 (0.0288 g of EPS [g of glucose](-1)). It was clearly shown that the amount of EPS produced declined upon prolonged fermentation. Degradation of EPS in fermentation processes was also assessed by measuring its molecular weights and viscosities. As these reductions might have a negative effect on the yield and viscosifying properties of EPS, it was essential to examine possible causes related to this breakdown. The decrease in viscosities and molecular weights of EPS withdrawn at different cultivation times permitted us to suspect the presence of a depolymerizing enzyme in the fermentation medium. Our study on enzymatic production profiles showed a large spectrum of glycohydrolases (alpha-D-glucosidase, beta-D-glucosidase, alpha-D-galactosidase, beta-D-galactosidase, beta-D-glucuronidase, and some traces of alpha-L-rhamnosidase). These enzymes were localized, two of them (alpha-D-glucosidase and beta-D-glucuronidase) were partially purified and characterized. When incubated with EPS, these enzymes were capable of lowering the viscosity of the polymer as well as liberating some reducing sugars. Upon prolonged incubation (27 h), the loss of viscosity was increased up to 33%.     

Optimization of exopolysaccharide overproduction by Lactobacillus confusus in solid state fermentation under high salinity stress

It is believed that high concentrations of sodium chloride (NaCl) suppress the biosynthesis of exopolysaccharide (EPS) in lactic acid bacteria (LAB). Nevertheless, overproduction of EPSs due to high salinity stress in solid state fermentation performed on an agar surface was demonstrated in this study using a response surface methodology via a central composite design (CCD). Under optimized conditions with NaCl 4.97% and sucrose 136.5 g/L at 40.79 h of incubation, the EPS yield was 259% (86.36 g/L of EPS), higher than the maximum yield produced with the modified MRS medium containing only 120 g/L of sucrose without NaCl (33.4 g/L of EPS). Biosynthesis of EPS by Lactobacillus confusus TISTR 1498 was independent of biomass production. Our results indicated that high salinity stress can enhance EPS production in solid state fermentation.     

Optimization of Exopolysaccharide Overproduction by Lactobacillus confusus in Solid State Fermentation under High Salinity Stress

It is believed that high concentrations of sodium chloride (NaCl) suppress the biosynthesis of exopolysaccharide (EPS) in lactic acid bacteria (LAB). Nevertheless, overproduction of EPSs due to high salinity stress in solid state fermentation performed on an agar surface was demonstrated in this study using a response surface methodology via a central composite design (CCD). Under optimized conditions with NaCl 4.97% and sucrose 136.5 g/L at 40.79 h of incubation, the EPS yield was 259% (86.36 g/L of EPS), higher than the maximum yield produced with the modified MRS medium containing only 120 g/L of sucrose without NaCl (33.4 g/L of EPS). Biosynthesis of EPS by Lactobacillus confusus TISTR 1498 was independent of biomass production. Our results indicated that high salinity stress can enhance EPS production in solid state fermentation.     

A Review of: “Progress in Separation and Purification Vol. 3, E. S. Perry and C. J,van Oss,eds., Willy/Intersciencc,New York, 1970; xi + 316 pares; hard cover; 515.95”

The optimal culture conditions of exopolysaccharides (EPS) production in submerged culture medium by Pleurotus geesteranus 5 ^# were determined using an orthogonal matrix method. The optimal defined medium (per liter) was 60.0 g maltose, 5.0 g tryptone, 1 mM NaCl, 5 mM KH₂PO₄, and initial pH 6.0 at 28 °C. In the optimal culture medium, the maximum EPS production was 16.97 g/L in a shake flask. Two groups of EPSs (designated as Fr-I and Fr-II) were obtained from the culture filtrates by size exclusion chromatography (SEC), and their molecular characteristics were examined by a multiangle laser-light scattering (MALLS) and refractive index (RI) detector system. The approximate weight-average molar masses of the Fr-I and Fr-II of EPS were determined to be 3.263 × 10⁴ and 5.738 × 10³ g/mol, respectively. The low values of polydispersity ratio (1.176 and 1.124 for Fr-I and Fr-II, respectively) of EPSs mean that these EPS molecules exist much less dispersed in aqueous solution without forming large aggregates. Furthermore, the experiments in vitro indicated that P. geesteranus 5^# EPS exhibit high antitumor and antioxidative effects.     

Glutathione reductase from Lactobacillus sanfranciscensis DSM20451T: contribution to oxygen tolerance and thiol exchange reactions in wheat sourdoughs

The effect of the glutathione reductase (GshR) activity of Lactobacillus sanfranciscensis DSM20451(T) on the thiol levels in fermented sourdoughs was determined, and the oxygen tolerance of the strain was also determined. The gshR gene coding for a putative GshR was sequenced and inactivated by single-crossover integration to yield strain L. sanfranciscensis DSM20451(T)DeltagshR. The gene disruption was verified by sequencing the truncated gshR and surrounding regions on the chromosome. The gshR activity of L. sanfranciscensis DSM20451(T)DeltagshR was strongly reduced compared to that of the wild-type strain, demonstrating that gshR indeed encodes an active GshR enzyme. The thiol levels in wheat doughs fermented with L. sanfranciscensis DSM20451 increased from 9 microM to 10.5 microM sulfhydryl/g of dough during a 24-h sourdough fermentation, but in sourdoughs fermented with L. sanfranciscensis DSM20451(T)DeltagshR and in chemically acidified doughs, the thiol levels decreased to 6.5 to 6.8 microM sulfhydryl/g of dough. Remarkably, the GshR-negative strains Lactobacillus pontis LTH2587 and Lactobacillus reuteri BR11 exerted effects on thiol levels in dough comparable to those of L. sanfranciscensis. In addition to the effect on thiol levels in sourdough, the loss of GshR activity in L. sanfranciscensis DSM20451(T)DeltagshR resulted in a loss of oxygen tolerance. The gshR mutant strain exhibited a strongly decreased aerobic growth rate on modified MRS medium compared to either the growth rate under anaerobic conditions or that of the wild-type strain, and aerobic growth was restored by the addition of cysteine. Moreover, the gshR mutant strain was more sensitive to the superoxide-generating agent paraquat.     

Schizophyllan production by newly isolated fungus <Emphasis Type="Italic">Schizophyllum commune</Emphasis> IBRC-M 30213: optimization of culture medium using response surface methodology

Schizophyllan (SPG) is a commercially attractive biopolymer produced by Schizophyllum commune. An investigation on the potential for SPG production by Iranian native S. commune was conducted based on culture medium, fermentation conditions and bioreactor type, . Nine native fungal strains were isolated from the northern forest of Iran at different times. Based on growth rate and SPG production, one strain was selected for further study. Optimal medium composition and inoculum size for maximizing SPG production and minimizing biomass were determined using central composite design by setting sucrose, yeast extract, inoculum size, carboxymethyl cellulose and oleic acid in the ranges of 50–200 g/L, 1–4 g/L, 2–10%, 2–12 g/L and 0.032–0.222%, respectively. The results showed that optimal results were obtained at 93.47 g/L sucrose, 1.87 g/L yeast extract, 7.68% inoculum size, 9.07 g/L carboxymethyl cellulose and 0.13% oleic acid, with maximum SPG production of 9.97 g/L and minimum biomass of 35.18 g/L. Under these optimal conditions, the production of SPG was studied in stirred tank and bubble column bioreactors. The results revealed greater production in the stirred tank because of better mixing of the culture medium. The SPG produced was characterized using rheometery, Fourier transform infrared spectroscopy, nuclear magnetic resonance), scanning electron microscopy and gel permeation chromatography. The results of these characterizations demonstrated the similarity of the SPG produced by S. commune IBRC-M 30213 to commercial SPG. Thus, the SPG produced shows good potential as a polysaccharide for use in various industries.     

Influence of auxins and sucrose in monoterpenoid oxindole alkaloid production by Uncaria tomentosa cell suspension cultures

Growth and alkaloid production in Uncaria tomentosa cell suspension cultures were studied in Murashige and Skoog medium supplemented with 10 microM 2,4-dichlorophenoxyacetic acid, 10 microM kinetin, and 58 mM sucrose for maintenance and with 10 microM indole-3-acetic acid, 10 microM kinetin, and 58 mM sucrose for production. A U. tomentosa pale Uth-3 cell line, cultured in the production medium, showed a reduced lag phase and a specific growth rate (mu) of 0.27 day(-1), while cells growing in the maintenance medium showed mu = 0.20 day(-1). U. tomentosa cells growing in the production medium produced monoterpenoid oxindole alkaloids (MOA) in amounts of 10.2 +/- 1.6 microg g(-1) dry weight (DW). The chemical profile of MOA produced by in vitro cell cultures was similar to that found in the plant. After 10 subcultures, maximum MOA production decreased to 2.0 +/- 0.7 microg g(-1) DW, while tryptamine alkaloids (TA) were produced with a maximum of 6.2 +/- 0.4 microg g(-1) DW. The increase of initial sucrose concentration up to 145 mM in the production medium enhanced the cell biomass by 3.2-fold (from 10.2 +/- 0.1 to 32.8 +/- 1.1 g DW L(-1)), reduced mu from 0.27 to 0.23 day(-1), and provoked a substantial accumulation of TA (23.1 +/- 4.7 microg g(-1) DW). A high sucrose concentration stimulated MOA production in the maintenance medium (2.7 +/- 0.5 microg g(-1) DW), even in the presence of 2,4-dichlorophenoxyacetic acid.     

Metabolism by bifidobacteria and lactic acid bacteria of polysaccharides from wheat and rye, and exopolysaccharides produced by Lactobacillus sanfranciscensis

AIMS: The metabolism by bifidobacteria of exopolysaccharide (EPS) produced by Lactobacillus sanfranciscensis was investigated. To evaluate the significance of the EPS produced by Lact. sanfranciscensis during dough fermentation on the overall prebiotic properties of bread, metabolism by bifidobacteria of water-soluble polysaccharides (WSP) from wheat and rye was investigated. METHODS AND RESULTS: Polyglucose and polyfructan contained in WSP from wheat and rye were metabolized by bifidobacteria. In contrast, WSP isolated from fermented doughs were not metabolized by bifidobacteria. The arabioxylan fraction of WSP was metabolized neither by bifidobacteria nor by lactobacilli. All the bifidobacteria tested were able to metabolize fructan from Lact. sanfranciscensis. The kinetics of EPS metabolism by various bifidobacteria were characterized by diauxic utilization of fructose and EPS. CONCLUSIONS: Bifidobacteria metabolize fructan from Lact. sanfranciscensis. Polyfructan and the starch fractions from wheat and rye, which possess a bifidogenic effect, were degraded by cereal enzymes during dough fermentation, while the EPS were retained. SIGNIFICANCE AND IMPACT OF THE STUDY: EPS produced by sourdough lactic acid bacteria will improve the nutritional properties of sourdough fermented products.     

Optimization of culture medium for enhanced production of exopolysaccharide from Aureobasidium pullulans

Polysaccharides produced by microorganisms are utilized for a variety of purposes, including the use in cosmetics and as food additives. More recently, polysaccharides have been exploited by the medical and pharmaceutical industries, and those originated from many species of mushrooms have been especially useful in industrial applications; however, the production and synthesis of these compounds is costly and time consuming. In this study, we developed a method for low-cost production of exopolysaccharide (EPS) that effectively screens components and optimizes medium composition using statistical methods (Plackett-Burman and Box-Behnken design). As a result, we obtained the following optimized medium: sucrose 165.73 g/L, sodium nitrate 3.08 g/L, dipotassium phosphate 1.00 g/L, potassium chloride 0.50 g/L, magnesium sulfate 0.50 g/L, ferrous sulfate 0.01 g/L, and 0.71 g/L of Ashbya gossypii extract. The maximum production of about 29 g/L EPS was achieved in the optimized medium during 84 h batch fermentation.     

Excessive excretion of cyclic beta-(1,2)-glucan by Rhizobium trifolii TA-1

At 25 degrees C, the optimal temperature for growth of Rhizobium trifolii TA-1, extracellular and capsular polysaccharide (EPS and CPS) were the main carbohydrate products synthesized in mannitol-rich medium (10 g of mannitol and 1 g of glutamic acid per liter). In the same medium at 33 degrees C, EPS and CPS production was inhibited, and up to 3.9 g of cyclic beta-(1,2)-glucan was produced during an incubation period of 20 days with a total biomass of 0.55 g of protein. In a medium containing 50 g of mannitol and 10 g of glutamic acid per liter, high cell densities (3.95 g of protein) were obtained at 25 degrees C. This biomass excreted 10.9 g of cyclic beta-(1,2)-glucan within 10 days. Concomitantly, 4.8 g of EPS were synthesized, while CPS production was strongly suppressed. The excreted cyclic beta-(1,2)-glucans were neutral and had degrees of polymerization ranging from 17 to 25, with a degree of polymerization of 19 as the major glucan cycle.     

Excessive excretion of cyclic beta-(1,2)-glucan by Rhizobium trifolii TA-1.

At 25 degrees C, the optimal temperature for growth of Rhizobium trifolii TA-1, extracellular and capsular polysaccharide (EPS and CPS) were the main carbohydrate products synthesized in mannitol-rich medium (10 g of mannitol and 1 g of glutamic acid per liter). In the same medium at 33 degrees C, EPS and CPS production was inhibited, and up to 3.9 g of cyclic beta-(1,2)-glucan was produced during an incubation period of 20 days with a total biomass of 0.55 g of protein. In a medium containing 50 g of mannitol and 10 g of glutamic acid per liter, high cell densities (3.95 g of protein) were obtained at 25 degrees C. This biomass excreted 10.9 g of cyclic beta-(1,2)-glucan within 10 days. Concomitantly, 4.8 g of EPS were synthesized, while CPS production was strongly suppressed. The excreted cyclic beta-(1,2)-glucans were neutral and had degrees of polymerization ranging from 17 to 25, with a degree of polymerization of 19 as the major glucan cycle.     

Characterization of reutericyclin produced by Lactobacillus reuteri LTH2584

Lactobacillus reuteri LTH2584 exhibits antimicrobial activity that can be attributed neither to bacteriocins nor to the production of reuterin or organic acids. We have purified the active compound, named reutericyclin, to homogeneity and characterized its antimicrobial activity. Reutericyclin exhibited a broad inhibitory spectrum including Lactobacillus spp., Bacillus subtilis, B. cereus, Enterococcus faecalis, Staphylococcus aureus, and Listeria innocua. It did not affect the growth of gram-negative bacteria; however, the growth of lipopolysaccharide mutant strains of Escherichia coli was inhibited. Reutericyclin exhibited a bactericidal mode of action against Lactobacillus sanfranciscensis, Staphylococcus aureus, and B. subtilis and triggered the lysis of cells of L. sanfranciscensis in a dose-dependent manner. Germination of spores of B. subtilis was inhibited, but the spores remained unaffected under conditions that do not permit germination. The fatty acid supply of the growth media had a strong effect on reutericyclin production and its distribution between producer cells and the culture supernatant. Reutericyclin was purified from cell extracts and culture supernatant of L. reuteri LTH2584 cultures grown in mMRS by solvent extraction, gel filtration, RP-C(8) chromatography, and anion-exchange chromatography, followed by rechromatography by reversed-phase high-pressure liquid chromatography. Reutericyclin was characterized as a negatively charged, highly hydrophobic molecule with a molecular mass of 349 Da. Structural characterization (A. H?ltzel, M. G. G?nzle, G. J. Nicholson, W. P. Hammes, and G. Jung, Angew. Chem. Int. Ed. 39:2766-2768, 2000) revealed that reutericyclin is a novel tetramic acid derivative. The inhibitory activity of culture supernatant of L. reuteri LTH2584 corresponded to that of purified as well as synthetic reutericyclin.     

Production of exopolysaccharides by Agrobacterium sp. CFR-24 using coconut water - a byproduct of food industry

AIMS: The work is intended to explore the suitability of underutilized coconut water (a byproduct of food industry) for the production of exopolysaccharides (EPS) by Agrobacterium sp. CFR 24. METHODS AND RESULTS: Besides checking the suitability of coconut water for the production of water-soluble (WS) and water-insoluble (WIS) EPS, certain fermentation parameters, such as initial pH, incubation period and kinetics of EPS production were investigated. The coconut water medium was found to support the production of both types of EPS. The optimal initial pH and temperature was found to be 6.0 and 30 degrees C, respectively. In shake flask (150 rev min(-1)) studies, high-cell density inoculum resulted in the production of 11.50 g l(-1) of WIS-EPS and 4.01 g l(-1) WS-EPS after 72 and 96 h of fermentation, respectively. CONCLUSIONS: Coconut water was found suitable for the production of microbial EPS by Agrobacterium sp. CFR 24 strain. Under optimum conditions, it produced a good amount of WIS-EPS, which is comparable with that of the sucrose medium (11 g l(-1)). SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first report on the use of coconut water as a fermentation medium for the production of any microbial EPS. Besides producing value-added products, use of this food industry byproduct, which is often being drained out, can significantly reduce the problem of environmental pollution.     

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.     

Production and partial characterization of the exopolysaccharide from Pleurotus sajor caju

Microbial exopolysaccharides (EPSs) are very important because they are used in biotechnological applications in different industrial areas. The aim of the study was to determine the best EPS producer Pleurotus sp., to optimize EPS production and to perform partial purification and characterization of the produced EPS. After the production conditions were optimized, the EPS was isolated and partially purified. EPS was characterized by HP-TLC, 1H-NMR, FT-IR, and TGA. Hydroxyl, superoxide, and DPPH radical scavenging activities of the EPS were also investigated spectrophotometrically. The best EPS producer and its incubation period in submerged fermentation were determined as Pleurotus sajor caju and on 5 days, respectively. Culture conditions to increase EPS production were optimized as follows (in per liter): 90 g of glucose, 10 g of yeast extract, 10 g of peptone, and 100 mM of Mg2+. The optimal initial pH, temperature, and an agitation rate of culture were determined as 5.0, 25 °C, and 150 rate min−1, respectively. The highest EPS production was determined as 33.32 ± 1.6 g L−1. After isolation of EPS, one active fraction was obtained by gel filtration chromatography. EPS is composed mainly of glucose according to HP-TLC analysis. To the results, EPS had a complex structure by having carbohydrate and protein contents. The produced EPS had high degradation temperature as well as high antioxidant activity.     

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.     

Links between morphology and physiology of Ganoderma lucidum in submerged culture for the production of exopolysaccharide

Ganoderma lucidum was grown in submerged culture in shake flasks on a medium containing peptone, yeast extract and glucose. In pre-cultures, inoculated from an agar-grown culture, morphological and metabolic events were linked: the pellets originally produced protuberances when glucose was present in the medium, although glucose was not consumed. The protuberances were then liberated into the medium as second-generation pellets, at which time glucose consumption began and the rate of exopolysaccharide (EPS) production increased. The synchrony between events was repeated in cultures fed with either glucose or peptone and yeast extract. In main cultures, inoculated from a 16-day-old pre-culture, the biomass concentration increased linearly, while glucose consumption and EPS production were initially slow but then accelerated. Protuberances were produced and liberated similarly to the pre-culture, but there was less synchrony amongst the pellets. When glucose was added to such a culture on day 10, an EPS concentration of 5.7 g L(-1) was achieved on day 13, this being the highest reliable EPS concentration yet reported for submerged culture of G. lucidum. We conclude that a greater understanding of the morphological and physiological events during the culture of G. lucidum will allow the proposal of culture strategies to improve EPS production.