Production of exopolysaccharides by submerged mycelial culture of a mushroom Tremella fuciformis

Fungal exopolysaccharide: production, composition and applications

Fungal exopolysaccharides (EPSs) have been recognized as high value biomacromolecules for the last two decades. These products, including pullulan, scleroglucan, and botryosphaeran, have several applications in industries, pharmaceuticals, medicine, foods etc. Although fungal EPSs are highly relevant, to date information concerning fungal biosynthesis is scarce and an extensive search for new fugal species that can produce novel EPSs is still needed. In most cases, the molecular weight variations and sugar compositions of fungal EPSs are dependent to culture medium composition and different physical conditions provided during fermentation. An inclusive and illustrative review on fungal EPS is presented here. The general outline of the present work includes fungal EPS production, their compositions and applications. An emphasis is also given to listing out different fungal strains that can produce EPSs.

Culture conditions and medium components for the production of mycelial biomass and exo-polysaccharides with Paecilomyces japonica in liquid culture

In this study, the liquid culture conditions were optimized for maximal production of mycelial biomass and exo-polysaccharide by Paecilomyces japonica. The effects of medium composition, C/N ratio and physical parameters were investigated. From these experiments, 30 g glucose, 20 g yeast extract, 0.5 g KH2PO4, and 0.1 g CuCl2 2H2O in 1-l distilled water were found to be the most suitable carbon, nitrogen, and mineral sources, respectively. The optimal temperature, initial pH, agitation, and aeration were determined to be 27°C, uncontrolled pH, 400 rpm, and 1.0 vvm, respectively. Under these optimal conditions, the maximum mycelial growth and polysaccharides production were 23.1 g/l and 2.5 g/l, respectively.

Lasiodiplodan, an exocellular (1→6)-β-d-glucan from Lasiodiplodia theobromae MMPI: production on glucose, fermentation kinetics, rheology and anti-proliferative activity

Lasiodiplodan, an exopolysaccharide of the (1→6)-β-d-glucan type, is produced by Lasiodiplodia theobromae MMPI when grown under submerged culture on glucose. The objective of this study was to evaluate lasiodiplodan production by examining the effects of carbon (glucose, fructose, maltose, sucrose) and nitrogen sources (KNO3, (NH4)2SO4, urea, yeast extract, peptone), its production in shake flasks compared to a stirred-tank bioreactor, and to study the rheology of lasiodiplodan, and lasiodiplodan’s anti-proliferative effect on breast cancer MCF-7 cells. Although glucose (2.05 ± 0.05 g L−1), maltose (2.08 ± 0.04 g L−1) and yeast extract (2.46 ± 0.06 g L−1) produced the highest amounts of lasiodiplodan, urea as N source resulted in more lasiodiplodan per unit biomass than yeast extract (0.74 ± 0.006 vs. 0.22 ± 0.008 g g−1). A comparison of the fermentative parameters of L. theobromae MMPI in shake flasks and a stirred-tank bioreactor at 120 h on glucose as carbon source showed maximum lasiodiplodan production in agitated flasks (7.01 ± 0.07 g L−1) with a specific yield of 0.25 ± 0.57 g g−1 and a volumetric productivity of 0.06 ± 0.001 g L−1 h−1. A factorial 22 statistical design developed to evaluate the effect of glucose concentration (20–60 g L−1) and impeller speed (100–200 rpm) on lasiodiplodan production in the bioreactor showed the highest production (6.32 g L−1) at 72 h. Lasiodiplodan presented pseudoplastic behaviour, and the apparent viscosity increased at 60°C in the presence of CaCl2. Anti-proliferative activity of lasiodiplodan was demonstrated in MCF-7 cells, which was time- and dose-dependent with an IC50 of 100 μg lasiodiplodan mL−1.

A three-stage culture process for improved exopolysaccharide production by Tremella fuciformis

Tremella fuciformis produces several bioactive secondary metabolites including exopolysaccharides. Cultivation of the fungus was carried out in a three-stage process consisting of a 1.5-day cultivation with orbital shaking at 200 rpm, a 1.5-day cultivation with reciprocal shaking at 200 strokes, and a 1.5-day cultivation with orbital shaking at 200 rpm. Exopolysaccharide production and specific production rate reached 5.80 g L(-1) and 0.15 d(-1), respectively, which is an increase of 260% and 200% compared with the corresponding values for fermentations with orbital shaking only, and of 243% and 150% compared with the corresponding values for fermentations with reciprocal shaking only. The three-stage culture method is time-saving and easy to operate.

Production, purification and characterisation of polysaccharides from Pleurotus ostreatus with antitumour activity

BACKGROUND

Mushroom polysaccharides play an important role in functional foods because they exhibit biological modulator properties such as antitumour, antiviral and antibacterial activities. The present study involved the production, purification and characterisation of intracellular and extracellular free and protein-bound polysaccharides from Pleurotus ostreatus and the investigation of their growth-inhibitory effect on human carcinoma cell lines.

RESULTS

Several fermentation parameters were obtained: batch polysaccharide productivities of 0.013 ± 8.12 × 10⁻⁵ and 0.037 ± 0.0005 g L⁻¹ day⁻¹ for intracellular and extracellular polysaccharides respectively, a maximum biomass concentration of 9.35 ± 0.18 g L⁻¹ , P(max) = 0.935 ± 0.018 g L⁻¹ day⁻¹, µ(max) = 0.218 ± 0.02 day⁻¹, Y(EP/X) = 0.040 ± 0.0015 g g⁻¹ and Y(IP/X) = 0.014 ± 0.0003 g g⁻¹ . Some polysaccharides exhibited superoxide dismutase (SOD)-like activity of 50-200 units. Fourier transform infrared analysis of the polysaccharides revealed absorption bands characteristic of such biological macromolecules. Cytotoxicity assays showed that both intracellular and extracellular polysaccharides exhibited antitumour activity towards several tested human carcinoma cell lines in a dose-dependent manner.

CONCLUSION

The polysaccharides of P. ostreatus exhibited high SOD-like activity, which strongly supports their biological effect on tumour cell lines. The extracellular polysaccharides presented the highest antitumour activity towards the RL95 carcinoma cell line and should be further investigated as an antitumour agent.

pH-control modes in a 5-L stirred-tank bioreactor for cell biomass and exopolysaccharide production by Tremella fuciformis spore

The effect of pH-control modes on cell growth and exopolysaccharide production by Tremella fuciformis was evaluated in a 5-L bioreactor. The results show that the maximal dry cell weight (DCW) and exopolysaccharide production were 23.57 and 4.48 g L⁻¹ in pH-stat fermentation, where the maximal specific growth rate (μ(max)) and specific production rate of exopolysaccharide (P(P/X)) were 1.03 and 0.24 d⁻¹, respectively; under pH-shift cultivation, the maximal DCW and exopolysaccharide production were 30.57 and 3.90 g L⁻¹, where the μ(max) and P(P/X) were 1.21 and 0.06 d⁻¹. Unlike batch fermentation, maximal DCW and exopolysaccharide production merely reached 15.04 and 2.0 g L⁻¹, where the μ(max) and P(P/X) were 0.86 and 0.05 d⁻¹, respectively. These results suggest that a pH-stat strategy is a more efficient way of performing the fermentation process to increase exopolysaccharide production. Furthermore, this research has also proved that the three-stage pH-control mode is effective for cell growth.

Performance of enhanced biological SBR process for aniline treatment by mycelial pellet as biomass carrier

Mycelial pellet of Aspergillus niger Y3 was used as a biomass carrier to immobilize the aniline-degrading bacterium, Acinetobacter calcoaceticus JH-9 and the mix culture of the COD rapid degradation bacteria. In order to investigate its removal effect on aniline and COD, the combined mycelial pellets were applied in the SBR. Comparison of the performances was conducted between another SBR inoculated with sole strain JH-9 and the above SBR. The results showed that the stable degradations of aniline and COD were observed in both reactors. In the SBR with combined mycelial pellet, the biological removal efficiency was about 0.9 mg aniline/(L·d). It was much higher than that in the activated sludge reactor. Meanwhile, the performances of the sedimentation velocity, liquid-solid phase separation and the effluent quality were better in the SBR. According to SEM images and PCR-DGGE analysis, the species immobilized on the biomass carrier were more predominant in this system.

Use of stimulatory agents to enhance the production of bioactive exopolysaccharide from pleurotus tuber-regium by submerged fermentation

Fatty acids, organic solvents and surfactants were investigated for their stimulatory effects on the growth of fungal mycelium and production of exopolysaccharide (EPS) by submerged fermentation of an edible mushroom Pleurotus tuber-regium. Addition of 3.0 g/L Tween 80 at the late stage of exponential growth phase provided the best stimulatory effect on mycelial biomass and fungal EPS production with a 51.3 and 41.8% increase, respectively. The chemical structure of the EPS produced with addition of Tween 80 was found to be a glucomannan with similar monosaccharide composition and glycosidic linkages but a significantly lower molecular weight (3.18 ± 0.09 × 10(6) Da), compared to the control (4.30 ± 0.12 × 10(6) Da). These two EPS could significantly inhibit the growth of chronic myelogenous leukemia K562 cells in a dose dependent manner, with an estimated IC(50) value of 43.7 and 47.6 μg/mL, respectively. The use of stimulatory agents to enhance production of bioactive fungal EPS can be applied in other fungal fermentation processes for enhancing production of useful metabolites.

Improved simultaneous production of mycelial biomass and polysaccharides by submerged culture of Hericium erinaceum: optimization using a central composite rotatable design (CCRD)

The aim of this study was to optimize the culture medium used for the mycelial growth and production of intracellular polysaccharides (IPS) and exopolysaccharides (EPS) in a submerged culture of Hericium erinaceum. Of the various factors examined, including carbon and nitrogen sources, vitamins, mineral elements, and initial pH, those that proved to have a significant effect were then tested using a 2(4) central composite rotatable design (CCRD). Under the optimal culture conditions, the maximal yield of biomass reached 14.24 +/- 0.45 g l(-1) and was 1.85-fold higher than in the basal medium. The kinetics of EPS biosynthesis in a bioreactor showed that although the highest yield of EPS (2.75 +/- 0.27 g l(-1)) could be obtained on day 8, the process of biosynthesizing high molecular weight polysaccharides proceeded until the depletion of the carbon source in the medium (after 14 days of cultivation). Our results could be very helpful in the large-scale production of bioactive polysaccharides from H. erinaceum.

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.

PA2663 (PpyR) increases biofilm formation in Pseudomonas aeruginosa PAO1 through the psl operon and stimulates virulence and quorum-sensing phenotypes

Previously, we identified the uncharacterized predicted membrane protein PA2663 of Pseudomonas aeruginosa PAO1 as a virulence factor using a poplar tree model; PA2663 was induced in the poplar rhizosphere and, upon inactivation, it caused 20-fold lower biofilm formation (Attila et al., Microb Biotechnol, 2008). Here, we confirmed that PA2663 is related to biofilm formation by restoring the wild-type phenotype by complementing the PA2663 mutation in trans and investigated the genetic basis of its influence on biofilm formation through whole-transcriptome and -phenotype studies. Upon inactivating PA2663 by transposon insertion, the psl operon that encodes a galactose- and mannose-rich exopolysaccharide was highly repressed (verified by RT-PCR). The inactivation of PA2663 also repressed 13 pyoverdine genes, which eliminated the production of the virulence factor pyoverdine in P. aeruginosa. The inactivation of PA2663 also affected other quorum-sensing-related phenotypes in that it repressed the Pseudomonas quinolone signal (PQS) genes, which abolished PQS production, and repressed lasB, which decreased elastase activity sevenfold. Genes were also induced for motility and attachment (PA0499, PA0993, PA2130, and PA4549) and for small molecule transport (PA0326, PA1541, PA1632, PA1971, PA2214, PA2215, PA2678, and PA3407). Phenotype arrays also showed that PA2663 represses growth on D: -gluconic acid, D: -mannitol, and N-phthaloyl-L: -glutamic acid. Hence, the PA2663 gene product increases biofilm formation by increasing the psl-operon-derived exopolysaccharides and increases pyoverdine synthesis, PQS production, and elastase activity while reducing swarming and swimming motility. We speculate that PA2663 performs these myriad functions as a novel membrane sensor.

Hypoglycemic effects of exopolysaccharides produced by mycelial cultures of two different mushrooms Tremella fuciformis and Phellinus baumii in ob/ob mice

The anti-diabetic activities of the exopolysaccharides (EPS) produced by submerged mycelial culture of two different mushrooms, Tremella fuciformis and Phellinus baumii, in ob/ob mice were investigated. All the animals were randomly divided into three groups with seven animals in each group: The control group received 0.9% NaCl solution; the diabetic groups were treated with EPS from T. fuciformis (Tf EPS) and P. baumii (Pb EPS) at the level of 200 mg/kg body weight using an oral zoned daily for 52 days. The plasma glucose levels in the EPS-fed mice were substantially reduced by about 52% (Tf EPS) and 32% (Pb EPS), respectively, as compared to control mice. The results of oral glucose tolerance test (OGTT) revealed that both EPS-fed groups significantly increased the glucose disposal after 52 days of EPS treatments. Furthermore, higher food efficiency ratios and reduced blood triglyceride levels were observed in the EPS-treated groups. Because peroxisome proliferator-activated receptor gamma (PPAR-gamma) is indeed a key regulator of insulin action, we investigated the expression pattern of adipose tissue PPAR-gamma messenger RNA (mRNA) and plasma levels of PPAR-gamma. It was revealed that PPAR-gamma was significantly activated in response to EPS treatments. The results suggested that both EPS exhibited considerable hypoglycemic effect and improved insulin sensitivity possibly through regulating PPAR-gamma-mediated lipid metabolism. Our results indicated that two mushroom-derived EPS might be developed as potential oral hypoglycemic agents or functional foods for the management of non-insulin-dependent diabetes mellitus.