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.

Inhibiting effect of bioactive metabolites produced by mushroom cultivation on bacterial quorum sensing-regulated behaviors.

AIMS: This study aimed to search for novel quorum sensing (QS) inhibitors from mushroom and to analyze their inhibitory activity, with a view to their possible use in controlling detrimental infections. METHODS: The bioactive metabolites produced by mushroom cultivation were tested for their abilities to inhibit QS-regulated behavior. All mushroom strains were cultivated in potato-dextrose medium by large-scale submerged fermentation. The culture supernatant was condensed into 0.2 vol by freeze-drying. The condensed supernatant was sterilized by filtration through a 0.22-µm membrane filter and added to Chromobacterium violaceum CV026 cultures, which were used to monitor QS inhibition. Inhibitory activity was measured by quantifying violacein production using a microplate reader. RESULTS: The results have revealed that, of 102 mushroom strains, the bioactive metabolites produced by 14 basidiomycetes were found to inhibit violacein production, a QS-regulated behavior in C. violaceum. CONCLUSIONS: Higher fungi can produce QS-inhibitory compounds.

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.