Optimization of exopolysaccharide production by Tremella mesenterica NRRL Y-6158 through implementation of fed-batch fermentation

Abstract

In liquid culture conditions, the yeast-like fungus Tremella mesenterica occurs in the yeast state and synthesizes an exopolysaccharide (EPS) capsule, which is eventually released into the culture fluid. It is composed of an alpha-1,3-D-mannan backbone, to which beta-1,2 side chains are attached, consisting of D-xylose and D-glucuronic acid. Potato dextrose broth (PDB) seemed to be an excellent medium for both growth of the yeast cells and synthesis of the EPS. This medium is composed solely of an extract of potatoes to which glucose was added. Yet an important disadvantage of this production medium is the presence of starch in the potato extract, since Tremella cells are not capable of metabolizing this component; furthermore, it coprecipitates upon isolation of the polymer [3]. In this respect, it was essential to remove the starch in order to achieve high polysaccharide production and recovery. A good method was the removal of starch through ultrafiltration of the PDB medium before inoculation of the strain. This resulted in an excellent starch-free medium in which other components essential for polysaccharide production were still present [3]. Through implementation of single and cyclic fed-batch fermentations with glucose feed, 1.6- and 2.2-fold increases in EPS yield were obtained, respectively. Lowering the carbon source level by using a cyclic fed-batch technique might decrease the osmotic effect of glucose or any catabolite regulation possibly exerted by this sugar on enzymes involved in EPS synthesis.

Effect of mycelial morphology on ergothioneine production during liquid fermentation of Lentinula edodes

“…5a). Similar results have been reported stating that an increased agitation speed enhances (Baets et al 2002;Sobczuk et al 2005). In contrast, a higher yield of ESH production (1.10 mg/g DW) was achieved in the fermentation with a lower agitation rate for 25 days of liquid fermentation (Fig.…”

Effect of Constant Glucose Feeding on the Production of Exopolysaccharides by Tremella fuciformis Spores

“…The strategy established in this study may be worth attempting with other mushroom fermentation processes for enhanced production of mushroom polysaccharides, particularly those with industrial potential. In fact, there are factors that most affect the production of exopolysaccharides by T. fuciformis spores [6] such as initial concentrations of carbon and nitrogen sources, initial pH, shear rates [12], dissolved oxygen, and aeration. Moreover, sporular morphological forms (e.g.…”

It's not all about us: evolution and maintenance ofCryptococcusvirulence requires selection outside the human host

“…In a clinical setting, the capsule has multiple functions including a reduction of host immune responses, regulation of phagocytosis by macrophages and providing an antioxidant defence mechanism inside macrophages [see references in (O'Meara and Alspaugh, )]. Although polysaccharide capsules are also important virulence factors in Gram‐negative and Gram‐positive bacterial pathogens [reviewed in (Park et al, )], Tremella mesenterica , a close non‐pathogenic relative of C. neoformans that grows primarily on dead tree branches, also produces a similar polysaccharide capsule (De Baets et al, ), as does Cryptococcus liquefaciaens , a related species commonly found in the high Arctic and hypersaline waters (Araujo, ). The capsule is thought to play an important role in environmental desiccation resistance (Granger et al, ; Park et al, ), which is consistent with the characterization of the ‘typical’ abiotic environment of Cryptococcus identified above.…”