Exopolysaccharide production by filamentous fungi: the example of Botryosphaeria rhodina

One-hundred and five fungal strains, belonging to 46 different species, were screened for exopolysaccharide production. Phytopathogenicity and, in particular, inability to produce conidia, were physiological characteristics positively associated and correlated with the fungal ability to produce polysaccharides. Among the 29 positive strains, Botryosphaeria rhodina DABAC-P82 was the most interesting reaching, when grown on optimal nitrogen source and concentration (NaNO3 and 2.0 g l(-1), respectively) and culture medium pH (3.7), 17.7 g l(-1) of exopolysaccharide production after only 24 h of fermentation; yield and productivity were 0.69 g g(-1) and 0.73 g l(-1) h(-1), respectively. The purified polysaccharide was characterised as a homopolysaccharide of glucose with a molecular weight of 4.875.10(6) Da. Studies of structural analysis indicated the presence of beta-1,3 and beta-1,6 linkages; the EPS structure was very similar to that of scleroglucan.