Cost-effective optimized scleroglucan production by Sclerotium rolfsii ATCC 201126 at bioreactor scale. A...

Exopolysaccharide (EPS) secretion by Sclerotium rolfsii ATCC 201126 in submerged cultures, already identified as high-osmolarity responsive, was assessed by reducing C-source without compromising EPS yields. A designed medium with 80 g sucrose L^-1 (MOPT₈₀) was tested at 3 L-bioreactor scale at different temperature, agitation, aeration and pH (uncontrolled vs. controlled) values. Optimal operative conditions (200 rpm, 28 °C, 0.5 vvm and initial pH -pH_i- 4.5) were validated, as well as the possibility to work at pH_i 5.5 to reduce biomass production. Purified EPSs produced in MOPT₈₀ at optimal and other valid operative conditions exhibited refined grade (<1 % proteins and ash, 3-4 % reducing sugars, 87-99 % total sugars). EPS purity, M_W and rheological parameters led to discourage pH controlled at 4.5. Relatively constant M_W (6-8 × 10⁶ Da) and outstanding viscosifying ability were found. Polyphasic EPS analysis (titre, purity, macromolecular features and rheological fitness) would support to properly select production conditions.