Pilot scale isolation of exopolysaccharides from Streptococcus thermophilus DGCC7710: Impact of methodical details on macromolecular properties and technofunctionality.

Exopolysaccharides (EPS) from Streptococcus thermophilus provide similar technofunctionality such as water binding, viscosity enhancing and emulsifying effects as commercial thickeners at a significant lower concentration. Despite their high technofunctional potential, hetero polysaccharides from lactic acid bacteria are still not commercially used in unfermented foods, as the small amount of synthesised EPS calls for a high isolation effort. This study aims to analyse the macromolecular properties of EPS and cell containing isolates from S. thermophilus DGCC7710 obtained by different isolation protocols, and to link these data to the technofunctionality in model food systems. The EPS content of the isolates was affected by the microfiltration/ultrafiltration membranes used for cell removal/dialysis, respectively, and was 89% at maximum. There was no link between purity of the isolates, molecular mass (3 × 106 Da) and intrinsic viscosity (0.53 - 0.59 mL/mg) of the EPS. After adding EPS containing isolates to milk, gel stiffness after acidification increased by 25% at maximum, depending on the type and concentration of the specific isolate. Partly purified, cell containing isolates were effective at low absolute EPS concentration (approx. 0.1 g/kg) and therefore represent, together with their simple isolation protocol, an interesting approach to introduce microbial EPS into non-fermented products.