Abstract:

The conditions of ethanol precipitation for Athelia rolfsii exopolysaccharides (AEPS) were optimized by response
surface methodology. Moisture-retention capacity and viscosity stability of AEPS were also determined. Using AEPS yield
as the response variable, optimal ethanol precipitation process for AEPS was determined by Box-Behnken design based on
single factor tests. Compared to chitosan and urea, the moisture-absorption and moisture-retention capacities of AEPS were
also studied. In addition, the effects of temperature, pH and ion concentration (Mg2+, Ca2+, Na+, and K+) on the viscosity
stability of AEPS were examined. The optimal conditions of ethanol precipitation for AEPS were determined as follows: 3-fold
condensation of the fermentation supernatant before 17 h precipitation at 5 ℃ with an ethanol/fermentation supernatant
ratio of 1.7:1 (V/V). Under these conditions, the AEPS yield was 12.24 g/L. The moisture-absorption and moisture-retention
capacities of AEPS were superior to those of chitosan and urea. The optimal concentration for moisture-retention was
1 mg/mL (57 mPa·s). At temperatures in the range of 5–95 ℃, the lowest viscosity of AEPS was 51 mPa·s at 35 ℃.
However, AEPS viscosity was very stable in the pH range of 1 to 12 and at ion concentrations ranging from 0 to 1.0 mol/L.

Key words: Athelia rolfsii exopolysaccharides (AEPS), ethanol precipitation, moisture-absorption capacity, moisture-retention capacity, viscosity stability