Abstract:

Foam separation was used for purifying polysaccharides from Lycium barbarum L. (LBPs) in this paper. LBPs
were detected by phenol-sulphuric acid method and evaluated by enrichment ratio (E) and recovery (R). The effects of
dilution fold, initial pH and gas velocity on separation efficiency were assessed based on a fitting model proposed by
response surface methodology with Box-Behnken design. The optimal levels of the three factors were established and
validated. A further study was performed to kinetically investigate the purification process. As a result, when dilution
fold was 7.6, initial pH 3.42, and gas velocity 295 mL/min, maximum predicted values of E and R (2.57 and 57.31%,
respectively) were obtained, indicating a relative error of 6.6% and 6.5% compared with the experimental values (2.41 and
61.28%), respectively. Kinetic experiments showed that the process could be described as a first-order reaction with an
equivalent rate constant of 0.006 02 min-1. This study has provided a novel method for purification of LBPs, and the kinetic
process may provide valuable guidance for enhancing the purification efficiency.

Key words: Lycium barbarum polysaccharides, foam separation, phenol-sulphuric acid method, response surface methodology, kinetic analysis