Purification of the mother liquor sugar from industrial stevia production through one-step adsorption by non-polar macroporous resin

Steviol glycosides (SGs)-enriched mother liquor sugar (MLS) used to be considered as a by-product of industrial stevia production. This work developed an efficient purification strategy to remove impurities from MLS. A non-polar macroporous adsorption resin (MAR) NDR-1 was selected as the adsorbent and ethanol solution was used as the mobile phase. The adsorption ratio of SGs and impurities was highly affected by ethanol concentration (v/v) due to the polarity difference and competition. In particular, in 25% (v/v) ethanol solution, SGs were mostly adsorbed on NDR-1 while impurities were completely dissolved in ethanol solution. After static adsorption in 25% ethanol solution and desorption in pure ethanol, the impurity content of MLS was decreased from 34.15% to 12.88%, with a high adsorption ratio of 92.24%. At the same condition, dynamic adsorption presented a better purification result with low impurity content of 4.78% and high SGs recovery rate of 89.88%.