2.6.3 Final rectification of PDO
The residue after separating the methanol and methyl esters was mixed with water at a mass ratio of 2:1. Subsequently, 1% active carbon (w/w) was added, and 50% NaOH solution was used to adjust the pH to 9. The mixture was then heated up to 60 oC with stirring for 1 h. The active carbon was removed by micro-filtration and the obtained permeate was fed to the rotary evaporator for complete water removal as described in 2.6.1. Finally, colorless and odorless PDO was evaporated and collected under the heating temperature of 145oC and vacuum pressure 20 mbar. The residue containing most of the glycerol was directly reused in fermentation or in the DSP for salt suspension.