Propyl gallate: enzymatic synthesis in a reverse micelle system

Tannase entrapment in reverse micelles (RM) for the production of the antioxidant propyl gallate (PG) from tannic acid (TA) was studied. The phase diagram of 0.2 m sodium 1,2 bis(2-ethylhexylcarbonyl) 1-ethane sulfonate (AOT) in heptane, propanol, water, TA, and buffering ions was analyzed to select the appropriate conditions for successful enzymatic activity. Domains where RM are presumably formed were defined. In mixtures of homogeneous domains consisting of 0–20% propanol, 5–7% H2O, and 0.1–0.3% TA, favorable results were obtained. The yields of PG production from TA were found to be considerably higher than in aqueous solutions. The dynamics of the reaction were studied and critical pH dependence of the enzymatic activity in the micellar system was observed. A preliminary reactor model employing the RM-entrapped enzyme was considered, and the material flow estimation was made. Thus 1 kg TA, 13 kg propanol, 1 g tannase, and 50 l of hydrocarbon/AOT will be required for each kilogram of PG produced. Further crucial questions regarding the system and its commercial application have been defined.