Solvent-free polyglycerol polyricinoleate synthesis mediated by lipase from Rhizopus arrhizus

The enzymatic biosynthesis of polyglycerol polyricinoleate (PGPR) (E-476) is described in detail for the first time. Starting from polyglycerol and polyricinoleic acid, Rhizopus arrhizus lipase was used as catalyst. The reaction, which is really a reversal of hydrolysis, takes place in the presence of a very limited amount of aqueous phase. No organic solvent is necessary to solubilise the substrates, which allows a reaction medium solely composed of the necessary substrates to be used.Immobilisation of the lipase by physical adsorption onto an anion exchange resin provided good results in terms of activity, enzyme stability and the reuse of immobilised derivative. Using this immobilised derivative, PGPR with an acid value of 16 mg KOH/g was obtained, far above the requirements of the European Commission Directive 2008/84/EC (<6 mg KOH/g). In an attempt to force the reaction equilibrium towards the synthetic pathway, polyglycerol polyricinoleate was synthesised under controlled atmosphere in a vacuum reactor with dry nitrogen intake. This equipment allowed us to synthesise PGPR with an acid value of 4.9 mg KOH/g, which complies with the European Commission Directive and the results were entirely reproducible. This investigation represents a good starting point for using the enzymatic procedure in the industrial biosynthesis of PGPR.

Research highlights
► We have obtained for the first time the food emulsifier E-476 enzymatically.
► Obtaining E-476 has been carried out in the absence of solvents and immobilised enzyme, fulfilling the main premises of green chemistry.
► The improved quality of the final product and the energy savings, makes this process a serous alternative for the production of PGPR (E-476).