Chemicals from agricultural biomass: chemoenzymatic approach for production of vinylphenols and polyvinylphenols from phenolic acids

Abstract

A two-step chemoenzymatic process for the preparation of polyvinylphenols from phenolic acids (PAs), being abundant aromatic constituents found in agricultural biomass, was developed. In the first step, conversion of 4-hydroxycinnamic acid derivatives to the corresponding vinylphenols, mediated by a recombinant phenolic acid decarboxylase, was evaluated using a variety of bioprocessing technologies that include biphasic whole cell and cell free extract biotransformations, a combination of biocatalyst with adsorbent resins for in situ product recovery, and fixed bed reactors using immobilized whole cells. The best yield (90%) with a high space time yield of 4.83 g/l/h was the result of a combination of crude enzyme extracts of the recombinant Escherichia coli (E. coli) with water immiscible organic solvents such as toluene. In the second step, cationic and radical polymerizations were tested to produce polyvinylguaiacol (PVG) from vinyl phenols. Characterization of PVG by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and nanoindentation test are reported here for the first time. The feasibility of the chemoenzymatic process for the production of aromatic polymers from biomass was demonstrated by the production of polymers from a mixture of ferulic acid (FA) and p-coumaric acid (pCA), obtained from alkaline hydrolysis of corn bran. Interestingly, nanoindentation tests showed that both PVG and “mixed” PVG polymers showed significantly higher performances than a commercial polystyrene polymer.

Keywords

• biorefinery
• biotransformation
• chemoenzymatic synthesis
• green polymers
• phenolic acids