Biocatalytic selective acylation of technical lignins: a new route for the design of new biobased additives for industrial formulations

Abstract

In this article, we describe a proof of concept of the potential use of a biocatalytic process for the functionalization of technical soda lignins from wheat straw through the selective acylation of primary hydroxy groups of lignin oligomers by acetate or hexanoate, thus preserving their free, unreacted phenols. The selectivity and efficiency of the method, although they depend on the structural complexity of the starting material, have been proven on model compounds. Applied to technical lignins, the acylation yield is only moderate, due to structural and chemical features induced by the industrial mode of preparation of the lignins rather than to the lack of efficiency of the method. However, most of the physicochemical properties of the lignins, including their antioxidant potential, are preserved, advocating the potential use of these modified lignins for industrial applications.

Controlling stabilization of oil‐in‐water emulsions with lignins through fractionation, functionalization, and formulation

“…Transmethylation followed by GC-MS of GL inducted a typical hexanoylation yield of 1.2% wt/wt corresponding to 12% mol/mol of transesterification on the aliphatic hydroxyl groups present in the lignin fraction. 44 The SEC chromatogram of GL showed a SEC profile very similar to CL one (Figure S1), proving that hexanoylation does not have a major impact on the molar mass distributions of lignins.…”

“…Enzymatic hexanoylation of lignins fractions has been performed according to our recent work 44 and upon direct treatment of TL. TLs were solubilized in MEK (25 g/L) with ethyl hexanoate (1:1 mass ratio to lignins) and CAL-B (20% mass of lignins) and the enzymatic hexanoylation was conducted for 48 h. The enzymatic hexanoylation could be schemed in Figure 1.…”

“…The quantification of the hexanoylation yield has been achieved by transmethylation of GL followed by GC-MS and quantification of the methyl ester obtained gave the % (in wt/wt) of initial hexanoyl moieties grafted on lignins. 44…”

“…Therefore, Protobind 1000 grade lignins was selected as a good model of the TL, recovered from an alkali process, that are known to encounter few structural modifications compared to native lignins, thereby being more easily processable than kraft and bisulfite lignins. A novel class of lowgrafted bio-based lignins derivatives issued from a biocatalytic process, conducted according to our recent work, 44 was prepared. The solubility of the resulting lignins derivatives was studied and accordingly, lignins' solubilization in water was modulated through pH adjustment and solvent addition to incorporate them via an aqueous phase in O/W emulsions.…”