Lignin from Annual Plants as Raw Material Source for Flavors and Basic Chemicals

Abstract

The enzymatic conversion of lignins, possibly in combination with electrochemical oxidation, makes aromatics such as syringol, guaiacol, vanillin and catechol available in the qualities required by the fragrance industry. The lignins were obtained by soda digestion from wheat straw and Miscanthus, characterized and then converted with laccases. The overall yield amounted up to 9 wt % with a product spectrum confined to four substances. Catechol was the major product, with a fraction of 75 %. It can easily be isolated by extraction with acetone.

Liquid Membranes for Efficient Recovery of Phenolic Compounds Such as Vanillin and Catechol

“…As already mentioned, the focus during extraction is on vanillin, for which reason the optimal conditions were defined for this compound. However, the previous enzymatic conversions mainly led to catechol [ 3 , 26 ], thus the optimal extraction parameters obtained for vanillin recovery will be set and used for the study of the recovery of catechol.…”

“…During lignin degradation, the monomers are usually present in different concentrations. Jahn et al [ 3 ] found that 1% vanillin and up to 6% catechol were generated from lignin after enzymatic conversion. With a 1 g/L lignin solution, this corresponds to concentrations of 10 mg/L and 60 mg/L, respectively.…”

“…In this sense, it could be interesting to investigate a smaller range (< 50 mg/L) to verify that the concentration of the monomer has no influence on its extraction. Lower concentrations are also interesting since lignin conversion also results in lower concentrations of other monomers [ 3 , 26 ], such as syringol or guaiacol. Moreover, the solvating extractants seem to be promising using FSSLM instead of DeOH to avoid carrier loss problems because of the higher water solubility compared to TBP/Cy923.…”

“…However, the transport differences were not high enough to consider an effective selective separation of these monomers. The use of the stream obtained after enzymatic conversion as feed phase could be a promising alternative in further research to investigate the selective separation, since the concentration of both monomers differs considerably, being the conversion of catechol in a range from 5 to 7% higher than vanillin [ 3 , 26 ]. Therefore, the diffusion coefficient differences between these monolignols could allow the complete catechol transport avoiding the co-transport of vanillin.…”

“…Besides vanillin, other aromatic substances such as guaiacol, acetovanillone, syringol, and catechol arise from lignin degradation. These are used in various fields, such as smoking flavor and sweet aroma in the food and fragrance industry or as fine chemicals in dyes, antiseptics, antioxidants as well as in other applications [ 3 , 4 , 5 ]. The high reactivity of vanillin renders it susceptible to oxidation to vanillic acid, though, which subsequently may decarboxylate to give guaiacol.…”