Chemoselective biocatalyzed production of biovanillin from vanillic acid.

PALAZZOLO M; MASCOTTI ML; LEWKOWICZ E; KURINA SANZ MB

Concepción

Simposio; 3rd Lignobiotech Symposium on Biotechnology applied to Lignocelluloses; 2014

Centro de Biotecnología, Concepción, Chile. Co-organiser: Unidad de Desarrollo Tecnológico, UDT

Vanillin is widely commercialized due to its organoleptic properties. As regulations demand, vanillin produced in biotechnological processes is distinguished from the chemically-obtained one by the biolabel. Most of the biocatalyzed procedures for its preparation involve the use of biobased ferulic acid as starting material. Although vanillic acid (VA) is also suitable as substrate and readily-available from lignin in large amounts, it is not often employed because of the occurrence of secondary reactions leading to lower vanillin yields (1). Hence, it becomes interesting to find efficient microbial catalysts for the production of biovanillin out of VA. Based on literature reports, we ran a screening to search for carboxylic acid reducing activity in different microorganisms (2) using VA as model substrate. Among these, Aspergillus sp. was the only strain capable of reducing the acid to the aldehyde. Thus, this species was selected to develop a biotechnological process for the production of vanillin with the biolabel from VA. In order to determine how much substrate could be transformed by the microbial catalyst, several biotransformations using VA loadings from 0.5 g/L to 8 g/L were carried out. Interestingly, Aspergillus sp. was not only active toward all the substrate range, but also exhibited complete chemoselectivity to the aldehyde in every case. Furthermore, using 0.5 g/L to 2 g/L of VA, complete conversions where reached after only 48 h. The substrate concentration was pushed even further to reach 10 g/L, but VA was fairly soluble in the reaction conditions. The highest productivity was observed when adding 2 g/L of substrate to the reaction flask (0.04 g/L.h). To improve this result, we tested a fed-batch mode. Thus, an experiment adding an initial dose of VA at 2 g/L, and then loading two equal substrate pulses at 48 h and 96 h, respectively was conducted. At 48 h of bio-reaction, Aspergillus sp. exhibited the behavior observed in standard conditions, but then an unknown elicitation product was detected in the reaction media. To sum, we designed a simple, single-step biocatalyzed process for the production of biovanillin from VA in a highly chemoselective fashion. Besides, since the employed starting material is both non-toxic and readily-available from lignocellulosic biomass, the developed procedure is not only sustainable but also economically feasible for commercial purposes.