The FunTech project was a feasibility study on the development of improved biomass-specific enzyme treatment for the valorization of lignin fractions from lignocellulose substrates.
Lignin is a major biomass constituent that provides firmness and rigidity to plants. The amount of lignin produced each year in the pulp and paper industry is approximately 50 million tons, of which only 2 percent is being used for the production of chemicals, while 98 percent is used as fuel for electricity and heat production.
Potential for lignin
Assuming that half of the ethanol requirement in the EU in 2020 (estimated at 50 - 60 million tons) will be produced from lignocellulose, an additional 20 million tons of lignin will become available from biorefinery processes with a calorific value of approximately 500 PJ. Added to the estimated amount of lignin in the European pulp and paper industry this gives a gross potential of at least 1000 PJ raw material in the form of lignin.
Novel approach to valorize lignin fractions
The technology to be ultimately developed will require extensive efforts and profound research. This feasibility study addressed the first step in a novel approach to valorize lignin fractions from lignocellulosic biomass into base chemicals.
The feasibility study aimed at the development and use of a number of recombinant esterase enzymes derived from hemi-cellulolytic fungi to open up bonds between the lignin moieties and the hemi-cellulose chains in plant biomass. Thus, FunTech aimed at a better delignification of lignocellulose to improve saccharification for bioethanol production and also to obtain a lignin fraction with less sugar contaminations attached to the lignin moiety. Moreover, it was anticipated that this process would involve a mild enzyme treatment in addition to the mild acid biomass pre-treatment. A desktop study included an update of currently available literature on the microbial or enzymatic conversion of lignin derivatives into a number of aromatic precursors for industrial base chemicals and materials.
Results demonstrate that the two recombinant Fae enzymes tested (feruloyl esterase types A [FaeA] and B [FaeB] from Aspergillus niger), as well as two glucuronyl esterase enzymes GueA (or GEA) from A. terreus and a novel GueD (or GED) from Dictyoglomus thermophilum, were well-expressed in Pichia pastoris for FaeA and FaeB yielding grams of enzyme per liter culture supernatant.
All enzymes showed activity (at temperatures ranging from 30 to 50°C), of which A. niger FaeA and A. terreus GE were most active (against artificial substrates methyl ferulate and 4-O-methyl-D-glucuronic acid, respectively). In addition, the results point out that the recombinant enzymes were active against mild acid pretreated wheat straw biomass. Treatment with FaeA resulted in the predominant release of the C5-sugar arabinose with the highest yield after 40h of incubation. Addition of FaeA to the commercial ligno-cellulolytic enzyme mixture GC220 further increased the arabinose yield. Treatment with FaeA also resulted in the prominent release of two aromatic compounds, ferulic acid and 4-hydroxybenzoic acid. These aromatic compounds were also identified to be of commercial interest in the desktop study.
Based on genome analysis, Chaetomium globosum was selected as an extremophilic species with a high potential for the production of ligno-cellulose degrading enzymes. When cultivated on pretreated wheat straw the highest production was observed for β-xylosidase (BXL) and β-glucosidase (BGL), but lower activities of the other enzymes were also detected.
The FunTech project has demonstrated proof of principle for the aims anticipated and provides an excellent starting point for further (commercial) exploitation of the results obtained.