More value from biomass with enzyme-based technologies
Biocatalysts – a keystone in the foundation of bio-economy
Many if not most industrial chemical processes are dependent on catalysts – substances that accelerate chemical reactions without themselves being consumed in the catalyzed reaction and can continue to act repeatedly. Because of this, only very small amounts of catalyst are required to have a dramatic effect on the reaction rate. Development of the affordable durable and efficient catalysts was vital for the establishment and economic viability of fossil-based chemistry and material science. Nature is using catalysts for performing virtually all biochemical reactions happening inside organisms, and often outside as well. Those natural catalysts – or bio-catalysts – are protein molecules called enzymes.
Bio-catalysis very attractive in many industrial applications
It is logical to assume that bio-based economy would be largely relying on bio-catalysis. Extremely high specificity and selectivity as well eco-friendliness makes enzymes potentially very attractive in many industrial applications. In spite of wide use of the enzymes in food and feed industries, they do not so readily penetrate to the chemicals and materials sector and other industries due to harsh industrial process conditions and challenging cost-efficiency. Modern molecular biology and bioengineering pave the way to a much wider use of enzymes in industry by making it possible to adapt enzymes to performing in unnatural conditions. As opposed to whole microorganism bio-conversions, more common in the past, enzymes provide faster and safer processes with broader operational range.
As opposed to whole microorganism bio-conversions, more common in the past, enzymes provide faster and safer processes with broader operational range
MetZyme®s: toughest enzymes on the market
MetGen Oy (www.metgen.com) is a Finnish SME founded in 2008, specialising in the design, manufacturing and tailoring of industrial enzymes especially focusing on enzymes working in challenging environments. MetGen sees its mission in empowering industries to get most out of biomass through enzymatic solutions. The company is based in two locations – main primacies are in Kaarina (Finland) and second site is in Brightlands Chemelot campus, Sittard-Geleen (the Netherlands). Current enzyme portfolio is predominantly serving Pulp and Paper and Biorefinery industries. MetGen markets its enzymes under trademark MetZyme®.
Through multiple collaborations and public projects MetGen has developed a number of unique enzymes for biomass conversion to enable the emerging value chains in biorefineries.
One of the remarkable projects in this area was RETAPP – Rethink All Plastic Packaging (2015-2018) funded by the European Union Horizon 2020 Research and Innovation Programme. The project was focused on the utilization of wood-based feedstock, rather than agricultural sugars, to produce polyester PEF (polyethylene furanoate), which is a technically superior replacement of the bulk polyester PET (polyethylene terephthalate) currently used for most plastic bottles. The starting material for chemical synthesis of PEF is fructose, which consortium set off to produce from woody biomass. The consortium combined three partners embracing the entire value chain from wood to plastic:
- SEKAB E-TECHNOLOGY (Sweden), a technology provider for the woody biomass pretreatment and hydrolysis;
- Avantium (Netherlands), developer of the world-leading production process for PEF from fructose;
- MetGen, coordinator of the project, was providing enzymatic solutions for efficient biomass hydrolysis and sugar bio-conversion.
During this project, MetGen developed a new enzyme for converting wood-based un-purified glucose to fructose for further chemical transformations. This type of enzymes was known and widely commercially available, however, commercial enzymes thus far were very sensitive to inhibitors present in the lingo-cellulosic biomass. MetGen’s MetZyme PURECO® showed unprecedented performance in the un-purified biomass hydrolysate.
The technology has been demonstrated in the Biorefinery Demo Plant in Örnsköldsvik (Sweden): it can be further utilized by other projects and clients for covering the need for industrial cellulosic sugars production for downstream biochemical product development. The successful demonstration of the wood-to-fructose value chain during the ReTAPP project aids the market introduction of an economically feasible sustainable alternative for fossil-based feedstocks for the production of base chemicals and eventually materials.
No matter the question, lignin is the answer
Lignin is a major component of wood, comprising over 30% of its dry weight. It’s a complex organic cross-linked phenolic polymer providing rigidity and strength and giving the brown colour to the wood. In the biorefinery context, lignin is often mostly regarded as a recalcitrance factor, fermentation inhibitor, sugar stream contaminant etc. Frustrating experience of lignocellulosic bioethanol hype of the past years triggered formation of a broader view of the biorefinery concept and understanding that valorisation of lignin is a vital component of the economics of the entire biorefinery business.
Main hurdles of lignin valorisation are its diverse chemical composition, recalcitrance, and poor solubility due to high molecular weight and branched structure. Controlled fragmentation of lignin and its activation (increasing the number of hydroxyl groups) could lead to its use in higher value products such as binders, coatings, fillers and other. This could be achieved by controlled oxidation, causing spontaneous brakeage of the polymer chains as well as demethylation of methoxy groups resulting in additional hydroxyl moieties.
It is important to understand that lignin preparations of different (defined) molecular weights can be further valorised and utilized in various industrial applications. Thus, the target of lignin depolymerisation is to create lignin fractions that are bioequivalent, for example, to oil-based compounds used as resins, adhesives, composites and foams. In this view, it is not necessarily desirable to depolymerize lignin to monomers in its entirety. In MetGen, we believe that it is beneficial from the economic and environmental point of view to pursue a less energy intensive transformation of the starting material, followed by efficient separation, which will provide valuable fractions for various applications. With this strategy in mind, enzymatic approach seems very attractive. To address this issues MetGen set on to develop an enzyme that could oxidise lignin in its most water soluble state – in highly alkaline conditions. Such enzyme (a laccase MetZyme® PURECO) was developed and scaled to industrial multi-ton production scale. This is the first laccase on the market that works in alkaline conditions, moreover it is fully functional and stable at pH as high as ten to eleven. The enzyme was able to decrease molecular size of raw lignin and substantially increase the number of free hydroxyl groups.
In order to demonstrate the relevance of this enzyme for industrial lignin valorisation, MetGen started to build a continuous process of lignin oxidation and separation to fractions of various molecular sizes. The experiments were carried out in the in-house pilot facility where all the process parameters could be controlled and process outcome carefully studied. To our great surprise and delight, properties of the out-coming lignin fractions could be modulated by tuning process parameters and reaction conditions. The degree of de-methylation and predominant molecular size could be controlled as well as other properties. It was possible, for example, by changing process conditions to obtain solvent-soluble lignin forming a viscous liquid ‘lignin oil’ when dissolved in small amount of solvent. Thus MetGen was able to build a lignin refining technology based on the enzymatic oxidation process.
Going industrial
These developments, however exciting, were bound to be meaningless if not taken further to the relevant application testing to validate the opportunities this technology was opening and direct further process development to the properties desirable for a particular application. Having a number of pilot-scale demonstrated technologies, and having built solid network with players from various fields of the bioeconomy, MetGen and partners aimed for an industrial demonstration of the entire biorefinery concept. In a fierce competition, the consortium won the funding of the flagship project of 2018 (the only flagship project in the bioeconomy sector) under the EU’s Horizon 2020 programme’s Bio-Based Industries financial instrument. SWEETWOODS is a 43-million-euro joint pilot project of which 21 million is granted by the EU. The project is implemented through collaborative efforts of nine partner companies. The SWEETWOODS project aims to develop a first-of-a-kind biofractionation flagship plant in Estonia that uses sustainable hardwood biomass. The process combines innovative pre-treatment technology with enzymatic solutions to provide sugar recovery levels of over 90 per cent with exceptionally high-quality lignin. Sugars and lignin can be further processed and converted to high-value biomaterials capable of replacing fossil based chemicals in a wide range of products. The project, which uses wood processing residues as a feedstock, will lead to wood-based biomaterials being produced on an industrial scale for the first time.
