Bringing plant cell wall‐degrading enzymes into the lignocellulosic biorefinery concept

Abstract

Recent decades have seen the growth of immense interest in lignocellulosic biomass conversion technologies. This interest is motivated by their huge potential for energy and bioproduct generation and reduced dependency on non-renewable feedstocks, leading to improved air quality and reduced emission of greenhouse gases. It is in this context that the lignocellulose biorefi nery concept arises. Among the lignocellulose conversion technologies available, enzymatic conversion has emerged as a promising candidate, since it represents a biomass management approach that integrates recycling and remediation in an environmentally friendly manner. Although already in existence, biorefi neries employing enzymatic conversion of lignocellulose are at an incipient stage. There remain many operational diffi culties, resulting in a very costly overall process that is refl ected in product price, reducing market competitiveness. Therefore, much research is still needed to improve the operational and fi nancial feasibility of this process. This paper covers general biorefi nery concepts, as well as new and associated concepts, such as the circular economy, bioeconomy, and waste biorefi nery. Subsequently, the global outlook, including examples of currently existing enzyme-based lignocellulose biorefi neries and their status, is described. The main technical and economic challenges are also discussed, and various potential tools for the optimization of biomass degradation in enzyme-based biorefi neries are presented. Finally, the future perspectives for the sector are considered, and models of the ideal biorefi nery and globally integrated biorefi nery hubs are proposed. These models may contribute to the future establishment of such biorefi neries as competitive industries, consistent with the sustainable bioelectro economy paradigm. (Brazil). His research focuses on the valorization of Brazilian agroindustrial residues, mainly sugarcane bagasse, as substrate for enzyme synthesis and conversion into bioproducts. He is currently involved in the investigation of pretreatment technologies to enhance holocellulase production when employing lignocellulosic materials as substrate for filamentous fungi. Raissa P. VazRaissa P. Vaz is a PhD student at the Department of Cell Biology of the University of Brasília (Brazil). Her work is focused mainly on immobilization, characterization, and applications of lignocellulose-degrading enzymes. Edivaldo X.F. FilhoEdivaldo X.F. Filho is Professor of Biochemistry at the Department of Cell Biology of the University of Brasília (Brazil). He conducts research in the fields of biochemistry and biotechnology, investigating the production, purification, characterization, and biotechnology applications of lignocellulose-degrading enzymes from filamentous fungi.

Analysis of the Transcriptome in Aspergillus tamarii During Enzymatic Degradation of Sugarcane Bagasse

“…Whilst the burning of bagasse currently serves as an energy source in bioethanol mills, as this biomass represents approximately one-third of the energy content of the crop, the conversion of the lignocellulose component of the cell wall into fermentable hexose (glucose) and pentose (e.g., D-xylose and L-arabinose) sugars offers considerable potential for increased 2G ethanol production, potentially by up to 40% (Amorim et al, 2011 ). Two Brazilian cellulosic ethanol plants came into operation in 2014, with capacities planned for production of up to 1 billion liters of ethanol per year from bagasse (Silva et al, 2017 ).…”

Transcriptome Profiling-Based Analysis of Carbohydrate-Active Enzymes in Aspergillus terreus Involved in Plant Biomass Degradation

“…The potential of biorefinery systems in the 21st Century is considerable, not only in terms of the contribution to global sustainable energy supply in the transition to greenhouse gas neutrality, but also in terms of other bio-products (e.g., chemicals, amino acids, polymers) in a circular economy format that favors socio-economic development ( King et al, 2010 ; Jungmeier et al, 2013 ; Silva et al, 2017 ). Countries with substantial agricultural industries, such as Brazil, produce large quantities of lignocellulosic waste, making them strategically placed to contribute to biorefining, either through the export of biomass materials or through in-country development of biorefinery hubs within agricultural zones.…”

“…Lignin can also be employed in the production of chemical commodities and polymers ( Windeisen and Wegener, 2012 ; de Jong and Gosselink, 2014 ). Given the global abundance of agricultural plant biomass residues, there is considerable potential today in such biorefinery-based applications in the production, amongst others, of bioethanol, industrial enzymes, organic acids, amino acids, secondary metabolites, pharmaceutical products, food, and animal feed ( Silva et al, 2017 ).…”

“…The enzymatic hydrolysis of plant lignocellulosic biomass is currently regarded as the most efficient biomass conversion method ( Silva et al, 2017 ). Here, enzyme consortia with different specificities are required for lignocellulose breakdown, including cellulases, hemi-cellulases, ligninases, lytic polysaccharide mono-oxygenases (LPMOs) and cellobiose dehydrogenases (CDHs), together with the action of proteins such as swollenins and expansins ( Van Dyk and Pletschke, 2012 ).…”

“…Here, enzyme consortia with different specificities are required for lignocellulose breakdown, including cellulases, hemi-cellulases, ligninases, lytic polysaccharide mono-oxygenases (LPMOs) and cellobiose dehydrogenases (CDHs), together with the action of proteins such as swollenins and expansins ( Van Dyk and Pletschke, 2012 ). Whilst such hydrolysis of plant cell wall polysaccharides to simple monomers has been a subject of considerable study, improved cost efficiency of enzymatic hydrolysis is essential for enzyme-based lignocellulosic biorefineries ( Maijala et al, 2012 ; Silva et al, 2017 ).…”