A review of biological delignification and detoxification methods for lignocellulosic bioethanol production

Abstract

Future biorefineries will integrate biomass conversion processes to produce fuels, power, heat and value-added chemicals. Due to its low price and wide distribution, lignocellulosic biomass is expected to play an important role toward this goal. Regarding renewable biofuel production, bioethanol from lignocellulosic feedstocks is considered the most feasible option for fossil fuels replacement since these raw materials do not compete with food or feed crops. In the overall process, lignin, the natural barrier of the lignocellulosic biomass, represents an important limiting factor in biomass digestibility. In order to reduce the recalcitrant structure of lignocellulose, biological pretreatments have been promoted as sustainable and environmentally friendly alternatives to traditional physico-chemical technologies, which are expensive and pollute the environment. These approaches include the use of diverse white-rot fungi and/or ligninolytic enzymes, which disrupt lignin polymers and facilitate the bioconversion of the sugar fraction into ethanol. As there is still no suitable biological pretreatment technology ready to scale up in an industrial context, white-rot fungi and/or ligninolytic enzymes have also been proposed to overcome, in a separated or in situ biodetoxification step, the effect of the inhibitors produced by non-biological pretreatments. The present work reviews the latest studies regarding the application of different microorganisms or enzymes as useful and environmentally friendly delignification and detoxification technologies for lignocellulosic biofuel production. This review also points out the main challenges and possible ways to make these technologies a reality for the bioethanol industry.

Laccases as a Potential Tool for the Efficient Conversion of Lignocellulosic Biomass: A Review

“…Among them, the utilization of laccase enzymes has been widely investigated, showing to be effective in removing and/or modifying the lignin polymer, and in reducing the phenolic content of pretreated lignocellulosic materials [9,10]. The present work focuses on review the use of laccases as delignification and detoxification agents for the efficient conversion of lignocellulosic biomass into value-added products, with special accent in the lignocellulosic ethanol production.…”

Progress and obstacles in the production and application of recombinant lignin-degrading peroxidases

“…1 Two of the components of lignocellulose (cellulose and hemicellulose) are readily accessible for industrial processes because they are easily degraded by known enzymes and by chemical hydrolysis. 2 However, the third component (lignin) is much more resistant to degradation.…”

The Confounding Effects of Particle Size and Substrate Bulk Density on Phanerochaete chrysosporium Pretreatment of Panicum virgatum

“…Biological pretreatment is attractive because it is generally thought to be more environmentally benign than other pretreatments, given the mild reaction conditions needed, yet still results in reasonable product yields (Moreno et al 2014;Pinto et al 2012). In addition, the biological pretreatment has few side reactions, decreased energy demand, reduced reactor requirements (temperature/pressure), and does not form compounds that hinder downstream reactions (Moreno et al 2014).…”

“…Biological pretreatment is attractive because it is generally thought to be more environmentally benign than other pretreatments, given the mild reaction conditions needed, yet still results in reasonable product yields (Moreno et al 2014;Pinto et al 2012). In addition, the biological pretreatment has few side reactions, decreased energy demand, reduced reactor requirements (temperature/pressure), and does not form compounds that hinder downstream reactions (Moreno et al 2014). Biological pretreatment involves growing white rot, brown rot, or soft rot fungi on the lignocellulosic substrate (Shirkavand et al 2016) in a high-solids environment and allowing the fungal lignolytic enzyme system to deconstruct the lignin (Couto and Sanroman 2005).…”