Progress in understanding and overcoming biomass recalcitrance: a BioEnergy Science Center (BESC) perspective

Abstract

The DOE BioEnergy Science Center has operated as a virtual center with multiple partners for a decade targeting overcoming biomass recalcitrance. BESC has redefined biomass recalcitrance from an observable phenotype to a better understood and manipulatable fundamental and operational property. These manipulations are the result of deeper biological understanding and can be combined with other advanced biotechnology improvements in biomass conversion to improve bioenergy processes and markets. This article provides an overview of key accomplishments in overcoming recalcitrance via better plants, better microbes, and better tools and combinations. A perspective on the aspects of successful center operation is presented.

Economic impact of yield and composition variation in bioenergy crops: Populus trichocarpa

“…The identification of the function of key genes for economic phenotypes allows either targeted genetic engineering or improved breeding by genomic selection 3 . High‐throughput pipelines have been developed that allow production of modified biomass targeting individual genes related to plant cell‐wall chemistry and anatomy 4,5 . These phenotypes require detailed analysis to determine which changes can be optimized for economically advantageous feedstock production.…”

“…3 High-throughput pipelines have been developed that allow production of modified biomass targeting individual genes related to plant cell-wall chemistry and anatomy. 4,5 These phenotypes require detailed analysis to determine which changes can be optimized for economically advantageous feedstock production. Cell-wall composition can be obtained through traditional wet chemistry methods but often involves both labor and time-intensive measurements.…”

Improved lignocellulose saccharification of a Miscanthus reddish stem mutant induced by heavy‐ion irradiation

“…One is the development of advanced pretreatment procedures to sufficiently deconstruct cell wall polymers and release moderate fermentable sugars entrapped (Holwerda et al., 2019; Sun et al., 2016). The other lies in the breeding of less recalcitrant bioenergy crops, which can be obtained through the genetic modification of plant cell wall compositions, or alternatively via the screening of natural germplasms or mutants induced by various physical and chemical mutagens (Gilna et al., 2017; Himmel et al., 2007; Kalluri et al., 2014). In this study, taking advantage of heavy‐ion irradiation, we successfully screened a Miscanthus mutant with a high lignocellulose saccharification efficiency without compromising biomass yield.…”

“…Genetic modification in bioenergy crops to produce less recalcitrant lignocellulosic biomass has attracted increasing attention and been successfully manipulated in several crops in the last decade (Gilna, Lynd, Mohnen, Davis, & Davison, 2017; Kalluri et al., 2014). For instance, downregulation of the expression of caffeic acid‐o‐methyltransferase (COMT) in switchgrass ( Panicum virgatum L.) leads to a significant reduction in lignin content and markedly improves the saccharification efficiency of lignocellulose (Fu et al., 2011).…”

Plant cell wall hydrolysis process reveals structure–activity relationships

“…Unfortunately, the crystalline nature of cellulose and the embedded connection with lignin in biomass leads to poor accessibility and weak degradation of cellulose during biomass processing [ 6 ]. Non-polysaccharide aromatic polymer lignin, poses significant resistance to microbial and enzymatic deconstruction [ 7 ]. Therefore, a selective and efficient pretreatment system and a hydrolysis process to make cellulose more accessible for conversion, are necessary to achieve efficient biomass utilization.…”