Lignocellulose Decomposition by Microbial Secretions

Abstract

Carbon storage in terrestrial ecosystems is contingent upon the natural resistance of plant cell wall polymers to rapid biological degradation. Nevertheless, certain microorganisms have evolved remarkable means to overcome this natural resistance. Lignocellulose decomposition by microorganisms comprises an essential step in closing the loop of the global carbon cycle as it facilitates the recycling of carbon reposited in the form of structural polymers in plant cell walls. The significance of microbial decomposition of lignocellulose has recently risen to greater heights with the revisitation of the potential of lignocellulosic biomass as a valuable and abundant feedstock for the renewable energy and bioproducts industry. The scope of this chapter is to succinctly touch upon the composition of lignocellulosic biomass, the major enzymes involved in decomposing lignocellulosic biomass, and the fungi and bacteria that secrete these enzymes.

Lignin degradation: microorganisms, enzymes involved, genomes analysis and evolution

“…These enzymes are usually secreted by given microorganisms as a family of isozymes whose relative composition and isoelectric points (pI) vary depending on the growth medium and nutrient conditions (Santhanam et al. 2012 ). The globular structure of LiP isolated from P. chrysosporium is composed of eight major and eight minor α-helices with limited β components and is organized into two domains that form an active center cavity composed of a heme-chelating single ferric ion (Choinowski et al.…”

Multi-catalysis reactions: new prospects and challenges of biotechnology to valorize lignin

“…However, they do not mineralize lignin to a large extent (Buswell and Odier 1987). These bacteria produce several extracellular enzymes that are involved in the degradation of lignocellulosic biomass like peroxidases, cellulases, and esterases (Santhanam et al 2012). However, at present, the enzymology of bacterial lignin degradation is not well understood (Bugg et al 2011).…”

Conversion of ammonia‐pretreated switchgrass to biofuel precursors by bacterial–fungal consortia under solid‐state and submerged‐state cultivation

“…Conversion of lignocellulosic feedstocks, such as switchgrass, requires a number of enzymes working synergistically to break down cellulose, hemicelluloses and lignin (Santhanam et al . ). The physical process of reducing the particle size, as observed in the rumen (Desvaux ) and termites (Watanabe and Tokuda ), increases the saccharification efficiency, (Vidal et al .…”

“…Its deconstruction is the rate-limiting step in this overall process. Conversion of lignocellulosic feedstocks, such as switchgrass, requires a number of enzymes working synergistically to break down cellulose, hemicelluloses and lignin (Santhanam et al 2012). The physical process of reducing the particle size, as observed in the rumen (Desvaux 2006) and termites (Watanabe and Tokuda 2010), increases the saccharification efficiency, (Vidal et al 2011) while the chemical removal of lignin increases susceptibility of the substrate to enzymes (Kumar et al 2009).…”

“…The chemical composition and structural organization of different feedstocks varies considerably (Malherbe and Cloete 2002;Pauly and Keegstra 2010;Santhanam et al 2012). These compositional factors emphasize that a single enzyme system may not be able to convert all the available lignocellulosic biomass feedstocks to soluble carbohydrates efficiently and, furthermore, different lignocellulosic biomass feedstocks may require different arsenals of enzymes or the same enzymes, but present in different proportions, for efficient conversion.…”