Destructuring plant biomass: Focus on fungal and extremophilic cell wall hydrolases

Abstract

The use of plant biomass as feedstock for biomaterial and biofuel production is relevant in the current bio-based economy scenario of valorizing renewable resources. Fungi, which degrade complex and recalcitrant plant polymers, secrete different enzymes that hydrolyze plant cell wall polysaccharides. The present review discusses the current research trends on fungal, as well as extremophilic cell wall hydrolases that can withstand extreme physico-chemical conditions required in efficient industrial processes. Secretomes of fungi from the phyla Ascomycota, Basidiomycota, Zygomycota and Neocalli-mastigomycota are presented along with metabolic cues (nutrient sensing, coordination of carbon and nitrogen metabolism) affecting their composition. We conclude the review by suggesting further research avenues focused on the one hand on a comprehensive analysis of the physiology and epigenetics underlying cell wall degrading enzyme production in fungi and on the other hand on the analysis of proteins with unknown function and metagenomics of extremophilic consortia. The current advances in consolidated bioprocessing, altered secretory pathways and creation of designer plants are also examined. Furthermore, recent developments in enhancing the activity, stability and reusability of enzymes based on synergistic, proximity and entropic effects, fusion enzymes, structure-guided recombination between homologous enzymes and magnetic enzymes are considered with a view to improving saccharification.

The feruloyl esterase genes are required for full pathogenicity of the apple tree canker pathogen Valsa mali

“…Most plant pathogens secrete a complex mixture of hydrolytic enzymes, which enable the pathogens to penetrate and infect the host (Kubicek et al, 2014). These extracellular hydrolytic enzymes are called cell wall-degrading enzymes (CWDEs) (Guerriero et al, 2015;Kikot et al, 2009;Walton, 1994). CWDEs are essential for phytopathogens that do not have specialized penetration structures (Kikot et al, 2009).…”

Lignocellulosic biomass: Biosynthesis, degradation, and industrial utilization

“…Relieving peroxidases of substrate (including H 2 O 2 ) inhibition and product inhibition is essential if efficient degradation of lignin from lignocelluosic biomass is to be achieved in an industrial context . One possible way to overcome substrate and product inhibition of peroxidases is to immobilize enzymes on nano‐magnetic particles that can be easily separated from the reaction products by using a magnet [ and references therein, 82]. The most interesting part of the study was that VP showed synergistic activation when both LiP and MnP were simultaneously and equally active compared to when either MnP or LiP was active alone .…”

Advances in Genetic Manipulation of Lignocellulose to Reduce Biomass Recalcitrance and Enhance Biofuel Production in Bioenergy Crops

“…Until now, lignin biosynthesis have been recognized in various plant species in particular in transgenic and genetic mutants plants (Table 2). For instance, in Arabidopsis overexpression of CCoAOMT results in enhanced plant height with concomitant increase in lignin compared to control plants [105], In addition, in sorghum four site mutations of COMT, have shown lower levels of lignin and improved biomass digestibility [106], while RNAi silencing of the Pv4CL1 gene in transgenic switchgrass leads to reduced lignin content and improved fermentable sugar yields [107]. Moreover, in sugarcane RNAi suppression of SbCOMT gene reduces lignin content and recalcitrance [108].…”