Fungal Bioconversion of Lignocellulosic Residues; Opportunities & Perspectives

Abstract

The development of alternative energy technology is critically important because of the rising prices of crude oil, security issues regarding the oil supply, and environmental issues such as global warming and air pollution. Bioconversion of biomass has significant advantages over other alternative energy strategies because biomass is the most abundant and also the most renewable biomaterial on our planet. Bioconversion of lignocellulosic residues is initiated primarily by microorganisms such as fungi and bacteria which are capable of degrading lignocellulolytic materials. Fungi such as Trichoderma reesei and Aspergillus niger produce large amounts of extracellular cellulolytic enzymes, whereas bacterial and a few anaerobic fungal strains mostly produce cellulolytic enzymes in a complex called cellulosome, which is associated with the cell wall. In filamentous fungi, cellulolytic enzymes including endoglucanases, cellobiohydrolases (exoglucanases) and β-glucosidases work efficiently on cellulolytic residues in a synergistic manner. In addition to cellulolytic/hemicellulolytic activities, higher fungi such as basidiomycetes (e.g. Phanerochaete chrysosporium) have unique oxidative systems which together with ligninolytic enzymes are responsible for lignocellulose degradation. This review gives an overview of different fungal lignocellulolytic enzymatic systems including extracellular and cellulosome-associated in aerobic and anaerobic fungi, respectively. In addition, oxidative lignocellulose-degradation mechanisms of higher fungi are discussed. Moreover, this paper reviews the current status of the technology for bioconversion of biomass by fungi, with focus on mutagenesis, co-culturing and heterologous gene expression attempts to improve fungal lignocellulolytic activities to create robust fungal strains.

Lignocellulosic Biomass Utilization Toward Biorefinery Using Meshophilic Clostridial Species

“…Interestingly, the same enzyme family may contain members from bacteria, fungi, and plants with several different activities and substrate specifications [48]. However, fungal cellulases (hydrolysis of β-1,4-glycosidic bonds) have been mostly found within a few GH families including 5,6,7,8,9,12,44,45,48,61, and 74 [47,49]. Cellulases have a small independently folded CBM that is connected to the catalytic domain by a flexible linker [48].…”

“…However, fungal cellulases (hydrolysis of β-1,4-glycosidic bonds) have been mostly found within a few GH families including 5,6,7,8,9,12,44,45,48,61, and 74 [47,49]. Cellulases have a small independently folded CBM that is connected to the catalytic domain by a flexible linker [48]. The CBMs are responsible for binding the enzyme to the crystalline cellulose, and thus enhance the enzyme activity [38].…”

An Overview on Fungal Cellulases with an Industrial Perspective

“…Increasing concern regarding the environmental pollutions and the exhaustion of fossil fuels compelled us to exploit alternative renewable energy resources so as to meet the ever increasing energy requirements [1]. Now-a-days, the concept of waste-to-energy has become the primary focus of many industries with an economic perspective, and sustainable processes signifying the utilization of biomass judiciouslythe most abundant organic renewable resource accounting for around 10-14% of the world's energy supply.…”

Using an artificial neural network to predict the optimal conditions for enzymatic hydrolysis of apple pomace

“…The production of biofuels from lignocellulosic wastes has received attention from researchers around the world (Dashtban et al 2009;Del Rio et al 2012;Garcia-Aparicio et al 2011). Biofuels can reduce the world's dependency on non-renewable fossil fuels, which also causes environmental pollution, global warming and conflict in some regions of the world (Dashtban et al 2009;Garcia-Aparicio et al 2011;Himmel et al 2007;Merino and Cherry 2007).…”

“…Biofuels can reduce the world's dependency on non-renewable fossil fuels, which also causes environmental pollution, global warming and conflict in some regions of the world (Dashtban et al 2009;Garcia-Aparicio et al 2011;Himmel et al 2007;Merino and Cherry 2007). Lignocellulosic biomass is heterogeneous and insoluble and requires multiple enzymes working in synergy for its degradation (Dashtban et al 2009;Teeri 1997). Apple pomace, a waste product from the apple juice industry, is a potential lignocellulosic feedstock for the production of biofuels and biorefinery chemicals (Gama et al 2015).…”