Physico-Chemical Conversion of Lignocellulose: Inhibitor Effects and Detoxification Strategies: A Mini Review

Abstract

A pretreatment of lignocellulosic biomass to produce biofuels, polymers, and other chemicals plays a vital role in the biochemical conversion process toward disrupting the closely associated structures of the cellulose-hemicellulose-lignin molecules. Various pretreatment steps alter the chemical/physical structure of lignocellulosic materials by solubilizing hemicellulose and/or lignin, decreasing the particle sizes of substrate and the crystalline portions of cellulose, and increasing the surface area of biomass. These modifications enhance the hydrolysis of cellulose by increasing accessibilities of acids or enzymes onto the surface of cellulose. However, lignocellulose-derived byproducts, which can inhibit and/or deactivate enzyme and microbial biocatalysts, are formed, including furan derivatives, lignin-derived phenolics, and carboxylic acids. These generation of compounds during pretreatment with inhibitory effects can lead to negative effects on subsequent steps in sugar flat-form processes. A number of physico-chemical pretreatment methods such as steam explosion, ammonia fiber explosion (AFEX), and liquid hot water (LHW) have been suggested and developed for minimizing formation of inhibitory compounds and alleviating their effects on ethanol production processes. This work reviews the physico-chemical pretreatment methods used for various biomass sources, formation of lignocellulose-derived inhibitors, and their contributions to enzymatic hydrolysis and microbial activities. Furthermore, we provide an overview of the current strategies to alleviate inhibitory compounds present in the hydrolysates or slurries.

New trends in application of nanotechnology for the pretreatment of lignocellulosic biomass

“…The common pretreatment methods routinely used for degradation of LB are broadly classified into physical, chemical, physicochemical, biological, biochemical, and multiple or combinatorial pretreatment methods. Various comprehensive reviews have been published emphasizing conventional pretreatment methods and their mechanical effects on plant cell walls . These methods are therefore discussed briefly in the present review.…”

“…Physicochemical pretreatment methods are another class of pretreatment. They are generally employed to overcome the problem of recalcitrance and easy separation of cellulose from biomass matrix, to make it more accessible for enzymatic hydrolysis . They mainly include steam explosion, liquid hot water, ammonia fiber explosion (AFEX), ammonia recycle percolation (ARP), and supercritical fluid pretreatment .…”

Pretreatment methods for lignocellulosic biofuels production: current advances, challenges and future prospects

“…Steam explosion applies high pressures of steam followed by sudden reduction of pressure, so as the biomass undergoes explosive decompression. This quick depressurization involves an initial temperature of 160 to 260°C for seconds and minutes in saturated steam prior to exposure to atmospheric pressure (Baruah et al, 2018;Kim, 2018). The method is known to be effective to disintegrate various lignocellulosic biomass feedstock, forest residues, and wastes at low cost and fast rate.…”

“…The method is known to be effective to disintegrate various lignocellulosic biomass feedstock, forest residues, and wastes at low cost and fast rate. Kim (2018) claimed that the steam explosion pretreatment uses 70% less energy compared to physical pretreatments. During the steam pretreatment stage, hemicellulose is hydrolyzed and acids are formed in-situ, further hydrolyzing the hemicellulose.…”

Chromosomal mutations in Escherichia coli that improve tolerance to nonvolatile side‐products from dilute acid treatment of sugarcane bagasse

“…Among these, dilute acid pretreatment of biomass at high temperature is independent of biomass type and can hydrolyze over 90% of hemicellulose to xylose. Due to the disruption of the cellulose/lignin linkage during this pretreatment, the rate of hydrolysis of cellulose in the slurry by commercial cellulases is also increased (Kim, ). However, dilute acid pretreatment also releases multiple side‐products, both volatile and nonvolatile, that act as inhibitors of depolymerizing enzymes and fermenting microorganisms (Jönsson, Alriksson, & Nilvebrant, ; Rajan & Carrier, ).…”