Production and Application of Lignin-Based Chemicals and Materials in the Cellulosic Ethanol Production: An Overview on Lignin Closed-Loop Biorefinery Approaches

Abstract

Lignocellulosic biomass is the most abundant biological resource on the planet and has been extensively researched to produce cellulosic ethanol. However, there is a consensus that the presence of lignin hinders the biomass conversion. Lignin is often considered a villain in cellulosic ethanol production studies due to its adverse effects on cellulases and yeasts. Despite this, recent studies indicate that lignins can be transformed into useful inputs to produce cellulosic ethanol. These approaches aim to establish closed-loop biorefineries to improve economic metrics and reduce the environmental impact due to the substitution of products based on fossil sources. The present review addresses the successful cases in transforming lignin into chemicals and materials to increase cellulosic ethanol titers. A contextualization was first carried out, considering aspects of biomass characteristics and lignin valorization. The impact of lignin-based chemicals and materials in the pretreatment, detoxification, and enzymatic hydrolysis steps was discussed in detail. Economic aspects and future perspectives were also included in this review. These reports open a new point of view on lignin valorization and its integration with the cellulosic ethanol production chain.

Catalytic Transfer Hydrogenolysis of Switchgrass Lignin with Ethanol Using Spinel-Type Mixed-Metal Oxide Catalysts Affords Control of the Oxidation State of Isolated Aromatic Products

“…The hypotheses were tested by conducting CTH reactions in stainless steel microreactors at 320 °C for 2 h. Ethanol was used as the solvent and reductant (Scheme ) because it can be easily isolated from biomass; in an industrial biorefinery, isolating cellulosic ethanol and upgraded small molecules from lignin as coproducts represents an economically and ecologically favorable industrial process. − GC/MS was used to monitor the concentrations of the molecules shown in Scheme , using durene as an internal standard and constructing a response factor curve for each molecule. Each catalyst species was tested as was a blank reaction with no catalyst present.…”

One-pot two-stage biocatalytic upgrading of biomass-derived aldehydes to optically active β-amino alcohols via sequential hydroxymethylation and asymmetric reduction amination

“…37 These compounds are mainly utilized as raw materials for the production of flavors and fragrances, or as intermediates for fine chemical production. 38 Unfortunately, conversion of these biomass-derived aldehydes into value-added chiral chemicals in a sustainable and environmentally friendly way remains a challenge. There is a pressing need to explore new applications of these readily available aldehydes, particularly in the synthesis of optically active compounds.…”

Ultrasound enhanced solubilization of forest biorefinery hydrolysis lignin in mild alkaline conditions

“…The modern chemical industry, stimulated by political and environmental concerns, is intensively looking for alternatives to petroleum resources. One such contender in this field is lignocellulosic forestry biomass, which is mainly comprised of three major polymers: cellulose (40–50 %), hemicellulose (20–30 %) and lignin (10–30 %) [ [1] , [2] , [3] , [4] , [5] ]. There are some approaches, where the main products are either cellulose or C5-C6 sugars and lignin is treated as a recalcitrant contaminant or cheap energy resource.…”