Combined Sugarcane Pretreatment for the Generation of Ethanol and Value-Added Products

Sidnei Emilio Bordignon,Olavo Micali Perrone,Michael R. Ladisch,Christiane da Costa Carreira Nunes,Edivaldo Ximenes Ferreira Filho,Maurício Boscolo,Eleni Gomes,Eduardo Ximenes,Roberto da Silva,Daehwan Kim

doi:10.3389/fenrg.2022.834966

Abstract

In this work, we have tested individual and combination of applications of ozonolysis and liquid hot water (LHW) to pretreat sugarcane bagasse (SCB) for the removal of enzyme and/or microbial inhibitors and generation of potential value-added chemicals. A solid content with 80% cellulose and a liquid phase (liquor) rich in phenolic derived compounds (3 g.L−1) from lignin, sugars (&gt;20 g.L−1), and other compounds, such as furfural and hydroxymethylfurfural (HMF), were generated. Maximal (59%) glucan conversion occurred in the presence of double-pretreated bagasse, which had 32–50% more glucan available than the samples that were individually LHW or ozone-pretreated, resulting in maximal ethanol production (92% after 42 h) from double-pretreated SCB enzyme hydrolyzate. In summary, this work showed that ozone reacts effectively with lignin without the use of any other chemical reagent, and LHW pretreatment, followed by a washing step, was effective in solubilizing and cleaning up the fiber enzyme and microbial inhibitory compounds with ozone being effective against phenolics. Moreover, the generated cellulose-rich substrate is readily fermentable. The acidic liquor fraction removed by sequential washings and containing mainly sugars and phenolic compounds may be evaluated for use in green chemistry bioconversions processes.

Highlights

The high resistance of cellulose to degradation is the main biological barrier to lignocellulosic processing on a large scale (Ximenes et al, 2021)
Liquid hot water (LHW) pretreatment of a variety of lignocellulosic materials has included a wide range of operational conditions, including temperature, resident time, particle size, and water-to-solid biomass ratio, among others, and aims to avoid the formation of enzyme and/or microbial inhibitors
The combination of ozonolysis and LHW pretreatments tested here to enhance enzymatic hydrolysis, and alleviate inhibition during saccharification and fermentation of sugarcane bagasse (SCB) is attractive for generating valued compounds from phenolic compounds derived from lignin

Summary

INTRODUCTION

The high resistance of cellulose to degradation is the main biological barrier to lignocellulosic processing on a large scale (Ximenes et al, 2021). When choosing operational conditions of pretreatment, it is important to consider the type of biomass as well as the formed lignocellulosic degradation products that are inhibitory to downstream biochemical reactions (Ko et al, 2015a,b,c; Jonsson and Martin, 2016, Ximenes et al, 2017; Ruiz et al, 2021). In this sense, LHW pretreatment of a variety of lignocellulosic materials has included a wide range of operational conditions, including temperature, resident time, particle size, and water-to-solid biomass ratio, among others, and aims to avoid the formation of enzyme and/or microbial inhibitors. The combination of ozonolysis and LHW pretreatments tested here to enhance enzymatic hydrolysis, and alleviate inhibition during saccharification and fermentation of sugarcane bagasse (SCB) is attractive for generating valued compounds from phenolic compounds derived from lignin

MATERIAL AND METHODS

Analytical Methods

RESULTS AND DISCUSSION

DATA AVAILABILITY STATEMENT

CONCLUSIONS