Estratégias para valorização biológica de lignina e hidrolisados lignocelulósicos

Author(s)

Victoria Ramos Sodré de Castro

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Biologia
• Defense date: 2021-12-17

Examining board members

Fabio Marcio Squina; Richard John Ward; Anete Pereira de Souza; Roberto do Nascimento Silva; César Rafael Fanchini Terrasan

• Advisor: Fabio Marcio Squina; André Ricardo de Lima Damásio

Abstract

Lignocellulosic biomass represents a cheap and abundant resource that might be used as feedstock for the biorefinery: the cellulose and hemicellulose fractions can be used for production of second-generation biofuels, and lignin may be exploited for generation of high-value aromatic molecules. While production of second-generation biofuels is a reality, the lignin fraction potential remains untapped, and lignin-rich streams derived from lignocellulosic biomass pretreatment are usually discarded or burned for generation of low-grade heat. The investigation of biological lignin-degradation systems in nature allows the identification of novel biocatalysts that could be used in the biorefinery for the deconstruction and bioconversion of lignin and lignocellulosic hydrolysates. In this thesis, we aimed to identify and use such enzymatic and microbial catalysts for the valorization of lignin and lignocellulosic hydrolysates. The first chapter addresses the generation of inhibitory compounds during chemical and or/physical pretreatment of biomass in the biorefinery, and reviews the use of microorganisms to effectively detoxify these fractions. Chapter II presents two published articles on the characterization of feruloyl-CoA synthetases (FCSs) and feruloyl-CoA hydratase/lyases (FCHL), prokaryotic enzymes from the catabolism of ferulic acid that were identified from the metagenomic analysis of a lignin-degrading microbial consortium. In Document 1 (Chapter II), the biochemical and biophysical characterization of a FCS – named FCS1 – is presented. We demonstrated that FCS1 is a homodimeric enzyme with accentuated stability and activity at alkaline pHs. In Document 2 (Chapter II), another FCS and a novel FCHL – named LM-FCS2 and LM-FCHL2 – are characterized and, notably, applied for the consolidated bioproduction of vanillin from sugarcane bagasse alkaline hydrolysates. In addition, interesting features on these enzymes were disclosed, such as LM-FCS2 broad substrate affinity, and LM-FCHL2 ability to convert ferulic acid to vanillin independently from FCS2. Chapters III to V present a series of works on the lignin-degrading bacterium Rhodococcus jostii RHA1, which has great potential as a microbial chassis for lignin valorization. Chapter III deals with the modulation of ferulic acid catabolism in R. jostii, and the application of mutant strains for production of 4-vinyl guaiacol from ferulic acid. Chapter IV investigates how R. jostii funnels oxidized lignin fragments to central metabolites, and how intermediates from this catabolic pathway may be converted in high-value pharmaceutical molecules. Finally, Chapter V describes our efforts to implement the CRISPR/Cas9 system in R. jostii, a non-model organism with currently limited molecular biology tools. We hope that this thesis will contribute to the field of biological lignin valorization (AU)

• FAPESP's process: 18/18101-1 - Development of the CRISPR/Cas9 system in Rhodococcus jostii RHA1 for production of high-value chemicals from lignin streams
• Grantee: Victoria Ramos Sodré de Castro
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)