The Multifaceted Role of Acinetobacter Baylyi ADP1 in Upgrading Lignocellulose

Abstract

The bioconversion of lignocellulosic biomass into valuable biochemicals holds significant promise for sustainable industrial processes. Lignocellulosic hydrolysates, derived from plant biomass, are rich in sugars that can be utilized by microorganisms for biochemical production. However, the efficient utilization of these hydrolysates is often hindered by their complex and heterogeneous composition, as well as the presence of toxic compounds such as furan aldehydes from carbohydrate degradation. These inhibitors, formed during pretreatment, can severely affect microbial growth and productivity. In addition to whole lignocellulosic hydrolysates, specific phenolic compounds derived from depolymerized lignin have also attracted interest for microbial conversion. However, lignin-derived phenolic compounds pose additional challenges due to their inhibitory effects and varying microbial assimilation capabilities. Addressing these challenges is crucial for advancing the bioconversion of lignocellulosic biomass into valuable biochemicals.

In this dissertation, the aim is to develop and study the multifaceted role of <i>Acinetobacter baylyi</i> ADP1 to address the challenges associated with upgrading lignocellulosic biomass. The detoxification of furfural and 5-hydroxymethylfurfural in <i>A. baylyi</i> ADP1 was first investigated in this work to reveal their detoxification metabolites and kinetics. Next, inspired by the detoxification capability of <i>A. baylyi</i> ADP1, its potential for contributing to the valorization of lignocellulosic hydrolysates was further investigated. A synthetic microbial consortium was established by co-culturing the emerging <i>A. baylyi</i> ADP1 with the well-established industrial yeast <i>Saccharomyces cerevisiae</i>, which resulted in increased lactic acid productivity from <i>S. cerevisiae</i> and optimization of carbon recovery. Given the challenge of lignin-derived phenolics, <i>A. baylyi</i> ADP1 was engineered for the production of <i>cis,cis</i>-muconic acid from lignin-derived phenolic compounds, utilizing a growth-coupled selection system to screen for enzymes that redirected carbon flow. Taken together, these findings establish <i>A. baylyi</i> ADP1 as a promising microbial chassis for lignocellulosic biomass valorization. By integrating its detoxification capabilities, metabolic flexibility, and compatibility in synthetic consortia, this study opens new avenues for optimizing microbial platforms in sustainable bioconversion processes.