Microorganisms as bioabatement agents in biomass to bioproducts applications

Abstract

The biorefinery concept for production of biofuels and chemicals, based on lignocellulosic biomass, represents an attractive and sustainable alternative to fossil fuel-based refineries. The inherent recalcitrance of lignocellulosic biomass requires a physical-chemical pretreatment prior to the biocatalytic conversion of monomeric constituents of plant cell walls into bioproducts. However, the pretreatment step often generates fermentation inhibitors, such as furfural, 5-hydroxymethylfurfural, aliphatic acids, and phenolic acids and aldehydes. Thus, a detoxification step prior, or simultaneous to microbial fermentation, is of prime importance to improve product yields. Among detoxification strategies, biological detoxification, also known as bioabatement, arises as an eco-friendlier, milder, and cheaper alternative to physical-chemical detoxification methods. In the present review, the state-of-the-art and recent advances in the field of microbial detoxification of lignocellulosic hydrolysates are thoroughly presented. After introducing the general aspects of the theme, including the generation of inhibitory compounds from lignocellulosic biomass pretreatment and their effects on enzymatic hydrolysis and cell physiology, in-depth analyses of biological detoxification strategies reported in the literature are presented for the following microbial groups: filamentous fungi, non-Saccharomyces yeasts, bacteria, and Saccharomyces cerevisiae. Furthermore, the advantages and disadvantages of microbial detoxification are discussed, and the main challenges currently faced by researchers in the field are addressed.