Exploiting Anaerobes for Biomass Breakdown and Sustainable Chemistry

Abstract

Renewable chemicals derived from plant biomass (mainly composed of cellulose and lignin) are attractive alternatives to those made from petroleum. To produce chemicals from biomass, enzymes are used to break down cellulose into simple sugars, which are later fermented into value-added products. However, since cellulose is tightly bound within a network of crystalline cellulosic fibers and lignin, existing biomass degrading enzymes are not very efficient. To develop new technologies to break down plant material into sugar, much can be learned by studying how microbes digest lignocellulose in biomass-rich environments, such as the digestive tract of large herbivores. Anaerobic fungi are native to the gut and rumen of these animals, where they have evolved powerful enzymes to degrade plant biomass. Our goal is to develop new experimental tools to engineer anaerobic fungi and anaerobic microbial consortia for lignocellulose breakdown and chemical production. To accomplish this goal, we isolated a panel of anaerobic fungi and associated microbes from different herbivores and screened for their ability to degrade several types of lignin-rich grasses and agricultural waste. By focusing on model anaerobic fungi from the Piromyces, Neocallimastix, and Anaeromycesgenera, we have employed next-generation sequencing to discover thousands of new genes, revealing hundreds of novel cellulases. Additionally, we have characterized key regulatory patterns for these cellulases, which depend on the environment of the fungus. Using this information, we are developing new genetic engineering strategies to manipulate gut fungi at the molecular level, along with 'bottom-up' strategies to synthesize microbial consortia for compartmentalized breakdown and bioproduclion.