Breakdown of plant biomass into simple sugars would translate into the production of renewable fuels via microbial fermentation. However, existing technologies are insufficient for industrial-scale production of biofuels due to difficulties associated with the recalcitrance of lignin-rich biomass, and the high cost/poor performance of known cellulolytic enzymes. Therefore, there is a critical need to develop new technologies to break down crude biomass into fermentable sugars for downstream fuel development. Towards this goal, much can be learned by studying how anaerobic gut fungi depolymerize lignocellulose in biomass-rich environments, such as the digestive tract of large herbivores. Anaerobic gut fungi are native to the gut and rumen of these animals, where they have evolved unique abilities to break down lignocellulosic biomass through invasive growth and the secretion of powerful enzymes and enzyme complexes (cellulosomes). Towards engineering gut fungi as novel platform organisms for biofuel production, we have partnered with the JGI and EMSL through the Joint EMSL/JGI user program to characterize the biomass-degrading machinery from novel Neocallimastix and Anaeromyces isolates. Each isolate thrives on lignocellulosic substrates, and secretes multi-protein cellulosome complexes of cellulases, hemicellulases, and cellulose binding domains. Therefore, transcriptomic and genomic sequencing is likely to reveal hundreds of novel enzymes that are useful for biomass breakdown. To determine the basic metabolic networks that govern biomass hydrolysis within anaerobic fungi, we are employing RNAseq at the JGI to quantify transcript abundance when simple sugars repress lignocellulosic degradation. Parallel proteomics efforts are underway at EMSL to compare the regulation of secreted fungal enzymes with those regulated at the transcriptional level. Through these efforts, we will determine how important enzyme groups are coordinated during biomass breakdown across fungal genera. Collectively, this information will establish the molecular framework for anaerobic fungal hydrolysis, and will guide in the development of lignocellulosic biofuels.

Identification and regulation of novel cellulases within anaerobic gut fungi

248th National Meeting (2014)

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