Monday, August 13, 2012
Columbia Hall, Terrace Level (Washington Hilton)
Hot acid biomass pretreatment is the preferred method for lignocellulose deconstruction but requires added steps to be compatible with commodity enzyme saccharification. Extremely thermoacidophilic microbes such as Sulfolobus solfataricus (Sso) are the key to a new consolidated bioprocessing strategy compatible with hot acid pretreatment. To clarify how Sso catabolizes soluble cellodextrins as sole carbon and energy sources, endoglucanases and transporters required for this process were identified using a combination of comparative genomics and genetics in assays that coupled substrate utilization to growth. Sso strain-specific genomic differences indicated that strain 98/2 lacks endoglucanase Sso1354 while two other endoglucanases are shared including Sso1949 and Sso2534. Plasmid-based expression of Sso1354 in strain 98/2 conferred the ability to rapidly hydrolyze longer oligosaccharides including cellohexaose (G6) through cellonanaose (G9). Protein transporters required for cellodextrin uptake were identified through mutagenesis and complementation of an ABC transporter cassette including a putative oligosaccharide binding protein, Sso3053. In addition, Sso3053 ablation compromised growth on glucose while inactivation of the glucose transporter, Sso2847, had no impact. These data demonstrate that Sso has redundant mechanisms for soluble cellodextrin catabolism comprised of both uptake and extracytoplasmic hydrolytic properties.