Submitted to: American Society for Microbiology General Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 3/14/2010
Publication Date: 5/27/2010
Citation: Soares, J.W., Ragauskas, A., Muller, W.S., Ziemer, C.J., Arcidiacano, S. 2010. Cellulose Degradation Kinetics of Two Novel Bacterial Isolates That Preferentially Hydrolyze Crystalline Domains [abstract]. American Society for Microbiology General Meeting, May 23-27, 2010, San Diego, CA. 2010 CD-ROM. Interpretive Summary:
Technical Abstract: Conversion of cellulosic biomass to bioenergy is extremely attractive in the recent climate of renewable energy research. Although a large number of organisms and fungi that have been isolated and characterized demonstrate an ability to hydrolyze both amorphous and crystalline domains of cellulose, overall hydrolysis efficiency is limited due to the preferential hydrolysis of the amorphous region. Therefore, a major challenge to achieving an optimal conversion is the hydrolysis efficiency of the crystalline domains. Hydrolysis of the most highly crystalline cellulose (Ia and Iß) serves as the rate limiting step in the overall conversion process. Previously, two novel cellulolytic bacteria were isolated and characterized for cellulolytic properties. Preliminary evaluations indicated both isolates were capable of preferentially hydrolyzing the recalcitrant crystalline material; crystallinity was reduced by 34-44%. There are no known reports of bacteria that preferentially target this type of cellulose. Here, a detailed investigation of the novel isolates’ growth and hydrolysis kinetics was conducted. Time course studies were performed by introducing cellulosic substrates ranging in crystallinity from 0-80% as the sole carbon source in batch cultures. The isolates’ growth kinetics were ascertained through protein and dye release assays and correlated to cellulose hydrolysis, predominantly determined through CP/MAS 13C solid state NMR. Furthermore, Congo Red overlay assays were conducted to qualitatively evaluate cellulose hydrolysis. Preliminary results indicate growth on crystalline cellulose, with a lack of growth on the amorphous substrate. Kinetic studies to determine the domains of crystalline cellulose that are preferentially hydrolyzed are ongoing. To understand the mechanism of the cellulose hydrolysis, cell turbidity studies were conducted. A reduction in turbidity upon exposure to cellulose is evident, which is indicative of a cellulosome. The realization of organisms that can preferentially hydrolyze crystalline cellulose has the potential for a breakthrough in bioenergy research.