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The Application of Fiber Quality Analysis (FQA) and Cellulose Accessibility Measurements To Better Elucidate the Impact of Fiber Curls and Kinks on the Enzymatic Hydrolysis of Fibers
- Chandra, Richard P., Wu, Jie, Saddler, Jack N.
- ACS sustainable chemistry & engineering 2019 v.7 no.9 pp. 8827-8833
- biomass, cellulose, enzymatic hydrolysis, enzymes, fiber quality, hydrochloric acid, hydrolysis, staining
- Fiber curls, kinks, microcompressions, nodes, crimps, and dislocations have been frequently associated with weak points in biomass fibers that exhibit increased accessibility to enzymes and chemicals. Rapid measurements using fiber quality analysis (FQA) showed that the curl and kink indices were increased by 300% in fibers that were processed at high solids loadings, but these indices were readily reversed by the application of a “straightening” treatment to the fibers. The curlation of fibers increased their susceptibility to shortening when they were exposed to endoglucanases and hydrochloric acid. Increased fiber curl also enhanced cellulose accessibility as measured by Simons staining (SS) and water retention value (WRV) and resulted in the formation of fiber networks with increased bulk. Upon straightening the fibers, these effects were reversed, with the exception of the increases in cellulose accessibility measured by SS and WRV. The induction of fiber curls and kinks also resulted in irreversible increases in cellulose hydrolysis yields of up to 17% that were more pronounced at higher solids loadings. The better hydrolysis at higher solids loadings was likely due to the well-known tendency of curled fibers to form bulkier fiber networks with decreased fiber bonding. The results suggest that it should be possible to simultaneously increase cellulose accessibility when hydrolysis is performed at high solids loadings by the application of appropriate physical treatments. It was apparent that the increased cellulose accessibility measured by SS and WRV and reflected by the enhancement in enzymatic hydrolysis yields was a byproduct of curl and kink induction and thus was not directly measurable using an FQA.