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Title: Dramatic performance of Clostridium thermocellum explained by its wide range of cellulase modalities

Clostridium thermocellum is the most efficient microorganism for solubilizing lignocellulosic biomass known to date. Its high cellulose digestion capability is attributed to efficient cellulases consisting of both a free-enzyme system and a tethered cellulosomal system wherein carbohydrate active enzymes (CAZymes) are organized by primary and secondary scaffoldin proteins to generate large protein complexes attached to the bacterial cell wall. This study demonstrates that C. thermocellum also uses a type of cellulosomal system not bound to the bacterial cell wall, called the “cell-free” cellulosomal system. The cell-free cellulosome complex can be seen as a “long range cellulosome” because it can diffuse away from the cell and degrade polysaccharide substrates remotely from the bacterial cell. The contribution of these two types of cellulosomal systems in C. thermocellum was elucidated by characterization of mutants with different combinations of scaffoldin gene deletions. The primary scaffoldin, CipA, was found to play the most important role in cellulose degradation by C. thermocellum, whereas the secondary scaffoldins have less important roles. Additionally, the distinct and efficient mode of action of the C. thermocellum exoproteome, wherein the cellulosomes splay or divide biomass particles, changes when either the primary or secondary scaffolds are removed, showing that the intact wild-typemore » cellulosomal system is necessary for this essential mode of action. As a result, this new transcriptional and proteomic evidence shows that a functional primary scaffoldin plays a more important role compared to secondary scaffoldins in the proper regulation of CAZyme genes, cellodextrin transport, and other cellular functions.« less
Authors:
 [1] ;  [2] ;  [1] ;  [3] ;  [1] ;  [1] ;  [4] ;  [4] ;  [5] ;  [1] ; ;  [4] ;  [4] ;  [5] ;  [6] ;  [1] ;  [1]
  1. National Renewable Energy Lab. (NREL), Golden, CO (United States); BioEnergy Science Center, Oak Ridge, TN (United States)
  2. BioEnergy Science Center, Oak Ridge, TN (United States); National Renewable Energy Lab. (NREL), Golden, CO (United States)
  3. National Renewable Energy Lab. (NREL), Golden, CO (United States)
  4. BioEnergy Science Center, Oak Ridge, TN (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  5. BioEnergy Science Center, Oak Ridge, TN (United States); Dartmouth College, Hanover, NH (United States)
  6. The Weizmann Institute of Science, Rehovot (Israel)
Publication Date:
Report Number(s):
NREL/JA--2700-65384
Journal ID: ISSN 2375-2548
Grant/Contract Number:
AC36-08GO28308
Type:
Accepted Manuscript
Journal Name:
Science Advances
Additional Journal Information:
Journal Volume: 2; Journal Issue: 2; Journal ID: ISSN 2375-2548
Publisher:
AAAS
Research Org:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org:
USDOE Office of Science (SC); USDOE Bioenergy Science Center (BESC)
Country of Publication:
United States
Language:
English
Subject:
09 BIOMASS FUELS; 59 BASIC BIOLOGICAL SCIENCES cell biology; biomass; biofuels; cellulases; cellulosomes
OSTI Identifier:
1244830
Alternate Identifier(s):
OSTI ID: 1244830