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Recent Advances in Consolidated Bioprocessing for Microbe-Assisted Biofuel Production
Published in Sonil Nanda, Prakash Kumar Sarangi, Dai-Viet N. Vo, Fuel Processing and Energy Utilization, 2019
Prakash Kumar Sarangi, Sonil Nanda
The major differences between the cellulosome and free enzyme systems are the scaffolding protein bearing several cohesin domains and enzymatic subunits having dockerin domains. Apart from the multiple cohesins, scaffolding also contains at least one cellulose-binding domain (CBD), which acts as a targeting agent to help the binding of the substrate to the catalytic domains. Cohesin dockerin interaction is highly species-specific, which provides highly ordered and position-specific assembly of catalytic domains. This protein multiplex is attached to the cell membrane indirectly by anchoring protein. This anchoring protein is attached to the scaffolding protein by Type II cohesion-dockerin interactions and is strongly attached to the cell surface using SLH domains. The attachment of this large multi-protein complex near the cell ensures that most of the liberated sugars from cellulose are absorbed and used by the cellulosome-expressing bacterium. Significant progress has been made in the heterologous expression and display of an attached cellulolytic system in non-cellulolytic microorganisms. One example is a genetically engineered Escherichia coli LY01 strain that expresses and displays an endoglucanase, exoglucanase and β-glucosidase from Clostridium cellulolyticum on its cell surface.
Natural enzymes used to convert feedstock to substrate
Published in Ruben Michael Ceballos, Bioethanol and Natural Resources, 2017
The cellulosome is an extracellular protein complex on bacterial and fungal cell surfaces that adhere to plant materials and deconstruct plant cell wall lignocellulose (Lamed et al., 1983b). Cellulosomes are composed of several subunits, each of which exhibits modular architecture. Some components of the cellulosome are structural, whereas others are catalytic. The core structural component is known as scaffoldin, which is the framework to which all other subunits attach (Tokatlidis et al., 1991). The catalytic components (e.g., enzymes) of the cellulosome contain noncatalytic dockerin domains (Hall et al., 1988). These dockerin modules bind to cohesins, which are the part of scaffoldins (Tokatlidis et al., 1991; Schaeffer et al., 2002; Carvalho et al., 2003). The cellulosome may consist of more than one dockerin type and more than one cohesin type. Dockerin–cohesin interactions may be used to link enzymes to a scaffoldin complex or may be used to anchor the scaffoldin complex to the cell wall. In either case, the high-affinity protein–protein interaction between dockerin and cohesin is fundamental to the assembly of a functional cellulosome endowed with a diverse array of enzymes integrated into the complex (Carvalho et al., 2003). Cellulosomes will also often feature a noncatalytic module called CBM within the scaffoldin framework. CBM anchors the entire complex onto the plant cell wall (Figure 3.8).
Cellulose, the Main Component of Biomass
Published in Jean-Luc Wertz, Magali Deleu, Séverine Coppée, Aurore Richel, Hemicelluloses and Lignin in Biorefineries, 2017
Jean-Luc Wertz, Magali Deleu, Séverine Coppée, Aurore Richel
The complexity and diversity of native cellulosomes prevent detailed analysis of the structural features responsible for their enhanced activity.99 In addition, the lack of specificity of the cohesin–dockerin interaction within a species is an obstacle for the construction of homogeneous simplified cellulosomes containing more than one enzyme. There has been interest in constructing designer cellulosomes (or designer nanosomes), in which enzymes can be incorporated into defined positions, for both basic and applied purposes.
Guided dietary fibre intake as a means of directing short-chain fatty acid production by the gut microbiota
Published in Journal of the Royal Society of New Zealand, 2020
Cellulosomes are multi-enzyme complexes at the bacterial cell surface that facilitate the degradation of cellulose and hemicelluloses by bacteria in the rumen and soil (Bayer et al. 2004). One species, Ruminococcus champanellensis, with this property has been detected in the human gut microbiota (Ben David et al. 2015). Cellulosomes bring hydrolytic enzymes, carbohydrate-binding domains, substrate, and cell surface into close proximity, facilitated by molecules called ‘dockerins’ and ‘cohesins’ (Bayer et al. 2004). A simpler type of multi-enzyme complex (the ‘amylosome’) is present on the cells of the starch-degrading species Ruminococcus bromii (Ze et al. 2015). This species has an exceptional ability to degrade particulate resistant starches when compared with other amylolytic bacterial species inhabiting the gut. The importance of starch in the life of R. bromii is confirmed by analysis of the genome sequence of strain L2-63: it encodes 21 glycosyl hydrolases of which 15 belong to the family GH13 (amylases, pullulanases) (Ze et al. 2012).