Dear Colleagues, 

The bioconversion of lignocellulosic biomass into simple sugars for subsequent fermentation is an essential platform for the sustainable production of biofuels and biochemicals. However, the degradation of polysaccharides in biomass to sugar is difficult, and it has become a rate-limiting step in the industrial process.

The crystallinity and insoluble forms of polysaccharides appear to be a barrier for enzymatic hydrolysis. Several studies have shown that carbohydrate-active enzymes, i.e., cellulases and xylanases, have modular structures, making the enzymes more active on the insoluble substrate than a single-catalytic domain enzyme. The additional modules include carbohydrate-binding modules (CBMs), fibronectin-like domains, and other modules with unknown functions. The functions of CBMs are to bring the enzymes to the insoluble substrate, concentrate the enzyme on the substrate surfaces, and prolong the adsorption. Fibronectin-like domains have been reported to be involved in anchoring enzymes to the large substrates or stabilizing the entire protein structure, for example. These modules are linked with a catalytic module(s) via short-peptide linkers to make the enzyme(s) modular, and the linkers are glycosylated to prevent proteolytic cleavage. The linkers are also believed to promote polysaccharide binding during catalysis.

Interestingly, some microorganisms develop their sophisticated enzyme system to degrade the crystalline form of polysaccharides efficiently. For example, the multienzyme “cellulosome” has shown the efficient degradation of crystalline cellulose.  Additionally, it contains enzyme components that actively degrade other polysaccharides, including xylan, starch, pectin, and mannan. Cellulosomal enzymes have a specialized module called dockerin, which interacts with the cohesin on the scaffolding protein. The assembly of the enzymes into the complex leads to enzyme proximity and synergy among the enzymes. However, mimicking the complex formation of the naturally occurring cellulosome complex is difficult. The limitations include an efficient protein expression system, proper glycosylation, protein folding, and ways to choose enzymes and orders of the enzymes for construction.

This Special Issue focuses on the modular structure of carbohydrate-active enzymes, the architecture of the entire protein structures, and their biological functions during catalysis. We welcome the submission of research articles, reviews, and perspectives related, but not limited to, the following themes of interest:

• Protein expression and development of hosts for expressing enzymes
• Enzymology of carbohydrates active enzymes and the cellulosome system
• Application of CBMs in protein purification, biomass characterization, or biomarker/reporter
• Application of carbohydrate-active enzymes in agriculture, food, feed, and the biofuel/chemical industry
• Modular structures and substrate–enzyme interactions
• Techniques for increasing enzymatic activity and stability
• Computational tools for designing enzymes
• Effects of pretreatment methods on biomass structure and enzymactic acitivity

Dr. Paripok Phitsuwan
Dr. Ken-Lin Chang
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Catalysts is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

• plant biomass
• lignocellulose
• biorefinery
• circular bioeconomy
• cellulose
• hemicellulose
• lignin
• green solvent
• gene manipulation
• enzyme kinetics
• molecular docking
• protein assembly
• protein
• hydrolysis
• polysaccharide degradation
• binding interaction