Current Status of Mining, Modification, and Application of Cellulases in Bioactive Substance Extraction

Abstract

Cellulases have been used to extract bioactive ingredients from medical plants; however, the poor enzymatic properties of current cellulases significantly limit their application. Two strategies are expected to address this concern: (1) new cellulase gene mining strategies have been promoted, optimized, and integrated, thanks to the improvement of gene sequencing, genomic data, and algorithm optimization, and (2) known cellulases are being modified, thanks to the development of protein engineering, crystal structure data, and computing power. Here, we focus on mining strategies and provide a systemic overview of two approaches based on sequencing and function. Strategies based on protein structure modification, such as introducing disulfide bonds, proline, salt bridges, N-glycosylation modification, and truncation of loop structures, have already been summarized. This review discusses four aspects of cellulase-assisted extraction. Initially, cellulase alone was used to extract bioactive substances, and later, mixed enzyme systems were developed. Physical methods such as ultrasound, microwave, and high hydrostatic pressure have assisted in improving extraction efficiency. Cellulase changes the structure of biomolecules during the extraction process to convert them into effective ingredients with better activity and bioavailability. The combination of cellulase with other enzymes and physical technologies is a promising strategy for future extraction applications.

Improved Ethanol Production From Sweet Sorghum Through Pretreatment With Enzymes From Its Endophytes

“…These findings indicated that the enzyme extracted from endophytic plant X-25 could significantly improve the yield of bioethanol. The superior chimerism between plant cell walls and endophytic cellulases significantly contributes to the formation of the cellulose reticular skeleton (Payne et al 2015;Hu et al 2021b). The mechanism underlying ethanol production by cellulase activity is as follows: the increased cellulase activity promotes the cleavage efficiency of the β1-4 glycosidic bond, increasing ethanol production.…”

Recent Advances in β-Glucosidase Sequence and Structure Engineering: A Brief Review

“…Structural comparison revealed that thermophilic and hyperthermophilic enzymes are more rigid than mesophilic enzymes. Since high temperatures unfold the highly flexible regions of the proteins quickly, flexibility can be used as an indicator to identify potential areas for modification to improve the thermal stability of BGLs [ 104 ]. Most of the current studies target mutations in flexible regions to increase protein rigidity and thermal stability.…”

“…One strategy is to enhance the stability of the enzyme by reducing the conformational entropy in the unfolded state [ 100 ], and common methods include introducing disulfide bonds in the flexible region or replacing glycine with the most rigid proline. It has been proposed that truncating the flexible loops of the protein can also reduce the conformational entropy of BGL [ 104 ]. Another strategy is to stabilize the folded state by increasing favorable interactions (including hydrophobic interactions and hydrogen bonds, etc.)…”

Recent Advances in β-glucosidase Engineering: A Brief Review

“…Structural comparison revealed that thermophilic and hyperthermophilic enzymes are more rigid than mesophilic enzymes. Since high temperatures unfold the highly flexible regions of the proteins at the first, flexibility can be used as an indicator to identify potential areas for modification to improve the thermal stability of BGLs [102]. Most of the current studies target mutations in flexible regions to increase protein rigidity and thermal stability.…”

“…One strategy is to enhance the stability of the enzyme by reducing the conformational entropy in the unfolded state [98], and common methods include introducing disulfide bonds in the flexible region or replacing glycine with the most rigid proline. It has been proposed that truncating the flexible loops of the protein can also reduce the conformational entropy of BGL [102]. Another strategy is to stabilize the folded state by increasing favorable interactions (including hydrophobic interactions and hydrogen bonds, etc.)…”