Effects of Thermobifida fusca cutinase-carbohydrate-binding module fusion proteins on cotton bioscouring

Synergism between Cutinase and Pectinase in the Hydrolysis of Cotton Fibers’ Cuticle

Scouring is one of the initial steps in the processing of natural textile fibers (e.g., cotton), performed to remove waxes and pectins, together with spinning oils and other impurities of the plant cell cuticle. Traditional chemical bleaching with boiling NaOH led to harsh removal of the entire fabric’s cuticle waxy layer accompanied by an unwanted alkaline waste. Extracellular lytic enzymes such as lipases, cellulases and pectinases play an essential role in host plant-pathogen interactions. They degrade the plant cuticle and tissue and enable pathogen invasion. Such enzymes, specifically cutinase and pectinase, have been considered potential bio-scouring agents to degrade the cotton fabric cuticle’s outer layer at low temperature and alleviate environmental pollution. In this work, the combined effect of cutinase, pectin lyase, or polygalacturonase on the scouring of cotton fabrics was studied using evaporative light-scattering reverse-phase HPLC and GC-MS analysis of the reaction components, and measuring changes in the cotton fabrics’ properties. The traditional method of cotton fabrics’ scouring with NaOH resulted in decreased pectin content and increased cellulose fibers accessibility, evaluated by specific staining. Treating the cotton fibers’ cuticle with cutinase led to the acidification of the reaction mixture, a decrease in enzyme-specific activity, and elevation in hexadecanoic acid and octadecanoic acids in the reaction fluid. These two saturated fatty acids are the main wax constituents of raw cotton fabrics, identified using GC-MS after dichloromethane reflux overnight. Treating cotton fabrics with each of the three enzymes, cutinase, pectin lyase, or polygalacturonase, increased their pectin removal, as measured by high concentrations of D-galacturonic acid and other pectin constituents in the reaction fluid. A synergistic effect was found in the combined treatment of cutinase and pectin lyase in the hydrolysis of the cotton fibers’ cuticle. This effect was expressed in high water absorbency of the treated fibers, increased fabric weight loss and sharp elevation of a cutin and pectin monomer’s related peaks (retention time [RT] = 4.1 min and 2.9, 4.5 min, respectively). A model was suggested for the synergistic action between cutinase and pectin lyase. It assumes that the cuticle’s digestion by cutinase results in the enlargement and formation of outer layer micropores, which enables the rapid penetration of pectinase into the inner pectin layer.

Structure-guided engineering of a Thermobifida fusca cutinase for enhanced hydrolysis on natural polyester substrate

Cutinases could degrade insoluble polyester, including natural cutin and synthetic plastic. However, their turnover efficiency for polyester remains too low for industrial application. Herein, we report the 1.54-Å resolution X-ray crystal structure of a cutinase from Thermobifida fusca and modeling structure in complex with a cutin mimic oligo-polyester C24H42O8. These efforts subsequently guided our design of cutinase variants with less bulky residues in the vicinity of the substrate binding site. The L90A and I213A variants exhibit increased hydrolysis activity (5- and 2.4-fold, respectively) toward cutin and also showed enhanced cotton scouring efficiency compared with the wild-type enzyme.

Evaluation and application of constitutive promoters for cutinase production by Saccharomyces cerevisiae

Cutinase as a promising biocatalyst has been intensively studied and applied in processes targeted for industrial scale. In this work, the cutinase gene tfu from Thermobifida fusca was artificially synthesized according to codon usage bias of Saccharomyces cerevisiae and investigated in Saccharomyces cerevisiae. Using the α-factor signal peptide, the T. fusca cutinase was successfully overexpressed and secreted with the GAL1 expression system. To increase the cutinase level and overcome some of the drawbacks of induction, four different strong promoters (ADH1, HXT1, TEF1, and TDH3) were comparatively evaluated for cutinase production. By comparison, promoter TEF1 exhibited an outstanding property and significantly increased the expression level. By fed-batch fermentation with a constant feeding approach, the activity of cutinase was increased to 29.7 U/ml. The result will contribute to apply constitutive promoter TEF1 as a tool for targeted cutinase production in S. cerevisiae cell factory.

The Plant Polyester Cutin: Biosynthesis, Structure, and Biological Roles

Cutin, a polyester composed mostly of oxygenated fatty acids, serves as the framework of the plant cuticle. The same types of cutin monomers occur across most plant lineages, although some evolutionary trends are evident. Additionally, cutins from some species have monomer profiles that are characteristic of the related polymer suberin. Compositional differences likely have profound structural consequences, but little is known about cutin's molecular organization and architectural heterogeneity. Its biological importance is suggested by the wide variety of associated mutants and gene-silencing lines that show a disruption of cuticular integrity, giving rise to numerous physiological and developmental abnormalities. Mapping and characterization of these mutants, along with suppression of gene paralogs through RNA interference, have revealed much of the biosynthetic pathway and several regulatory factors; however, the mechanisms of cutin polymerization and its interactions with other cuticle and cell wall components are only now beginning to be resolved.

Synthetic polyester-hydrolyzing enzymes from thermophilic actinomycetes

Thermophilic actinomycetes produce enzymes capable of hydrolyzing synthetic polyesters such as polyethylene terephthalate (PET). In addition to carboxylesterases, which have hydrolytic activity predominantly against PET oligomers, esterases related to cutinases also hydrolyze synthetic polymers. The production of these enzymes by actinomycetes as well as their recombinant expression in heterologous hosts is described and their catalytic activity against polyester substrates is compared. Assays to analyze the enzymatic hydrolysis of synthetic polyesters are evaluated, and a kinetic model describing the enzymatic heterogeneous hydrolysis process is discussed. Structure-function and structure-stability relationships of actinomycete polyester hydrolases are compared based on molecular dynamics simulations and recently solved protein structures. In addition, recent progress in enhancing their activity and thermal stability by random or site-directed mutagenesis is presented.