Combined Bio‐carbonization and Dyeing of Wool: A Possibility Using Cell Wall‐Degrading Enzymes and 1:1 Metal–Complex Dyes

Abstract

This study was undertaken to investigate the possibility of a new process to remove plant residues from wool, using enzymes as biocatalysts together with a dyeing process in a two-step exhaustion process, performed in a single bath. The enzymes were selected in order to hydrolyze the polysaccharides in primary plant cell walls and middle lamella, resulting in more fragile residues easier to be removed. Commercial enzymatic preparations of Trichoderma reesei and Aspergillus aculeatus were used, after appropriate optimization. A total enzyme loading of 1.0 mL/L of each enzymatic preparation yielded an equivalent amount of 241.2 mg of glucose per gram of plant residue, under the optimal conditions: 40.5°C, pH 4.0, and 0.75 mL/L of a non-ionic wetting agent. Reducing groups of the total released sugars were determined with the Miller reactive 3,5-dinitrosalicilic acid (DNS), which has been used for the indirect measurement of the efficiency of the process. Furthermore, to enhance the degradation of the plant residues, dyeing processes using the incubation bath and several acid and metalcomplex dyes, usually applied on wool dyeing, were tested. The dyeing procedure with 1:1 metal-complex dyes adjusted to pH 1.9 with sulfuric acid has promoted a higher degradation of the plant residues without damaging wool fibers. Accordingly, higher concentration of glucose was detected by the DNS reagent and higher weight losses of the plant residues were obtained when compared to enzymatic treatment without dyeing. The low pH used in the dyeing procedure increases the degradation of the cell wall polysaccharides, by acid catalysis. Also, scanning electron microscopy was used to show the plant cell wall degradation.

Evaluation of Uses of Some Enzymes in Removal of Plant Impurities from Raw Wool Fabrics

“…This process is based on the principle of converting cellulose into an easily removable hydro cellulose using a strong acid, sulfuric acid. Instead of processing using strong and dangerous chemicals, the use of enzymes reduces wool fiber damage, waste load, and energy consumption (Gouveia et al, 2008). In this study, the effects of crude cellulase from the new isolate Bacillus subtilis 171ES and crude phytase enzymes from Bacillus megaterium EBD9-1 and commercial pectinase enzyme on the removal of cellulosic or plant impurities in wool fabrics were investigated.…”

Enzymatic processing of natural fibres: white biotechnology for sustainable development

“…Enzymatic treatment using cellulases and pectinases may promote the degradation of vegetable matter resulting in its easy removal and thus minimize the concentration of sulfuric acid needed for the carbonizing process. 211,212 Shrink-proofing treatment is one of the most important quality enhancing steps in wool finishing processes. 213 The commercially practised shrink-proofing processes can be grouped into three categories: subtractive (oxidation, reduction), additive (synthetic resin layer) and a combined process (e.g.…”