Biological enzyme is a non-toxic and environment-friendly biocatalyst, and its chemical essence is protein. The production and application of enzymes have a history of more than 80 years at home and abroad. In the 1980s, bioengineering, as a new high-tech technology, has developed rapidly in China. The fields of enzyme production and application have gradually expanded, and the application of enzymes in the textile industry has become more and more mature. From desizing of cotton fabrics and degumming of silk in the past, it has been widely used in various fields of textile dyeing and finishing, which reflects the advantages of biological enzymes in the dyeing and finishing industry. At present, the enzyme treatment process has been recognized as a green production process that meets the requirements of environmental protection. It not only improves the wearability of textiles, but also is beneficial to ecological and environmental protection because of its innocuity, low dosage, biodegradable wastewater and no pollution.
Action mechanism of biological enzyme
The difference between enzyme protein and other protein lies in that all enzymes have active centers. Enzymes can be divided into four structures: the first structure is the arrangement order of amino acids; The secondary structure is the planar spatial conformation of peptide chain; The tertiary structure is the three-dimensional conformation of peptide chain; The quaternary structure is that peptide chains are combined with each other by non-* * valence bonds to form a complete protein molecule. What really plays a decisive role is the primary structure of the enzyme, and its change will change the nature of the enzyme (inactivation or denaturation). The mechanism of action of enzymes is recognized by Koshland's theory of "induced fit", which mainly includes: when the substrate binds to the active site of the enzyme, the conformation of the enzyme changes. The correct orientation of catalytic groups is necessary for catalysis. Substrate induces the conformational change of enzyme protein, which leads to the correct positioning of catalytic groups and the combination of substrate to the active site of enzyme.
Types of biological enzymes used in dyeing and finishing industry
The application of biological enzyme technology in dyeing and finishing mainly includes two aspects: (1) pretreatment of natural fiber fabric, and removal of impurities on fiber or fabric with biological enzyme, which creates conditions for subsequent dyeing and finishing. (2) After finishing the fabric, biological enzyme is used to remove the fluff on the fiber surface, or to reduce the amount of fiber, so as to improve the appearance, feel and style of the fabric. At present, the biological enzymes used mainly include the following.
pectinase
Pectinase is mainly composed of pectin lyase, polygalacturonase, pectinate lyase and pectinesterase. Pectin substance is highly esterified polygalacturonic acid. When pectinase acts on pectin, pectin lyase, polygalacturonase and pectate lyase directly act on the sugar bond inside the molecular chain of pectin polymer, while pectinesterase hydrolyzes polygalacturonase, creating more positions for polygalacturonase and pectate lyase.
lipase
Lipase can hydrolyze fat into glycerol and fatty acids, and fatty acids are further oxidized by B, and one C2 substance is removed at a time to generate acetyl-CoA (N-cyclohexyloctylamine), which enters TCA (tricarboxylic acid) ring for complete oxidation or glyoxylic acid ring to synthesize sugars.
proteinase
Proteases secreted by microorganisms vary from strain to strain. For example, Bacillus subtilis secretes gelatinase and caseinase, which can hydrolyze gelatin and casein. Streptomyces fischeri secretes keratinase, which can hydrolyze keratin of animal hair, horn and hoof. Protein is decomposed into peptides by protease, and then hydrolyzed into amino acids by peptidase.
cellulase
Cellulase is a multi-component enzyme system, and most of the cellulases used in textile industry are made by Trichoderma fungi. Cellulose disaccharide hydrolase, also known as exo-cellulase, consists of two enzymes, CHB I and CHB II, while endoglucanase, also known as endo-cellulase, consists of at least five cellulases (EG I, EG II, EG HI, EG IV, EG V). In addition, there is 13-glucuronidase. These cellulases have synergistic effect in the hydrolysis of cellulose.