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To explore high-quality microbial resources with the capability of ramie degumming, we collected soil samples from rotten ramie and straw heaps. After enrichment culture by ramie raw materials, bacterial strains with the potential ramie-degumming function were screened using a pectin-hydrolysis plate. Dominant bacteria were identified by combining colonial morphological characteristics with the molecular biology method, and their ramie-degumming effects were verified through comprehensive biological degumming indices. Results demonstrated that Bacillus aryabhattai, Bacillus thuringiensis, Lysinibacillus fusiformis, and Acidovorax temperans were successfully obtained. The highest pectinase activity, 98.2 U/mg, was found by A. temperans. B. thuringiensis showed the best ramie-degumming effect. The residual gum content, single-fiber linear density, and bundle-breaking strength of the degummed ramie fiber treated with B. thuringiensis were 8.32%, 6.80 dtex, and 7.84 cN/dtex, respectively. The residual gum content of the ramie fiber treated with B. thuringiensis met the textile requirement (<10%), and the values of all other indicators were also satisfactory. Therefore, B. thuringiensis was an excellent strain for ramie degumming, indicating potential industrial applications. [ABSTRACT FROM AUTHOR]

Pectinase plays a crucial role in ramie bio-degumming. A pectate lyase gene (pel 4J4) from the high-efficiency degumming bacteria Dickeya dadantii DCE-01 of bast fibers was cloned and connected to pET28a, and then the recombinant plasmid was successfully transformed into Escherichia coli BL21(DE3). The pectate lyase (Pel4J4) induced was purified by ultrafiltration and Sephadex G-100 gel chromatography. The enzymatic properties of Pel4J4 were studied in detail. pel 4J4 (GenBank accession number: KC900167) had a sequence length of 1179 bp, encoding 392 amino acids. The extracellular pectate lyase activity of pET28a- pel -BL was up to 204.4 IU/mL. The optimal temperature and pH of the purified Pel4J4 were 55℃ and 8.5, respectively. The stable temperature and pH of Pel4J4 activity were 45℃ and 8.5–10.0, respectively. The catalytic activity is Ca2+ dependent and promoted by 1 mmol/L Zn2+, Fe3+, Ca2+, and NH4+, but seriously inhibited by Cu2+ and Pb2+. The optimal substrate is citrus pectin with more than 85% esterification. The heat-resistant alkaline Pel4J4 could strongly degrade natural ramie pectin, indicating a promising application prospect in ramie bio-degumming. [ABSTRACT FROM AUTHOR]

Xylanase plays an important role in the hydrolysis of hemicellulose and has gained much attention in the field of biological degumming. The research for xylanases with cellulase-free and high activity for biological degumming has intensified in recent years. In the present research, heterologous expression of a novel endo-β-1,4-xylanase (GH30) from Dickeya dadantii DCE-01 in Escherichia coli BL21 (DE3) was reported. Biochemical characterization of the enzyme and a potential application in ramie biological degumming was discussed. The results showed that the xylanase gene consists of 1251 nucleotides, belonging to glycoside hydrolase family 30 (GH30). The optimal activity of the xylanase was observed at 50℃ and a pH value of 6.4. The Km and Vmax values for beechwood xylan were 14.25 mg/mL and 296.6 μmol/mg, respectively. The catalytic activity was enhanced by addition of 1 mM Cu2+, Ca2+, Mg2+, and K+. The recombinant enzyme was specific for xylan substrates. The enzyme exhibited hydrolytic activity toward ramie hemicellulose. The recombinant xylanase could be effectively applied to ramie degumming. [ABSTRACT FROM AUTHOR]

Apocynum venetum fiber is known as the “king of wild fibers”. The traditional chemical degumming method for A. venetum limits the development of the industry due to serious pollution and fiber damage. By machine rolling preprocessing, bacteria culture, soaking fermentation, inactivation, water scrubbing, and drying under fermentation conditions of bath ratio 1:15, inoculum size 2%, temperature 33℃, and fermentation time 16 h, A. venetum fiber could be extracted from A. venetum bast. Strain Pectobacterium sp. DCE-01 simultaneously secreted pectinase, mannanase, and xylanase, which can decompose the main components of A. venetum non-cellulose. The catalytic activities of pectase, mannanase, xylanase, and cellulase at 16 h were 12.47, 7.56, 6.02, and 2.82 U/ml respectively. Compared with chemical degumming, bio-degumming exhibited 22.56% higher residual gum content, 18.14% higher breaking strength, and 44.33% lower chemical oxygen demand. [ABSTRACT FROM AUTHOR]