Evaluation of bamboo water-retting for fiber bundle extraction

Bamboo fiber bundles were successfully extracted from bamboo culms using water-retting, taking advantage of enzymes secreted by microorganisms in the retting liquid. The harvest year and place of origin of the bamboo and the source of water impacted the products of the retting process. One-month-old bamboo was decomposed completely, whereas the one-year-old sample was hardly changed after 24-day retting. Moisture regain and crystallinity varied with the different origins of the bamboo. However, all samples resulted in similar chemical structures and thermal properties. The best operational conditions for water-retting were 3-month-old bamboo from Wuxi incubated in deionized water. Enzyme activities, including cellulase, xylanase, pectinase, and ligninolytic enzymes (lignin peroxidase, manganese peroxidase, and laccase) were monitored during a 24-day retting. Manganese peroxidase was the primary enzyme used to degrade lignin, resulting in absorbance at 294 nm of UV-Vis spectra. In addition, xylanase played a leading role in hydrolyzing hemicellulose, which was consistent with the change in reducing sugar yield. In addition, variations in dissolved oxygen and pH values were also recorded, indicating the changes in bacterial strains and the enzymatic system. The wastewater from bamboo retting showed good biodegradability but a lack of nitrogen and phosphorus. Overall, a manganese peroxidase–xylanase combined enzyme-retting treatment would offer a more environmentally friendly approach for extracting bamboo fibers.