Abstract:

Objective Bamboo pulp fibers are a type of regenerated cellulose fiber, produced from bamboo pulp by wet spinning method, and the bamboo pulp is cellulose substance extracted from natural bamboo through a series of chemical processes. Bamboo pulp fibers have excellent properties such as moisture absorption, permeable properties, and good antibacterial properties. However, the antibacterial mechanism of bamboo pulp fibers has not been fully elucidated yet. The objective of this study is to explore the antibacterial activity and functional components of bamboo pulp fibers, thereby establishing a theoretical foundation for the development and practical application of related products.

Method The shaking flask method was employed to determine the antibacterial rate of bamboo pulp fibers. The morphological structure, elemental composition, and chemical group composition of fibers were tested by scanning electron microscopy (SEM), organic elemental analysis and infrared spectroscopy. In order to further seperate antibacterial components in the bamboo pulp fibers, the method of dissolving bamboo pulp fibers with N-methylmorpholine-N-oxide (NMMO) and alkali/urea were used, then cellulose was precipitated in a non-solvent. Finally, the bamboo pulp fibers were degraded by sulfuric acid hydrolysis. A two-step sulfuric acid degradation method was adopted, and bamboo fibers were degraded with a concentrated sulfuric acid solution at low temperature, followed by dilute acid at an elevated temperature. Gas chromatography-mass spectrometry (GC-MS) was adopted to separate and analyze the components in the bamboo pulp fibers.

Results The SEM results showed that uneven grooves and cracks appeared in the surface of bamboo pulp fibers, making the fibers dry, which is unfavorable for bacterial survival and reproduction. Organic elemental analysis results indicated that bamboo pulp fibers are mainly composed of carbon, hydrogen, and oxygen elements, together with 0.20% nitrogen element. The infrared spectroscopy results indicated that bamboo pulp fibers have the characteristic absorption peaks of cellulose. After extraction with solvents such as methanol, ethanol and ethyl acetate, the antibacterial rate of bamboo pulp fibers decreased slightly but remained 70% or above, indicating that the antibacterial components in bamboo pulp fibers were not effectively separated. The regenerated cellulose from bamboo pulp fibers dissolved by NMMO had an antibacterial rate of 48.20% against Escherichia coli, while that dissolved by the alkali/urea system had an antibacterial rate of 67.60% against Escherichia coli, indicating that the antibacterial components in bamboo pulp fibers were not completely isolated, which proved that some antibacterial components were tightly bound to cellulose. The experiments on degradation of bamboo pulp fibers demonstrated that the sugar yield was the highest when the sulfuric acid concentration was 53%. Barium salt was added to remove sulfate ions from the bamboo fiber degradation solution. The GC-MS results analysis indicated that the hydrolysate of bamboo pulp fibers contained 27 compounds including carbohydrates, aldehydes, phenols, ketones and other substances. Among them, 5 chemical components, namely furfuryl alcohol, furfural, 2-undecan-one, maltol, and 2-hydroxy-4-methoxybenzaldehyde, had been confirmed to possess antibacterial activity and are the main antibacterial components in bamboo pulp fibers.

Conclusion The study on the antibacterial activity and antibacterial components of bamboo pulp fibers demonstrated that bamboo pulp fibers exert a stable inhibitory effect on Escherichia coli. The antibacterial activity of bamboo pulp fibers originates from the synergistic effect of multiple antibacterial components and the micromorphological structure. The study on the antibacterial activity and antibacterial components of bamboo pulp fibers provides a theoretical basis for the development of bamboo pulp fiber products.

Key words: bamboo pulp fiber, antibacterial property, sulfuric acid hydrolysis method, antibacterial component, cellulosic fiber, regenerated cellulose, gas chromatography-mass spectrometry