Microbial degumming offers an environmentally sustainable route for the extraction of natural ramie fibers. However, there are currently no genetically engineered bacteria suitable for large-scale industrial production. In this study, Dickeya dadantii strain DCE-01, a dominant ramie-degumming bacterium, was systematically investigated using time-resolved quantitative proteomics. This research revealed a temporally coordinated, multi-enzyme catalytic mechanism, in which pectate lyases were highly expressed at the initial stage to rapidly depolymerize surface pectin, followed by sustained expression of hemicellulases that ensured the complete removal of residual non-cellulosic materials. Quantitative real-time PCR (qRT–PCR) results showed strong concordance with the proteomic data, confirming that transcriptional regulation drives the dynamic enzymatic response. This integrative analysis, linking macroscopic morphological evolution with microscopic molecular changes, elucidates the intrinsic mechanism underlying efficient biological degumming by D. dadantii strain DCE-01 and provides valuable insights for the rational design of high-performance engineered bacteria for industrial fiber processing.

Exploring the metabolic regulatory mechanisms of bacteria for ramie degumming and constructing more efficient engineered strains are preferred strategies to solve the technical bottleneck of high residual gum content in fibers. Bacillus subtilis strain 168, an advantageous bacterium for microbial degumming, was previously found to significantly up-regulate the expression of bast two-component system (TCS) response regulators CitT, YvcP, and YycI when using ramie as the sole carbon source. In this study, the genes encoding CitT, YvcP, and YycI proteins were knocked out and compared the effects between these gene knockouts and the original strain on the degumming efficiency. The aim was to identify the key TCS response regulators that significantly affect degumming efficiency and to explore the functions of these different response regulators. The results demonstrated that knockout of citT, yvcP, or yycI genes significantly reduced degumming efficiency. Specifically, CitT protein primarily regulated the degradation of pectin, YvcP protein mainly regulated the degradation of hemicellulose, and YycI protein was involved in the regulation of both pectin and hemicellulose degradation. Notably, the absence of CitT protein caused the most significant reduction in degumming efficiency. These findings provide valuable insights into the construction of engineered strains with high degumming efficiency for ramie fibers.

Efficient and eco-friendly bioscouring of ramie fabric is a critical step in the textile industry. To obtain polygalacturonase (DdpgA) suitable for the bioscouring of ramie fabric, a novel polygalacturonase gene (ddpgA) from the ramie-biodegumming strain Dickeya dadantii DCE-01 was subjected to bioinformatic analysis and heterologous expression. The recombinant plasmid pET28a-ddpgA was introduced into E. coli BL21(DE3), and the engineering strain BL21/pET28a-ddpgA was constructed; then induction conditions were optimized by response surface methodology. The recombinant DdpgA was purified and enzymatically characterized and further applied to the treatment of greige ramie fabric in combination with mannanase and xylanase. The results showed that the optimal pH of DdpgA was 5.0 and the optimal temperature was 55 °C; the enzyme was stable over the pH range of 3.0–6.0 and retained more than 50% of its activity after incubation at 55 °C for 60 min. DdpgA exhibited the highest catalytic activity toward sodium polygalacturonate. Mn²⁺ significantly activated DdpgA, whereas Ba²⁺, Pb²⁺, and Cu²⁺ inhibited its activity. Compound-enzyme scouring of ramie fabric formulated with DdpgA achieved a weight loss rate of 15.22%, a pectin removal rate of 51.28%, and a water-drop wetting time of less than 2 s; scanning electron microscopy confirmed the effective removal of gummy composites from the ramie fiber surface. This enzymatic scouring for ramie fabric avoids the strong alkali and high temperature required by conventional alkalic scouring, and thus represents an environmentally friendly alternative for ramie-fiber processing. Therefore, this study achieved high-level soluble expression of ddpgA in E. coli and obtained an acidic mesophilic polygalacturonase with demonstrated ramie bioscouring performance.

Ramie fabrics suffer from inherent prickle sensation due to rigid fiber morphology, limiting their applications. This study aims to alleviate this issue through an eco-friendly enzymatic modification. Six enzymes (cellulase, laccase, hemicellulase, xylanase, pectinase, alkaline protease) were used. Single-factor experiments optimized enzyme dosage, liquid-to-solid ratio, and treatment time; response surface methodology (RSM) further refined conditions, followed by compound enzyme treatments to explore synergies. Scanning electron microscopy (SEM) validated changes. Results showed the optimal multi-enzyme combination (2% hemicellulase, 3% cellulase, 3% laccase) reduced prickle sensation score by 43.8% (to 1.8 vs. 3.2 for untreated), with SEM confirming less surface fuzz and improved uniformity. This effective enzymatic strategy provides a green approach to enhance ramie fabric comfort, with practical implications for textile processing.

This study systematically investigated the liposoluble components and their potential correlation with antibacterial activity in six bast fiber varieties—Apocynum venetum, Corchorus capsularis, Hibiscus cannabinus, Linum usitatissimum, Cannabis sativa, and Boehmeria nivea—using gas chromatography-mass spectrometry (GC-MS). The analysis identified a range of compounds including alkanes, phenols, sterols, esters, and triterpenoids, with notable compositional differences among the fibers. Tetracontane was predominant in A. venetum (40.39%) and H. cannabinus (22.47%), while γ-sitosterol was highest in C. capsularis (12.80%). L. usitatissimum was rich in n-hexadecanoic acid (9.16%), C. sativa in heptacosanal (8.96%), and B. nivea in both tetracontane (45.42%) and tetracosane (10.09%). Based on existing literature, components such as 2,4-di-tert-butylphenol, γ-sitosterol, n-hexadecanoic acid, lupeol, and betulin were inferred as key antibacterial constituents. A comprehensive review of reported antimicrobial activities revealed distinct antibacterial spectra and intensities across the varieties, aligning with their unique liposoluble profiles. This study provides a systematic chemical profile of bast fibers and offers a predictive assessment of their antibacterial potential. The findings lay a chemical foundation for future targeted research and development of antibacterial materials derived from specific bast fiber varieties.