. 2023 Mar 7;11:e14966. doi: 10.7717/peerj.14966

Table 4. Degumming methods and the quality of fiber obtained from A. venetum (studies between 2012 to 2022).

Degumming type	Processing method	Fiber quality	Impact on the environment	Reference
Bio-chemical combined degumming process	Apocynum fibers > > Boiling (12 g/L pectinase, Material: Liquor (M: L)-1:30, time: 2 h, temperature: 50 °C, PH8-10) > > washing > > boiling (12 g/L NaOH, M: L-1:30, time: 1.5 h) > > washing > > bleaching (20 g/L H₂O₂, M: L-1:30, time: 1.5 h, temperature: 95 °C) > > washing > > oven-dried (temperature: 80 °C)	Fiber breaking strength: 22.84 cN/dtex; Whiteness: 73.9; Fineness:4.97 dtex; Crystallinity: 74.5%; Moisture regain: 7.7380%.	This method could reduce the pollution caused by chemicals.	Chen et al. (2022a), Chen et al. (2022b)
Biodegumming (Bacterial strain Pectobacterium wasabiae)	Oscillating fermentation (fermentation time: 12 h, inoculum size: 2%, M: L -1:10, temperature: 33 °C, shaking rate:180 rpm) > > boiling (temperature: 100 °C, time: 20 min) > > washing by machine	Residual gum content: 12.57%; Percentage of raw material weight loss: 30.05%; The fiber counts:1,002 m/g	Chemical Oxygen Demand: 3,119 mg/L	Duan et al. (2021)
Microwave-assisted ultrasonic degumming	Sample > > Microwave pretreatment (10 g/L NaOH, M: L-1:20, time: 20 min, temperature:120 °C, power: 600W) > > rinsing > > drying > > ultrasonic degumming > > soaking (10 g/L NaOH and 1 g/L H₂O₂, M: L-1:20, time: 60 min, temperature:50 °C, power: 800W, frequency: 28 Hz	Residual gum content: 5.15%; Fiber breaking strength: 7.67 cN/dtex; Fiber length:32.5mm; Whiteness: 83%; Fineness: 4.05 dtex;	For degumming 1 kg of raw AV bast needed 0.6 kg of chemical reagents	Li et al. (2020)
Chemical degumming	Stripped bast by machine > > pretreatment (0.2%Al₂(SO₄)₃, room temperature, M: L- 1:15, time: 7h) > > fiber washing > > cooking (1%NaOH, 0.25% thiourea, M: L- 1:15, temperature:95 °C, time intervals:2, 3, 5 h) > > washing > > acid soaking (2% CH₃COOH, room temperature, M: L- 1:15, time: 2 min) > > washing > > bleaching (2% H₂O₂, 0.1% tween-80 surfactant, temperature: 94 °C, M: L- 1:15, time: 1 h) > > washing > > drying (oven-dried at 105 °C).	Moisture regain: 7.0%; The cooking processes of three different time intervals: Residual gum content: 3.64, 3.03, 2.70%, respectively; Crystallinity: 81.14, 78.80 73.75%, respectively; Tenacity: 8.63, 7.00, 6.93 cN/dtex, respectively; Fiber diameter: 2.52, 2.37, 2.14 dtex, respectively.	The method uses metal salts of aluminum for pretreatment, which is more sustainable.	Halim et al. (2020)
Deep eutectic solvents (DES) with the assistance of microwave	DES Configuring (choline chloride and car bamide-1:2 molar ratio (w/w) > > oil bathing (temperature: 80 °C, M: L- 1:20, time: 1 h) > > immersing with microwave oven (temperature:110 °C, M: L- 1:20, time: 1 h ) > > washing > > cooking (1%NaOH, time: 1 h) > > washing > > oven-dried	Residual gum content: 6.54%; Fiber breaking strength:14.14 cN/dtex; Crystallinity: 77.92%. Average fiber fineness: 4.05 dtex.	DES reagent selected for this method is biodegradable	Song et al. (2019)
Degumming with Ionic Liquid (IL:1-butyl-3-methylimidazolium acetate-water mixtures.) Pretreatment	A.venetum fibers > > pretreatment > > water boiling (temperature: 70 °C, M: L- 1:20, time: 3 h) > > rinsing with hot water (60 °C) > > rinsing with tap water > > degumming with IL-water mixtures (80% IL-water mixtures, temperature: 90 °C M: L- 1:20, time: 4 h) > >chemical degumming (10 g/L NaOH and 2% Na₃P₃O₁₀, M: L- 1:20 temperature: 95 °C, time: 2 h) > > acid rinsing (1.5 g/LH₂SO₄, room temperature, M: L- 1:20, time: 5 min) > > washing with tap water > > drying	Residual gum content: 3.90%; Fiber breaking strength: 452.7 cN/dtex; Fineness: 0.7 um Crystallinity:76.62%	Mild conditions and low toxicity.	Yang et al. (2019)
Chemical degumming	Pre-acid treatment (2% H₂SO₄, temperature: 60 °C, M: L- 1:15, time: 1 h) > > washing > > first-cooking (5% NaOH, 3% Na₂SiO₃, 2.5% Na₂SO₃, temperature: 100 °C, M: L- 1:10, time: 2.5 h) > > washing > > second-cooking (15% NaOH, 3% Na₂SiO₃, 2% sodium tripolyphosphate, temperature: 100 °C, M: L- 1:10, time: 2.5 h) > > washing > > acid rinsing (1 g/L H₂SO₄) > > washing > > dewatering > > shaking > > drying	Fiber breaking strength:401.56 cN/dtex; The average length:29.68 mm; Fineness:4673.25 nm; Color: reddish yellow; Moisture regain: 8.70%; Crystallinity:70.36%;	–	Lou et al. (2019)
Bio-degumming (Pectobacterium sp. DCE-01)	Machine rolling preprocessing > > bacteria culture (Pectobacterium sp. DCE-01, temperature: 34 °C, time: 6 h, speed: 180rpm, culture medium: 1.0% glucose, 0.5% NaCl, 0.5% beef extract, 0.5% peptone, and 100 mL water, pH 6.5–7.0.) > > Bacterial liquid preparation (water containing: 0.05% NH₄H₂PO₄ and 0.05% K₂HPO_4, pH 6.5–7.0) > > fermentation and degumming (temperature: 33 °C, M: L- 1:15, bacterial solution: fermentation water-2:100, time: 16 h, speed: 180 rpm) > > boiling (temperature: 33 °C, time: 20 min) > > washing by a fiber washer > > drying	Residual gum content: 12.22%; Fiber breaking strength: 5.47 cN/dtex;	Chemical Oxygen Demand: 3,245 mg/L	Duan et al. (2017)
A novel ionic liquid degumming	Boiling (1 g/L H₂SO₄, temperature: 50 °C, M: L- 1:20, time: 2 h ) > > washing (until the washings were neutral) > > degumming (80% 1-butyl-3-methylimidazolium acetate, temperature: 130 °C, M: L- 1:20, time: 3 h ) > > washing > > drying	Residual gum content: 9.80%; Fiber breaking strength: 4.64 cN/dtex; Length:24.44 mm Fineness: 4.10 dtex; Crystallinity:78.66%	The degumming process was mild compared to the traditional chemical process.	Yang et al. (2015)