Nanofiber production from agricultural straw biomass using pressurized fluids and ultrasound processing for tissue engineering scaffolds

• Author / Creator

  Huerta, Raquel

• Agricultural straw is an abundant lignocellulosic biomass mainly composed of cellulose (33-75%), hemicellulose (13-37%) and lignin (3-31%) that offers great potential as a feed material for a biorefinery. Emerging technologies such as pressurized fluid fractionation and high-intensity ultrasound are promising alternatives to be employed for straw biomass refining towards bioactive compounds like phenolic compounds, and nanofiber production. Specifically, cellulose nanofibers have been considered as potential scaffold for tissue engineering applications. Therefore, the objective of this thesis was to employ pressurized fluids such as subcritical water and pressurized aqueous ethanol to fractionate canola straw biomass, and then nanofibrillate the treated fiber via high-intensity ultrasound to produce self-assembled scaffolds, and investigate their cytocompatibility for human gingival fibroblast cells. First, the straw biomass was treated using pressurized fluids at 140-220 °C, 50-200 bar, 0-100% v/v ethanol, with a constant flow rate of 5 mL/min for 40 min. Pressurized aqueous ethanol (20% v/v) at 180 °C and 50 bar, resulted in a hydrolysate with maximum total carbohydrates (443-528 mg GE/g straw) and phenolics (45-53 mg GAE/g straw) contents, and a solid residue mainly composed of 63% cellulose, 9% hemicellulose and 20% lignin. Then, the obtained enriched cellulose fiber was nanofibrillated using high-intensity ultrasound at specific energies of 4-20 kJ/g to obtain lignocellulosic nanofibers with maximum fibrillation yield of 36 wt.%, and an average diameter of 21 nm. Further bleaching of the enriched cellulose fiber (at 75 °C for 2-6 h) removed large amount of lignin and resulted in a bleached cellulose fiber mainly composed of 71-82% cellulose, 4-5% hemicellulose and 8-18% lignin. The nanofibrillation process of bleached fibers using high-intensity ultrasound at specific energies of 4-20 kJ/g led to nanofibers with maximum fibrillation yield of 46 wt.% and an average diameter of 14 nm, which were self-assembled into a three-dimensional hydrogel structure. Cytocompatibility test performed using the dried hydrogel scaffolds showed no cytotoxicity of the residual lignin of up to 18%, and an increased cell proliferation compared to the control (glass slip) up to day 11. Finally, clove essential oil up to 0.5 wt.%, and cellulose nanofiber hydrogel were used as an emulsion-filled gel system for tissue engineering scaffolds with no cytotoxicity and cell viability of 74-101%. The results suggested that pressurized fluid fractionation followed by high-intensity ultrasound is a promising strategy for biorefinering of straw biomass towards nanofiber and tissue engineering scaffold production. Furthermore, the emulsion-filled gel using clove essential oil and cellulose nanofiber hydrogel could provide scaffolds with unique antimicrobial properties, suggesting its potential use in the biomedical field.

• Subjects / Keywords

  • Ultrasound
  • Pressurized fluids
  • Cellulose
  • Nanofibers
  • Lignin
  • Scaffold
  • Straw

• Graduation date

  Spring 2020

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/r3-tt6y-y033

• License

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