Jessie (Zhengjie) Liu | ALES Graduate Seminar

Event details: A graduate exam seminar is a presentation of the student’s final research project for their degree.
This is an ALES PhD Final Exam Seminar by Jessie (Zhengjie) Liu. This seminar is open to the general public to attend.

PhD with Dr. Marleny Aranda Saldana.

Zoom Link: https://ualberta.ca.zoom.us/j/93449381426?pwd=K1SC713zVDpnKHP1hGejP4njcwkOMh.1

Thesis Topic: Conversion of barley straw and shrimp shell to value-added hydrogels and aerogels using green technologies: Pressurized fluid, high intensity ultrasound, and supercritical CO2 drying

Abstract: 

Upcycling refers to the process of transforming low value biomass to new materials of higher quality, price, or functionality. Barley straw, an agricultural biomass mainly composed of cellulose (30-40%), hemicellulose (20-25%) and lignin (15-17%), and shrimp shell, an animal biomass composed of chitin (15-22%) and protein (41-49%), are underutilized byproducts with low market value. The main objective of this thesis was to use pressurized fluids (PF) to fractionate barley straw and shrimp shell, and then bleach and nanofibrillate the obtained cellulose fiber via high-intensity ultrasound (HIUS) to produce self-assembled scaffolds. In addition, deacetylated chitosan (CS), a natural cross-linker, was used to produce composite scaffolds with cellulose nanofiber (CNF), which were loaded with collagen (COL) peptides that can be potentially used as scaffolds for cartilage healing and regeneration. Specifically, barley straw and shrimp shell were first upcycled to obtain CNF and CS, respectively.

The first two studies investigated the catalytic effect of aqueous ethanol and carboxylic acid at subcritical water (sCW) conditions on the hydrolysis of barley straw (180- 220°C, 50-200 bar, flow rate of 5 mL/min for 40 min, 0-100% v/v ethanol) and shrimp shell (140-260o C, 50 bar, 5 mL/min for 10-60 min, 0-10 wt.% citric and malic acid). The maximum hemicellulose sugars were removed from barley straw after sCW fractionation at 200°C/40 min, resulting in a cellulose-rich residue (purity 68.43%). Pressurized aqueous ethanol (PAE 60%) at 220o C removed more phenolic compounds (75.38 mg GAE/g straw) and lignin (63.77%). On the other hand, sCW treatment of shrimp shell at 260o C for 60 min resulted in the highest chitin yield of 26.39%, with deproteinization degree of 58.05%, and deacetylation degree of 66.29%. The sCW + malic acid (10 wt.%) treatment at 260o C/60 min improved amino acid iii removal to 140.11 mg/g shrimp shell. These results indicated that PAE and sCW + carboxylic acid can catalyze the delignification and deproteinization of barley straw and shrimp shell, respectively.

The third and fourth studies investigated the effect of HIUS treatment on delignification and nanofibrillation of the obtained cellulose-rich residue. Three different bleaching processes (acidic sodium chlorite bleaching, alkaline hydrogen peroxide bleaching, and HIUS assisted bleaching) at 75-80°C for 2-6 h were investigated, resulting in cellulose fiber with purity of 91%, and diameter of 3-5 μm. Then, cellulose fiber was nanofibrillated using the HIUS treatment (24-72 kJ/g) to obtain CNF hydrogels with a maximum fibrillation yield of 62 wt.% at 72 kJ/g. After, hydrogels were supercritical CO2 (SC-CO2) dried to form aerogels. The addition of shrimp shell CS improved aerogel stiffness to 3.2 bar, which is good for scaffolds.

The last study loaded COL peptide (1-10 wt.%) in CNF + CS composite hydrogels using a HIUS treatment and freeze-dried to form aerogels. The release of COL peptides from CNF + CS aerogels followed a biphasic pattern, where 5.42 ± 0.34 and 10.05 ± 0.42 mg/g COL peptides were released within 1 and 48 h, respectively.

In summary, the results suggested that PF fractionation followed by HIUS and SCCO2 or freeze drying is a promising strategy for biorefining barley straw and shrimp shell towards nanofiber and potential tissue engineering scaffold production.