Azadeh Aghashahi | ALES Graduate Seminar

A graduate exam seminar is a presentation of the student’s final research project for their degree.
This is an ALES MSc Final Exam Seminar by Azadeh Aghashahi. This seminar is open to the general public to attend.
Thesis Topic: Oligosaccharides production and purification from barley bran by-product using supercritical CO₂ extraction, subcritical water hydrolysis and membrane filtration

MSc with Dr. Marleny Aranda Saldana.

Seminar Abstract:

Barley bran is a by-product of the food industry, and a good source of lipid, protein and arabinoxylan. In this thesis, fractionation of barley bran was carried out to remove lipid, starch and protein to obtain enriched arabinoxylan sample. Defatted-destarched bran was used for further hydrolysis, targeting production of xylo-oligosaccharides (XOS) with DP 2-4. Lipid was extracted using supercritical CO₂, followed by enzymatic hydrolysis to remove starch. Defatted bran with 0.3% lipid was obtained. Defatted-destarched bran had 1% starch and 26.3% db arabinoxylan. Subcritical water (SCW) was used as an environmentally friendly approach to hydrolyse defatted-destarched bran. Temperature had a significant effect on the XOS production. The highest XOS content was produced at 180℃, where 112.5 mg of total XOS was obtained within 30 min, with no significant difference after 60 min hydrolysis. Deproteinized bran with 42.2% db arabinoxylan was hydrolyzed using SCW at 180℃/50 bar/30 min. Amounts of 100.9, 120.6, 112.4 and 334 mg of xylobiose, xylotriose, xylotetraose and total XOS were obtained in the hydrolysate. Deproteinized bran was also treated using enzymatic hydrolysis with endo–xylanase. Maximum amount of total XOS was 21.11 mg obtained using 10 U of enzyme at 40℃, pH of 4.5 after 4 h incubation. The recovery of total XOS from initial xylan of deproteinized bran was 78.4 and 45.1% for SCW and enzymatic hydrolysis, respectively. Purification of deproteinized bran SCW hydrolysate was performed using ultrafiltration with 1 kDa membrane to remove compounds with high molecular weight. In total, 68% of initial total XOS was recovered after passing through 1 kDa membrane. This permeate was treated by activated carbon adsorption (10% w/w) to remove monomers (arabinose and xylose) from XOS. Activated carbon was washed with ethanol solutions (15 and 30% v/v) to liberate the adsorbed XOS. Finally, 55% of xylose and 51% of arabinose were removed and 52% of total XOS was recovered in the ethanol fraction. The results suggest that SCW hydrolysis is a promising method to produce XOS from barley bran by-product in a short time with higher recovery than the enzymatic hydrolysis. The obtained XOS has potential use in the functional food area as prebiotics.