Purification and isolation of β-glucans from barley: Downstream process intensification

• β-glucan liquid extracts were purified by means of enzymes and membrane technology.
• Starch concentration was reduced by 90% after 9 min hydrolysis (55 °C).
• β-glucan extraction and enzymatic starch hydrolysis were integrated in one step.
• Process intensification: 7 min at 55 °C to extract β-glucans and remove starch.
• Starch hydrolysis products were separated from β-glucan by diafiltration.

The purpose of this work was to study the purification and isolation (downstream process) of the β-glucan extracted from barley in an ultrasound assisted extraction (UAE) process. The co-extracted starch (average concentration 5.2 ± 0.1 g/L) was hydrolyzed by means of α-amylase. The optimization of the hydrolysis length, temperature and enzyme dose led to removal efficiencies higher than 90% (9 min hydrolysis length and enzyme doses of 100 μL/g at 55 °C), compared to the traditional hydrolysis processes (1 h at 95 °C). In a second step, a significant intensification of the process has been achieved by dosing the enzyme during the UAE step (7 min at 55 °C), resulting in a starch removal of 90%.Dextrins and other oligosaccharides were formed as a consequence of the enzymatic hydrolysis. In order to separate these low molecular weight molecules from the β-glucan (239 kDa), an ultrafiltration process (polysulfone membrane, nominal MWCO 100 kDa) was tried in a tangential flow cell: diafiltration successfully eliminated more than 45% of the oligosaccharides present in the liquid, providing a significant increase in the concentration of β-glucan and with the possibility of improving the percentage of elimination.The combination of these three technologies (UAE, enzymatic hydrolysis and diafiltration) allows getting high purity β-glucan concentrates (greater than 70%).

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