Abstract
In this work, the use of polymeric ultrafiltration and nanofiltration membranes was investigated in order to recover glycyrrhizin and phenolic compounds from licorice wastewaters. Filtration experiments were performed on a laboratory scale using four polyamide thin-film composite membranes (GK, GH, GE, and DK, from GE Osmonics) with different molecular weight cut-offs (from 150 to 3500 Da). The permeate flux and retention values of glycyrrhizin, the total polyphenols, the caffeic acid, the total carbohydrate, and the total antioxidant activity as a function of the transmembrane pressure (TMP) and weight reduction factor (WRF) were evaluated. In selected operating conditions, the membrane productivity decreased in the order of GK > DK > GH > GE, with a similar trend to that of water permeability. Glycyrrhizin was totally rejected by selected membranes, independently of TMP and WRF. For the other antioxidant compounds, the retention values increased by increasing both of the parameters. According to the experimental results, a combination of membranes in a sequential design was proposed as a viable approach to produce concentrated fractions enriched in bioactive compounds and purified water from licorice wastewater.
Highlights
Licorice (Glycyrrhiza glabra L.) is a ligneous perennial shrub of the fabaceae family, growing mainly in central Asia, the Middle East, and south eastern Europe
Solution, they were allowed of the theinitial initialwater waterpermeability permeability membrane. These results indicate that the internal fouling effects were more effective than the cake layer effects. These results indicate that the internal fouling effects were more effective than the cake layer effects during the clarification of licorice wastewater
The potential of the commercial spiral-wound UF and NF membranes for the recovery of high-added value compounds from licorice wastewaters was evaluated
Summary
Licorice (Glycyrrhiza glabra L.) is a ligneous perennial shrub of the fabaceae family, growing mainly in central Asia, the Middle East, and south eastern Europe. The dried roots of licorice are widely used as a food flavoring agent and for various medicinal purposes since ancient times [1]. Preparations of licorice root are recognized for their significant antioxidant, anti-inflammatory, anti-microbial, anti-viral, and anti-carcinogenic activity [2], as well as for their hepatoprotective effects [3]. These activities are linked to a characteristic chemical composition, which includes several bioactive compounds, including glycyrrhizin (~16%), different sugars (up to 18%), flavonoids, saponoids, sterols, starches, amino acids, gums, and essential oils [4]. A characteristic wastewater stream, yellow to Molecules 2019, 24, 2279; doi:10.3390/molecules24122279 www.mdpi.com/journal/molecules
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