Nanofiltration concentration process of Ganoderma lucidum glycopeptides and membrane fouling mechanism based on the ultrasonic-regulated adsorption and concentration kinetics

Abstract

Lingzhi is the dried fruiting body of the fungus Ganoderma lucidum from the polyporaceae. It's non-toxic and has medicinal and edible use. The active ingredient Ganoderma lucidum glycopeptide presents a manufacturing problem of nanofiltration membrane contamination during concentration at room temperature because of its heat sensitivity. During the nanofiltration concentration process of Ganoderma lucidum glycopeptides, membrane fouling leads to low production efficiency, which is the primary problem limiting industrial production. In this study, a nanofiltration concentration model appropriate for industrial application has been developed and the nanofiltration contamination mechanism of Ganoderma lucidum glycopeptides was elucidated using ultrasound-assisted separation. Adsorption kinetics, concentration kinetics, and concentration polarization coefficient models were used to investigate the nanofiltration separation and contamination behavior of Ganoderma lucidum glycopeptides regulated by ultrasound. The nanofiltration contamination mechanism of Ganoderma lucidum glycopeptides was elucidated in conjunction with the membrane surface microstructure analysis. The ultrasonic-assisted membrane separation parameters were optimized to be transmembrane pressure 0.6 MPa, ultrasonic power 432 W, and pH 8.00, with rejections of triterpenoids, proteins, and sugars of 99.7%-94.4%, 97.8%-95.2%, and 91.8%-85.7%, respectively, as the fermentation broth volume increased from 2 L to 50 L. Accordingly, the SCQ-9200E ultrasonic apparatus has a bath tank, an ultrasonic frequency of 40 kHz, a power density of 0.24 W/cm2, and an amplitude of 20.78 μm. The membrane flux ranged from 19.23 to 13.97 L/m2·h. Adsorption rates for triterpenoids, proteins, and sugar components were 10.5%–0.8%, 2.1%–0.1%, and 3.9%–0.2%, respectively. The primary cause of concentration polarization under pressure, which results in membrane flux attenuation, is the accumulation of glycopeptide components on the membrane surface. According to the solute's adsorption kinetics model and the concentration rate constant, the triterpenoids and sugars were primarily physically adsorbed on the surface of the composite polyamide membrane material, while the protein components were primarily chemically adsorbed with physical adsorption as a supplement. Ultrasonic-assisted concentration may significantly increase component recovery rate, shorten concentration time, and improve nanofiltration separation efficiency. The membrane fouling model developed in this study can help clarify the fouling mechanism during nanofiltration concentration of plant fermentation solutions high in sugar and protein. By adjusting ultrasonic-assisted separation parameters, it simultaneously tackles the technological problem that makes it difficult to industrialize nanofiltration concentration at room temperature.