β-Glucan recovery from Ganoderma lucidum by means of pressurized hot water and supercritical CO2

• (1,3)-(1,6)-β-d-Glucans were extracted from mushroom Ganoderma lucidum.
• Pressurized hot water was used as solvent in a fixed bed unit.
• High temperatures favored the extraction but richness decreased dramatically.
• Mixtures PHW and supercritical CO2 improved the extractability of β-glucans.

(1,3)-(1,6)-β-d-Glucans were extracted from Ganoderma lucidum (34.2%, w/w) using pressurized hot water as solvent (P = 5 MPa) in a fixed bed laboratory scale unit. A RSM Box–Behnken experimental design was used to evaluate the effect of the temperature (135–175 °C), flow rate (0.7–1.3 mL/min) and solvent to biomass ratio (20–60 mL/g) on the extraction yield of β-glucans and the content in β-glucans of the final product. A dramatic effect of the temperature was observed: the higher the temperature, the higher the extraction yield; however, at temperatures above 158 °C the β-glucan content in the final product began to decrease. It was also seen that experiments longer than 80 min are required to get the β-glucans dissolved. Finally, the effect of the flow rate on the extraction yield was not significant, indicating that external mass transport was not controlling the extraction process. The extraction conditions that maximize both extraction yield of β-glucan (64.9 ± 0.8%) and led to the highest content in β-glucans in the final product (61.7 ± 1.0%) are 158 °C, 1.3 mL/min and 60 mL/g.The addition of supercritical CO2 to the pressurized hot water throughout the extraction (done at 155 °C, 1 mL/min of PHW and 40 mL/g) produced a significant improvement of the extraction yield up to 72.5% in the best tested conditions; effect primarily attributed to the acidification of the media obtained by the supercritical CO2.

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