Valorization of spent shiitake substrate for recovery of antitumor fungal sterols by ultrasound-assisted extraction

Practical applications The ongoing expansion of mushroom industries has generated enormous spent mushroom substrate with the potential for production of valuable chemicals. This study aimed to investigate ultrasound-assisted extraction (UAE) of fungal sterols from spent shiitake (Lentinula edodes) substrate (SSS) by response surface methodology. The results showed that three variables, including ultrasonic power, extraction time, and liquid-solid ratio, had considerable influence on the extraction efficiency of total fungal sterols with liquid-solid ratio being highly significant for the process. The optimal UAE conditions included liquid-solid ratio 22mL/g, ultrasonic power 432W, and extraction time 16min for the maximum recovery of fungal sterols (151.62mg ergosterol equivalents/100g dry weight) from SSS. Further GC-MS analysis indicated that the extracts yielded under the optimal conditions contained ergosterol, ergosta-7,22-dienol, and -sitosterol, in which ergosterol was the most abundant mycosterol. The extracts also showed a comparable antitumor effect against three cancer cell lines. Spent mushroom substrate, a major by-product of mushroom industries, remains a big challenge for the profitability of mushroom industries. Our results indicated that spent shiitake substrate can be valorized by UAE for production of fungal sterols.