Enhancement of Cellulase Production by Penicillium oxalicum Using Traditional Chinese Medicine Residue and Its Application in Flavonoid Extraction

Cellulase is an inducible enzyme. By using traditional Chinese medicine residues (TCMRs) as inducer for microbial cellulase, the enzyme’s production yield can be improved. Additionally, this approach enables the resource utilization and harmless treatment of TCMRs. In this study, a fungus that can use TCMRs as a substrate was screened and identified as Penicillium oxalicum. The fungus grew well in the culture medium containing TCMRs, and the highest filter paper activity (FPA) reached 2.06 IU/mL in forsythia leaves residue (FR). After fermentation, the FR exhibited the highest weight loss rate, reaching 22.67%. Enzyme production conditions were optimized using the Plackett–Burman (PB) and Central –Composite Design (CCD) methods. The FPA could reach 2.75 IU/mL under the optimal conditions of FR concentration of 24.84 g/L, (NH4)2SO4 concentration of 2 g/L, temperature of 34.44 °C, pH 6.20, rotational speed of 200 rpm, and inoculum size of 6%, which was 33.50% higher than that before optimization. The crude cellulase was used to extract total flavonoids from TCMRs, and the extraction rate of total flavonoids increased by 24.2–55.1%. The results demonstrated that TCMRs are effective for inducing substrates for cellulase production by Penicillium oxalicum Ti-11. Furthermore, the crude cellulase produced significantly promoted total flavonoids extraction from TCMRs.