Shiraia fruiting body-associated fungi regulate the biosynthesis of hypocrellin A

Abstract:

The fruiting bodies of fungi of genus Shiraia inhabiting bamboo have a medicinal use in traditional Chinese medicine. Hypocrellin A (HA), the main bioactive perylenequinone pigment from S. bambusicola fruiting bodies is a novel non-porphyrin photosensitizer with antitumor and antimicrobial properties.Objective To investigate the effects of Shiraia fruiting body-associated fungi on HA biosynthesis and develop a co-culture method for enhancing HA production.Methods Shiraia fruiting body-associated fungi were isolated and the strains influencing HA biosynthesis were screened by a plate confrontation assay. The effects of intracellular and extracellular metabolites of the strains on HA production were evaluated. A co-culture system for Shiraia sp. S9 and associated fungi was established and optimized for enhancing HA production.Results There were 34 fungal strains including 6 host Shiraia strains isolated from the fruiting bodies. Among them, Fusarium sp. SF12 and its extracellular polysaccharides significantly promoted HA biosynthesis. Fusarium sp. SF12 did not noticeably affect the growth of Shiraia sp. S9 but regulated HA synthesis by upregulating the transcription levels of key enzyme genes involved in HA biosynthesis. The total HA yield was enhanced to 209.46 mg/L on day 8 after adding spores (100 cell/mL) from Fusarium sp. SF12 to the Shiraia culture at the time point of 24 h, which was 1.93 times that of the control.Conclusion There are diverse fungi in Shiraia fruiting bodies. The co-culture of the associated fungus Fusarium sp. SF12 and the host Shiraia sp. S9 is a new technique to improve HA production.