High Oxygen Treatments Enhance the Contents of Phenolic Compound and Ganoderic Acid, and the Antioxidant and DNA Damage Protective Activities of Ganoderma lingzhi Fruiting Body.

Qingying Dong,Yueyue Li,Huabin Zhou,Zhiwei Zhang,Gaoqiang Liu,Hailong Yang

doi:10.3389/fmicb.2019.02363

Abstract

Ganoderma lingzhi is a famous medicinal mushroom used as Chinese medicine or functional food and has been accepted across the globe. It is important to enhance the contents of bioactive compounds, which in turn improves the quality and biological activity of G. lingzhi fruiting body. In this work, freshly harvested G. lingzhi fruiting bodies were treated continuously with air or with 60 and 80% oxygen for 6 days. Samples were collected and determined initially and at 1 day interval during treatment. A high total ganoderic acid content of 29.44 g kg–1 was obtained in samples treated with 60% oxygen at day 3. Quantitative reverse transcriptase (qRT)-PCR and high-performance liquid chromatography (HPLC) analysis showed that the expression levels of hydroxymethylglutaryl-CoA synthase, squalene synthase, and oxidosqualene cyclase genes were substantially increased, resulting in the increase of ganoderic acids A, B, and C2 and ganoderenic acid B. The scavenging activities with 1,1-diphenyl-2-picrylhydrazyl radical, 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical, hydroxyl radical, and superoxide radical and the DNA damage protective activity were also enhanced by high oxygen treatment. The results of this work provided a potential method to enhance the active metabolite synthesis in the fruiting body of G. lingzhi.

Highlights

Ganoderma lingzhi, formerly named Ganoderma lucidum, has been used to strengthen health and treat disease in traditional Chinese and Japanese medicine for more than 2,000 years (Bishop et al, 2015; Si et al, 2019)
High oxygen treatment could enhance the biosynthesis of phenolic compounds in Ganoderma lingzhi fruiting body, and 60% oxygen treatment showed the best effect in which the highest total phenolic content (3.69 g GAE kg−1) was determined at day 3, which was 1.31-fold higher than that of control
The highperformance liquid chromatography (HPLC) chromatograms of standard phenolic compounds and example of the HPLC profiles of phenolic compounds from G. lingzhi are shown in Supplementary Figures S1, S2, respectively

Summary

Introduction

Formerly named Ganoderma lucidum, has been used to strengthen health and treat disease in traditional Chinese and Japanese medicine for more than 2,000 years (Bishop et al, 2015; Si et al, 2019). A class of high oxidized lanostane-tetracyclic triterpenes, are deemed to be one of the most important bioactive secondary metabolites of G. lingzhi. To improve the biosynthesis of ganoderic acids, several bioprocessing strategies such as media optimization (Xu et al, 2008), shaking combining static culture (Xu et al, 2010a), and overexpression of squalene synthase gene (Zhou et al, 2014) have been developed. These techniques are all based on mycelia growth and submerged culture of G. lingzhi. It is more important to enhance the contents of bioactive constituents in the fruiting body of G. lingzhi

Objectives

Methods

Results

Discussion

Conclusion