Search for hydrophilic marine fungal metabolites: a rational approach for their production and extraction in a bioactivity screening context.

Carine Le Ker,Joël Fleurence,Jean-François Biard,Karina-Ethel Petit

doi:10.3390/md9010082

Abstract

In the search for bioactive natural products, our lab screens hydrophobic extracts from marine fungal strains. While hydrophilic active substances were recently identified from marine macro-organisms, there was a lack of reported metabolites in the marine fungi area. As such, we decided to develop a general procedure for screening of hydrophobic metabolites. The aim of this study was to compare different processes of fermentation and extraction, using six representative marine fungal strains, in order to define the optimized method for production. The parameters studied were (a) which polar solvent to select, (b) which fermentation method to choose between solid and liquid cultures, (c) which raw material, the mycelium or its medium, to extract and (d) which extraction process to apply. The biochemical analysis and biological evaluations of obtained extracts led to the conclusion that the culture of marine fungi by agar surface fermentation followed by the separate extraction of the mycelium and its medium by a cryo-crushing and an enzymatic digestion with agarase, respectively, was the best procedure when screening for hydrophilic bioactive metabolites. During this development, several bioactivities were detected, confirming the potential of hydrophilic crude extracts in the search for bioactive natural products.

Highlights

Marine fungi are efficient producers of organic molecules with original chemical skeletons and various associated bioactivities [1,2]
Biochemical analyses (Table 1) on agar surface fermentation (ASF) showed that extraction by the aqueous process (EAP) was more efficient than by the organic process (EOP)
Compared with EOP, protein yields from EAP were greater by a factor of about five for mycelium (14.19 mg/g dw vs. 2.75 mg/g dw) and agar-agar

Summary

Introduction

Marine fungi are efficient producers of organic molecules with original chemical skeletons and various associated bioactivities [1,2]. In the same way, promising hydrophilic pharmaceutical substances have been isolated from other marine organisms [7] or from terrestrial micro and macro fungi [8]. This fact prompted us to broaden our bioactivity screening method to the search for hydrophilic fungal metabolites. Fungi are known to adapt their metabolic pathways according to their environment [9], so they could produce a different variety of metabolites in other cultural conditions, such as in solid state fermentation (SSF) like agar surface fermentation (ASF)

Objectives

Results

Conclusion