Influence of Culturing Conditions on Bioprospecting and the Antimicrobial Potential of Endophytic Fungi from Schinus terebinthifolius

Abstract

In this study, we analyzed the antimicrobial activity of extracts harvested from 17 endophytic fungi isolated from the medicinal plant Schinus terebinthifolius. Morphological and molecular analyses indicated that these fungal species belonged to the genera Alternaria, Bjerkandera, Colletotrichum, Diaporthe, Penicillium, and Xylaria. Of the endophytes analyzed, 64.7 % produced antimicrobial compounds under at least one of the fermentation conditions tested. Nine isolates produced compounds that inhibited growth of Staphylococcus aureus, four produced compounds that inhibited Candida albicans, and two that inhibited Pseudomonas aeruginosa. The fermentation conditions of the following endophytes were optimized: Alternaria sp. Sect. Alternata-LGMF626, Xylaria sp.-LGMF673, and Bjerkandera sp.-LGMF713. Specifically, the carbon and nitrogen sources, initial pH, temperature, and length of incubation were varied. In general, production of antimicrobial compounds was greatest when galactose was used as a carbon source, and acidification of the growth medium enhanced the production of compounds that inhibited C. albicans. Upon large-scale fermentation, Alternaria sp. Sect. Alternata-LGMF626 produced an extract containing two fractions that were active against methicillin-resistant S. aureus. One of the extracts exhibited high activity (minimum inhibitory concentration of 18.52 µg/mL), and the other exhibited moderate activity (minimum inhibitory concentration of 55.55 µg/mL). The compounds E-2-hexyl-cinnamaldehyde and two compounds of the pyrrolopyrazine alkaloids class were identified in the active fractions by gas chromatography-mass spectrometry.

Brazilian Plants: An Unexplored Source of Endophytes as Producers of Active Metabolites

“…Bjerkandera centroamericana (Fig. 6S) B. centroamericana was described after the publications of the cited paper [48] LGMF627…”

Endophytes Potential Use in Crop Production

“…Endophytes can remove pollutants by employing either the biosorption or the bioaccumulation mechanisms [83,[86][87][88][89][90]. They have the ability of decreasing and/ or removing contaminants from soil, water, sediments, and air.…”

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“…Endophytes have great importance in the production of compounds with a unique structure, which may result from several biological interactions [47], however, the challenge for drug discovery is how to access this chemical potential. Most of the studies on endophytic biodiversity published in Brazil (2012-2017) present some bioprospecting studies, such as evaluation of antibiotic, antioxidant, antiparasitic, or cytotoxicity activities, or the use of endophytes to promote plant growth or reactive dye discoloration [40,[48][49][50][51][52][53][54] (▶ Table 3). As a result of the success obtained in terms of discovering active metabolite-producing endophytes, a large number of compounds [2,[55][56][57] or known compounds with unreported biological properties [33,36,[58][59][60] have been reported.…”

“…To evaluate the influence of culture conditions on the antibacterial activity of endophytic isolates of the medicinal plant Schinus terebinthifolius, Tonial et al [48] explored the production of metabolites using 4 N (Nitrogen) and 3 C (Carbon) sources, different temperatures, pHs, and incubation time. Interestingly, independent of the species analyzed, galactose was the most effective source of carbon to produce active metabolites, acidification provided the best results in terms of activity against Candida albicans, while optimal temperature and nitrogen source varied depending on the strain.…”

“…Bjerkandera centroamericana (Fig. 6S) B. centroamericana was described after the publications of the cited paper [48] LGMF627 KM510503 Diaporthe sp.…”