Biossurfactantes de fungos endofíticos isolados de Gustavia cf. hexapetala (Alb.) Sm. (Lecythidaceae) na Amazônia, contra patógenos da cavidade oral.

Abstract

Biosurfactants (BS) are amphiphilic molecules which, due to their chemical characteristics, have been of great industrial interest. There is evidence of application in dentistry due to their antimicrobial action against pathogens of interest. Thus, this study evaluated the production of BS in strains of endophytic fungi isolated from Gustavia cf. hexapetala, in the city of Manaus, with antimicrobial action against pathogens in the oral cavity. The isolation of endophytic fungi from branches and leaves, purification, conservation and morphological characterization of the isolates were carried out. Screening was performed to select BS-producing fungi grown in liquid (BDL and mineral) supplemented with soybean oil. The culture conditions were: pH 7.0, temperature of 28 °C at 170 rpm, for 10 days. BS production was evaluated using the emulsification index (E24) and the Surface Tension (ST) of the culture medium. A new culture was made on an expanded scale for the extraction of BS. With the raw BS, it was possible to determine the CMC, antimicrobial tests and chemical profile. The selected fungi were identified using molecular techniques. Three hundred ninety-nine (399) fungi and a black yeast of G. cf. hexapétala were isolated. The isolation frequency was 74.6% from branches and 49.6% from leaves. They were grouped into 20 morphogroups with eight identified genera: Colletotrichum, Fusarium, Pestalotiopsis, Penicillium, Guigniardia, Phomopsis, Xylaria, Diaphorte and the others, unknown (Micelia sterilia). One hundred eighty-seven (187) endophytic fungi were conserved, of which 24 were evaluated, and of these, nine stood out as BS producers, and five were selected: three branch isolates were identified as Fusarium decemcellulare (FF17), Diaporthe sp. (FF36) and Fusarium solani (FF45); two leaf isolates were identified as Fusarium solani (FF51) and Coletotrichum vietnamensi (FF33). The best E24 results were: C. vietnamensi (FF33) with 33.99%, Diaporthe sp. (FF36) with 31.97%, and F. solani (FF51) with 26.70%. There was ST reduction below 35.0 mN/m in 09 strains, with emphasis on F. solani (FF51) with 28.7 and 30.1 mN/m; F. solani (FF45) with 31.5 and 30.1 mN / m; C. vietnamensi (FF33) with 32.4 and 31.8 mN/m; Diaporthe sp. (FF36) with 32.7 and 30.9 mN/m grown in BDL and mineral medium, respectively. The ST of the mineral medium decreased from 61.0 mN/m to 30.9 mN/m (49.3% reduction) for fungus Diaporthe sp. (FF36), and for fungi F. solani (FF45 and FF51) with 30.1 mN/m (50.6% reduction). The highest yield of BS production was 0.66 g/L, obtained from the extract of fungus C. vietnamensi (FF33). This endophyte produced a BS with the lowest CMC (1.08 mg/mL) reducing the ST of ultrapure water from 70.6 to 31.94 mN/m (54.8% reduction). In the antimicrobial tests, the MIC of F. decemcellulare (FF17) extract against Streptococcus mutans (ATCC25175) was 0.4 mg/mL and the MBC was 0.5 mg/mL; for Lactobacillus casei (ATCC7469), the MIC was 1.5 mg/ml, and the MBC was 1.75 mg/ml. The bioactives produced by Diaporthe sp. (FF36) showed an MIC of 2.4 mg/mL against S. mutans. The MIC of F. solani mycelium extract (FF51) for L. casei was 1.8 mg/mL. The mycelium extract of F. solani (FF45) showed bacteriostatic action for L. casei and fungistatic for C. albicans (MIC of 2.1 mg/mL and 4.2 mg/mL, respectively). The results indicate the importance of research aimed at the prospection of endophytic fungi with a potential to produce BS and other bioactives of biotechnological interest, against pathogens in the oral cavity, allowing the use of natural molecules to control oral diseases.