Potential biosurfactant producing endophytic and epiphytic fungi, isolated from macrophytes in the Negro River in Manaus, Amazonas, Brazil

Endophytic and epiphytic fungi isolated from Eichhornia crassipes (Mart.) Solms and Cyperus ligularis L., macrophytes collected from oil-contaminated waters, were studied to assess their potential for producing biosurfactants; the most promising ones were identified by means of the rDNA region sequencing. In the selection, in the hydrocarbonate biodegradation activity, 2.6-indophenol (DCPIP) in oil-added Bushnell-Haas (BH) medium was the indicator used. The following tests were performed to ascertain the biosurfactant, bioemulsifier activity: emulsification measurement, drop-collapse, surface tension and production slope. Of the twenty fungi isolated, six promoted DCPIP discoloration. The isolate (S31) Phoma sp. showed emulsification of diesel (1.5 cm or 52%) and reduction of the surface tension of 51.03 mN/m water identified as Phoma sp. The other five fungi were identified as Rhizopus oryzae (S24), Fusarium sp. (S32, S33, S42, S46), presenting potential for biodegradation of hydrocarbons, as well. New studies on Phoma sp. (S31), including its cultivation in different carbon sources will be necessary to improve the production of secondary compounds involved in surface tension bioemulsification and reduction.