Avaliação do potencial de produção de biossurfactantes por micro-organismos endofíticos e epifíticos de macrófitas aquáticas coletadas em afluentes do Rio Negro contaminados por petróleo

Abstract

Biosurfactants are compounds produced by fungi and bacteriain different behavioral and environmental conditions, and can be used as an option for the bioremediation of environments contaminated by oil and its derivatives. The selection of fungi, endophytic and epiphytic bacteria, with potential biosurfactant activity, was evaluated through the following tests: Biodegradability using discoloration of 2,6 Dichloro Phenol Indophenol (DCPIP); oil drop-collapse; and emulsification, through surface tension evaluation with Du Nouy ring and the resulting production curve of the most promising microorganisms. Eight fungal samples were effective in the biodegradability test, since they promoted discoloration of indophenol in 24 and 48 hours: S31 Phoma sp, S36 Phoma sp, S24 Rhizopus oryzae, S46 Fusarium sp., S42 Fusarium sp., S32 Fusarium sp, S33 Fusarium sp. and S51 Fusarium sp. All of these fungal isolates produced laccase, pectinase, amylase and lipase. Of these, the S31 Phoma sp. isolate presented a diesel emulsion of 1.5 cm, or 52%, to reduce water surface tension from 72.43 mN/m to 51.03 mN/m. Among the bacteria selected, the M87 Microbacterium sp. isolate presented the best correlation between the tests. This isolate produced 3.0 g/L of biosurfactants, and the fractions promoted reduction of water surface tension below 40 mN/m. The best fraction (F1) was analyzed through FT-IR infrared UFLC-MS and 1H NMR which demonstrated the presence of compounds probably related to fatty acids, a type of non-ionic biosurfactant, that could be used in the cosmetic industry or as an emulsifier in bioremediation processes. No toxic activity was detected either in the bacterial lyophilized aqueous extract or the fungal aqueous extract. Further studies are required in order to: Promote the growth of these, pure or consortium, cultures; identify the best carbon source for the production of biosurfactants; and perform a more thorough chemical characterization of the different biosurfactants and bioemulsifiers from the fungi and bacteria selected.