Rhamnolipids inhibit aflatoxins production in Aspergillus flavus by causing structural damages in the fungal hyphae and down-regulating the expression of their biosynthetic genes

• Autor(a) principal: Rodrigues, Ana Isabel Geraldes
• Data de Publicação: 2021
• Outros Autores: Gudiña, Eduardo José, Abrunhosa, Luís, Malheiro, Ana R., Fernandes, Rui, Teixeira, J. A., Rodrigues, L. R.
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/1822/72521
• topic: Biological control; Biopesticide; Biosurfactant; Fungicide; Mycotoxin; Sporulation; Science & Technology

Aflatoxins are hepatotoxic and carcinogenic fungal secondary metabolites that usually contaminate crops and represent a serious health hazard for humans and animals worldwide. In this work, the effect of rhamnolipids (RLs) produced by Pseudomonas aeruginosa #112 on the growth and aflatoxins production by Aspergillus flavus MUM 17.14 was studied in vitro. At concentrations between 45 and 1500 mg/L, RLs reduced the mycelial growth of A. flavus by 2340% and the production of aflatoxins by 93.999.5%. Purified mono-RLs and di-RLs exhibited a similar inhibitory activity on fungal growth. However, the RL mixture had a stronger inhibitory effect on aflatoxins production at concentrations up to 190 mg/L, probably due to a synergistic effect resulting from the combination of both congeners. Using transmission electron microscopy, it was demonstrated that RLs damaged the cell wall and the cytoplasmic membrane of the fungus, leading to the loss of intracellular content. This disruptive phenomenon explains the growth inhibition observed. Furthermore, RLs down-regulated the expression of genes aflC, aflE, aflP and aflQ involved in the aflatoxins biosynthetic pathway (6.4, 44.3, 38.1 and 2.0-fold, respectively), which is in agreement with the almost complete inhibition of aflatoxins production. Overall, the results herein gathered demonstrate for the first time that RLs could be used against aflatoxigenic fungi to attenuate the production of aflatoxins, and unraveled some of their mechanisms of action.