CONVERSION OF AGRO-INDUSTRIAL SUBSTRATES BY ABSIDIA CYLINDROSPORA VAR. CYLINDROSPORA UCP 1301 FOR THE SUSTAINABLE PRODUCTION OF A BIOSURFACTANT WITH ANTIFUNGAL ACTIVITY

Abstract

Fungal phytopathogens are among the main factors limiting agricultural productivity, increasing the demand for sustainable alternatives to conventional fungicides. In this context, microbial biosurfactants have attracted considerable interest because of their surface-active properties and potential biological activities. The present study aimed to investigate biosurfactant production by Absidia cylindrospora var. cylindrospora UCP 1301 using low-cost agro-industrial substrates, characterize its physicochemical properties, and evaluate its antifungal activity against phytopathogenic fungi. Biosurfactant production was carried out according to a Central Composite Rotatable Design, with crude glycerol concentration, initial pH, and trace element solution concentration as independent variables and surface tension as the response variable. Among the experimental conditions evaluated, the lowest surface tension was 26.7 mN/m. The highest recovery yield was 2.356 g L⁻¹ using 70% ethanol at a 1:2 (v/v) ratio. The isolated biosurfactant exhibited a critical micelle concentration of 100 mg L⁻¹, a zeta potential of −79 mV, stability over a wide range of pH, temperature, and salinity conditions, and a composition consisting of 53% proteins and 47% lipids. FTIR analysis revealed functional groups consistent with peptide and lipid moieties, supporting a lipopeptide-like nature. The biosurfactant also exhibited species-dependent effects on mycelial growth and markedly reduced conidial production in both Curvularia lunata and Fusarium oxysporum. These findings demonstrate the potential of A. cylindrospora var. cylindrospora UCP 1301 as a promising source of biosurfactants for sustainable agricultural applications and encourage further studies on process scale-up and field evaluation.