Aplicação de Candida intermedia na remoção de glifosato em soluções aquosas

Abstract

Glyphosate is a widely used pesticide, but its accumulation in soil and water bodies can cause various environmental impacts and problems for organisms. Some ecological strategies for its degradation may be employed, such as those involving microorganisms like yeasts. To make the production of these organisms viable and enable their use in pesticide decontamination, it is essential to optimize cultivation conditions and utilize agro-industrial residues, such as corn steep liquor, to reduce costs and increase biomass production. Thus, the objective of this study was to optimize the cultivation parameters for Candida intermedia and enable biomass production using corn steep liquor, as well as to evaluate this yeast’s potential for glyphosate degradation. First, contaminated soil was collected to isolate possible glyphosate-resistant and/or degrading microorganisms, then identifying a microorganism of interest using the MALDI-TOF-MS method. To verify if the isolated fungus could grow in glyphosate, an experiment was conducted where the microorganism was inoculated in a nutrient basal medium with 1, 2.5, and 5 mg/L of the herbicide, incubated at 28°C, 110 rpm, for 72 hours. After incubation, the material was centrifuged and dried in an oven at 50°C for 48 hours. With growth confirmed in the herbicide-containing medium, a fractional Plackett-Burman experimental design was performed with seven factors: glucose, biotin, cultivation time, nitrogen source, inoculum amount, pH, and temperature, with two levels (-1 and +1). The response variable was the biomass production of C. Intermedia. Following the initial experiment, it was necessary to optimize the levels of nitrogen and glucose, with ammonium nitrate and glucose used as the respective sources. A cultivation trial was conducted using the optimal levels in corn-steep liquor. Finally, glyphosate consumption was analyzed over 24 hours with a 5 mg/L concentration. Statistical analyses were performed using STATISTICA and Graph Pad Prism software. The results showed that the microorganism could grow in the herbicide-containing medium, with biomass production observed even at the highest concentration, indicating that the yeast was either biosorbing or consuming the pesticide. The experimental design revealed that biotin and the nitrogen source significantly influenced yeast production, followed by glucose. In contrast, cultivation time, pH, temperature, and initial inoculum concentration were not significant for the response variable. The Box-Behnken design determined that level 0, for both glucose and ammonium nitrate, provided optimal concentrations for yeast biomass production. Growth in corn steep liquor resulted in higher microorganism yields than in synthetic medium. Glyphosate consumption showed pesticide removal rates above 60% when using dead yeast, highlighting the biosorption process. Therefore, this study demonstrated the best cultivation parameters for C. Intermedia and the possibility of growing it in agro-industrial waste. Additionally, it highlighted its potential use as a biosorbent with good contaminant removal capacity.