| Congresso Brasileiro de Microbiologia 2023 | Resumo: 294-2 | ||||
Resumo:Among herbicides, dichlorophenoxyacetic acid (2,4-D) is one of the most used around the world and several investigations demonstrate its harmful effects on the environment, including humans. An alternative method for the removal of organochlorine residues is the use of white-rot fungi (WRF). This study aimed to investigate the growth, laccase activity, and role of L. crinitus (L.) Fr. as a bioremediation agent for wastewater contaminated with 2,4-D. First, preliminary tests were performed to detect the maximum concentration of 2,4-D in which the mycelium could develop. L. crinitus fungal mycelium was added to a synthetic culture medium (glucose, sodium nitrate, dibasic potassium phosphate, magnesium sulfate heptahydrate, potassium chloride, malt extract, and ferrous sulfate heptahydrate), containing different concentrations of 2,4-D, ranging from 0 to 670 g L-1. The verification of the development of L. crinitus was through the biomass estimation after the 21-day incubation period, resulting in 5.025 g L-1 of 2,4-D as the higher performance of fungus growth. Then, it was analyzed the growth and laccase activity for L. crinitus using a complete factorial experimental design with variations in glucose (16.65 – 33.35 g L-1), malt extract (0.825 – 9.175 g L-1) and 2,4-D (0.01 – 5 gL-1) concentrations (16 treatments). After 28 days of incubation, dry fungal biomass, pH, glucose consumption, laccase, and manganese peroxidase (MnP) activity, and concentrations of 2,4-D and 2,4-DCP in the liquid medium were determined, and the 2,4-D tolerance index (TI) was calculated. Biomass concentrations only reached values of about 1.5 g L-1 for initial glucose and malt extract concentrations up to 20 and between 3-8 g L-1, respectively, in the presence of 2,4-D. The ability of L. crinitus to remove 2,4-D after 28 days was demonstrated by a decrease in concentrations of 2,4-D by up to 10-15.7% more than in the treatments without the incorporation of fungus and occurred with both low (< 2 g L-1) and high (> 10 g L-1) glucose consumption conditions. Also, TI values were higher in the tests corresponding to the highest removal of 2,4-D. No MnP activity was detected in any of the samples and the laccase activity of the fungus depends on the initial amount of glucose (up to 18 g L-1) and 2,4-D (up to 4 g L-1). The laccase activity in cases with removal of 2,4-D > 10% was between 3 and 6 g L-1, approximately, after 28 days. The presence of chlorine in the fungal mycelium may represent its adsorption and/or accumulation in the L. crinitus biomass. As the concentration of biomass decreases, the amount (mg g-1) of chlorine absorbed and retained in the mycelium by the fungus increases. Results also show that for the highest value in the initial pesticide concentration, the highest percentage of chlorine in the mycelium (4.0%) and the highest amount of chlorine absorbed by the fungus (4255,06 mg g-1). This can be the first description of 2,4-D biotransformation by L. crinitus. The mycelial development of L. crinitus could allow the transformation of organochlorine compounds such as 2,4-D, achieving a greater reduction of this herbicide in liquid media, compared to treatments without the incorporation of fungus. Palavras-chave: basidiomycete fungus, effluent biodegradation, fungal bioprocesses, herbicide Agência de fomento:Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES). | |||||