Otimização das condições de cultivo do fungo endofítico Botryosphaeria mamane isolado do crajiru (Arrabidaea chica) para aumento do rendimento do extrato fúngico enriquecido em compostos fenólicos.

Abstract

The yield of fungal extracts and the production of secondary metabolites can be significantly affected by variations in the cultivation environment. Phenolic compounds are secondary metabolites of pharmacological interest, due to their biological activities, such as antimicrobial and antioxidant. In this sense, the objective of this study was to evaluate how some nutritional and environmental factors influence the increase in extract yield and the production of phenolic compounds by the endophytic fungus Botryosphaeria mamane, isolated from the Arrabidaea chica (crajiru) plant. In addition, antioxidant and antimicrobial activities were investigated for the fungal extract produced that showed the highest concentration of phenolic compounds. A Fractional Factorial Design 24−1 was conducted with four independent variables (carbon source, nitrogen source, temperature, and pH). The pH was the only variable that significantly influenced the production of phenolic compounds. The carbon source and temperature were the variables that significantly affected (p<0.05) the yield and were therefore chosen for optimization of the cultivation conditions through a Central Composite Rotatable Design (CCRD), with variables nitrogen and pH fixed at 3.0 g/L and 6.5, respectively. The maximization of fungal extract yield and the increase in phenolic compound concentration were efficiently understood through the application of statistical methods, polynomial models, and response surface analyses. It was possible to identify the critical cultivation point for yield (C = 12,119 g/L and T = 33,93 °C) and observe that temperature played a fundamental role in increasing the concentration of phenolics in the fungal extract. The selected sample for investigation of biological activities showed antimicrobial activity against Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa strains with Minimum Inhibitory Concentration of 2,5, 5,0, and 2,5 mg/mL, respectively, and also demonstrated antioxidant activity by the DPPH radical scavenging method with an efficient concentration necessary for scavenging 50% of radicals (EC50) of 14,94 mg/mL. With this work, it was possible to optimize the cultivation conditions of an Amazonian endophytic fungus for the increase in yield of an extract rich in phenolic compounds, which shows antimicrobial and antioxidant activity.