Identification, Characterization, and Production Optimization of 6-Methoxy-1H-Indole-2-Carboxylic Acid Antifungal Metabolite Produced by Bacillus toyonensis Isolate OQ071612

Abstract

Fungal infections currently pose a real threat to human lives. In the current study, soil bacterial isolates were screened for the production of antifungal compounds to combat human fungal pathogens. Notably, the bacterial F1 isolate exhibited antimycotic action towards the Candida albicans ATCC 10231 and Aspergillus niger clinical isolates. By employing phenotypic and molecular techniques, we identified the F1 isolate as the Bacillus toyonensis isolate OQ071612. The purified extract showed stability within a pH range of 6–7 and at temperatures of up to 50 °C. It demonstrated potential antifungal activity in the presence of various surfactants, detergents, and enzymes. The purified extract was identified as 6-methoxy-1H-Indole-2-carboxylic acid using advanced spectroscopic techniques. To optimize the antifungal metabolite production, we utilized response surface methodology (RSM) with a face-centered central composite design, considering nutritional and environmental variables. The optimal conditions were as follows: starch (5 g/L), peptone (5 g/L), agitation rate of 150 rpm, pH 6, and 40 °C temperature. A confirmatory experiment validated the accuracy of the optimization process, resulting in an approximately 3.49-fold increase in production. This is the first documented report on the production and characterization of 6-methoxy-1H-Indole-2-carboxylic acid (MICA) antifungal metabolite from Bacillus toyonensis.

Nanosponge hydrogel of octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propanoate of Alcaligenes faecalis

“…We used the Box-Behnken design to optimize the process parameters to achieve an effective and economical result (Ahmed et al 2022 ). This model of design was successfully employed in previous studies to optimize production of rhamnolipids (El-Housseiny et al 2016 ), antibiotics (Ibrahim et al 2019 ; El-Housseiny et al 2021 ), and antifungal metabolites by their producing isolates (El-Sayed et al 2023 , 2020b ). Measurement of entrapment efficiency can be performed indirectly where the amount of free unentrapped drug is measured spectrophotometrically at the corresponding wavelength (i.e., λ max ), and thus the entrapped amount of drug can be calculated according to Fahmy et al ( 2023 ) by subtracting the drug content in the supernatant (after the first and second centrifugations) from the initial amount of drug added to the nano-system and dividing it by the total drug content.…”