Isolation, characterization, and antifungal behavior of humic acid and fulvic acid fractions from biowaste-derived vermiproducts

Humic substances, formed through the decomposition of plant and animal matter, are prevalent world-wide. These substances primarily consist of humin, humic acid (HA), and fulvic acid (FA). There is existing evidence for antifungal properties of these humic constituents. This study aimed to isolate and determine the humic materials derived from organic materials and vermicompost produced using Perionyx excavatus, and to evaluate their antifungal activity against human fungal pathogens, specifically Candida species. Characterization of the humic and FAs was conducted using various techniques, UV-Vis spectroscopy, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and x-ray diffraction (XRD). The results revealed that HA possesses a honeycomb-like structure with fragments and flakes attached to its surface, along with a lumpy and close-grained physical appearance. SEM and XRD analyses further demonstrated the presence of specific crystalline forms in all humic and FA samples. The absorption peaks observed between 250 and 500 nm were indicative of the significant nature of HA. Additionally, the study identified the presence of hydroxyls, amines, alkyl groups, alcoholic contents, and acidic functional groups. Notably, the growth of Candida species was significantly inhibited by both humic and FAs, suggesting that these natural substances could potentially reduce the reliance on chemical antifungal drugs, which often have adverse side effects. Earthworms play a crucial role in breaking down organic matter to form humic substances, as evidenced in vermicompost, vermicast, and vermiwash. Thus, humic and FAs derived from vermiproducts demonstrate potential as alternative therapies for human fungal pathogens.