Bile Esculin Agar as a Screening Medium for Detecting β-Glucosidase Activity in Fungi Isolated from Fruit Waste Dump Sites

Abstract

Fungi are widely recognized for their ability to produce β-glucosidase, an enzyme of significant industrial and biotechnological importance. However, conventional screening methods often rely on substrates that are difficult to access. Bile esculin agar, a selective and differential medium for bacteria, contains components that can enable the detection of β-glucosidase activity. This study, therefore, aimed to isolate fungi from fruit dumpsite soils and evaluate their potential for β-glucosidase production using bile esculin agar as a screening medium. Soil samples were collected from five fruit dumpsite locations in Ilorin, Nigeria, and fungi were isolated, characterized, and identified using standard microbiological techniques. The isolates were screened for β-glucosidase activity on bile esculin agar, and their growth-support capacity was also evaluated. Five fungal isolates belonging to the genera Aspergillus, Penicillium, Trichoderma, and Mucor were identified. All isolates (100%) exhibited β-glucosidase activity, with significant variation observed (p < 0.05). Trichoderma sp. showed the highest activity (40.00 ± 1.00 mm), while Aspergillus sp. recorded the lowest (29.00 ± 1.00 mm). Although bile esculin agar supported fungal growth, colony diameters were lower on bile esculin agar (20.00–32.67 mm) compared to potato dextrose agar (21.67–52.33 mm), with a significant difference observed (p < 0.05). In conclusion, these findings demonstrate that bile esculin agar can be effectively applied for screening β-glucosidase-producing fungi and highlight fruit dumpsite soils as a promising source of such organisms.