Isolation of β-glucosidase-producing fungi from pineapple peel waste and screening via bile esculin agar hydrolysis

Abstract

The increasing demand for sustainable enzyme production has led to the exploration of agro-industrial wastes as low-cost substrates for microbial processes. This study evaluated pineapple (Ananas comosus) peel waste as a source of fungi with potential β-glucosidase activity. Fungal isolates were obtained from naturally spoiled pineapple peels collected from local markets and identified based on macroscopic and microscopic characteristics. Total fungal counts ranged from 15.0 ×10⁵ to 62.0 ×10⁵ CFU/g, indicating significant microbial presence in the substrate. Five fungal isolates were identified as Aspergillus fumigatus, Aspergillus fischeri, Aspergillus niger, Rhizopus stolonifer, and Aspergillus fuscicans. Screening for β-glucosidase activity was carried out using Bile Esculin Agar (BEA), cinnamon-supplemented Potato Dextrose Agar (C-PDA), and cinnamon-supplemented Potato Dextrose Agar containing ferric citrate. All isolates demonstrated positive activity, with Aspergillus fischeri (PP2) exhibiting the highest hydrolysis zone (41.5 mm), while Rhizopus stolonifer showed the lowest activity (14.0 mm). No growth was observed on cinnamon-supplemented media, suggesting inhibitory effects on fungal growth and enzyme expression. The study demonstrates that pineapple peel waste supports the growth of β-glucosidase-producing fungi and can serve as a potential low-cost substrate for enzyme screening and future biotechnological applications.