Assessment of Aspergillus species isolated from different soil samples in Jos Metropolis for protease, amylase, lipase and cellulase enzymes production potential

Aspergillus is a genus of filamentous and cosmopolitan fungi that includes important species used in the pharmaceutical and fermentation industries, medical mycology, food production, basic research, and agro-industry. Soil represents an important reservoir of these filamentous fungi, with considerable potential for the production of industrially relevant extracellular enzymes. This study assessed Aspergillus species isolated from different soil environments in Jos Metropolis, Plateau State, Nigeria, for their potential to produce protease, amylase, lipase, and cellulase. Soil samples were collected in triplicate from ten distinct environments, including cultivated, garden, abattoir, industrial, mechanic workshop, and oil-contaminated soils. Fungal isolates were recovered using the serial dilution plate technique on chloramphenicol-supplemented Potato Dextrose Agar, purified, and identified based on their macroscopic and microscopic characteristics. Enzyme production was screened using substrate-specific agar media, and enzyme activity was evaluated by measuring the zones of hydrolysis. Thirty-six Aspergillus isolates were recovered, with A. niger being the most predominant species (41.7%), followed by A. fumigatus (36.1%), A. flavus (19.4%), and A. nidulans (2.8%). Amylase activity was highest in A. niger isolate HG (45.50 ± 2.43 mm), while cellulase activity was highest in A. flavus isolate AE (70.00 ± 1.96 mm). Lipase activity was comparatively low, with the highest activity recorded in A. niger isolate ND (4.50 ± 0.37 mm). Lipase activity was not detected in several isolates, and no protease activity was detected in any of the cultures. The results demonstrate considerable isolate-dependent variation in extracellular enzyme production, with cellulolytic activity generally exceeding amylolytic and lipolytic activity. The study concludes that indigenous Aspergillus species from Jos Metropolis, particularly selected A. niger and A. flavus isolates, have potential for industrial enzyme production.