Isolation and Screening of Amylase from Moulds Associated with the Spoilage of Some Fermented Cereal Foods

Aims: The aim of the study is to isolate moulds from spoilt samples of three fermented cereal foods (ogi, eko, pap) and screen the mould for amylase production.

Study Design: Primary screening for amylase production by the mould isolates was determined on starch agar. Isolates having the widest zones of hydrolysis were further screened by Solid state fermentation [SSF]

Methodology: Molds were isolated on Sabouraud Dextrose Agar [SDA] incubated at 28°C±2°C for 72h and identified by standard microbiological methods. Screening of moulds for amylase activity was determined on starch agar medium and flooed with gram’s iodine. The isolates were screened quantitatively for the production of α-amylase and glucoamylase using Solid state fermentation [SSF] while the enzyme activities were determined spectrophotometrically.

Results: Mean mould population observed on the spoilt food samples ranged from 5.06 log cfu/g for ogi to 5.80 log cfu/g for eko wrapped in leaves. Twenty seven moulds isolated from the samples were identified as Aspergillus flavus, Aspergillus niger, Aspergillus fumigatus, Penicillium citrinum and Rhizopus stolonifer. Majority (70.4%) of the isolated mould produced amylase on starch agar indicated by clear zones around the colonies. Diameter of the zone of hydrolysis ranged from 3.0 mm for Aspergillus niger EL4 to 22.0 mm for Aspergillus flavus OG1. The highest amylase activity was 30.8% from A. flavus OGI while the least was 21.2% from A. flavus EN4. Glucoamylase activities observed were between 100 U/ml and 240 U/ml. respectively.

Conclusion: This study contributes to catalogued local fungal isolates that can be used for amylase production and provides additional information to support future research about the industrial enzymes potential of these microorganisms. More work is however needed to determine the optimal production conditions of the enzymes.