Screening of Fungi Species Isolated from Fermented Milk for Extracellular Beta-galactosidase Production Potentials

Abstract

An attempt was made to isolate and screen fungal species from fermented cow, sheep and goat milk for their potential to produce extracellular beta-galactosidase. Samples of fresh cow, sheep and goat milk were collected and allowed to ferment spontaneously. Thereafter, fungal species were isolated and characterized from the fermented milk samples using standard mycological techniques. The fungal isolates were further screened for qualitative and quantitative beta-galactosidase production using Yeast Extract Peptone (YEP) broth method. Selected fungal strain with the best beta-galactosidase production potential was identified using molecular technique. A total of 14 fungi strains were isolated from the fermented milk samples including Aspergillus niger (21.4%), Aspergillus flavus (21.4%), Geotrichum candidum (14.3%), Penicillium sp. (14.3%), Candida sp. (14.3%), Aspergillus fumigatus (7.1%) and Aspergillus terreus (7.1%). Qualitative screening of the fungal isolates for beta-galactosidase production showed Aspergillus niger FGMTF1, Aspergillus niger FSMTF6 and Geotrichum candidum FSMTF2 were positive for the enzyme production. Further quantitative screening of the fungal isolates revealed Aspergillus niger FGMTF01 to be the highest beta-galactosidase producer with enzyme activity of 19.60U/ml followed by Geotrichum candidum FSMTF2 and Aspergillus niger FSMTF6 with enzyme activities of 18.55U/ml and 18.22U/ml respectively. Molecular identification confirmed the best enzyme producing fungal isolate to be Aspergillus niger. These organisms can be potential candidates for large scale production of beta-galactosidases. All the fungal isolated from this investigation can also be screened for production of other industrially important metabolites.