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Journal of Biological Sciences 2 (10): 639-644, 2002.
Production of Lipase by Certain Soil Fungi. I: Optimization of Cultural Conditions and Genetic Characterization of Lipolytic Strains of Aspergilli Using Protein Patterns and Random Amplified Polymorphic DNA (RAPD)
G.M. Abdel-Fattah and Ibtisam Hammad
Filamentous fungi isolated from soil were screened for their ability to produce extracellular lipase. Among ten filamentous fungi tested, two strains identified as Aspergillus niger and Aspergillus terreus were selected as the highest lipase producer. Maximum lipase production was obtained in 5 days cultures utilized 0.4% (w/v) corn oil as a carbon source. Optimum pH for crude lipase production by the tested fugal strains was 6.0, while L-glutamic acid as a nitrogen source gave the highest lipase production. PCR-RAPD analysis of genomic DNA using 5 primers (OPB-05, OPB-17, OPA-09, OPA-12, OPA-13) showed that DNA of genus Aspergillus was characterized by the presence of 14, 10, 14, 4 and 3 fragments in case of primer OP-05, OPB-17, OPA-09, OPA-12 and OPA-13 respectively. All these fragments could be considered as Aspergillus specific fragments because they have been detected with both species. Results obtained from the comparison between two species of Aspergillus showed differences in sizes and numbers of amplified fragments per primer for each species. DNA extracted from Aspergillus niger species was characterized by having 3 special fragments more than Aspergillus terreus with primer OPB-05, one fragment more with primer OPB-17, two fragments more with primer OPA-12 and 4 fragments with the primer OPA-13. Thus, some bands were found to be associated with both fungal strains, but some others were specific for Aspergillus niger. Analysis of protein bands showed that some bands were specific to the tested Aspergilli and other more specific to Aspergillus niger. It was concluded that the excess of DNA fragments through both the PCR-RAPD reaction and bands of protein patterns of Aspergillus niger could be responsible for their highest activity of lipase enzyme.