Isolation and molecular characterization of inulinaseproducing thermophilic fungi from waste dumpsite located at Apete-Awotan in Ibadan, south-western Nigeria

Abstract

In this study, attempts were made to isolate and characterized inulinase-producing thermophilic fungi from waste dump site located at Awota-Apete, Ibadan, South-Western Nigeria. The thermostability of the inulinase produced was also investigated by incubating inulinase produced at 65 °C for three hours and thereafter measuring the residual inulinase activity. Eight different fungi capable of growing on inulin agar at 50 °C were isolated. They were identified as Aspergillus flavus, A. tamarii, A. parasiticus, A. niger, A. oryzae, Rhizopus sp., Penicillium citrinum and Neurospora sp. using cultural, microscopic and the sequence of the Internal Transcribed Spacer regions 1 and 2 (ITS1/ITS2) of the fungal genome. Thermostability studies on the produced inulinase revealed that inulinase from A. tamarii-INU4 retained 13.7U/ml of its activity after incubation at 65°C for 3 hr. This was followed by extracellular inulinase produced by A. flavus-INU2 with 5.4U/ml residual activity after incubation at 65°C for 3hrs. Extracellular inulinase by Penicilium citrinum had the lowest residual activity of 0.2U/ml after incubation at the same condition. Conclusively, this paper reports potential sources of thermostable inulinase- a property which is necessary for the complete hydrolysis of inulin by inulinases in the production of fructose and fructo-oligosaccharides.