Screening of Endophytic Fungi for Cholestesterol Oxidase Producer

Abstract

Increasing concern for cholesterol related disorders, like atherosclerosis, cardiovascular disease and myocardial infarctions, has made Cholesterol oxidase the second largest diagnostic enzyme in demand, after Glucose oxidase, in clinical industry. Moreover, ChOx has been used in various other applications, such as, in insect resistant GM-crops, monitoring and regulation of cholesterol levels in food stuffs and many more such uses in food, agriculture and clinical industries. Investigators have been searching novel Cholesterol oxidase sources, with high level of production capacity, so that this high demand of ChOx in the market can be met efficiently. In the current study, we explored a new group of microorganisms, the endophytic fungi, for the production of cholesterol oxidase. The potential of endophytic fungi to degrade/utilize cholesterol was assessed by growing fungi on a solid medium containing cholesterol as a sole carbon source. Isolates those are capable of growing on such medium showed either the filamentous growth or a clear zone around the colony, indicating utilization of cholesterol. Such isolates were then raised in production medium (Vogel’s Cholesterol Broth supplemented with 0.02% cholesterol). Four of the culture filtrate viz. #1022 AMSTITYEL, #1048 AMSTITYEL, #1082 AMSTITYEL, and #23(a) RSSTNEY showed acceptable activity against cholesterol, wherein, #23(a) RSSTNEY showed maximum potential. #23(a) RSSTNEY is an endophytic fungus isolated from Rawolfia serpentina, a medicinal plant. Enzyme activity in crude protein precipitate obtained from cell free filtrate of this isolate was assessed by an enzyme assay, designed on the basis of the method described by Waybenga et al. (1970), and the enzyme activity staining. Further studies on protein purification, characterization, kinetics would open up possibilities of protein engineering for commercial exploitation of this enzyme.