Abstract
BackgroundPichia pastoris is a yeast widely used in expressing recombinant proteins from eukaryotic organisms. In the present study, the total RNA was extracted from a eukaryotic fungus; Aspergillus oryzae DRDFS13 and reverse transcribed into cDNA using specific primers. The gene for aspartic protease was amplified and sequenced and then cloned into pGAPZαA for further expression in P. pastoris. The recombinant yeast (P. patoris X-33Ap) was cultivated in YPD media at pH 5 and 7 for 6 days and the production of recombinant proteins was checked by total protein determination, milk-clotting activity assay, and SDS-PAGE analysis. ResultsThe gene sequence results showed 98% similarity with aspartic protease gene from A. oryzae RIB40. The aspartic protease gene cloned into pGAPZαA (later pMKAP) was successfully expressed in P. pastoris as an active extracellular protease with the highest MCA (190.47 MCU/mL) of secreted enzyme from the recombinant yeast was obtained at pH 5 and 6 days of incubation time. The major protein expressed by the recombinant P. Pastoris X-33 AP has a molecular mass between 32 and 46 kDa. When analyzed for clotting activity, the protein was able to clot skim-milk in 2 min. The clotting activity was found to be 190.47 U/mL.ConclusionThus, the milk-clotting protease extracted form the recombinant yeast in the present study could be a suitable candidate for cheese production. However, further study of the recombinant proteins need to be carried out and its application in cheese production by analyzing the organoleptic and chemical properties of the cheese produced.
Characterisation of a recombinant β-xylosidase (xylA) from Aspergillus oryzae expressed in Pichia pastoris
