Cloning and expression of an industrial enzyme in Pichia pastoris

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, fulfilment of the requirements for the degree of Master of Science. Johannesburg 2017.Pichia pastoris is an established platform for the production of industrial enzymes. This nonfermentative methylotrophic yeast has many attractive features for the production of heterologous protein both in the laboratory and in industry. The PichiaPinkTM multi-copy secreted expression system was selected for the heterologous production of the fluorinase from Streptomyces cattleya. Fluorinase enzymes are useful for the production of fluorinated compounds which are applied in the agrochemical and pharmaceutical industries. The gene was cloned into the pPinkα-HC vector and used to transform four host srains by electroporation. Protein production was induced with 0.5% methanol and expression and activity was analysed by SDS-PAGE and a HPLC activity assay. Construction of the pPinkαHC-fLA expression plasmid and transformation of the host strains proved succesful. The PichiaPinkTM integrants showed genetic instability as the expression cassette showed signs of gene excision, thereby reducing the gene copy number. The wild-type strain1 efficiently secreted the foreign protein into the culture media, but the α-MF secretion signal was not processed correctly and secretion failed for the three protease knockout strains. However, the enzyme in both the secreted and intracellular protein fraction showed activity. Secretion methods need to be optimised and intracellular expression should be explored. The fluorinase enzyme was successfully cloned and expressed in four PichiaPinkTM strains and a biologically active protein was produced.XL201