Consistently high yield expression of hIFNγ in Pichia pastoris is not generally achievable. Further optimising of hIFNγ expression in P. pastoris did not result in viable commercial production potential. Lowering the minimal free energy of the mRNA did yield a 10-fold enhancement of expression of hIFNγ. Low abundance of hIFNγ mRNA in the recombinant P. pastoris, might be the reason for low expression. Results suggest that mammalian expression systems yield higher hIFNγ expression with suitable glycosylation patterns.