Yield Improvement by PH-Stabilization of Enzymes

A method of improving the yield and/or productivity of an enzyme, said method comprising the steps of:

• a) providing a host cell comprising an expression gene library of mutated polynucleotides encoding one or more variant of a parent enzyme of interest, wherein the one or more variant comprises at least one amino acid alteration compared to the parent enzyme;
• b) cultivating the host cell under conditions conducive for the production of the one or more variant enzyme;
• c) selecting a host cell that produces a variant enzyme which has at least the specific enzymatic activity of the parent enzyme as well as an improved pH-stability in the pH range of 5-9, wherein the yield and/or productivity of the variant enzyme is improved compared to that of the parent;
• and optionally
• d) recovering the variant enzyme.