Increasing the half-life of therapeutic proteins in the bloodstream is a critical goal for improving their efficacy, reducing the frequency of administration, and improving patient compliance. Half-life extension (HLE) of recombinant proteins can be achieved by a variety of methods. For example, the bioactive protein can be genetically fused to the C- or N-terminums of recombinant human albumin or conjugated to the free-thiol in albumin. In the case of albumin fusion proteins, Phenotypeca has a range of optimised yeast strains specially designed for this purpose. Alternatively, chemical modification of the bioactive protein may be performed after purification from yeast, for example by PEGylation to increase hydrodynamic radius or by lipidation to promote albumin-binding. Similarly, fusion to albumin binding proteins, such as VHHs can be deployed using Phenotypeca’s strains optimised for VHH expression.