10 μl of the assembly mix was used for transforming 100 μl of competent E. coli DH5α cells. The transformation mix was plated on LB agar plates (Luria-Bertani, 1% tryptone, 0.5% yeast extract, 1% NaCl, 1.5% agar) containing 75 μg/ml ampicillin. Transformation yielded a lot of colonies confirming that the ampicillin resistance gene was functional. Sequencing with 3'AOX1 primer (GCAAATGGCATTCTGACATCC) was carried out to confirm that MCS was free of errors. P. pastoris GS115H (GS115 with HIS4 phenotype, obtained by transforming GS115 with pPIC3.5 linearised with StuI) was transformed with the empty pAOXHygR vector (linearised with BglII) and plated on YPD agar plates (1% yeast extract, 2% peptone, 2% dextrose, 2% agar) containing 100 μg/ml hygromycin B. Many colonies were obtained, demonstrating that the hygromycin B resistance marker was functional. The vector sequence can be found in the Supplementary files of the manuscript.