A novel platform for the production of nonhydroxylated gelatins based on the methylotrophic yeast Hansenula polymorpha

The use of yeast as a host for heterologous expression of proteins that are normally derived from animal tissue is a promising way to ensure defined products that are devoid of potential harmful animal side products. Here we report on the production and secretion of a custom-designed gelatin, Hu3-His8, by the yeast Hansenula polymorpha. We observed that Hu3-His8 was poorly secreted by the heterologous Saccharomyces cerevisiae invertase secretion signal. In contrast, the S. cerevisiae mating factor alpha prepro sequence efficiently directed secretion into the culture medium. However, at higher copy numbers, intracellular accumulation of Hu3-His8 precursors occurred. Overproduction of Erv29p, a protein required for packaging of the glycosylated pro-alpha factor into COPII vesicles, did not improve gelatin secretion in the multicopy strain. Previously, H. polymorpha was reported to hydroxylate proline residues in gelatinous sequences. In contrast, we were unable to detect hydroxyprolines in the secreted Hu3-His8. Also, we failed to identify a gene encoding prolyl-4-hydroxylase in the H. polymorpha genome.