The methylotrophic yeast Hansenula polymorpha : its use in fundamental research and as a cell factory

During the last decade methylotrophic yeasts havegained increasing interest, both for fundamental(van der Klei and Veenhuis, 1996) and appliedpurposes (van Dijk et al., 2000; Gellissen, 2000).The special value of these yeasts (mainly Pichiapastoris and Hansenula polymorpha) in fundamentalresearch is undoubtedly related to studies on theprinciples of peroxisome homeostasis (biogenesis vs.degradation). In particular, the morphologicalfeatures of peroxisome development and selectivedegradation are more strongly pronounced than inSaccharomyces cerevisiae, which makes it possibleto induce and follow the details in mutants moreeasily. In addition, peroxisome induction in baker’syeast is restricted to growth on oleate (and thusb-oxidation), whereas in the methylotrophic yeastsvarious peroxisomal metabolic pathways mayoccur, depending on the composition of thegrowth medium. These organisms also display thestrongest induction rates that may rise to a level atwhich up to 80% of the total cell volume is occupiedby peroxisomes.The extremely high expression rates necessary toachieve this drew the attention of biotechnologists,who studied the use of these organisms as host forthe production of valuable, heterologous proteins.Initially, P. pastoris was predominantly used; nowH. polymorpha is gaining more and more attention.The H. polymorpha system was shown to provide aremarkably versatile technology platform for het-erologous gene expression. The Hansenula toolboxnow includes a variety of host strains, new integra-tion sites and several novel strong promotersbeyond those derived from methanol metabolismgenes. In the rst H. polymorpha worldwide net-work (HPWN) conference, the recent developmentsin the use of this organism were discussed in a livelyfashion. This report highlights several superb pre-sentations of important, interesting and novelresearch.