BACKGROUND: The effects of low-shear modeled microgravity (LSMMG) on the production of recombinant proteins in a eukaryotic expression host have been investigated. The gene (GenBank Accession No.EU095019) derived from Penicillium purpurogenum Stoll (CGMCC 3. 3708) encoding beta-D-glucuronidase (EC 3.2.1.31, PGUS) was expressed in Pichia pastoris GS115. The behavior of P. pastoris growth and recombinant PGUS production during the methanol induction stage were examined in a high-aspect ratio vessel (HARV) that could model the microgravity environment. RESULTS: The recombinant P. pastoris showed better growth under LSMMG than normal gravity (NG) during the methanol induction phase. It was also found that the efficiencies of PGUS production were enhanced 1.51 to 2.21-fold under LSMMG compared with NG control at four different rotary speeds (P < 0.05), and 15 rpm was found to be the optimal for PGUS expression. Furthermore, the efficiency of PGUS secretion was also enhanced under LSMMG (all values above 30%). CONCLUSIONS: The LSMMG environment significantly enhances production and secretion of the recombinant PGUS expressed in P. pastoris GS115. Results suggest that simulated microgravity techniques could be used for the efficient production of recombinant proteins by microbial hosts. (C) 2010 Society of Chemical Industry