Mewes Boettner

Establishing a versatile fermentation and purification procedure for human proteins expressed in the yeasts Saccharomyces cerevisiae and Pichia pastoris for structural genomics

We describe the introduction of the yeasts Saccharomyces cerevisiae and Pichia pastoris as eukaryotic hosts for the routine production of recombinant proteins for a structural genomics initiative. We have previously shown that human cDNAs can be efficiently expressed in both hosts using high throughput procedures. Expression clones derived from these screening procedures were grown in bioreactors and the over-expressed human proteins were purified, resulting in obtaining significant amounts suitable for structural analysis. We have also developed and optimized protocols enabling a high throughput, low cost fermentation and purification strategy for recombinant proteins for both S. cerevisiae and P. pastoris on a scale of 5 to 10 mg. Both batch and fed batch fermentation methods were applied to S. cerevisiae. The fed batch fermentations yielded a higher biomass production in all the strains as well as a higher productivity for some of the proteins. We carried out only fed batch fermentations on P. pastoris strains. Biomass was produced by cultivation on glycerol, followed by feeding methanol as carbon source to induce protein expression. The recombinant proteins were expressed as fusion proteins that include a N-terminal His-tag and a C-terminal Strep-tag. They were then purified by a two-step chromatographic procedure using metal-affinity chromatography and StrepTactin-affinity chromatography. This was followed by gel filtration for further purification and for buffer exchange. This three-step purification procedure is necessary to obtain highly purified proteins from yeast. The purified proteins have successfully been subjected to crystallization and biophysical analysis.

Significant Reduction in Helicobacter pylori Load in Humans with Non-viable Lactobacillus reuteri DSM17648: A Pilot Study.

Abstract Reducing the amount of Helicobacter pylori in the stomach by selective bacterial–bacterial cell interaction was sought as an effective and novel method for combating the stomach pathogen. Lactobacillus reuteri DSM17648 was identified as a highly specific binding antagonist to H. pylori among more than 700 wild-type strains of Lactobacillus species. Applying a stringent screening procedure, the strain DSM17648 was identified as selective binder to H. pylori cells under in vivo gastric conditions. The strain DSM17648 co-aggregates the pathogen in vivo and in vitro. The specific co-aggregation occurs between Lact. reuteri DSM17648 and different H. pylori strains and serotypes, as well as H. heilmannii, but not with Campylobacter jejuni or other commensal oral and intestinal bacteria. Lact. reuteri DSM17648 was shown in a proof-of-concept single-blinded, randomized, placebo-controlled pilot study to significantly reduce the load of H. pylori in healthy yet infected adults. Reducing the amount of H. pylori in the stomach by selective bacterial–bacterial cell interaction might be an effective and novel method for combating the stomach pathogen. Lact. reuteri DSM17648 might prove useful as an adhesion blocker in antibiotic-free H. pylori therapies.