Peter Niederberger

Bio: Peter Niederberger is an academic researcher from Nestlé. The author has contributed to research in topics: Chemostat & Pyruvate carboxylase. The author has an hindex of 9, co-authored 20 publications receiving 1272 citations.

Protein expression and secretion in the yeast Yarrowia lipolytica.

Abstract: Strains and vectors for protein expression and secretion have been developed in the yeast Yarrowia lipolytica. Host strains were constructed with non-reverting auxotrophic markers, deletions of protease-encoding genes, and carrying a docking platform. To drive transcription, either the synthetic hp4d or the inducible POX2 promoter were used. Protein secretion is either directed by the targeting sequence of the alkaline extracellular protease or the extracellular lipase (LIP2p) signal sequence. We describe a set of vectors based on these promoters, targeting sequences and two URA3 alleles as selection markers. The wild-type URA3 allele, ura3d1, was used for single-copy integration and a mutant URA3 allele, ura3d4, was used to select for multi-copy integration into the genome. These vectors were used to express the Y. lipolytica extracellular lipase LIP2p and the Aspergillus oryzae leucine amino peptidase II. Lipase production under the control of the hp4d promoter by a strain containing a single copy reached 1000 U ml(-1) in shake flasks, while a strain containing multiple integrations reached 2000 U ml(-1) in shake flasks, 11500 U ml(-1) in batch and 90500 U ml(-1) in fed batch. Leucine amino peptidase production under the control of the hp4d promoter reached 320 mU ml(-1) in batch with a mono-copy lapA integrant and 28000 mU ml(-1) in fed batch with a multi-copy transformant.

Lovastatin Biosynthesis by Aspergillus terreus in a Chemically Defined Medium

Abstract: Lovastatin is a secondary metabolite produced by Aspergillus terreus. A chemically defined medium was developed in order to investigate the influence of carbon and nitrogen sources on lovastatin biosynthesis. Among several organic and inorganic defined nitrogen sources metabolized by A. terreus, glutamate and histidine gave the highest lovastatin biosynthesis level. For cultures on glucose and glutamate, lovastatin synthesis initiated when glucose consumption levelled off. When A. terreus was grown on lactose, lovastatin production initiated in the presence of residual lactose. Experimental results showed that carbon source starvation is required in addition to relief of glucose repression, while glutamate did not repress biosynthesis. A threefold-higher specific productivity was found with the defined medium on glucose and glutamate, compared to growth on complex medium with glucose, peptonized milk, and yeast extract.

Effect of 26-Oxygenosterols from Ganoderma lucidum and Their Activity as Cholesterol Synthesis Inhibitors

Abstract: Ganoderma lucidum is a medicinal fungus belonging to the Polyporaceae family which has long been known in Japan as Reishi and has been used extensively in traditional Chinese medicine. We report the isolation and identification of the 26-oxygenosterols ganoderol A, ganoderol B, ganoderal A, and ganoderic acid Y and their biological effects on cholesterol synthesis in a human hepatic cell line in vitro. We also investigated the site of inhibition in the cholesterol synthesis pathway. We found that these oxygenated sterols from G. lucidum inhibited cholesterol biosynthesis via conversion of acetate or mevalonate as a precursor of cholesterol. By incorporation of 24,25-dihydro-[24,25-3H2]lanosterol and [3-3H]lathosterol in the presence of ganoderol A, we determined that the point of inhibition of cholesterol synthesis is between lanosterol and lathosterol. These results demonstrate that the lanosterol 14α-demethylase, which converts 24,25-dihydrolanosterol to cholesterol, can be inhibited by the 26-oxygenosterols from G. lucidum. These 26-oxygenosterols could lead to novel therapeutic agents that lower blood cholesterol.

Cholesterol-lowering properties of Ganoderma lucidum in vitro , ex vivo , and in hamsters and minipigs

Abstract: Introduction There has been renewed interest in mushroom medicinal properties We studied cholesterol lowering properties of Ganoderma lucidum (Gl), a renowned medicinal species

Logic of the Yeast Metabolic Cycle: Temporal Compartmentalization of Cellular Processes

Abstract: Budding yeast grown under continuous, nutrient-limited conditions exhibit robust, highly periodic cycles in the form of respiratory bursts. Microarray studies reveal that over half of the yeast genome is expressed periodically during these metabolic cycles. Genes encoding proteins having a common function exhibit similar temporal expression patterns, and genes specifying functions associated with energy and metabolism tend to be expressed with exceptionally robust periodicity. Essential cellular and metabolic events occur in synchrony with the metabolic cycle, demonstrating that key processes in a simple eukaryotic cell are compartmentalized in time.

Production of amorphadiene in yeast, and its conversion to dihydroartemisinic acid, precursor to the antimalarial agent artemisinin

Abstract: Malaria, caused by Plasmodium sp, results in almost one million deaths and over 200 million new infections annually. The World Health Organization has recommended that artemisinin-based combination therapies be used for treatment of malaria. Artemisinin is a sesquiterpene lactone isolated from the plant Artemisia annua. However, the supply and price of artemisinin fluctuate greatly, and an alternative production method would be valuable to increase availability. We describe progress toward the goal of developing a supply of semisynthetic artemisinin based on production of the artemisinin precursor amorpha-4,11-diene by fermentation from engineered Saccharomyces cerevisiae, and its chemical conversion to dihydroartemisinic acid, which can be subsequently converted to artemisinin. Previous efforts to produce artemisinin precursors used S. cerevisiae S288C overexpressing selected genes of the mevalonate pathway [Ro et al. (2006) Nature 440:940–943]. We have now overexpressed every enzyme of the mevalonate pathway to ERG20 in S. cerevisiae CEN.PK2, and compared production to CEN.PK2 engineered identically to the previously engineered S288C strain. Overexpressing every enzyme of the mevalonate pathway doubled artemisinic acid production, however, amorpha-4,11-diene production was 10-fold higher than artemisinic acid. We therefore focused on amorpha-4,11-diene production. Development of fermentation processes for the reengineered CEN.PK2 amorpha-4,11-diene strain led to production of > 40 g/L product. A chemical process was developed to convert amorpha-4,11-diene to dihydroartemisinic acid, which could subsequently be converted to artemisinin. The strains and procedures described represent a complete process for production of semisynthetic artemisinin.

Progress in Metabolic Engineering of Saccharomyces cerevisiae

Abstract: Summary: The traditional use of the yeast Saccharomyces cerevisiae in alcoholic fermentation has, over time, resulted in substantial accumulated knowledge concerning genetics, physiology, and biochemistry as well as genetic engineering and fermentation technologies. S. cerevisiae has become a platform organism for developing metabolic engineering strategies, methods, and tools. The current review discusses the relevance of several engineering strategies, such as rational and inverse metabolic engineering, evolutionary engineering, and global transcription machinery engineering, in yeast strain improvement. It also summarizes existing tools for fine-tuning and regulating enzyme activities and thus metabolic pathways. Recent examples of yeast metabolic engineering for food, beverage, and industrial biotechnology (bioethanol and bulk and fine chemicals) follow. S. cerevisiae currently enjoys increasing popularity as a production organism in industrial (“white”) biotechnology due to its inherent tolerance of low pH values and high ethanol and inhibitor concentrations and its ability to grow anaerobically. Attention is paid to utilizing lignocellulosic biomass as a potential substrate.