Assembly of highly standardized gene fragments for high-level production of porphyrins in E. coli.

Standardization of molecular cloning greatly facilitates advanced DNA engineering, parts sharing, and collaborative efforts such as the iGEM competition. All of these attributes facilitate exploitation of the wealth of genetic information made available by genome and RNA sequencing. Standardization also comes at the cost of reduced flexibility. We addressed this paradox by formulating a set of design principles aimed at maximizing standardization while maintaining high flexibility in choice of cloning technique and minimizing the impact of standard sequences. The design principles were applied to formulate a molecular cloning pipeline and iteratively assemble and optimize a six-gene pathway for protoporphyrin IX synthesis in Escherichia coli. State of the art production levels were achieved through two simple cycles of engineering and screening. The principles defined here are generally applicable and simplifies the experimental design of projects aimed at biosynthetic pathway construction or engineering.

Linking genotype and phenotype of Saccharomyces cerevisiae strains reveals metabolic engineering targets and leads to triterpene hyper-producers.

BACKGROUND: Metabolic engineering is an attractive approach in order to improve the microbial production of drugs. Triterpenes is a chemically diverse class of compounds and many among them are of interest from a human health perspective. A systematic experimental or computational survey of all feasible gene modifications to determine the genotype yielding the optimal triterpene production phenotype is a laborious and time-consuming process. METHODOLOGY/PRINCIPAL FINDINGS: Based on the recent genome-wide sequencing of Saccharomyces cerevisiae CEN.PK 113-7D and its phenotypic differences with the S288C strain, we implemented a strategy for the construction of a ß-amyrin production platform. The genes Erg8, Erg9 and HFA1 contained non-silent SNPs that were computationally analyzed to evaluate the changes that cause in the respective protein structures. Subsequently, Erg8, Erg9 and HFA1 were correlated with the increased levels of ergosterol and fatty acids in CEN.PK 113-7D and single, double, and triple gene over-expression strains were constructed. CONCLUSIONS: The six out of seven gene over-expression constructs had a considerable impact on both ergosterol and ß-amyrin production. In the case of ß-amyrin formation the triple over-expression construct exhibited a nearly 500% increase over the control strain making our metabolic engineering strategy the most successful design of triterpene microbial producers.