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Biological production of hydrocarbons is an attractive strategy to produce drop-in replacement transportation fuels. Several methods for converting microbially-produced fatty acids into reduced compounds compatible with petrodiesel have been reported. For these processes to become economically viable, microorganisms must be engineered to approach the theoretical yield of fatty acid products from renewable feedstocks such as glucose. Strains with increased titers can be obtained through both rational and random approaches. While powerful, random approaches require a genetic selection or facile screen that is amenable to high throughput platforms. Here, we present the use of a high throughput screen for fatty acids based on the hydrophobic dye Nile red. The method was applied to screening a transposon library of a free fatty acid overproducing strain of Escherichia coli in search of high producing mutants. Ten gene targets were identified via primary and secondary screening. A strain comprising a clean knockout of one of the identified genes led to a 20% increase in titer over the baseline strain. A selection strategy that combines these findings and can act in an iterative fashion has been developed and can be used for future strain optimization in hydrocarbon producing strains.

Biological production of hydrocarbons is an attractive strategy to produce drop-in replacement transportation fuels. Several methods for converting microbially produced fatty acids into reduced compounds compatible with petrodiesel have been reported. For these processes to become economically viable, microorganisms must be engineered to approach the theoretical yield of fatty acid products from renewable feedstocks such as glucose. Strains with increased titers can be obtained through both rational and random approaches. While powerful, random approaches require a genetic selection or facile screen that is amenable to high throughput platforms. Here, we present the use of a high throughput screen for fatty acids based on the hydrophobic dye Nile red. The method was applied to screening a transposon library of a free fatty acid overproducing strain of Escherichia coli in search of high producing mutants. Ten gene targets were identified via primary and secondary screening. A strain comprising a clean knockout of one of the identified genes led to a 20% increase in titer over the baseline strain. A selection strategy that combines these findings and can act in an iterative fashion has been developed and can be used for future strain optimization in hydrocarbon producing strains. © 2011 American Institute of Chemical Engineers Environ Prog, 2012

Isoprenoids are the most numerous and structurally diverse family of natural products. Terpenoids, a class of isoprenoids often isolated from plants, are used as commercial flavor and fragrance compounds and antimalarial or anticancer drugs. Because plant tissue extractions typically yield low terpenoid concentrations, we sought an alternative method to produce high-value terpenoid compounds, such as the antimalarial drug artemisinin, in a microbial host. We engineered the expression of a synthetic amorpha-4,11-diene synthase gene and the mevalonate isoprenoid pathway from Saccharomyces cerevisiae in Escherichia coli. Concentrations of amorphadiene, the sesquiterpene olefin precursor to artemisinin, reached 24 microg caryophyllene equivalent/ml. Because isopentenyl and dimethylallyl pyrophosphates are the universal precursors to all isoprenoids, the strains developed in this study can serve as platform hosts for the production of any terpenoid compound for which a terpene synthase gene is available.

Synthetic biology depends on the ability to rapidly produce strains with improved phenotypes but is limited by the ability to rapidly produce strain collections with directed mutations. Here, we present a system capable of overcoming this limitation through automated P1-phage transductions of Escherichia coli. By combining the Keio collection of single-gene deletion E. coli mutants with P1-phage, it is possible to generate an engineered host-strain collection consisting of every possible gene deletion mutant. This strategy was tested by transducing 355 genetic markers from the Keio collection into five different host strains, and it achieved a 98% success rate. This method offers an improved mechanism for rapidly engineering collections of microbes and provides one method for rapidly deploying a broader synthetic biology effort.

We have developed a novel method to clone terpene synthase genes. This method relies on the inherent toxicity of the prenyl diphosphate precursors to terpenes, which resulted in a reduced-growth phenotype. When these precursors were consumed by a terpene synthase, normal growth was restored. We have demonstrated that this method is capable of enriching a population of engineered Escherichia coli for those clones that express the sesquiterpene-producing amorphadiene synthase. In addition, we enriched a library of genomic DNA from the isoprene-producing bacterium Bacillus subtilis strain 6051 in E. coli engineered to produce elevated levels of isopentenyl diphosphate and dimethylallyl diphosphate. The selection resulted in the discovery of two genes ( yhfR and nudF ) whose protein products acted directly on the prenyl diphosphate precursors and produced isopentenol. Expression of nudF in E. coli engineered with the mevalonate-based isopentenyl pyrophosphate biosynthetic pathway resulted in the production of isopentenol.

Isoprenoid secondary metabolites are a rich source of commercial products that have not been fully explored. At present, there are isoprenoid products used in cancer therapy, the treatment of infectious diseases, and crop protection. All isoprenoids share universal prenyl diphosphate precursors synthesized via two distinct pathways. From these universal precursors, the biosynthetic pathways to specific isoprenoids diverge resulting in a staggering array of products. Taking advantage of this diversity has been the focus of much effort in metabolic engineering heterologous hosts. In addition, the engineering of the mevalonate pathway has increased levels of the universal precursors available for heterologous production. Finally, we will describe the efforts to produce to commercial terpenoids, paclitaxel and artemisinin.

Drug-resistant strains of the malaria parasite are widespread, and as a result mortality due to malaria has increased significantly in recent years. Artemisinin, isolated from the herb Artemisia annua (sweet wormwood), is one drug that shows a high efficacy in killing multi-resistant strains of the parasite. The drug is extremely expensive, and high demand has led to a shortage of artemisinin, available only by extraction from the plant source. Ro et al. now report the development of a yeast strain engineered to carry a cytochrome P450 monooxygenase from A. annua that can produce the drug precursor, artemisinic acid. Artemisinin can be synthesized from this precursor. If the efficiency of this process can be improved, this engineered yeast strain has the potential to alleviate the drug shortage. Through the bio-engineering of Saccharomyces cerevisiae high titres of artemisinic acid were produced using a novel cytochrome P450 monooxygenase. Optimization of this process on an industrial scale may significantly reduce the cost of artemisinin, which could then be used to combat malaria in resource-poor settings. Malaria is a global health problem that threatens 300–500 million people and kills more than one million people annually1. Disease control is hampered by the occurrence of multi-drug-resistant strains of the malaria parasite Plasmodium falciparum2,3. Synthetic antimalarial drugs and malarial vaccines are currently being developed, but their efficacy against malaria awaits rigorous clinical testing4,5. Artemisinin, a sesquiterpene lactone endoperoxide extracted from Artemisia annua L (family Asteraceae; commonly known as sweet wormwood), is highly effective against multi-drug-resistant Plasmodium spp., but is in short supply and unaffordable to most malaria sufferers6. Although total synthesis of artemisinin is difficult and costly7, the semi-synthesis of artemisinin or any derivative from microbially sourced artemisinic acid, its immediate precursor, could be a cost-effective, environmentally friendly, high-quality and reliable source of artemisinin8,9. Here we report the engineering of Saccharomyces cerevisiae to produce high titres (up to 100 mg l-1) of artemisinic acid using an engineered mevalonate pathway, amorphadiene synthase, and a novel cytochrome P450 monooxygenase (CYP71AV1) from A. annua that performs a three-step oxidation of amorpha-4,11-diene to artemisinic acid. The synthesized artemisinic acid is transported out and retained on the outside of the engineered yeast, meaning that a simple and inexpensive purification process can be used to obtain the desired product. Although the engineered yeast is already capable of producing artemisinic acid at a significantly higher specific productivity than A. annua, yield optimization and industrial scale-up will be required to raise artemisinic acid production to a level high enough to reduce artemisinin combination therapies to significantly below their current prices.

The circulating DNA found in human plasma is enriched for genomic DNA from minority tissues such as tumors, fetuses, and transplanted tissue. This sub fraction of blood has become an area of interest for development and disease as the nucleic acid recovered may represent a source of biomarkers for study. One milliliter of plasma typically yields between 1 ng and 50 ng of DNA. The current commercial DNA purification methods limit researchers' ability to scale their samples in both volume and number. Automated solutions are not available to process large numbers of samples with volumes greater than 1 ml, and manual methods can process up to 5 ml of plasma. Here we present a fully automated solution to extract DNA from 1-64 samples up to 8 ml in volume. The system provides an intuitive user interface to select run options and enter barcodes for reagents and samples. Any combination of sample volumes may be processed together in a single run. Samples are eluted in 50 µl of nuclease-free water in either plates or tubes. We have found that the performance of our system meets or exceeds common commercial alternatives over their common sample input volume. Citation Format: Sydnor T. Withers, Mary Dressler, Cristopher A. Cowan. Automated circulating DNA purification from large volumes of plasma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1516. doi:10.1158/1538-7445.AM2014-1516