Yeast central carbon metabolism has been engineered to achieve a more efficient isoprenoid biosynthesis pathway, an advance that brings commodity-scale production of such compounds a step closer. These authors have re-engineered the central carbon metabolism of Saccharomyces cerevisiae to improve redox balance and eliminate carbon and energy waste associated with acetyl-CoA biosynthesis. The resulting strains can produce the acetyl-CoA-based hydrocarbon β-farnesene—an important precursor to many fragrances, fuels and therapeutics—in greater quantities than the starting yeast strain while consuming less oxygen. Cultures can be grown effectively in 200,000-litre industrial bioreactors. This system points the way towards a platform for high-productivity, feedstock-efficient production for all isoprenoids and other acetyl-CoA-derived compounds. A bio-based economy has the potential to provide sustainable substitutes for petroleum-based products and new chemical building blocks for advanced materials. We previously engineered Saccharomyces cerevisiae for industrial production of the isoprenoid artemisinic acid for use in antimalarial treatments1. Adapting these strains for biosynthesis of other isoprenoids such as β-farnesene (C15H24), a plant sesquiterpene with versatile industrial applications2,3,4,5, is straightforward. However, S. cerevisiae uses a chemically inefficient pathway for isoprenoid biosynthesis, resulting in yield and productivity limitations incompatible with commodity-scale production. Here we use four non-native metabolic reactions to rewire central carbon metabolism in S. cerevisiae, enabling biosynthesis of cytosolic acetyl coenzyme A (acetyl-CoA, the two-carbon isoprenoid precursor) with a reduced ATP requirement, reduced loss of carbon to CO2-emitting reactions, and improved pathway redox balance. We show that strains with rewired central metabolism can devote an identical quantity of sugar to farnesene production as control strains, yet produce 25% more farnesene with that sugar while requiring 75% less oxygen. These changes lower feedstock costs and dramatically increase productivity in industrial fermentations which are by necessity oxygen-constrained6. Despite altering key regulatory nodes, engineered strains grow robustly under taxing industrial conditions, maintaining stable yield for two weeks in broth that reaches >15% farnesene by volume. This illustrates that rewiring yeast central metabolism is a viable strategy for cost-effective, large-scale production of acetyl-CoA-derived molecules.

Rewriting yeast central carbon metabolism for industrial isoprenoid production

Production of industrial chemicals using renewable biomass feedstock is becoming increasingly important to address limited fossil resources, climate change and other environmental problems. To develop high-performance microbial cell factories, equivalent to chemical plants, microorganisms undergo systematic metabolic engineering to efficiently convert biomass-derived carbon sources into target chemicals. Over the past two decades, many engineered microorganisms capable of producing natural and non-natural chemicals have been developed. This Review details the current status of representative industrial chemicals that are produced through biological and/or chemical reactions. We present a comprehensive bio-based chemicals map that highlights the strategies and pathways of single or multiple biological reactions, chemical reactions and combinations thereof towards production of particular chemicals of interest. Future challenges are also discussed to enable production of even more diverse chemicals and more efficient production of chemicals from renewable feedstocks.

A comprehensive metabolic map for production of bio-based chemicals

Synthetic Biology Tools to Engineer Microbial Communities for Biotechnology

Metabolic engineers endeavor to create a bio-based manufacturing industry using microbes to produce fuels, chemicals, and medicines. Plant natural products (PNPs) are historically challenging to produce and are ubiquitous in medicines, flavors, and fragrances. Engineering PNP pathways into new hosts requires finding or modifying a suitable host to accommodate the pathway, planning and implementing a biosynthetic route to the compound, and discovering or engineering enzymes for missing steps. In this review, we describe recent developments in metabolic engineering at the level of host, pathway, and enzyme, and discuss how the field is approaching ever more complex biosynthetic opportunities.

/pdf/synthetic-biology-strategies-for-microbial-biosynthesis-of-35h7fhfbvp.pdf

Synthetic biology strategies for microbial biosynthesis of plant natural products

https://backend.orbit.dtu.dk/ws/files/161201597/1_s2.0_S109671761830288X_main.pdf

Robert H. Dahl

Papers

Rewriting yeast central carbon metabolism for industrial isoprenoid production

Use of pantothenate as a metabolic switch increases the genetic stability of farnesene producing Saccharomyces cerevisiae