Our society urgently requires a transition from fossil fuel dependence to a biosustainable economy. Engineering assembly-line or multi-domain megasynthases, such as type I polyketide synthases (PKSs), holds significant promise for replacing parts of petroleum-based chemical synthesis. We have developed a modular PKS-based platform that integrates a versatile loading module and terminal thioester reductases, enabling the production of diverse medium- and branched-chain diols, amino alcohols, and hydroxy acids with programmable access to branched structures at high titers in Streptomyces. Additionally, we further extended PKS applications to the sustainable synthesis of high-energy polycyclopropanated fatty acids (POP-FAs) as next-generation biofuels. Through engineering of an iterative PKS (iPKS) system, informed by computational modeling and domain swapping, we achieved the microbial production of designer POP-FAs with precise control over chain length and cyclopropanation, and with superior energy density and freezing point characteristics for sustainable aviation fuels. Collectively, these studies demonstrate the transformative potential of PKS engineering to access new chemical space and enable the biosynthesis of tailor-made molecules, from specialty chemicals to advanced biofuels.

Learning Objectives:

1. Explain the principles of polyketide synthase (PKS) engineering

2. Describe how PKSs can be engineered to produce tailor-made diols and high-energy biofuels

3. Assess the potential of PKS-based biosynthesis for replacing petroleum-derived synthesis