05.18.2017 // Kyle Lauersen, Center for Biotechnology, Bielefeld University

Advances in genetic engineering empower the eukaryotic microalga Chlamydomonas reinhardtii for sustainable light-driven bio-production 

Photosynthetic microalgae hold promise as green cell factories for sustainable light-driven bio-production processes. These organisms can be cultivated with freely available sunlight energy and CO2 as a sole carbon source, making them ideal chassis for sustainable production processes. Microalgae are already natural sources of many interesting bio-products including carotenoids, lipids, and polysaccharides. However, expanding the range as well as value of the compounds produced by microalgae through genetic engineering can increase the economic competitiveness of light-driven algal production platforms. In comparison to bacteria or yeasts, genetic engineering of eukaryotic microalgae has lagged significantly behind due to characteristically low transgene expression levels. Work in our research group has focused on engineering increased and reliable levels of nuclear transgene expression in the fast growing, Chlorophyceaen microalga Chlamydomonas reinhardtii, with the aim of generating heterologous bio-products from this photosynthetic host. We employ several levels of optimization in transgene design, followed by synthetic development of nuclear cassettes in order to ensure robust expression of target constructs. Recently in our group, the development of a fully synthetic and optimized nuclear gene expression vector (pOptimized) further increased the range of possibilities for nuclear encoded transgene expression in C. reinhardtii. We have applied this system for numerous tasks including: recombinant protein production via secretion into culture media, in vivo localization of fluorescent reporter-fusions for pathway elucidation, and metabolic engineering for novel isoprenoid generation. Our high-throughput workflow allows a level of reliable nuclear transgene engineering, which was previously unattainable in this host. This presentation will overview our recent successes in engineering nuclear transgene expression in C.reinhardtii for numerous applications, with a highlight on the production of non-native isoprenoids.