Eukaryotic microalgae as hosts for light-driven heterologous isoprenoid production

Lauersen, Kyle J.

doi:10.1007/s00425-018-3048-x

Cited by 83 publications

(79 citation statements)

References 133 publications

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“…Indeed, C. reinhardtii has been shown amenable to scale up in air-lift bioreactors even under outdoor conditions (Lauersen, 2018) and it may be that cultivation of cell-wall deficient astaxanthin producing C. reinhardtii presents the best case of rapid growth and ease of pigment extractability. Given the robust activity of the CrBKT, it may be likely that further customizations of the carotenoid biosynthesis can be readily achieved in this alga.…”

Section: Discussionmentioning

confidence: 99%

Turning a green alga red: engineering astaxanthin biosynthesis by intragenic pseudogene revival in Chlamydomonas reinhardtii

Perozeni

Cazzaniga

Baier

et al. 2019

Preprint

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The green alga Chlamydomonas reinhardtii does not synthesize high-value ketocarotenoids like canthaxanthin and astaxanthin, however, a β-carotene ketolase (CrBKT) can be found in its genome.CrBKT is poorly expressed, contains a long C-terminal extension not found in homologues and likely represents a pseudogene in this alga. Here, we used synthetic re-design of this gene to enable its constitutive overexpression from the nuclear genome of C. reinhardtii. Overexpression of the optimized CrBKT extended native carotenoid biosynthesis to generate ketocarotenoids in the algal host causing noticeable changes the green algal colour to a reddish-brown. We found that up to 50% of native carotenoids could be converted into astaxanthin and more than 70% into other ketocarotenoids by robust CrBKT overexpression. Modification of the carotenoid metabolism did not impair growth or biomass productivity of C. reinhardtii, even at high light intensities. Under different growth conditions, the best performing CrBKT overexpression strain was found to reach ketocarotenoid productivities up to 4.5 mg L -1 day -1 . Astaxanthin productivity in engineered C. reinhardtii shown here is competitive with that reported for Haematococcus lacustris (formerly pluvialis) which is currently the main organism cultivated for industrial astaxanthin production. In addition, the extractability and bio-accessibility of these pigments was much higher in cell wall deficient C. reinhardtii than the resting cysts of H. lacustris. Engineered C. reinhardtii strains could thus be a promising alternative to natural astaxanthin producing algal strains and may open the possibility of other tailor-made pigments from this host.

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Section: Discussionmentioning

confidence: 99%

Turning a green alga red: engineering astaxanthin biosynthesis by intragenic pseudogene revival in Chlamydomonas reinhardtii

Perozeni

Cazzaniga

Baier

et al. 2019

Preprint

Self Cite

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“…First, oleaginous strains, especially diatoms, were engineered to optimize the fatty acid chain-length profile for biodiesel production [141]. Secondly, isoprenoid biosynthesis pathway has been engineered to redirect carbon flux towards specific and high values products for chemical industry and/or as biofuels [176].…”

Section: Discussionmentioning

confidence: 99%

Potential and Challenges of Improving Photosynthesis in Algae

Vecchi

Barera

Bassi

et al. 2020

Plants

108

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Sunlight energy largely exceeds the energy required by anthropic activities, and therefore its exploitation represents a major target in the field of renewable energies. The interest in the mass cultivation of green microalgae has grown in the last decades, as algal biomass could be employed to cover a significant portion of global energy demand. Advantages of microalgal vs. plant biomass production include higher light-use efficiency, efficient carbon capture and the valorization of marginal lands and wastewaters. Realization of this potential requires a decrease of the current production costs, which can be obtained by increasing the productivity of the most common industrial strains, by the identification of factors limiting biomass yield, and by removing bottlenecks, namely through domestication strategies aimed to fill the gap between the theoretical and real productivity of algal cultures. In particular, the light-to-biomass conversion efficiency represents one of the major constraints for achieving a significant improvement of algal cell lines. This review outlines the molecular events of photosynthesis, which regulate the conversion of light into biomass, and discusses how these can be targeted to enhance productivity through mutagenesis, strain selection or genetic engineering. This review highlights the most recent results in the manipulation of the fundamental mechanisms of algal photosynthesis, which revealed that a significant yield enhancement is feasible. Moreover, metabolic engineering of microalgae, focused upon the development of renewable fuel biorefineries, has also drawn attention and resulted in efforts for enhancing productivity of oil or isoprenoids.

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“…Whilst there is considerable interest in the integration of microalgae such as Chlamydomonas reinhardtii into industrial biotechnology-and much has been written regarding their potential as low-cost, light-driven cell factories for making valuable recombinant proteins and metabolites (e.g. Gimpel et al 2015a, Lauersen 2019, Taunt et al 2017)-the economic and technical challenges of crop protection when cultivating microalgae at scale are often overlooked. Even in 'closed' systems such as photobioreactors or internally lit fermentors, the potential for spoilage through contamination with bacteria, fungi or other algae is high, especially if operated over an extended time period or in continuous mode (Day et al 2012;Wang et al 2013).…”

Section: Discussionmentioning

confidence: 99%

“…In principle, our ptxD variant could be introduced into any existing strain of C. reinhardtii including those engineered to synthesise novel products such as recombinant proteins, biofuels and novel metabolites. During the completion of this work, the group of Badillo-Corona also reported the successful expression of a separate version of ptxD in the C. reinhardtii chloroplast (Sandoval-Vargas et al 2018, 2019.…”

Section: Introductionmentioning

confidence: 96%

The phosphite oxidoreductase gene, ptxD as a bio-contained chloroplast marker and crop-protection tool for algal biotechnology using Chlamydomonas

Changko

Rajakumar

Young

et al. 2019

Appl Microbiol Biotechnol

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Edible microalgae have potential as low-cost cell factories for the production and oral delivery of recombinant proteins such as vaccines, anti-bacterials and gut-active enzymes that are beneficial to farmed animals including livestock, poultry and fish. However, a major economic and technical problem associated with large-scale cultivation of microalgae, even in closed photobioreactors, is invasion by contaminating microorganisms. Avoiding this requires costly media sterilisation, aseptic techniques during setup and implementation of 'crop-protection' strategies during cultivation. Here, we report a strain improvement approach in which the chloroplast of Chlamydomonas reinhardtii is engineered to allow oxidation of phosphite to its bioavailable form: phosphate. We have designed a synthetic version of the bacterial gene (ptxD)-encoding phosphite oxidoreductase such that it is highly expressed in the chloroplast but has a Trp→Opal codon reassignment for bio-containment of the transgene. Under mixotrophic conditions, the growth rate of the engineered alga is unaffected when phosphate is replaced with phosphite in the medium. Furthermore, under non-sterile conditions, growth of contaminating microorganisms is severely impeded in phosphite medium. This, therefore, offers the possibility of producing algal biomass under non-sterile conditions. The ptxD gene can also serve as a dominant marker for genetic engineering of any C. reinhardtii strain, thereby avoiding the use of antibiotic resistance genes as markers and allowing the 'retro-fitting' of existing engineered strains. As a proof of concept, we demonstrate the application of our ptxD technology to a strain expressing a subunit vaccine targeting a major viral pathogen of farmed fish.

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Eukaryotic microalgae as hosts for light-driven heterologous isoprenoid production

Cited by 83 publications

References 133 publications

Turning a green alga red: engineering astaxanthin biosynthesis by intragenic pseudogene revival in Chlamydomonas reinhardtii

Turning a green alga red: engineering astaxanthin biosynthesis by intragenic pseudogene revival in Chlamydomonas reinhardtii

Potential and Challenges of Improving Photosynthesis in Algae

The phosphite oxidoreductase gene, ptxD as a bio-contained chloroplast marker and crop-protection tool for algal biotechnology using Chlamydomonas

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