Abstract
The need to reduce the CO2 footprint of human activities calls for the utilization of new means of production and new sources of products. Microalgae are a very promising source of a large variety of products, from fuels to chemicals for multiple industrial applications (e.g. dies, pharmaceutical products, cosmetics, food and feed, new materials for high tech manufacture), and for processes such as wastewater treatment. Algae, as photosynthetic organisms, use light to energize the synthesis of organic matter and differently from most terrestrial plants, can be cultured on land that are not used for crop production. We describe the main factors contributing to microalgae productivity in artificial cultivation systems and discuss the research areas that still need investigation in order to pave the way to the generation of photosynthetic cell factories. We shall comment on the main caveats of the possible mode of improving photosynthetic efficiency and to optimize the partitioning of fixed C to products of commercial relevance. We address the problem of the selection of the appropriate strain and of the consequences of their diverse physiology and culture conditions for a successful commercial application. Finally, we shall provide state of the art information on cell factories chassis by means of synthetic biology approaches to produce chemicals of interest.
Highlights
Climate changes presently occurring on Earth point toward the need to reduce the CO2 anthropogenic emissions and call for the utilization of renewable sources of products, especially of fuels
Since a higher growth rate is consequent to an increased nutrient use efficiency, bubbling cultures with CO2 stimulates growth if C is the limiting nutrient, as it might be the case in concentrating mechanisms (CCMs) lacking species (Beardall and Giordano, 2002; Raven et al, 2011, 2012; Venuleo et al, 2018), or if a decreased cost for CCM allows a higher energy investment into making new cells (Raven et al, 2014; Li et al, 2015)
Microalgae metabolic engineering shall be applied at multiple levels, from enhancing the catalytic efficiency of native enzymes to introducing novel functions, like product secretion, which will ease the harvesting of commercial product (Figure 5)
Summary
Climate changes presently occurring on Earth point toward the need to reduce the CO2 anthropogenic emissions and call for the utilization of renewable sources of products, especially of fuels. It turns detrimental for the productivity of photosynthetic organisms in commercial application, as it leads to the dissipation of most of the energy harvested, up to 80-90%, in saturating light conditions (Wilhelm and Selmar, 2011; Peers, 2014; Figure 2).
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