Scientists may have upended photosynthesis, the biological process that is at the root of the energy chain on planet Earth—or, at least the key determinants of this process. To most of us, a cell-free system capable of converting carbon dioxide into sugar, harnessing solar or chemical energy, might sound like sci-fi. However, as per a study published in Science, scientists have developed an artificial chloroplast, the site for photosynthesis in plants.
The carbon-fixing part of photosynthesis, as it occurs in nature, is limited by the ability of RuBisCo, the enzyme that kickstarts this conversion, to bind with only 5-10 molecules of CO2. The CETCH cycle—the alternate pathway designed by Tobias Erb and Thomas Schwander, scientists at the Mac Planck Institute for Terrestrial Microbiology, both of whom are also associated with the present study—replaced RuBisCO with a bacterial enzyme and employed 16 other enzymes from nine organisms, and proved 20% more efficient than natural processes.
However, the problem of using sunlight to fuel the process in vitro remained. Pre-existing research on the ability of thylakoid membranes, the site of the light-dependent part of photosynthesis, to operate outside cells inspired Erb et al to isolate the light-harvesting thylakoids from spinach leaves and pair them with the CETCH cycle—this allowed for the continuous conversion of CO2 into glycolate, a metabolite that could be used for making useful organic products.
There are however, issues of scale, including in vitro lifespan of thylakoid membranes, and the difficulty in continually isolating them from spinach leaves. Potentially, though, this advancement could have an impact on therapeutic medicine, agriculture, and environment. It could open up the option of genetically engineering plants to create crop varieties that are much faster growing than present ones. The improved efficiency in fixing CO2 may even be used to remove excess atmospheric CO2
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