To convert optical energy into electric energy in a clean and sustainable way, Optopia is designed as a photovoltaic system consisting of two subsystems: photosynthetic microorganism system (Synechocystis sp. or Rhodopseudomonas palustris) and electrogenic microorganism system (Shewanella oneidensis). Synthetic biology strategies are applied to the system to trigger production and export of lactate in photosynthetic microorganisms, as well as to improve efficiency of lactate utilization and extracellular electron generation in electrogenic microorganism system.
Synechocystis, one kind of cyanobacteria, is more mature than Rhodopseudomonas in lactate production, but generating lots of oxygen during photosynthesis. Given the fact that Shewanella favors anaerobic environment for electricity production, Rhodopseudomonas may serve as a better carbon resource provider for Shewanella, not only because of its anaerobic photosynthesis maintaining an anaerobic environment required for extracellular electron generation in Shewanella, but also due to its capacity of reusing the waste from Shewanella. Hence, we construct a Synechocystis- Shewanella MFC and a Rhodopseudomonas - Shewanella MFC to find an optimized version of Optopia, maximzing the conversion of optical energy to electric energy.
Part1: Photosynthetic microorganism system
Part2: Electrogenic microorganism system
Part3: Whole design
Part4: Future plan
4.1 Since the whole circuits of lactate utilization part and NADH production part are separated, we could not improve lactate utilization and NADH production at the same time. We would find a method to integrate these two circuits and get a full-function Shewanella, which has the electrogenesis efficiency to maximum extent.
4.2 As Synechocystis PCC6803 and Rhodopseudomonas palustris are used to transfer light energy to lactate, we would like to replace the promoter with light inducible promoter, which would make the engineered bacteria more intelligent.
4.3 Sewage is a type of waste water which contains many kinds of nutrients. We want to replace LB medium with sewage and make our device much more environmentally friendly.
4.4 We also want to integrate the targeted genes into the genome of engineered bacteria so that we can not only use medium without antibiotics which would reduce the growth rate of bacteria, but also have no need to take the plasmid loss into consideration.
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