Review Poster
A CYBORG CHLOROPLAST: ENHANCING CO2 FIXATION ASHA SASTYA and MAYANK PRATAP SINGH BANGARI
Department of Crop Physiology, UAS, GKVK, Bengaluru-65 ABSTRACT Carbon dioxide (CO2) is not only an inexpensive and boundless source of carbon but also a despicable greenhouse gas. Owing to the evolutionary limitations of existing CO2 fixing enzymes and pathways, plant chemistry lacks the suitable enzyme for the efficient assimilation of CO2. Earlier studies focused on producing bio fuel from atmospheric CO2 and H2O; called artificial leaf. Till date synthetic chemistry lacks the suitable enzyme for functionalization of atmospheric CO2. There is need to not only give emphasis on exploiting CO2 mechanism offered by nature but also a necessity to optimize an artificial pathway to create synthetic CO2 fixing module. Here we discuss how manipulation in the existing cycles can be effective in plant photosynthetic production. One of the CO2 fixing module is “CETCH cycle” which is 8 times faster than natural occurring cycle and takes 20% less energy per CO2 fixed. Recent advancement in droplet-based microfluidics (water in oil emulsion) explores a new era in synthetic biology. By encapsulating spinach thylakoid into this microfluidic droplet along with the enzymes of CETCH cycle, it was possible to transform this microfluidic entity into a “self-energised synthetic chloroplast or a mini reactor”.
INTRODUCTION: A cyborg chloroplast CO2 is a greenhouse gas responsible for global warming. Autotrophs have ability to fix CO2 by photosynthesis in cellular compartments known as chloroplast that house a very important enzyme called RuBisCO, which has ability to convert CO2 into organic compound. In photosynthesis, RuBisCO is a double edge sword, as on one-end, it is involved in the most vital process carboxylation, but on the other end, it is very sensitive to O2 which evokes an undesirable process called photorespiration. One of the synthetic CO2 fixation module CETCH (Crotonyl Co-A/ethylmelonyl Co-A/hydroxy butyryl Co-A) designed by Schwander et al., 2016 is capable of converting CO2 into glycolate in vitro. CETCH cycle involves a main carboxylation enzyme called ECR (Enoyl-CoA Carboxylase/Reductase) for this conversion.. ECR can fix 80 molecules of CO2 per sec (8x more than RuBisCO) and rewardingly is insensitive to oxygen, which makes this design a complete remarkable breakthrough in designing synthetic chloroplast. Using microfluidics, co-encapsulation of the energy module (thylakoid membrane), isolated from spinach with energy co-factor (NADPH and ATP) required for CETCH cycle, “magic droplets” were created that were capable of continuous CO2 fixation, now called an “artificial chloroplast”.
METHODOLOGY :Create new to nature
RESULT: Mimicking Nature A
Encapsulation of thylakoid into droplet by drop-maker
D
E Enzyme isolated from different organism
F
C
• High Resolution LC-MS/MS, UP-MS/MS, HPLC, Spectrophotomery were used for analysis. • For image processing: fluorescence inverted microscope was used.
A: CETCH cycle cycle. B: 13C-labelling trends and cumulative amounts of methylmalonyl-CoA (blue) and ethylmalonyl-CoA (orange) over time light and dark, respectively. C: Glycolate production. D: TEM is operating inside microdroplets. E: Energy status of the droplets can be controlled by using light as an external signal. F: TEM+CETCH performing efficiently in microfluidics
DISCUSSION: Bridging the gap between biology and chemistry • • • •
Light is required to operate the cycle energy status of the droplets and can be controlled by using light as an external signal TEM has the potential to control full metabolic cycle for continuous fixation of CO2 through a light switch. Hence, Glycolate production take place. Synthetic CETCH cycle may be mechanically coupled to native energy machines to shape several carbon compounds from CO2. This synthetic chloroplast has a capability to harness light and covert it into chemical energy by utilizing chemical energy it fixes atmospheric CO2.
FUTURE ASPECTS: Seek for opportunities Transformation of greenhouse gases into useful product such as fuel and food. With the aid of these mini reactors, biosynthesis of metabolites, amino acids and drug production can be made possible via natural pathway. REFRENCE: 1. Miller, Tarryn E., et al. "Light-powered CO2 fixation in a chloroplast mimic with natural and synthetic parts." Science 368.6491 (2020): 649-654. 2. Schwander, Thomas, et al. "A synthetic pathway for the fixation of carbon dioxide in vitro." Science 354.6314 (2016): 900-904.
Try and leave this world a little better Than you found it. Robert Baden-Powell (1857-1941)