Abstract
Photosynthetic organisms fix inorganic carbon through carbon capture machinery (CCM) that regulates the assimilation and accumulation of carbon around ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco). However, few constraints that govern the central carbon metabolism are regulated by the carbon capture and partitioning machinery. In order to divert the cellular metabolism toward lipids and/or biorenewables it is important to investigate and understand the molecular mechanisms of the CO2-driven carbon partitioning. In this context, strategies for enhancement of CO2 fixation which will increase the overall biomass and lipid yields, can provide clues on understanding the carbon assimilation pathway, and may lead to new targets for genetic engineering in microalgae. In the present study, we have focused on the physiological and metabolomic response occurring within marine oleaginous microalgae Microchloropsis gaditana NIES 2587, under the influence of very-low CO2 (VLC; 300 ppm, or 0.03%) and high CO2 (HC; 30,000 ppm, or 3% v/v). Our results demonstrate that HC supplementation in M. gaditana channelizes the carbon flux toward the production of long chain polyunsaturated fatty acids (LC-PUFAs) and also increases the overall biomass productivities (up to 2.0 fold). Also, the qualitative metabolomics has identified nearly 31 essential metabolites, among which there is a significant fold change observed in accumulation of sugars and alcohols such as galactose and phytol in VLC as compared to HC. In conclusion, our focus is to understand the entire carbon partitioning and metabolic regulation within these photosynthetic cell factories, which will be further evaluated through multiomics approach for enhanced productivities of biomass, biofuels, and bioproducts (B3).
Highlights
Environmental pollution by the greenhouse emissions led to global warming and accumulation of 440 ppm of CO2 which is one of the significant gas released into the atmosphere contributing for adverse environmental issues (Ng et al, 2018)
The data predicts that the photosynthetic machinery of M. gaditana in response to high CO2 (HC) is highly active rather than very-low CO2 (VLC), which demonstrates lowering of doubling time and enhanced growth rates
The cellular physiology governs the channelization of the carbon flux toward biomass and biosynthesis of energy storage molecules
Summary
Environmental pollution by the greenhouse emissions led to global warming and accumulation of 440 ppm of CO2 which is one of the significant gas released into the atmosphere contributing for adverse environmental issues (Ng et al, 2018). Increase in atmospheric CO2 may be caused due to following reasons such as deforestation (9%), burning of fossil fuels (87%), and remaining (4%) presumably by others like industrial manufacturing (Le Quere et al, 2013; Mistry et al, 2019). Capturing of the atmospheric CO2 and converting them into reduced form without contributing to global warming by maintaining the balance in the environment is referred as carbon sequestration (Lal, 2008; Zeng, 2008). These photosynthetic cell factories are capable of sequestering atmosphere CO2 for the production of biofuel precursors (Rittmann, 2008; Mistry et al, 2019). The potential of industrially relevant oleaginous microalgae to minimize the excess CO2 present in the atmosphere can be employed via carbon concentrating mechanism (CCM) (Long et al, 2016)
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