Photosynthetic and Lipogenic Response Under Elevated CO2 and H2 Conditions—High Carbon Uptake and Fatty Acids Unsaturation

Abstract

Microalgae are most versatile organisms having ability to grow under diverse conditions and utilize both organic and inorganic carbon sources. Microalgal photosynthesis can be employed to transform carbon dioxide (CO 2 ) into essential bioactives and photofuels. In this study, microalgal growth under modified headspace gas compositions which are CO 2 + H 2 (1:1), CO 2 , H 2 and Air was evaluated to determine the photosynthetic efficiency and bioactives production. A marked enhancement was observed in quantum yield (Fv/Fm: 0.77) and CO 2 biosequestration rate (0.39 g.L −1. d −1 ) under CO 2 + H 2 headspace gas condition as compared to the other experimental variations. The chemoselective functioning of Rubisco under varying gas concentrations was determined, where elevated CO 2 conditions negate the oxygenase activity under a high CO 2 /O 2 ratio which enabled higher CO 2 sequestration. The enhanced CO 2 sequestration and altered redox conditions through H 2 addition under the monophasic operation have also led to a higher average degree of unsaturation (DU) and carbon chain length (CCL) of the fatty acids produced. This study provides an approach to augment photosynthetic efficiency and lipogenesis through non-genetic modifications along with the feasibility to cultivate microalgae in integration with industrial flue gases. Exploiting the true potential of microalgae would provide sustenance from climatic changes and environmental pollution concurrently producing biobased products analogous to the fossil-derived products.

Augmented CO2 tolerance by expressing a single H+-pump enables microalgal valorization of industrial flue gas

“…When exposed to high CO 2 levels, microalgae attempt to maintain their cytosolic pH, namely, pH homeostasis, against the environment by (i) upregulating proton extrusion extracellularly in response to the inward diffusion of H + ; (ii) inactivating the carbon concentrating mechanism (CCM) to minimize the collateral intracellular acidification caused by enriched CO 2 and facilitating CO 2 hydration intracellularly; (iii) modifying the composition of the cellular membrane to strengthen its role as a proton barrier; and iv) increasing ATP synthesis to provide biological energy for the operation of ATP-driven transporters and protein recovery processes 7 , 8 , 12 , 13 . Therefore, we probed the expression levels of several genes of interest related to the four abovementioned cellular responses based on a transcriptome analysis to examine whether these tolerance mechanisms function properly.…”

The role of microalgae culture modes in aquaculture: a brief opinion

“…Then, they convert light energy into usable reduced coenzyme II [NAD(P)H] and ATP ( Sun et al, 2016 ). CO 2 and light (light period and light intensity) are the main factors affecting the growth of photoautotrophic microalgae, and light energy is converted into cellular substances ( Butti and Mohan, 2018 ). In aquaculture, photoautotrophic microalgae have obvious economic advantages.…”