Assessing the potential of a genetically modified Parachlorella kessleri-I with low CO₂ inducible proteins for enhanced biomass and biofuel productivity

The biological process is one of the promising approaches for CO₂ capture and storage. Recently, biological sequestration using microalgae has gained much interest due to its capability to utilize CO₂ as a carbon source to generate valorizable biomass. This algal biomass further can be used as a feedstock for bioenergy and different value-added products. Here, we have heterogeneously overexpressed the low CO₂ inducible proteins (LCIA & LCIB) from Chlamydomonas reinhardtii in the marine alga Parachlorella kessleri-I. Incorporation of these two genes boosted the endogenous CCM leading to a hybrid system and improved overall carbon acquisition. The combination of these CCM proteins enhanced the supply of inorganic carbon to RuBisCO with positive effects on growth and biomass productivity. Biochemical analyses revealed that the hybrid CCM in P. kessleri-I was characterised by 2- fold higher carbonic anhydrase activity, increased starch, and 2X more lipid yield in comparison to wild type (WT) strain. Moreover, the semi-continuous cultivation of GM strain with supply of 1 % CO₂ led to around 60 % rise in the overall biomass productivity. These traits also persisted in scale-up studies leading to 2X more biomass productivity in the GM strain than WT in 100 L PBR. A comparative life-cycle assessment underlines the sustainability of the process of carbon capture and both biofuel and biochar production from P. kessleri-I with a hybrid CCM.