Impacts of Elevated CO₂Concentration on Biochemical Composition, Carbonic Anhydrase, and Nitrate Reductase Activity of Freshwater Green Algae

Abstract

To investigate the biochemical response of freshwater green algae to elevated CO 2 concentrations, Chlorella pyrenoidosa Chick and Chlamydomonas reinhardtii Dang cells were cultured at different CO 2 concentrations within the range 3-186 µmol/L and the biochemical composition, carbonic anhydrase (CA), and nitrate reductase activities of the cells were investigated. Chlorophylls (Chl), carotenoids, carbonhydrate, and protein contents were enhanced to varying extents with increasing CO 2 concentration from 3-186 µmol/L. The CO 2 enrichment significantly increased the Chl a/Chl b ratio in Chlorella pyrenoidosa, but not in Chlamydomonas reinhardtii. The CO 2 concentration had significant effects on CA and nitrate reductase activity. Elevating CO 2 concentration to 186 µmol/L caused a decline in intracellular and extracellullar CA activity. Nitrate reductase activity, under either light or dark conditions, in C. reinhardtii and C. pyrenoidosa was also significantly decreased with CO 2 enrichment. From this study, it can be concluded that CO 2 enrichment can affect biochemical composition, CA, and nitrate reductase activity, and that the biochemical response was species dependent.

Carbon and Nitrogen Fixation byAnabaena fertilissimaunder Elevated CO2and Temperature

“…Our study showed that the activity of carbonic anhydrase of A. fertilissima was significantly higher under ambient C 0 2 than the carbonic anhydrase reported in Nostoc calcicola and Anabaena sp. by Jaiswal et al (2005) and Chlorellapyrenoidosa and Chlamydomonas reinhardtii by Xia and Gao (2005) under elevated COz, suggesting that susceptibility of carbonic anhydrase to higher C 0 2 levels varies from organism to organism.…”

Growth, physiological and biochemical responses of Meliaceae species - Azadirachta indica and Melia dubia to elevated CO2 concentrations

“…Studies on CO 2 enrichment report changes in biochemical composition, carbonic anhydrase, and nitrate reductase activity, and that the response is species specific [38]. Elevated CO 2 concentration of 600 ppm was favourable for enhancement of total chlorophylls in A. indica and M. dubia.…”

Microalgae as a Feedstock for Biofuel Precursors and Value-Added Products: Green Fuels and Golden Opportunities

“…Several studies report improvements of both biomass growth rate and enhancing of starch accumulation as result of shifting from the ambient level (0.04%) to 2% CO2 in enriched air Tanadul et al 2014) or increasing the dissolved CO2 concentration from 3 to 190 mol L -1 in an aqueous medium by pH adjustment (Xia and Gao 2005). However, the algal response to high CO2 content has been found to be species-specific.…”

“…For example, Cheng et al (2015) found that starch content was nearly two times higher in Chlorella vulgaris and C. variabilis when cultured with 2% CO2, but it did not increase in C. sorokiniana and C. minutissima. Similarly, the activities of carbonic anhydrase and nitrate reductase enzymes in C. pyrenoidosa and Chlamydomonas reinhardtii exhibited different responses to elevation of dissolved CO2 content (Xia and Gao 2005). Moreover, other studies demonstrated that increasing CO2 content from ambient to 2-5% improves biomass growth but has either negative (up to 2-3 fold reduction) or no effect on starch accumulation when applied without the cell arrest (Thyssen et al 2001;Izumo et al 2007;Li et al 2013).…”