Eco-friendly approach for tannery effluent treatment and CO2 sequestration using unicellular green oleaginous microalga Tetradesmus obliquus TS03

The present study explored the process of bioremediation, sequestration of carbon dioxide, and biofuel production using multifarious potent freshwater microalgae Tetradesmus obliquus TS03. The heavy metals were reduced, viz., 8.34 mg of cadmium (95.13%), 4.56 mg of chromium (97.28%), 1.34 mg of copper (98.67%), 1.24 mg of cobalt (98.19%), 1.93 mg of lead (96.72%), 2.31 mg of nickel (97.14%), and 2.23 mgL(-1) of zinc (96.59%) using photobioreactor microalgal treatment method. The heavy metal biosorption capacity rate (q(max)) was 98.90% determined by the Langmuir and Freundlich isotherm kinetics model at 10 days of effluent treatment using Tetradesmus obliquus TS03. The microalgae T. obliquus TS03 utilized 98.34% of carbon dioxide (CO2) enhanced by acetyl CoA carboxylase and RuBisCO enzymes. The biodiesel was extracted from microalga and identified 32 fatty acid methyl ester major compounds viz., tetradecanoate methyl ester, hexadecanoic acid methyl ester, tridecanoic acid methyl ester, heptadecatrienoic acid methyl ester, octadecanoic acid methyl ester, eicosanoic acid methyl ester, pentadecanoic acid methyl ester, and cis-methylicosanoate using gas mass chromatography (GCMS). The biodiesel functional groups were identified, viz., amides, phenols, alcohols, alkynes, carboxylic acids, carbonyls, and ketones groups using Fourier transformation infrared (FTIR). The bioethanol was identified using high-performance liquid chromatography (HPLC) and determined the peak presented at RT of 4.35 min (75,693.1046 mu V s(-1)).

Automated summary

The present study investigated the bioremediation process, carbon dioxide sequestration, and biofuel production using the versatile freshwater microalgae, Tetradesmus obliquus TS03. The photobioreactor microalgal treatment method reduced heavy metals, such as cadmium (95.13%), chromium (97.28%), copper (98.67%), cobalt (98.19%), lead (96.72%), nickel (97.14%), and zinc (96.59%). The Langmuir and Freundlich isotherm kinetics models determined a heavy metal biosorption capacity rate (q(max)) of 98.90% after 10 days of effluent treatment with Tetradesmus obliquus TS03. T. obliquus TS03 utilized 98.34% of carbon dioxide (CO2) through acetyl CoA carboxylase and RuBisCO enzymes. Biodiesel extracted from the microalgae contained major fatty acid methyl esters identified by gas mass chromatography (GCMS), while bioethanol was detected using high-performance liquid chromatography (HPLC) at a retention time (RT) of 4.35 min (75,693.1046 mu V s(-1)).