Utilization of microalgae for agricultural runoff remediation and sustainable biofuel production through an integrated biorefinery approach

Qurrat Ul Ain Rana; Saira Latif; Saleha Perveen; Abdul Haq; Sidra Ali; Muhammad Irfan; Rahul Gauttam; Tawaf Ali Shah; Turki M Dawoud; Gezahign Fentahun Wondmie; Mohammed Bourhia; Malik Badshah

doi:10.1186/s40643-023-00720-w

Utilization of microalgae for agricultural runoff remediation and sustainable biofuel production through an integrated biorefinery approach

Bioresour Bioprocess. 2024 Jan 11;11(1):8. doi: 10.1186/s40643-023-00720-w.

Authors

Qurrat Ul Ain Rana^{1

2}, Saira Latif¹, Saleha Perveen¹, Abdul Haq^{1

3}, Sidra Ali¹, Muhammad Irfan⁴, Rahul Gauttam⁵, Tawaf Ali Shah⁶, Turki M Dawoud⁷, Gezahign Fentahun Wondmie⁸, Mohammed Bourhia⁹, Malik Badshah¹⁰

Affiliations

¹ Sustainable Bioenergy and Biorefinery Laboratory, Department of Microbiology, Quaid-I-Azam University, Islamabad, 45320, Pakistan.
² Joint Genome Institute, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
³ Peshawar Laboratories Complex, Pakistan Council of Scientific & Industrial Research, Islamabad, 25120, Pakistan.
⁴ Department of Oral Biology, College of Dentistry, University of Florida, Gainesville, FL, USA.
⁵ The Joint Bioenergy Institute, Emeryville, CA, USA.
⁶ Collee of Agriculture Engineering and Food Sciences, Shandong University of Technology, Zibo, China.
⁷ Department of Botany and Microbiology, College of Science, King Saud University, P. O. BOX 2455, 11451, Riyadh, Saudi Arabia.
⁸ Department of Biology, College of Science, Bahir Dar University, P.O Box 79, Bahir Dar, Ethiopia. resercherfent@gmail.com.
⁹ Department of Chemistry and Biochemistry, Faculty of Medicine and Pharmacy, Ibn Zohr University, 70000, Laayoune, Morocco.
¹⁰ Sustainable Bioenergy and Biorefinery Laboratory, Department of Microbiology, Quaid-I-Azam University, Islamabad, 45320, Pakistan. malikbadshah@qau.edu.pk.

Abstract

Generally wastewater such agricultural runoff is considered a nuisance; however, it could be harnessed as a potential source of nutrients like nitrates and phosphates in integrated biorefinery context. In the current study, microalgae Chlorella sp. S5 was used for bioremediation of agricultural runoff and the leftover algal biomass was used as a potential source for production of biofuels in an integrated biorefinery context. The microalgae Chlorella sp. S5 was cultivated on Blue Green (BG 11) medium and a comprehensive optimization of different parameters including phosphates, nitrates, and pH was carried out to acquire maximum algal biomass enriched with high lipids content. Dry biomass was quantified using the solvent extraction technique, while the identification of nitrates and phosphates in agricultural runoff was carried out using commercial kits. The algal extracted lipids (oils) were employed in enzymatic trans-esterification for biodiesel production using whole-cell biomass of Bacillus subtilis Q4 MZ841642. The resultant fatty acid methyl esters (FAMEs) were analyzed using Fourier transform infrared (FTIR) spectroscopy and gas chromatography coupled with mass spectrometry (GC-MS). Subsequently, both the intact algal biomass and its lipid-depleted algal biomass were used for biogas production within a batch anaerobic digestion setup. Interestingly, Chlorella sp. S5 demonstrated a substantial reduction of 95% in nitrate and 91% in phosphate from agricultural runoff. The biodiesel derived from algal biomass exhibited a noteworthy total FAME content of 98.2%, meeting the quality standards set by American Society for Testing and Materials (ASTM) and European union (EU) standards. Furthermore, the biomethane yields obtained from whole biomass and lipid-depleted biomass were 330.34 NmL/g VS_added and 364.34 NmL/g VS_added, respectively. In conclusion, the findings underscore the potent utility of Chlorella sp. S5 as a multi-faceted resource, proficiently employed in a sequential cascade for treating agricultural runoff, producing biodiesel, and generating biogas within the integrated biorefinery concept.

Keywords: Bacillus subtilis; Anaerobic digestion; Biodiesel; Biogas; Chlorella; Lipase.