Valorization of Chlorella thermophila biomass cultivated in dairy wastewater for biopesticide production against bacterial rice blight: a circular biorefinery approach.

Biopesticides offer a sustainable and efficient alternative to synthetic pesticides, providing a safer and more eco-friendly solution to pest management. The present work proposes an innovative approach that integrates crop protection and wastewater treatment using thermophilic microalgal strain Chlorella thermophila (CT) cultivated in nutrient-rich dairy wastewater as a growth medium. The microalgae was cultivated mixotrophically and was able to reduce both organic carbon as well as nutrient load of the dairy wastewater efficiently. The integrated circular biorefinery approach combines biomass cultivation, extraction of biopesticide compounds, and conversion to biocrude. The antimicrobial activity of the biopesticidal extracts against Xanthomonas oryzae and Pantoea agglomerans, the causative agent of bacterial rice blight, is assessed through in vitro studies. The biomass extract obtained is able to inhibit the growth of both the above-mentioned plant pathogens successfully. Mass spectroscopy analysis indicates the presence of Neophytadiene that has previously been reported for the inhibition of several pathogenic bacteria and fungi. Several other value-added products such as linoleic acid and nervonic acids were also been detected in the microalgal biomass which have extremely high nutraceutical and medicinal values. Furthermore, the study investigates the potential for co-production of biocrude from the biorefinery process via hydrothermal liquefaction. Overall, the findings of this present work represent an innovative and sustainable approach that combines wastewater treatment and crop protection using microalgal biomass.