Valorisation of organic carbons and organo-solvents by mixotrophic cultivation of methylotrophic Tetraselmis indica for enhanced biomolecules production

Abstract

Microalgal biomass is a sustainable bioresource for producing a wide range of biomolecules such as lipids and chlorophylls, astaxanthin, and β-carotene. The mixotrophic cultivation using organic carbon (OCs) and traditional organo-solvents (OSs), especially methanol (MeOH), has been shown to improve biomass productivity and biomolecule yield. However, limited studies have explored the utilization of OSs as an external carbon source to produce microalgal biomass and for subsequent biorefinery. Thus, the present study evaluates the effects on the cultivation of industrial important microalgal Tetraselmis indica BDUG001 (T. indica BDUG001) through supplementation of various OCs and OSs at different day-night cycles under sterile mixotrophic conditions. Among all the OCs and OSs, MeOH showed the best growth, biomass, and biomolecule production. Interestingly, MeOH at a varying concentration (0–10 g/L) was an ideal carbon source for enhancing T. indica BDUG001 growth, biomass, and biomolecules productivity. At the 7.5 g/L concentration of MeOH, T. indica BDUG001 showed maximized biomass production (2.45 ± 0.07 g/L), lipid content (42.85 ± 1.20%), total lipid yield (1.05 ± 0.03 g/L), photosynthetic pigments [chl-a (3.27 mg/L), chl-b (2.25 mg/L) and TCs (1.27 mg/L]. While the maximum astaxanthin (0.77 μg/gm) and β-carotene (5.21 μg/mg) were observed at 10 and 5.0 g/L, respectively. The present investigation will aid in the microalgal research pipeline for the selection of novel OSs tolerant microalgae strains and utilization of waste OSs for mass-scale sterile mixotrophic cultivation. Moreover, the proposed cultivation system will help to develop low-cost algal biorefinery systems to attain high-quality industrial important biomolecules.