PhD Oral Defence: Micro-algae assisted bioremediation of simulated dairy effluent and valorization
PhD Oral Defence of Bhalamurugan Gatamaneni Loganathan, Bioresource Engineering
The current research evaluated the influence of various media (BG11, MN8, MZM) including simulated dairy wastewater (10D, 10D+Y) on the growth, biomass productivity and lutein content of an under-examined algal strain Chlorella variabilis. The study demonstrated that the algal strain performed better in 10D with a biomass productivity of 0.037 g/L/day and enhanced lutein content to 9.6 mg/g. The results from this study also proved that 10D could be used as a cultivation medium for the large scale production of the alga with huge economic benefits. In order to overcome the problems associated with culture crashes, it was decided to employ a microalgal consortia for further studies. The effect of light wavelengths (blue, red, amber, amber+blue and cool-fluorescent) on the growth, biomass productivity, and lutein content of the microalgal consortia composed of Chlorella variabilis and Scenedesmus obliquus cultivated on simulated dairy wastewater was evaluated and the results showed that cool fluorescent light was the best choice with a biomass productivity of 0.042 g/L/day and lutein content of 7.22 mg/g when compared to other light treatments. A Central Composite design was employed to optimize the biomass productivity, lutein content and pollutant removal capability of the microalgal consortia with respect to inoculum concentration, light intensity and time. It was found that at optimal conditions of 40% inoculum concentration, 25 µmol m-2s-1 and time of 10 days, the microalgal consortia had a biomass productivity of 29.13 mg/L/day and lutein content of 12.59 mg/g. The lutein content exhibited in this study is the highest ever reported for any microalgal consortia studied so far and could be a commercial source of lutein in the future. Finally, based on the results obtained from the optimization study, the effect of the microalgal consortia as a biofertilizer on the plant growth of corn and soybean was also evaluated. The results demonstrated that 40% algal concentration showed better plant growth in both corn and soybean with improved secondary characteristics when compared to other treatments. Overall, the thesis showed that the microalgal consortia of Chlorella variabilis and Scenedesmus obliquus could be the first of its kind with the potentiel of being incorporated into a biorefinery concept with huge multifaceted benefits.