Development of sustainable bioprocess for biodiesel production from novel freshwater microalga Chlorella sorokiniana FC6 IITG

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Exhaustive fuel reserves worldwide has renewed and invigorated interest towards alternate sources of fuel which would serve dual function of being renewable and sustainable to the environment. In purview of modern trends, microalgal cultivation has gained significant interest as a pioneer for the sustainable production of biodiesel attributed to its innate ability to accumulate substantially large amounts of neutral lipids as compared to oil plants. Current state of art makes it economically infeasible for commercialization which can be accounted to the several bottlenecks that persist during the upstream and downstream processes. Rationale for strain improvement as well as process strategy modification are being essential for development towards a more sustainable process as far as biodiesel production is concerned. In the present study, indigenous microalgal strains were isolated and screened for maximum neutral lipid accumulation. The best strain with inherent ability to accumulate neutral lipid was further taken for detailed characterization and evaluation under different cultivation conditions such as photoautotrophic, heterotrophic and mixotrophic mode. Oil quality in terms of fatty acid compositions of the biomass obtained from different cultivation conditions were also evaluated by gas chromatography (GC). In order to achieve enhanced biomass and lipid productivity two process engineering strategies were developed: (i) one stage two phase high cell density mixotrophic fed-batch cultivation and (ii) synchronized growth and neutral lipid accumulation under mixotrophic growth in fed-batch and chemostat mode achieved via manipulation of substrates feeding mode and supplementation of lipid elicitors in the growth medium. Finally, electrochemical harvesting method was employed to pre-concentrate the microalgal culture broth as a sustainable alternatives to the existing methods and the biomass was converted to biodiesel via in situ transesterification.
Supervisor: Debasish Das