Bioprocessing Microalgae for Its Applications in Therapeutics and Bioresource Management

Abstract

Microalgae are dynamic biological resource with various applications. In recent years, the scope of application has expanded to include algal based nutritional health foods, pharmaceuticals, agricultural and industrial products along with the application in environmental remediation and bioenergy production. At the same time, methods and technologies to bioprocess microalgae for the desired applications have also been evolved. However, there is still significant progress needed to explore the high potential of microalgae applications. The current work aims to improve the efficiency of algal feed-stocks bioprocessing them with cost-effective and environmentally sustainable techniques for their applications in therapeutics and bioresource management. The current study is composed of three main objectives. In the first objective, microalgae based biogenic silver nanoparticles (AgNPs) were used to target microbial and cancer infected cells with significant biocompatibility. The AgNPs provided comparative study synthesized through ethanol extracts of various freshwater microalgae species, Dictyosphaerium sp. HM1 (DHM1), Dictyosphaerium sp. HM2 (DHM2) and Pectinodesmus sp. HM3 (PHM3). Noteworthy activity against 14 bacterial strains, the fungal strain Candida albicans, breast cancer (MCF7) cell line, hepatocellular carcinoma (HepG2) cell line, and Huh7 cells infected by Newcastle Disease Virus (NDV) suggested the likely use of microalgae mediated biogenic nanoparticles in pharmaceutics and biomedicine for drug delivery. The second objective investigated the impact of supplementing Graphene Quantum Dots (GQD) to Chlamydomonas reinhardtii cc503. The core purpose was to improve the absorption of light in the blue portion of spectrum. However, despite increasing photosynthetic activity significantly high biomass production was observed and the results indicated an unusual corelation of GQDs and their impact on fluorescence quenching activity of the system. Regardless of fluorescence quenching, cells showed normal growth. However, a substantial increase in lipid production was observed, representing lipid accumulation of up to 46.5 ± 1.4%. v In the third objective, phase-restricted AD system (phase I only) was studied for Phosphorus (P) release, production of Volatile Fatty Acids (VFA), ammonia (as NH4 + ) and biogas by digesting Chlorella vulgaris grown on agricultural waste-water using sewage sludge as inoculum. In this phase I AD system, the digester hydraulic retention time (HRT) was changed that resulted in altered P, NH4 + and VFA concentrations in the effluent and biogas production. The reactor operated at 10 days HRT released maximum inorganic P (orthophosphate) in the effluent with a value of 199 ± 1 mg/L which is the highest amongst considered HRTs. Maximum nitrogen (N) in the phase-restricted AD system was observed at 14 days HRT with final concentration of 118 ± 1 mg NH4 + /L. The Gas Chromatography (GC) analysis indicated that VFA were present in all phase I AD reactors, with 10 days HRT digester featuring the highest concentration at 233 mg/L. Furthermore, phase restricted AD approach had positive impact on biogas generation. The 14 days HRT digester exhibited greatest biogas production at 522 ± 1 mL in the digester’s headspace, followed by the 10 days HRT. Results gained through this thesis have established that proposed technologies can present better approach to bioprocess microalgae for its applications to benefit humankind. In addition, if successfully implemented these approaches will provide economic development and reduce cost of living for society in general and specifically for rural and underdeveloped communities that are challenged by health and energy crises.