Downstream Processing Of Microalgae Research Articles

Harvesting of Scenedesmus obliquus Cells by Chemical Flocculation: The Effects of Various Flocculants in Bio-recovery of Carotenoids

One of the major challenges in the downstream processing of microalgae is harvesting cells from the culture medium, which account for 20-30% of the production cost. Several harvesting methods and their combinations are available efficiency of which depends on algal sp. and biomass concentration. However, the bio recovery of algal metabolites for quite a number of harvesting methods is rarely reported. In the present study, an experiment was carried out to determine the effects of different flocculants (AlCl2, FeCl3 and ZnSO4, MgSO4) in harvesting Scenedesmus obliquus and its bio recovery of carotenoids. From the result obtained FeCl3 was the best flocculant harvesting up to 99.69% algal cells at the first 30 minutes of reaction time. Similarly, in terms of carotenoid bio-recovery, the highest carotenoids content was recorded in cells harvested with ferric chloride (i.e., 2.81 mg/ml) as compared to other coagulants.

Microalgae-based bioplastics: Future solution towards mitigation of plastic wastes

Global demand for plastic materials has severely harm the environment and marine sea life. Therefore, bioplastics have emerged as an environmentally friendly alternative due to sustainability, minimal carbon footprint, less toxicity and high degradability. This review highlights the sustainable and environmentally friendly approach towards bioplastic production by utilizing microalgae as a feed source in several ways. First, the microalgae biomass obtained through the biorefinery approach can be processed into PHA under certain nutrient limitations. Additionally, microalgae biomass can act as potential filler and reinforcement towards the enhancement of bioplastic either blending with conventional bioplastic or synthetic polymer. The downstream processing of microalgae via suitable extraction and pre-treatment of bioactive compounds such as lipids and cellulose are found to be promising for the production of bioplastics. Moving on, the intermediate processing of bioplastic via lactic acid synthesized from microalgae has favoured the microwave-assisted synthesis of polylactic acid due to cost efficiency, minimum solvent usage, low energy consumption, and fast rate of reaction. Moreover, the reliability and effectiveness of microalgae-based bioplastics are further evaluated in terms of techno-economic analysis and degradation mechanism. Future improvement and recommendations are listed towards proper genetic modification of algae strains, large-scale biofilm technology, low-cost cultivation medium, and novel avocado seed-microalgae bioplastic blend.

Plant-based biopolymers: emerging bio-flocculants for microalgal biomass recovery

The production of microalgal biomass and its derived products on a large-scale requires the development of sustainable and cost-effective harvesting technologies. Biomass recovery is the primary step in the downstream processing of microalgae and it is a costly operation because microalgal cultures are stable hydrophilic colloidal suspensions. Bio-flocculation has been proposed as a low-cost technology that can be employed to dewater microalgal cultures thus making secondary harvesting methods like filtration and centrifugation less energy-intensive. This review provides an overview of increasing applications of plant-based biopolymers in microalgal biomass harvesting on laboratory and pilot-scale culture volumes. The structure, preparation, and flocculation activity of natural and chemically cationized plant biopolymers are presented. Recent studies demonstrating microalgal biomass recovery have been summarized discussing the advantages and limitations of plant-based biopolymers as emerging bio-flocculants. Future perspectives on biopolymers with special attention to studies reported on nutrient medium recycling, environmental impact assessment and techno-economic analysis of plant-based bio-flocculants facilitated bio-flocculation have been discussed.