Conversion of wastewater-originated waste grease to polyunsaturated fatty acid-rich algae with phagotrophic capability

Revalorization of Microalgae Biomass for Synergistic Interaction and Sustainable Applications: Bioplastic Generation

Microalgae and cyanobacteria are photosynthetic microorganisms' sources of renewable biomass that can be used for bioplastic production. These microorganisms have high growth rates, and contrary to other feedstocks, such as land crops, they do not require arable land. In addition, they can be used as feedstock for bioplastic production while not competing with food sources (e.g., corn, wheat, and soy protein). In this study, we review the macromolecules from microalgae and cyanobacteria that can serve for the production of bioplastics, including starch and glycogen, polyhydroxyalkanoates (PHAs), cellulose, polylactic acid (PLA), and triacylglycerols (TAGs). In addition, we focus on the cultivation of microalgae and cyanobacteria for wastewater treatment. This approach would allow reducing nutrient supply for biomass production while treating wastewater. Thus, the combination of wastewater treatment and the production of biomass that can serve as feedstock for bioplastic production is discussed. The comprehensive information provided in this communication would expand the scope of interdisciplinary and translational research.

Application of phagotrophic algae in waste activated sludge conversion and stabilization

Phagotrophic algae can consume bacteria that are the predominant microorganisms present in the waste activated sludge (WAS) generated from municipal wastewater treatment processes. In this study, we developed a combined ultrasonication-phagotrophic algal process for WAS conversion. The ultrasonic pretreatment released small volatile solids (VS) including bacteria from WAS flocs. A phagotrophic alga Ochromonas danica then grew by consuming more than 80% of the released VS, with approximately 30% (w/w) algal cell yield. The process reduced the overall WAS VS by 42.4% in 1 day, comparing very favorably with the 27% reduction in 10 days by aerobic digestion. For stabilizing the solids remaining from the ultrasonic step, the total oxygen uptake required was 65%-92% lower than that for the original WAS, indicating substantially reduced aeration cost. Overall, this novel process enhanced the WAS digestion at lower energy requirements and produced microalgae for other potential uses. © 2021 Water Environment Federation PRACTITIONER POINTS: At least 80% of released VS from WAS can be processed by phagotrophic algae. Significant amounts of algae can be produced from WAS. Ultrasonication-phagotrophic algal process can make sludge management more sustainable.

Potential applications of algae in biochemical and bioenergy sector

Algae have gained substantial importance as the most promising potential green fuel source across the globe and is on growing demand due to their antioxidant, anticancer, antiviral, antihypertensive, cholesterol reducing and thickening properties. Therefore, it has vast range of application in medicines, pharmaceutical, cosmetics, paper and nutraceutical industries. In this work, the remarkable ability of algae to convert CO₂ and other toxic compounds in atmosphere to potential biofuels, foods, feeds and high-value bioactive compounds is reviewed. Algae produce approximately 50% of the earth's oxygen using its photosynthetic activity, thus acting as a potent tool to mitigate the effects of air pollution. Further, the applicability of algae as a desirable energy source has also been discussed, as they have the potential to serve as an effective alternative to intermittent renewable energy; and also, to combustion-based fossil fuel energy, making them effective for advanced biofuel conversions. This work also evaluates the current applications of algae and the implications of it as a potential substrate for bioplastic, natural alternative to inks and for making paper besides high-value products. In addition, the scope for integrated biorefinery approach is also briefly explored in terms of economic aspects at the industrial scale, as such energy conversion mechanisms are directly linked with sustainability, thus providing a positive overall energy outlook.