Cell disruption is very important for the value-added biocompounds (VAB) to come out from microalgae. Among the most demanding microalgae at industrial level, diatoms and Haematococcus pluvialis have hooked the race. However, they at the same time face difficulty in their cell wall disruption for the VAB to come out as it is very rigid and thick. This is among the major barrier in construction of diatom solar panels for biofuel production. Different diatom walls experience different shear forces for harvesting its biomass. This results in raising the overall cost of photobioreactors controlling their growth and recovery of biomass and VAB. In order to lower the cost, the cell wall of microalgae needs to milk the metabolites without itself getting sacrificed. The current review in depth discusses the techniques to break the cell wall of microalgae especially diatoms and Haematococcus using nanotechnological approaches without lysing the cell. The research gaps, commercial applications, and future research directions have been identified and discussed to strengthen the environmental and economical sustainability.

Nanotechnological approaches to disrupt the rigid cell walled microalgae grown in wastewater for value-added biocompounds: commercial applications, challenges, and breakthrough

The search for novel sources of nutrients is among the basic goals for achievement of sustainable progress. In this context, microalgae are relevant organisms, being rich in high-value compounds and able to grow in open ponds or photobioreactors, thus enabling profitable exploitation of aquatic resources. Microalgae, a huge taxon containing photosynthetic microorganisms living in freshwater, as well as in brackish and marine waters, typically unicellular and eukaryotic, include green algae (Chlorophyceae), red algae (Rhodophyceae), brown algae (Phaeophyceae) and diatoms (Bacillariophyceae). In recent decades, diatoms have been considered the most sustainable sources of nutrients for humans with respect to other microalgae. This review focuses on studies exploring their bio-pharmacological activities when relevant for human disease prevention and/or treatment. In addition, we considered diatoms and their extracts (or purified compounds) when relevant for specific nutraceutical applications.

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Bioactive Molecules from Marine Diatoms and Their Value for the Nutraceutical Industry

Algae Mediated Pesticides Bioremediation: Mechanisms, Approaches, Limitations, and Prospects for Future Research

The biological state-of-the-art purification of wastewaters has gained momentum in recent times. The microalgal capability to reduce N and P contaminants, as well as chemical oxygen demand (COD), is implemented in wastewater treatment processes. This green microalgal strategy to integrate wastewater treatment and to achieve better energy efficiency mainly depends on the purpose, scalability, nutrient uptake of algal species and economic feasibility. Therefore, the microalgal approach is sustainable as compared to conventional methods of wastewater treatments because it generates no toxic waste and can grow in limited resources to meet the soaring energy demand of the world. In this chapter, we discuss the successful trials on pretreatment methods employing microalgae to treat a variety of wastewaters based on a different selection criterion. Further, we focused on different microalgae cultivation systems with an emphasis on their benefits and drawbacks. Then, a brief evaluation of the microalgae biorefinery technologies was done to generate renewable energy and high-value chemicals. Lastly, the challenges faced in integrated microalgal wastewater treatment processes were outlined for wide-scale applications on bioenergy production. 

The Multifaceted Microalgal Approach to Wastewater Treatment to Generate Energy and Essential Chemicals

Diatoms are the reservoir of bioactive compounds which have immense application in nutrition, industrial commodities and ecological studies. In the oceans, diatoms form a large bloom of silica under favourable conditions, whereas, in lentic and lotic systems, they colonize according to seasonal disturbances. Notably, the survival of diatoms in a stressed environment is because of their uniqueness; therefore, diatoms serve as an ideal candidate to understand the evolutionary paradigm and successional dynamics. This review outlines the biological uniqueness of diatoms, their role in biogeochemical cycles and the recolonization pattern of diatoms in anthropic disturbed habitats. Furthermore, a detailed discussion on different technologies for extracting valuable biomolecules with an emphasis on lipid extraction has been carried out. Moreover, the diatom-based photosynthetic biorefinery approach for a better understanding of the renewable usage of biomass is done.

Yagya Sharma

Papers

Facets of diatom biology and their potential applications