Microalgae mediated bioremediation of polycyclic aromatic hydrocarbons: Strategies, advancement and regulations.

Polycyclic aromatic hydrocarbons (PAHs) are pervasive in the atmosphere and are one of the emerging pollutants that cause harmful effects in living systems. There are some natural and anthropogenic sources that can produce PAHs in an uncontrolled way. Several health hazards associated with PAHs like abnormality in the reproductive system, endocrine system as well as immune system have been explained. The mutagenic or carcinogenic effects of hydrocarbons in living systems including algae, vertebrates and invertebrates have been discussed. For controlling PAHs, biodegradation has been suggested as an effective and eco-friendly process. Microalgae-based biosorption and biodegradation resulted in the removal of toxic contaminants. Microalgae both in unialgal form and in consortium (with bacteria or fungi) performed good results in bioaccumulation and biodegradation. In the present review, we highlighted the general information about the PAHs, conventional versus advanced technology for removal. In addition microalgae based removal and toxicity is discussed. Furthermore this work provides an idea on modern scientific applications like genetic and metabolic engineering, nanomaterials-based technologies, artificial neural network (ANN), machine learning (ML) etc. As rapid and effective methods for bioremediation of PAHs. With several pros and cons, biological treatments using microalgae are found to be better for PAH removal than any other conventional technologies.

Diatoms: Miniscule biological entities with immense importance in synthesis of targeted novel bioparticles and biomonitoring.

Diatoms are the most abundant microscopic unicellular protists in natural lotic ecosystems. They are the major component of the producer community in aquatic ecosystems that also play important roles in biostratigraphy, paleoclimatology and overall ecosystem functioning. In recent times as ultrastructural details of diatom frustule has been established, it has become evident that frustule nanoscale structures play a significant role in adsorption and bioaccumulation of heavy metals. Physical processes like bioaccumulation in conjunction with cell surface ligands and functional groups allow diatoms to convert toxic forms of metals to their more utilizable forms. This unique aspect of diatom has been exploited in recent times for the synthesis of novel nanoparticles under in vitro conditions. Moreover, biomonitoring using diatoms is increasingly becoming a preferred choice for assessment of water quality due to their time-integrative characteristic. Although both these aspects include diatom and metal speciation under in vitro and in situ conditions, a comprehensive study addressing both these areas has remained obscure. Thus, the present work aims at integrating the aspects of novel metal particle synthesis and biomonitoring of habitats with diatom as the principal biological entity involved in these processes.