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Remediation of soil contaminated with pollutants using biological agents is more a sustainable and greener approach as compared to physico-chemical technologies. We recently confirmed that a microalga, Chlorella sp.MM3, and a bacterium, Rhodococcus wratislaviensis strain 9, can degrade high-molecular weight PAHs. In this study, an algal–bacterial system of these two strains was developed by long-term growth on a mixture of phenanthrene,pyrene, and benzo[a]pyrene (BaP). In a soil spiked with 50 mg L−1 phenanthrene, 10mg L−1 of pyrene and10 mg L−1 of BaP, the algal–bacterial system degraded these PAHs almost completely in slurry phase within 30 days.Also, the algal–bacterial system was able to successfully remediate these three PAHs in a soil long-term contaminated with 245.1 mg kg−1 of 16 PAHs and several heavy metals under slurry phase in 21 days. Use of such appropriate assays as chlorophyll estimation for the microalga and semi-quantitative PCR for the bacterium confirmed survival of both the strains during soil bioremediation. Moreover, the residual toxicity test involving Escherichiacoli DH5α that expresses green fluorescent protein indicated the successful bioremediation of PAHs contaminated soil in slurry phase. For the first time, here we demonstrate the great potential of an algal–bacterial synergy in bioremediation of soil long-term contaminated with PAHs even in the presence of toxic heavy metals. Refereed/Peer-reviewed

The phytoremediation technique has been demonstrated to be a viable option for the remediation of polycyclic aromatic hydrocarbons (PAHs) contaminated sites. This study evaluated the potential applicability of plants with C3 and C4 carbon fixation pathways for the phytoremediation of recalcitrant high molecular weight (HMW) PAHs contaminated soil. A 60 and 120-day greenhouse study was conducted which showed higher degradation of HMW PAHs in soil grown with C4 plants when compared to C3 plants. Also, no PAHs were detected in the maize cobs, sunflower, wallaby, and Sudan grass seeds at the end of the experiment. The effect of plants in modifying the microbial community and dynamics in the rhizosphere was also examined by measuring soil biochemical properties such as dehydrogenase activity and water-soluble phenols. The results demonstrate a substantial difference in the microbial populations between planted and unplanted soils, which in turn facilitate the degradation of PAHs. To the best of our knowledge, this study for the first time evaluated the phytoremediation efficacy through the A. cepa cyto- and genotoxicity assay which should be considered as an integral part of all remediation experiments.

The larger-scale generation of piggery and winery wastewaters and consequent eutrophication are quite alarming, necessitating the use of a cost-effective treatment. This study attempted to remediate wastewaters from piggery and winery mixed in the ratios of 20:80, 50:50, 80:20, 100:0 and 0:100, in terms of nutrient removal and subsequent lipid accumulation by soil microalga, Chlorella sp. MM3. The per cent removal of total nitrogen and phosphates by the alga from mixed wastewaters within 10-days ranged between 51 and 89 and 26–49, respectively. As determined by FTIR spectroscopy, the lipid accumulation in the microalgal cells grown in wastewater mixtures ranged between 29 and 51%. Our results suggest that Chlorella sp. MM3 could be a potential candidate for bioremediation of wastewaters derived from piggery farm and winery industry, and that mixing of these wastewaters in 20:80 ratio would be an efficient approach for phycoremediation of mineral-rich effluents and subsequent yield of fairly good amounts of biofuel. Refereed/Peer-reviewed

Derelict mines pose potential risks to environmental health. Several factors such as soil structure, organic matter, and nutrient content are the greatly affected qualities in mined soils. Soil microbial communities are an important element for successful reclamation because of their major role in nutrient cycling, plant establishment, geochemical transformations, and soil formation. Yet, microorganisms generally remain an undervalued asset in mined sites. The microbial diversity in derelict mine sites consists of diverse species belonging to four key phyla: Proteobacteria, Acidobacteria, Firmicutes, and Bacteroidetes. The activity of plant symbiotic microorganisms including root-colonizing rhizobacteria and ectomycorrhizal fungi of existing vegetation in the mined sites is very high since most of these microbes are extremophiles. This review outlines the importance of microorganisms to soil health and the rehabilitation of derelict mines and how microbial activity and diversity can be exploited to better plan the soil rehabilitation. Besides highlighting the major breakthroughs in the application of microorganisms for mined site reclamation, we provide a critical view on plant−microbiome interactions to improve revegetation at the mined sites. Also, the need has been emphasized for deciphering the molecular mechanisms of adaptation and resistance of rhizosphere and non-rhizosphere microbes in abandoned mine sites, understanding their role in remediation, and subsequent harnessing of their potential to pave the way in future rehabilitation strategies for mined sites. Refereed/Peer-reviewed

Millions of natural and synthetic organic chemical substances are present in both soil and aquatic environments. Toxicity and/or persistence determine the polluting principle of these substances. The biological responses to these pollutants include accumulation and degradation. The responses of environments with organic pollutants are perceptible from the dwindling degradative abilities of microorganisms. Among different biological members, cyanobacteria and microalgae are highly adaptive through many eons, and can grow autotrophically, heterotrophically or mixotrophically. Mixotrophy in cyanobacteria and microalgae can provide many competitive advantages over bacteria and fungi in degrading organic pollutants. Laboratory culturing of strict phototrophic algae has limited the realization of their potential as bioremediation agents. In the natural assemblages, mixotrophic algae can contribute to sequestration of carbon, which is otherwise emitted as carbon dioxide to the atmosphere under heterotrophic conditions by other organisms. Molecular methods and metabolic and genomic information will help not only in identification and selection of mixotrophic species of cyanobacteria and microalgae with capabilities to degrade organic pollutants but also in monitoring the efficiency of remediation efforts under the field conditions. These organisms are relatively easier for genetic engineering with desirable traits. This review presents a new premise from the literature that mixotrophic algae and cyanobacteria are distinctive bioremediation agents with capabilities to sequester carbon in the environment. Keywords: Cyanobacteria, Microalgae, Mixotrophy, Biological agents, Organic pollutants, Biodegradation