Faculty Publications
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Item Exploring the fungal protein cadre in the biosynthesis of PbSe quantum dots(Elsevier B.V., 2017) Jacob, J.M.; Sharma, S.; Mohan Balakrishnan, R.M.While a large number of microbial sources have recently emerged as potent sources for biosynthesis of chalcogenide quantum dots (QDs), studies regarding their biomimetic strategies that initiate QD biosynthesis are scarce. The present study describes several mechanistic aspects of PbSe QD biosynthesis using marine Aspergillus terreus. Scanning electron microscopic (SEM) studies indicated distinctive morphological features such as abrasion and agglomeration on the fungal biomass after the biosynthesis reaction. Further, the biomass subsequent to the heavy metal/metalloid precursor was characterized with spectral signatures typical to primary and secondary stress factors such as thiol compounds and oxalic acid using Fourier Transform Infra-Red Spectroscopic (FTIR) analysis. An increase in the total protein content in the reaction mixture after biosynthesis was another noteworthy observation. Further, metal-phytochelatins were identified as the prominent metal-ion trafficking components in the reaction mixture using Liquid Chromatography Mass Spectroscopic analysis (LCMS). Subsequent assays confirmed the involvement of metal binding peptides namely metallothioneins and other anti-oxidant enzymes that might have played a prominent role in the microbial metal detoxification system for the biosynthesis of PbSe QDs. Based on these findings a possible mechanism for the biosynthesis of PbSe QDs by marine A. terreus has been elucidated. © 2016 Elsevier B.V.Item Kinetic and thermodynamic studies on the adsorption of heavy metals from aqueous solution by melanin nanopigment obtained from marine source: Pseudomonas stutzeri(Academic Press, 2018) Manirethan, V.; Raval, K.; Rajan, R.; Thaira, H.; Mohan Balakrishnan, R.M.The difficulty in removal of heavy metals at concentrations below 10 mg/L has led to the exploration of efficient adsorbents for removal of heavy metals. The adsorption capacity of biosynthesized melanin for Mercury (Hg(II)), Chromium (Cr(VI)), Lead (Pb(II)) and Copper (Cu(II)) was investigated at different operating conditions like pH, time, initial concentration and temperature. The heavy metals adsorption process was well illustrated by the Lagergren's pseudo-second-order kinetic model and the equilibrium data fitted excellently to Langmuir isotherm. Maximum adsorption capacity obtained from Langmuir isotherm for Hg(II) was 82.4 mg/g, Cr(VI) was 126.9 mg/g, Pb(II) was 147.5 mg/g and Cu(II) was 167.8 mg/g. The thermodynamic parameters revealed that the adsorption of heavy metals on melanin is favorable, spontaneous and endothermic in nature. Binding of heavy metals on melanin surface was proved by Fourier Transform Infrared Spectroscopy (FT-IR) and X-ray Photoelectron Spectroscopy (XPS). Contemplating the results, biosynthesized melanin can be a potential adsorbent for efficient removal of Hg(II), Cr(VI), Pb(II) and Cu(II) ions from aqueous solution. © 2018 Elsevier LtdItem Melanin nano-pigments for heavy metal remediation from water(Taylor and Francis Inc. 325 Chestnut St, Suite 800 Philadelphia PA 19106, 2019) Thaira, H.; Raval, K.; Manirethan, V.; Mohan Balakrishnan, R.M.Melanins are water insoluble polyphenol compounds. The metal ion chelating property of natural melanin is exploited for removal of heavy metals from contaminated water. We optimized biosynthesis of melanin from marine bacterium using different growth media, media components, and operating conditions. Optimized medium yielded 513 mg/L melanin at 36 h of incubation, which was 3.15 times higher than the yield before optimization. Particle size analysis of the biosynthesized melanin indicated a size of 32 ± 0.98 nm. Preliminary investigation indicated that melanin nanoparticles could adsorb different heavy metals such as chromium, selenium, and lead from very low initial concentrations. © 2018, © 2018 Taylor & Francis.Item Mycosensing of soil contaminants by Ganoderma lucidum and Omphalotus subilludens including the insights on growth media requirements(Elsevier Ltd, 2019) Gupta, C.; Mohan Balakrishnan, R.M.; Uddandarao, P.; Arivalagan, A.Heavy metals are regarded as one of the major threats to environmental biota due to prolonged soil residence time. In this scenario, mycoremediation emerged as an effective tool for the removal of heavy metal contaminants. The present study reports the responses of two wild mushroom species Ganoderma lucidum and Omphalotus subilludens under metal stress conditions and the nutritional requirements of the mushroom species. The media was screened wherein the media containing glucose and sucrose as carbon source showed better growth for Ganoderma lucidum and Omphalotus subilludens respectively. In addition, peptone as a nitrogen source is required for the growth of both Ganoderma lucidum and Omphalotus subilludens. Further, it is observed that macronutrients play a crucial role in the stimulation of enzymes and the micronutrients are mandatory for intermediary metabolism of the fungi in both the species. Tolerance studies are carried out in-vitro and the results reveal that the Ganoderma lucidum showed tolerance towards Cr (VI), Ni (II), Pb (II) and Cd (II) at maximum tolerant concentrations of 1000 mg/kg, 500 mg/kg, 100 mg/kg and 10 mg/kg, in case of, Omphalotus subilludens showed tolerance towards Cr (VI), Ni (II) and Pb (II) at maximum tolerant concentration of 700 mg/kg, 700 mg/kg and 500 mg/kg respectively. Moreover, FTIR spectral analysis indicated the presence of components like oxalic acid and thiol compounds during metal stress conditions. © 2019 Elsevier LtdItem Batch and continuous studies on the removal of heavy metals using biosynthesised melanin impregnated activated carbon(Elsevier B.V., 2020) Manirethan, V.; Mohan Balakrishnan, R.M.The adversity associated with the removal of melanin nanoparticles after adsorbing heavy metals led to the development of a system involving activated carbon on which melanin was effectively impregnated. The melanin impregnated activated carbon was handily removed from the aqueous medium by simple filtration. The batch studies performed to scrutinise the optimum conditions for maximum adsorption concluded the contact time needed to attain equilibrium to be 90 min for all metals of study. Maximum adsorption of Cr (VI) was shown at pH 3 while Hg (II), Pb (II) and Cu (II) was adsorbed efficiently at pH 5. Increase in temperature favoured the adsorption process for all metals showing maximum removal at 328 K. Melanin impregnated activated carbon could adsorb 84.59% Hg (II), 86.6% Cr (VI), 91.1% Pb (II) and 93.8% Cu (II) from 5 mg/L heavy metal solution. Dynamic studies were conducted by varying the parameters like flow rate, inlet heavy metal concentration and adsorbent loading. Optimum conditions for a maximum breakthrough was obtained with a flow rate of 0.5 mL/min, heavy metal inlet concentration of 1 mg/L and adsorbent loading of 100 mg. Experimental data modelled in equilibrium isotherms showed the best fitting with the Thomas model when compared with the Adam–Boharts model using determined coefficient and error analysis. Efficient chemical desorption of Hg (II), Pb (II) and Cu (II) was obtained using 3N HCl and Cr (VI) using 1N citric acid. © 2020 Elsevier B.V.