Bioremediation of toxic metal ions from coal washery effluent

This investigation has dealt with bioremediation of heavy metal ions from the coal washery effluent (CWE) by Pleurotus florida (P.florida).The CWE was characterized as per the guidelines of American Standard and Testing Methods.The surface characterization of P. florida was done by scanning electron microscopy, Fourier-transform infrared spectroscopy, and energy-dispersive X-ray analysis.Metal ion concentration in fruit body and substrate (paddy straw) was determined by inductively coupled plasma optical emission spectrometry.The fitness functions of exponential and linear extension growth models were evaluated mathematically (goodness of fit) at boundary conditions at t = 0 and t = t.The metal toxicity stress markers produced in P. florida (control and CWE exposed) were estimated through standard protocols described in various references (which have been described later in the manuscript).The physicochemical characterization of CWE showed its acidic nature (pH 5.1 ± 0.26) together with contamination of toxic heavy metals like Pb, Cr, Cd, Zn, As, Mn, Ni, and Ti.The surface characterization of P. florida showed that the surface of P. florida was rough, heterogeneous in nature together with negatively charged functional groups like carboxyl, hydroxyl, ketonic, and esters.The elemental composition of P. florida revealed the abundance of carbon and oxygen in biomass compared to other elements such as nitrogen and phosphorus.Growth modeling of P. florida revealed the fact that experimental and theoretical values of linear extension growth rate K r (mm d -1 ) constant were not only close to each other but also they ranged from 1.36 to 2.21 mm d -1 and 1.41 to 2.03 mm d -1 .This showed the supremacy of the linear growth extension model over the exponential rate model.The metal toxicity stress markers like metallothionein (35.21 µg g -1 ), superoxide dismutase (9.4 U mg -1 ), lipid peroxidase (2.5 nmol mg -1 ), catalase (2.15 Pkat mg -1 ) and reduced glutathione (28.09 µg g -1 ) had higher level expression in the fruit bodies of P. florida grown in CWE compared to control.The simultaneous increase of metallothionein concentration from 2.50 to 35.21 µg g -1 with an increase in the concentration of metal ions in the term of CWE concentration (25%-100%) in media showed the bioaccumulation of metal ions in the intracellular space.The maximum heavy metal uptake capacity of P. florida was found as 10. 65, 1.12, 13.46, 3.0, 1.21, 19.11, 0.47, and 0.23 µg g -1 for Pb, Cr, Cd, Zn, As, Mn, Ni, and Ti respectively.The maximum heavy metal removal from substrate (paddy straw) was found 99.53% (Cd), 70.85% (Cr), 77.77% (Ni), 76.23% (Zn), 42.63% (Mn), 52.10% (Pb), 49.07%(Ti), and 51.66% (As).The negatively charged rough surface, high amount of carbon and oxygen in biomass, and the induced production of intracellular metal stress markers on exposure to heavy metals illustrated the immense bioaccumulation ability of P. florida in CWE.