Assessment of corn-cobs as potential biofilm carrier in degradation of mixed pulp and bleachery effluent employing repeated batch process
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Date
2016-07
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G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
Two fungi (LDF00204 and LDF21) having ligninolytic enzyme activity were isolated from contaminated pulp and paper mill soil sludge and selected for decolorization and degradation of mixed pulp and bleachery effluent. Based on ITS region, the fungal isolates LDF00204 and LDF21 were identified as Nigrospora sp. (accession no. KP732542) and Curvularia lunata (accession no. KU664593), respectively. The constructed fungal consortium was identified by scanning electron microscopy (SEM) that revealed mutual intermingling between both the fungal isolates. The optimized process parameters, employing suspended fungal consortium were observed as glucose (carbon), peptone (nitrogen), C:N 1.5:0.5, temperature 30ºC, pH 5, inoculum constituent ratio 1:2, and agitation 140 rpm, which resulted in an approximate 2.1 fold increase in fungal biomass production in second treatment cycle as compared to 1.2 fold increase in third treatment cycle. As a result of optimization, conspicuous reduction of color (83.15%), lignin (78.40%), BOD (92.50%), and COD (87.31%) was observed in second cycle of treatment process. Further, to enhance the degradation process for large volume effluent in moving bed biofilm reactor (MBBR), fungal consortium was immobilized on corn cobs which resulted into reduction in color by 89.90%, lignin 82.21%, BOD 90.55%, and COD 88.15% after fifth cycle of treatment in a repeated batch process. Changes in corn cobs composition during the effluent degradation were exhibited by loss of cellulose 19.14%, hemicelluloses 11.63% and lignin 9.83%. Maximum activity of Lac 1.13 U/ml, LiP 0.72 U/ml and MnP 0.59 U/ml and was recorded in second, and third treatment cycles, respectively. Morphological changes in suspended and immobilized fungal mycelium after treatment were studied by scanning electron microscope (SEM), which revealed the swollen and damaged mycelium, and densely aggregated fungal consortium in rough and porous surface of corn cobs, respectively after completion of fifth treatment cycle. FTIR study revealed intense spectral bands in lipid region, and shifts in protein, lipids and polysaccharides peaks of suspended fungal mycelium, whereas shift in carbohydrates, protein–lipids peaks of corn cobs was observed after effluent treatment in repeated batch treatment process. Total ion chromatogram obtained from GC-MS analysis asserts degradation of toxic compounds and generation of new metabolites viz., pentadecanoic acid, tricosane, tetracontane, and hexadecane by free fungal biomass as well as immobilized cell biomass, which favors the enhanced capacity of attached fungal biofilm during long term effluent treatment in MBBR and thus underlines corn-cobs as perspective biofilm carrier in degradation of industrial effluent.
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