Decolorization of biomethanated spentwash by native microorganisms

Abstract

As many as 92 microbial isolates were isolated from samples collected from newlinemangroves, fly ash dumpsites, saline soils and spentwash dumpsites. All the isolates were newlineinitially screened for their potential to decolorize spentwash. Two fungal (K1 and Ku3) and two newlinebacterial (RTB2 and EB4) isolates were found promising and brought about significantly higher newlinedecolorization yields at all the concentrations of spentwash tested. Incidentally, they also newlineshowed higher phenol degradation and COD reduction. RTB2 was tentatively identified as newlineEnterobacter sp. EB4 as Pseudomonas fluorescens, K1 as Aspergillus sp. and Ku3 as newlinePleurotus sp. newlineThe culture parameters for maximum decolorization by four isolates were optimized. newlineAll of them required an additional carbon source and preferred glucose. The optimum glucose newlineconcentration was 1.0 per cent in all the strains. The best nitrogen source was yeast extract newlineand the optimum concentration was 1.0 per cent. Optimum pH for bacteria was 7.0 and for newlinefungi, it was 5.0. The optimum temperature was 300C in all the strains and two per cent newlineinoculum level was found optimum. newlineThe mechanism of decolorization was elucidated. The involvement of glucose newlineoxidase (GOX) activity in decolorization by the promising organisms was tested. All the newlinestrains produced gluconic acid as evidenced through TLC. GOX is known to produce H2O2 newlineand this being a strong oxidizing agent, might have decolorized spentwash. Degradation of newlinemelanoidin and caramel was confirmed by UV and IR spectral analysis. Decrease in OD newlinemelanoidin and caramel and appearance of new peaks and changes in functional groups of newlinecompounds in the IR spectra with respect to control suggest their degradation. Integrating newlinechemical method with biological method augmented decolorization yields. Aspergillus newlinetreatment followed by FeCl3 treatment resulted in 92 per cent decolorization of 30 per cent newlinespentwash, while with KMnO4 (3000 ppm) treatment, it resulted in 90 per cent decolorization. newline