pigmented organic compounds probably repolymerize during conventional biological treatment processes. However, melanoidins and polyphenols exhibit antioxidant
and antimicrobial properties which make difficult the treatment of distillery effluent
(Arimi et al. 2014). Thus, advanced techniques are strongly required to eliminate the
OM and coloring compounds from the distillery effluent, which has been increasingly recognized as a tough challenge (Tsioptsias et al. 2015; Prajapati and
Chaudhari 2015). Due to anionic nature of melanoidins in distillery effluent, it
binds with a mixture of various HMs and some other organic compounds which
makes more difficult its biological degradation. Melanoidins show variable absorption range in the UV region which makes more difficult to understand the mechanism of melanoidins degradation and decolorization and characterization of its
metabolic products (Chandra et al. 2018a). But most of the decolorization and
degradation studies of MM are reported at 475 nm only based on purified melanoidin
absorption maxima with specific MW, while the MM contains a mixture of MRPs
(i.e., initial, intermediate, and advanced stages with variable MW) (Kumar and
Chandra 2018). Therefore, prior to attempting the decolorization and degradation
of distillery effluent, the degradation of model melanoidins with a mixture of
complex MRPs should be evaluated for its degradability. However, due to the
presence of a mixture of different MW MRPs in distiller effluent, it shows variable
absorption spectrum at a different wavelength. But absorption and elimination
patterns of different peaks in melanoidins are not reported so far. Therefore, it is
vital to reveal the decline pattern of the specific peak of MM in degradation and
generation of its metabolites formed during the decolorization process. In addition,
the details of the enzyme and its mode of action also need to be revealed. Moreover,
the effect of sulfides and metals along with phenolic compounds required systematic
studies to establish the mechanism of biological decolorization prior to its scope to
develop an industrial-scale decolorization technique for safe disposal. Further,
sulfate and heavy metals present in distillery effluent are reduced into black-colored
precipitate of metal sulfides which act as a competitive inhibitor for sulfate-reducing
bacteria and non-sulfate-reducing bacteria leading to inhibition of methanogenesis or
sulfate reduction and giving toxicity to PMDE. Recently, the applications of bacteria
and wetland plants in two-step/sequential treatment have been reported to be very
promising technology for detoxification, but this has to be optimized yet with
detailed physiology wetland plants, microbiology of plant rhizospheres, and detoxification mechanism. The bacterial communities grown in such an adverse environment are very much important to understand the microbiology of distillery waste.
Acknowledgments The financial support from Department of Biotechnology (DBT), Govt. of
India, to Professor Ram Chandra (Grant No. BT/PR13922/BCE/8/1129) and Rajiv Gandhi National
Fellowship (RGNF) from University Grants Commission (UGC), New Delhi, to Mr. Vineet Kumar,
Ph.D. student, is highly acknowledged.
20 Bioremediation of Melanoidins Containing Distillery Waste for. . .
523
and antimicrobial properties which make difficult the treatment of distillery effluent
(Arimi et al. 2014). Thus, advanced techniques are strongly required to eliminate the
OM and coloring compounds from the distillery effluent, which has been increasingly recognized as a tough challenge (Tsioptsias et al. 2015; Prajapati and
Chaudhari 2015). Due to anionic nature of melanoidins in distillery effluent, it
binds with a mixture of various HMs and some other organic compounds which
makes more difficult its biological degradation. Melanoidins show variable absorption range in the UV region which makes more difficult to understand the mechanism of melanoidins degradation and decolorization and characterization of its
metabolic products (Chandra et al. 2018a). But most of the decolorization and
degradation studies of MM are reported at 475 nm only based on purified melanoidin
absorption maxima with specific MW, while the MM contains a mixture of MRPs
(i.e., initial, intermediate, and advanced stages with variable MW) (Kumar and
Chandra 2018). Therefore, prior to attempting the decolorization and degradation
of distillery effluent, the degradation of model melanoidins with a mixture of
complex MRPs should be evaluated for its degradability. However, due to the
presence of a mixture of different MW MRPs in distiller effluent, it shows variable
absorption spectrum at a different wavelength. But absorption and elimination
patterns of different peaks in melanoidins are not reported so far. Therefore, it is
vital to reveal the decline pattern of the specific peak of MM in degradation and
generation of its metabolites formed during the decolorization process. In addition,
the details of the enzyme and its mode of action also need to be revealed. Moreover,
the effect of sulfides and metals along with phenolic compounds required systematic
studies to establish the mechanism of biological decolorization prior to its scope to
develop an industrial-scale decolorization technique for safe disposal. Further,
sulfate and heavy metals present in distillery effluent are reduced into black-colored
precipitate of metal sulfides which act as a competitive inhibitor for sulfate-reducing
bacteria and non-sulfate-reducing bacteria leading to inhibition of methanogenesis or
sulfate reduction and giving toxicity to PMDE. Recently, the applications of bacteria
and wetland plants in two-step/sequential treatment have been reported to be very
promising technology for detoxification, but this has to be optimized yet with
detailed physiology wetland plants, microbiology of plant rhizospheres, and detoxification mechanism. The bacterial communities grown in such an adverse environment are very much important to understand the microbiology of distillery waste.
Acknowledgments The financial support from Department of Biotechnology (DBT), Govt. of
India, to Professor Ram Chandra (Grant No. BT/PR13922/BCE/8/1129) and Rajiv Gandhi National
Fellowship (RGNF) from University Grants Commission (UGC), New Delhi, to Mr. Vineet Kumar,
Ph.D. student, is highly acknowledged.
20 Bioremediation of Melanoidins Containing Distillery Waste for. . .
523