Textile Dyes Degradation: A Microbial Approach for Biodegradation of Pollutants - Microbial Degradation of Synthetic Dyes in Wastewaters - page 189

that the Pseudomonas aeruginosa was able to detoxify the dye, Direct Orange 39
(1,000 ppm each day) effectively. Similarly, Roushdy and Abdel-Shakour ( 2011 )
observed zone of inhibition with control Malachite green with some microbial
strains and found no growth inhibition by the degraded products. These

ndings
clearly suggest non-toxic nature of the degradation products formed by the bio-
logical degradation.
The ability of actinomycetes to decolorize several anthraquinone and azo dyes
has also been reported by several workers. The anthraquinonic dyes Remazol
Brilliant Blue R, Poly B-411 and Poly R-478 were decolorized by Streptomyces sp.
and Thermomonospora sp. Some species of Streptomycetes also decolorized azo
dyes 4 (3-methoxy-4-hydroxy-phenylazo)-azobenzene-3,4 ′ -disulfonic acid, 3-

methoxy-4-hydroxy-azobenzene-4 -sulfonic acid and Orange I. Actinomycetes can

catalyze hydroxylations; O, N, and S oxidations; and O- and N-dealkylation
reactions against various xenobiotic compounds. Streptomyces chromofuscus,a
member of actinomycetes group, was found capable to degrade azo dye in the
presence of verytal alcohol (Paszczynski and Crowford 1991 ). The ability of
S. chromofuscus to mineralize these dyes and guaiacol-substituted azo dye was of
much signi

′

cance, since azo dyes and some of its substitutes are resistant to aerobic
degradation by most of soil bacteria. The genus Streptomyces has been reported to
degrade benzene derivatives via classic aromatic catabolic pathways. A little
research has been devoted to determining whether actinomycetes efciently degrade
condensed polycyclic aromatics, although some strains are able to metabolize
naphthalene derivatives. Streptomyces spp. degrade some recalcitrant compounds,
such as carbamates, diazinon, and bromoxynil. Actinomycetes were also found to
degrade organo-chlorine compounds in spent sul uent. Further,

evidences also indicate that Streptomyces sp. can act synergistically with other soil
microorganisms to degrade recalcitrant compounds (Gunner and Zuckman 1968 ).

te bleach plant ef

5 Mechanisms and Basic Steps During Biodegradation

The aerobic and anaerobic biological wastewater treatment has been the oldest
known biodegradation based process technology. Several technologies have been
evolved over the past decades since the development of conventional activated
sludge plant in United Kingdom in 1914. Degradation of complex compounds takes
place in several stages, for example, in the case of halogenated compounds, de-
halogenation often occurs early in the over all processes. Dehalogenation of many
compounds containing chlorine, bromine, or uorine occurs faster under anaerobic

than aerobic conditions. The study of reductive dehalogenation, especially for its
commercial application, is gaining importance. Once the anaerobic dehalogenation
steps are completed, degradation of the main structure of many xenobiotics often
proceeds more rapidly in the presence of O 2 . Observations of natural and synthetic
organic compound accumulation in natural environment, however, began to raise
questions about the ability of microorganisms to degrade these varied substances