Biodegradation of industrial raw materials and their products
Date
2011-07-20
Authors
Ramsuran, Nisha
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Abstract
Biodegradation and green chemistry technologies have become increasing
common demands in the industrial sector. The fate and potential impact of
industrial raw materials on the natural environment has come under scrutiny. One
of the classes of industrial raw materials that we found most interesting was
preservatives. A commonly used preservative, formaldehyde, had recently been
reclassified by the International Agency for Research on Cancer (IARC) from
“probably carcinogenic to humans” to “carcinogenic to humans.” The aim of the
first part of this study was to synthesize alternative preservatives to formaldehyde.
The isothiazolinone backbone was chosen and was achieved by first producing the
Z-adduct from the base catalyzed reaction between propynoic acid and toluene- -
thiol to produce (Z)-3-benzylsulfanylpropenoic acid in a yield of 74%. (Z)-3-
benzylsulfanylpropenoic acid was then activated with diphenylphosphinic chloride
to furnish the phosphinic ester, which was not isolated but allowed to react directly
with a range of amines to produce the corresponding amides. These amides were
then allowed to react with 3-chloroperbenzoic acid in dichloromethane to furnish
the corresponding sulfoxides. The sulfoxides were then treated with trichloroacetic
anhydride to furnish the corresponding N-alkyl-isothiazol-3(2H)-ones. N-(2-
ethylphenylisothiazol-3(2H)-one was successfully produced in a yield of 56%. The
second part of the study involved the revival of gram positive (B. pumilus) and
gram negative (Citrobacter freundi) bacterial strains as well as a sewage
consortium that were previously isolated. This was successfully achieved using
tryptone soy broth as the growth medium at a temperature of 30 °C over 24 hours.
The third part of the study was to select a range of preservatives (diazolidinyl urea,
imidazolidinyl urea, formaldehyde and the isothiazolinone derivatives) and
evaluate the biodegradation of these raw materials under conditions that simulated
that of a natural wastewater treatment plant over a period of 50 days. The
difference in biodegradation between the sewage consortium and pure strains of
gram positive (B. pumilus) and gram negative (Citrobacter freundii) bacteria was
then assessed. Formaldehyde and the isothiazolinone derivative, N-(2-ethylphenylisothiazol-3(2H)-one, could not be detected in the experimental
medium and therefore no results were available. Diazolidinyl urea was best
biodegraded by gram negative bacteria, citrobacter freundii, showing a percentage
biodegradation of 51.4% whereas imidazolinyl urea was best biodegraded by the
sewage consortium, showing a percentage biodegradation of 9.0%.