Biodegradation of industrial raw materials and their products

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%.