A comparative study on degradation of complex malathion organophosphate using of Escherichia coli IES-02 and a novel carboxylesterase.

Malathion organophosphates considered as the major constituent of herbicides, pesticides and insecticides. Extensively used in agricultural, horticultures and for numerous household applications contributes to precedence organic pollutants leading antagonistic effects on human health and environment. Therefore detoxification of malathion from contaminated site is of general interest. Simultaneously it is very emerging to isolated novel indigenous microbial strains from contaminated site with a record of pesticide application. In this study Escherichia coli IES-02 isolated from malathion contaminant effluent and the strain showed maximum efficiency in malathion degradation that utilized it as the sole source of carbon. Carboxylesterase (33.0, 30.0, 28.0 kDa) were purified (1685.71 U/mg) from Escherichia coli IES-02 showed significant results in malathion degradation approximately 81% within 20 min as compared with Escherichia coli IES-02 cells within 4 h (99.0 to 95.0%) into monocarboxylic acid and diacid derivatives. The generation time of Escherichia coli was also observed at 60 min with 0.1 ppm, 68 min with 0.5 ppm, 74.5 min with 2.0 ppm and 91.37 min with 50 ppm of malathion. The degradation rate and transformation metabolites were estimated by Gas Chromatography-Mass Spectrometry respectively. Malathion metabolites pathway proposed in this study which revealed the potential application against lethal environmental pollution.

Agar-agar immobilization: An alternative approach for the entrapment of protease to improve the catalytic efficiency, thermal stability and recycling efficiency.

The catalytic performance of an immobilized enzyme could be enhanced by using entrapment technique. In this contemporary study agar-agar, a natural polysaccharide, is subjected to entrap serine-protease produced by Aspergillus niger KIBGE-IB36. The results revealed that maximum enzymatic activity was attained when 3.0% agar-agar was used. It was observed that in case of both free and entrapped forms the enzyme was stable at pH-5.0. While, an increment in reaction temperature and time was noticed from 50 to 55 °C and 15.0 to 20.0 min, respectively. Km value increased from 1.883 mM to 2.399 mM and Vmax value decreased from 1753 U mg-1 to 1372 U mg-1 after agar-agar entrapment of protease as compared to soluble enzyme. Additionally, entrapped protease within the polymer exhibited significant increase in the thermal stability at various temperatures and retained approximately 68.0% of its residual activity at 60 °C. However, at this extreme temperature the soluble protease lost its catalytic performance. Storage stability considerably improved as entrapped protease revealed enzymatic activity up to 30 days as compared to soluble enzyme. Recycling efficiency was calculated up to eight cycles which is an exceptional characteristic for economic feasibility and continuous reusability of protease.