Drug–polymer conjugation is a simple and efficient approach to synthesizing new, effective, and potent antimicrobial agents to counter the problem of microbial resistance. In the present study, a PEGylated dopamine ester (PDE) was synthesized using the PEGylation process and synthesis of PDE was confirmed by Fourier-transform infrared spectroscopy, elemental analysis (CHNS–O), and atomic force microscopy techniques. Later, the antimicrobial activity of PDE was assessed against four strains of bacteria (Bacillus subtilis, Staphylococcus aureus, Pseudomonas aeruginosa, and Proteus vulgaris; Gram (−)) and two fungi (Aspergillus niger and Aspergillus fumigatus) by the agar well diffusion method. The minimum inhibitory concentration (MIC) of PDE was also determined by the broth dilution method against bacteria. PDE showed significant zones of inhibition ranged from 21 to 27 mm for bacteria and 16 to 20 mm for fungi under study, which were much higher than those for dopamine hydrochloride. MIC values of PDE showed its potential antimicrobial property.

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Introduction Lipases triacylglycerol ester hydrolases E.C. 3.1.1.3 are ubiquitous enzymes that catalyse the breakdown of fats and oils with subsequent release of free fatty acid, diacylglycerol, monoacylglycerol and glycerol 1 4. They are found in animals, plants, fungi and bacteria and are of considerable physiological significance and industrial potential 5. However, the most suitable sources for lipase production are the microorganisms which can produce high quality lipases in lower cost and shorter time 6. Fungi are more preferred sources of lipases because of their stability at different temperature and pH 7. Purification of enzymes allows successful determination of their primary amino acid sequence and three-dimensional structure. Purified lipase preparations are needed in industries employing the enzymes for the biocatalytic production of food additives flavour modifying enzymes , industrial reagents glyceride hydrolyzing enzyme , stain removing agents detergent additives , digestive drugs, diagnostic enzymes in medical applications, nutraceuticals, surfactants and additives in cosmetics 8 10. Esters of short chain carboxylic acid and alcohols belong to the highly important natural aroma compounds. The production of natural aroma compounds by fermentation and enzymatic reactions in aqueous 11 , organic solvent 12, 13

In the present study, the lipase from Aspergillus fumigatus was purified which was found to be stable to commercial detergents and oxidising agents. A purification fold of 6.96 and yield of 11.03% were achieved when the enzyme was purified using Octyl Sepharose column chromatography. In presence of various oxidizing agents, the highest activity of lipase was 15.56 U/mg with hydrogen peroxide. Among various surfactants used, the maximum activity exhibited by lipase was with Tween 80. While studying the effect of various detergents, the highest activity of 9.3 U/mg was achieved with "Vanish" detergent. Wash performance was studied with various detergents out of which "Vanish" showed highest oil removal of 79%. Lipase from Aspergillus fumigatus possessed better stability with various surfactants and oxidizing agents. The results of this study have shown that the lipase from Aspergillus fumigatus along with detergent "Vanish" (0.7%) under optimized conditions (5 μg/ml lipase, 40°C wash temperature and 40 min wash duration) improved oil removal from cotton fabric stained with mustard oil by 84%.