Indian Journal of Fibre & Textile Research Vol. 39, March 2014, pp. 65-71 Optimum conditions for polyamide fabric modification by protease enzyme produced by Bacillus sp Samiha M Abo El-Ola 1 , Maysa E Moharam 2 , Maha M Eladwi 3 & Magda A El-Bendary a,2 1 Proteinic and Synthetic Fibre Department, 2 Microbial Chemistry Department, National Research Center, Dokki, Giza, Egypt 3 Women’s College, Ain Shams University, Helliopolis, Cairo, Egypt Received 19 October 2012; revised received and accepted 22 February 2013 The optimum conditions for surface modification of polyamide 6 (PA) by protease enzyme produced by Bacillus isolate 16P have been studied. These conditions are found to be 0.05 mg/mL enzyme concentration, 0.5 h treatment time, room temperature (30ºC) and pH 8 under shaking conditions. The effect of hydrolytic activity of enzymatic process on the weight loss of PA fabric after enzymatic treatment shows negligible difference. Printing both untreated and treated PA fabrics with transfer printing shows high leveling properties as regard to E values which are considered as acceptable values of color differences. PA treated with different sources of protease enzyme under optimum conditions shows good physical properties. SEM of the surface of protease treated PA samples shows etches and voids compared to smooth surface of untreated PA fabric. Keywords: Bacillus sp, Physical properties, Polyamide modification, Protease enzyme 1 Introduction The most common synthetic polyamides (PA) are polyamide 6 (Nylon 6) and polyamide 6.6 (Nylon 6.6). The annual world production of polyamide is 4 million tonns 1 . Nylon filaments are used as yarns for textile, industrial and carpet applications and a growing demand has been reported especially for industrial and textile applications 2 . Nylon based textiles show the great disadvantage of being uncomfortable to wear and difficult to finish due to their hydrophobicity. Therefore, enhancement of the hydrophilicity of nylon is a key requirement for many applications and can be achieved by chemical, physical and enzymatic methods. Chemical modification requires harsh reaction due to which strength properties of polymer get affected. Physical methods include plasma treatment, UV irradiation, corona discharge and flame treatment. These methods are very difficult to optimize, require complicated machinery and are difficult to repeat. Enzyme treatments can be chosen as green alternatives for polymer surface modification as they offer many advantages over chemical and physical methods such as they are very specific, act under moderate reaction conditions which lead to less or negligible damage of the strength properties of synthetic polymers, cost effective, ecofriendly, the scale up is possible and gives reproducible results 3,4 . It is to be expected that, within 5-10 years, wet textile production processing will be shifted substantially towards sustainable processes, because of increasing governmental and environmental restrictions and the decreasing availability of fresh water. Biocatalysts have proven to be a flexible and reliable tool in wet textile processing and a promising technology for fulfilling expected future requirements 5 . Treatment of PA with hydrolases shows potential for targeted surface modification without changes of bulk properties 6 . Enzymes that can hydrolyze PA are proteases, cutinases and polyamidases 7 . These enzymes have been successfully used for surface targeted hydrolysis of PA leading to hydrophilization 6,8,9 . Surface hydrolysis of PA leads to increasing of polar groups (free amino and carboxylate end groups) on the surface. The enzymatic hydrolysis of surface moieties of PA has been demonstrated to be a powerful mild strategy for improving hydrophilicity and activating materials for further processing, which is the key requirement for many applications including painting, _________ a Corresponding author. E-mail: tasnim41@yahoo.com