ORIGINAL PAPER De-oiled neem cake as potential bio-additive for low-salt raw skin preservation: a process for salinity reduction in tanneries N. Vedaraman 1 • K. V. Sandhya 1 • V. Brindha 2 • A. Tamil Selvi 2 • K. C. Velappan 1 • V. John Sundar 3 • J. Kanagaraj 3 • C. Muralidharan 3 Received: 28 July 2015 / Revised: 16 February 2016 / Accepted: 12 April 2016 / Published online: 27 April 2016 Ó Islamic Azad University (IAU) 2016 Abstract Animal skin, a proteinaceous material con- taining about 60–65 % moisture, is an ideal substrate for the growth of microorganisms, if not preserved properly. Conventionally, large quantities of sodium chloride are used for skin preservation. De-salting and soaking carried out during processing of the skin generates serious envi- ronmental constraints. In view of this, low-salt skin preservation with de-oiled neem cake is attempted. To ensure the antimicrobial properties of de-oiled neem cake, aqueous and solvent extracts of the cake were studied against bacteria and fungi which were isolated from raw skin. The antimicrobial assay was performed using the well diffusion method for aqueous, methanol and hexane extract of de-oiled neem cake, which showed maximum zone of clearance for aqueous and methanolic extract against the isolated bacteria and fungi, respectively, present in raw skin. The percentage of inhibition study reveals that the methanolic extract showed 100 % inhibition against many organisms and the water extract against some organisms. The raw skin was cured using de-oiled neem cake with reduced amount of salt and left for a period of 21 days. The skins were checked periodically for microbial growth as per the conventional methods. Finally, the low-salt pre- served skins were processed into chrome-tanned leathers and their strength properties were compared with leathers which were preserved by the conventional method. The results suggest that de-oiled neem cake along with minimal salt has adequate curing efficiency on raw skin and if this system is implemented, pollution caused due to sodium chloride would be significantly minimized. Keywords Antimicrobial activity Á Skin curing Á Sodium chloride Á Leather processing Á Environmental pollution Introduction Neem products such as neem oil, de-oiled neem cake, neem based biochemicals such as azadirachtins, neem coated urea are of industrial importance. Neem seed is collected in large quantities, mainly for production of neem oil. The water-washed neem seed kernel cake (Verma et al. 1995), urea-ammoniated neem seed kernel (Anandan et al. 1996) and processed neem kernel (Anandan et al. 1999; Kesava Rao et al. 2003) have been reported as a good food source for goats. De-oiled neem cake is a by-product of the oil industry, and it is relatively low in price and mainly used in agriculture as bio-fertilizer. This is available in large quantities in tropical countries. Animal skin is a fibrous proteinaceous sheet containing hair, sweat glands, fat and blood vessels, moisture as well as its basic constituent—collagen fibres (Kanagaraj et al. 2005). It is more susceptible for bacterial attack derived from sources like air, water, soil, manure and extraneous filth (Birbir and Ilgaz 1995) leading to disintegration of skin matrix because of their collagenolytic, lipolytic and proteolytic enzymes (Tyagi et al. 2012). So it is important to preserve the skin protein as the leather quality depends upon this protein collagen. The traditional process followed for skin preservation before processing into leather is by & N. Vedaraman vedaraman.clri@gmail.com 1 Chemical Engineering Division, CSIR-CLRI, Adyar, Chennai 600 020, India 2 CHORD Division, CSIR-CLRI, Adyar, Chennai 600 020, India 3 Tannery Division, CSIR-CLRI, Adyar, Chennai 600 020, India 123 Int. J. Environ. Sci. Technol. (2016) 13:1563–1572 DOI 10.1007/s13762-016-0994-3