INTERNATIONAL JOURNAL OF AGRICULTURE & BIOLOGY 1560–8530 /2004 /06–5–758–761 http://www.ijab.org Digestion of Solid Tannery Wastes by Strains of Bacillus Sp Isolated From Compost in Morocco ZERDANI, I., M. FAID 1 † AND A. MALKI Faculté des Sciences Ben M’sik Université Hassan II-Mohammadia PO Box 79-55 Sidi Otman Casablanca, Morocco †Department of Food Engineering and Technology, Hassan II Institute of Agronomy and Veterinary Medicine, Rabat, Morocco 1 Corresponding author’s email: faidmohamed@yahoo.fr ABSTRACT Eight strains of Bacillus were isolated from non treated soil, characterized and used for the digestion of crude leather wastes in the laboratory. Non-protein nitrogen (NPN) and total protein (TP) were determined during the incubation time and the microbial counts of the different strains during leather hydrolysis were also monitored. Results of the screening tests showed that the solid pieces of leather wastes were completely digested by all the strains. The most efficient isolated strain (Bacillus subtilis strains 11) was compared with Bacillus subtilis ATCC 6633. Results showed that the total nitrogen was decreased from 1032.1 to 93.5 mg/100 g by our strains and from 1064.4 to 385 mg/100 g by the standard strains B. subtilis ATCC 6633. The NPN reached the concentration of 30 mg/100 g for our strains and only 10.8 mg/10 g by the standard strains. This may show a suitable biotechnological process for the treatment of solid wastes from the tannery industry. The obtained product may also be used as fertilizer or as a source of nitrogen for microbial populations. Keys Words: Leather; Tannery; Waste; Collagen; Bacillus INTRODUCTION The tannery industry is one of the most representative strategic industries in Morocco and may constitute an important economic component besides other activities. The environmental aspects in this industry are generally ignored and the processes used for leather production are still more traditional than modern. Huge amounts of solid leather wastes are discarded directly with the urban wastes. Several works in the field of bioengineering were carried out on enzymatic hydrolysis of collagen which is the most representative protein of leather wastes (Kawahara et al., 1993; Matsushita et al., 1994; Asdormithee et al., 1994). This hydrolysis was carried out by collagensases which are enzymes that can hydrolyze both native and denatured collagens. The enzymes are widely used not only in chemical and medical industries but also in food and basic biological science (Hisano et al., 1989; Raju et al., 1996; Rao et al., 1998; Tran & Nagano, 2002). However, most of the microorganisms isolated from soil presented low collagenase activity and their applications were limited, therefore the strains most efficient in tannery wastes hydrolysis are needed for more efficient yield and application because these organic wastes are hard to treat and have potential recycling into useful products (Chen et al., 2001; Taylor et al., 2002). The objective of the present investigation is to accelerate leather digestion process by inoculating with collagenolytic species of Bacillus isolated from soil. MATERIALS AND METHODS Chemical determination. The pH of medium was checked by the use of a pH-meter type Crison MicropH 2000. The dry matter of the crude tannery waste was determined by oven drying a weighed amount of the product at 105°C until constant weight. Ash was determined by incineration in a furnace at 550°C for 6 h. Total nitrogen (TN) was determined by the Kjeldhal method described by the APHA (1989). Non Protein Nitrogen (NPN) was determined by the Kjeldhal method on the filtrate after precipitating with a 10% trichloracetic acid solution. Minerals (Ca, P, K, Fe, Mg, Zn & Cu) were determined by an atomic absorption spectrophotometer apparatus (Type JENWAY PFP 7). Isolation and characterization of bacterial strains. Samples of natural composted materials were taken from the soil of the dumping-ground unit near the city of Casablanca (Morocco). All the samples (500 g each) were transported in sterile plastic bags to the laboratory. Initial dilution from each sample was prepared by adding 10 g of the compost to 90 mL of sterilized saline water. This dilution was heat activated at 70°C during 15 min and dilutions up to 10 6 in sterilized saline water were prepared in tubes. All the dilutions were plated on trypticase soy agar (TSA, Difco, USA) and incubated at 30°C for 24 h. The appeared colonies were checked for spore presence and streaked on agar slants for further characterization. Characterization. All the collected strains were grown on TSA to obtain fresh cultures. Spore production and localization were examined by microscopic observations.