Scientific World , Vol. 9, No. 9, July 2011 93 INTRODUCTION Rapid and haphazard urbanization has led to increasing volumes of waste being generated in the urban area of Nepal. Various studies carried out since 1976 indicate that around two-thirds of the municipal solid waste generated in Kathmandu Metropolitan City is organic; this has remained relatively unchanged over the years (ICIMOD, 2007; Udas, 2004; IUCN, 1992). Of the rest inorganic components, majority can be recycled and reused with a little amount requiring land-filling (MOPE, 2001). Therefore, the increasing volume of waste being generated would not be a problem if waste was viewed as a resource and managed properly. Majority of the organic fraction of the waste constitutes of starch, lipid, protein, cellulose, hemicellulose and lignin. Almost all of these components can be degraded via specific enzymes. Protein degradation initiates and continues in the presence of proteases. Various proteolytic microorganisms are capable of producing the enzyme protease. This study was carried out to isolate the bacteria exhibiting higher degree of proteolytic activity from solid waste. The research project aims to explore useful microbial flora and their implications in solid waste management through protein degradation. MATERIALS AND METHODS The study was carried out at Research Laboratory of Central Department of Microbiology, Tribhuvan University, Kirtipur. The waste samples (3 from each site) were collected from 20 different sampling sites of Kathmandu Valley by random sampling method. The sampling was carried out in wide- mouthed sterilized glass bottle with the help of sterile forceps. Temperature of the waste was measured at the site using thermometer while pH was measured after transporting the samples to the laboratory using pH meter. The degradable fraction of the waste was segregated. The gelatin degrading bacteria were screened by dilution technique and spread plate method on mineral base agar amended with 1% gelatin following incubation at 30 o C for 24h. The proteolytic bacteria were detected by observing the zone of hydrolysis after flooding the incubated plate with freshly prepared mercuric chloride. The isolates exhibiting higher degree of activity were selected and subjected to the production of enzyme by fermentation at 30 0 C and 150 rpm. The enzyme was extracted by centrifugation at 10000 rpm for 10 minutes at 4 0 C and partially purified by acetone precipitation method (Khatiwada, 2004). The enzyme was assayed by radial agar well diffusion method in nutrient agar supplemented with 1% gelatin (Dingle et al, 1953). The enzymes revealing higher degree of activity were fractionated with ammonium sulphate crystals to different saturation. The effect of different incubation temperature (4, 15, 26, 37, 45, 60, 70 and 80 0 C) and pH (4, 5, 6, 7, 8 and 9) of STUDY OF PROTEASE ACTIVITY OF BACTERIA ISOLATED FROM SOLID WASTE Smriti Mainali *, Nanu Maiya Khadka *, Bijaya Laxmi Maharjan ** and Binod Lekhak * *Central Department of Microbiology, TU, Kathmandu, Nepal. ** Nepal Academy of Science and Technology, Khumaltar, Lalitpur, Nepal. Abstract: Solid waste is one of the most visible environmental nuisances and major causes of pollution in the urban areas. But a considerable proportion of this waste is decomposable organic matter. The study was designed to study the activity of protease enzyme produced by proteolytic bacteria isolated from solid waste. Solid waste samples were collected from 20 different sites of Kathmandu valley and proteolytic bacteria were isolated by serial dilution and spread plate technique using gelatin incorporated agar media. Among 113 isolates 22 (3 being potent ones) were found to be proteolytic bacteria. Protease enzyme was extracted from the most potent ones by fermentation technology and purified by acetone precipitation method and ammonium sulphate fractionation. The enzyme from Micrococcus spp. was optimally active at 4 0 C and pH 8 while that from another isolate, which remained unidentified, was optimally active at 37 0 C and pH 9. The activity of 60% salt fraction of the enzymes from both the isolates was maximum. This indicates the possibility of implementation of these enzymes for the management of solid waste by decomposing the proteinous components of the waste. Key words: Solid waste; Enzyme activity; Proteolytic bacteria. Author for Correspondence: Mainali S, Central Department of Microbiology, TU, Kathmandu, Nepal. Email: nairanjana1@gmail.com.