Biological Treatment of Used Engine Oil by Single and Mixed Bacterial Cultures Isolated from Soil of Mechanic Workshops

Abstract

The accumulation of hydrocarbon waste, such as used engine oils in environments, has many impacts on humans and other organisms, therefore many researches were achieved to degrade or remove or consume these pollutants. The aim of the current study is to get a local bacterial isolates has high ability to degrade the spent engine oil as a single or mixed culture. Five soil samples contaminated with spent engine oil were collected from mechanic workshops in Baghdad city to isolate degrading bacteria using Bushnell Hans medium (BHM), pH 7 with 5% of used engine oil. While the growth patterns and gravimetric analysis was used to reveal the ability of these isolates to degrade spent engine oil in liquid BHM medium. The best three isolates A4, B6 and D5 were identified and the optimal temperature and pH for biodegradation of spending engine oil were studied. Also, the consortium culture of three isolates was tested their ability to utilize spent engine oil under the same conditions for single isolate. Twenty five bacterial isolates were obtained from contaminated soil samples and three isolates appeared a maximum degradation rate 74.6, 70.2 and 78.5% respectively. The results from identification tests were showing these isolates belong to Bacillus sp., Acinetobacter sp. and Pseudomonas sp., respectively. The studied three isolates gave the best degradation when incubated at 30°C in BHM medium pH 7. While other results were indicated that consortium cultures are more effective 90.2% than all experiments that used single isolate.