Screening and Characterization of Industrially Important Lipase Producing Bacterial Isolates from Soil and Water Samples Collected from Lake Ziway, Oromia Regional State, Ethiopia

Abstract

Lipases are group of enzymes which have various applications in different industries such as food, detergent, leather, pharmaceutical, paper and cosmetics. Production of these enzymes from microbial sources will have more advantages compared to those produced from plant and animal sources. Economic and environmental issues are major problems that can be reduced by using these microbial enzymes. Therefore, the purpose of this study was to screen and characterize industrially important lipase producing bacteria from water and soil samples collected from Lake Ziway. To this end, soil, water and sludge samples were collected from Lake Ziway and Adama Science and Technology University wastewater treatment plant and screened for lipase producing bacterial isolates. Tributyrin agar and phenol red agar were used for the screening purpose. Gram staining and biochemical tests such as citrate utilization, motility test, sulfur production and other tests were performed for the purpose of characterization of the isolates. MALDI-TOF MS and ABIS bacteria identification software (version 12) were used for identification purpose. A total of 11 lipase positive bacterial isolates were obtained depending on their growth characteristics on the growth medium. Among those, four isolates were selected for further analysis. The four isolates were characterized as LPBI-1 (Pseudomonas aeruginosa), LPBI-2 (Aeromonas veronii), LPBI-3 (Aeromonas veronii) and LPBI-4 (Pseudomonas aeruginosa). LPBI-4(Pseudomonas aeruginosa) was selected to determine its physio-chemical requirements. The isolate showed its best growth when olive oil and Tryptone was used as a carbon and nitrogen source respectively. Its best growth also recorded when pH value 6.5 and temperature at 37oC. Submerged fermentation method was used for the production of lipase and the enzyme was collected by centrifugation process. Hydrolysis of milk fat by the enzyme was examined in order to check the efficiency of the enzyme. Disappearance of pink color of the solution was taken as positive result of the test. It was concluded that Pseudomonas aeruginosa and Aeromonas veronii species were best candidates for lipase production.