Thesis (M.Sc.)--Chulalongkorn University, 1999

Two of 350 lipase producing bacterial strains isolated from soils were selected, name ALP-40.3 and ALP-42.11, and identified biochemically and bacteriologically to possibly be Psuedomomas sp. ALP-40.3 strain grew under optimum conditions, i.e., at 35 °C and wide pH range 6-10. ALP-42.11 grew optimally in lower temperature ranged from 25 °-35 °C and also wide pH range, and a large number of lipases were excreted when 2.5% olive oil was added into the growth medium. Some characteristics of both lipases were summarized as follow: under optimum conditions, i.e., at 45 °C, the highest activity of crude ALP-40.3 lipases was found (702 units/ml), and quite high activity would have maintained in a wide range of temperature from 35 °C-65 °C (328-702 units/ml). At 65 ํC, the highest activity of crude ALP-42.11 lipases was found (561 units/ml), and similar to the first lipase extract, quite high activity of the second lipases extract would have maintained in a wide range of temperature from 15 °-65 °C. It is noted that the effect of pH on activities of both lipase was quite stronger than effect of temperature. The highest activities of ALP-40.3 and ALP-42.11 lipases were found at pH 8 and 9, respectively, however, the activity of them has maintained in pH range 8-9. It is possible to say that they are alkaline lipases.