A simple method for detection of lipolytic microorganisms in soils

Media selective for the isolation of bacteria, actinomycetes and fungi were amended with 0.1% sunflower oil emulsified with 0.01% Tween 80. Lipase-producing microorganisms produced clear zones on these media. When lipase-producing bacteria were cultured on a polycarbonate membrane laid on the selective medium for bacteria, clear zones were produced on the medium when the membrane along with bacteria was removed. The agar disc cut from the clear zone also produced a clear zone when placed on the fresh medium, indicating that clear zone formation is the result of the activity of extracellular lipases. The largest population of lipase-producing microorganisms in an agricultural soil was actinomycetes followed by bacteria and fungi. Ranging from 12 to 75% of bacteria, actinomycetes and fungi isolates from soils collected from three different locations were capable of producing lipases. In general, relatively small percentages of soil bacteria were lipase producers, and lipase producers were more common among soil actinomycetes and fungi. These three groups of microorganisms appear to be all important in decomposition of oils in organic matters in soils.