EFFECT OF TEMPERATURE ON OIL DEGRADATION BY A PSYCHROTROPHIC YEAST INLIQUID CULTURE AND IN SOIL

The influence of temperature (4-30 degrees C) on diesel oil biodegrada tion in a mineral medium and in soil was tested. The abiotic loss of d iesel oil increased with incubation time and with temperature and was lower in mineral medium than in soil. The maximum degradation activity of a psychrotrophic yeast (Yarrowia lipolytica) in liquid culture (co ntaining 5000 mg diesel oil 1(-1)) occurred at 10-20 degrees C. When i noculated into an alpine soil (containing 5000 mg diesel oil kg-l soil dry weight), degradation activity of the inoculum was only observed a t temperatures less than or equal to 15 degrees C and was significantl y lower than in the liquid culture. The indigenous soil microorganisms degraded diesel oil over the whole temperature range tested. With inc reasing incubation time and temperature, diesel oil utilization by the inoculum in the soil decreased, whereas degradation activity of the i ndigenous soil microorganisms and abiotic losses increased.