Efek suhu terhadap aktivitas spesifik enzim pereduksi Cr(VI) oleh Bacillus cereus isolat AB13 dari tanah serpentin

Abstract

Chromium hexavalent is a toxic and has potential to pollute the environment. One way to reduce the toxic is by converting Cr(VI) into Cr(III) by means of bioremediation using enzymes from the bacteria isolated from Cr soil-resistant. This is because Cr(III) which is less toxic than Cr(VI). One of the bacteria that has the potential as a bioremediation agent is Bacillus cereus isolate AB13 from serpentine soil. However, some changes in environmental conditions will affect the activity of an enzyme. Inappropriate temperature will cause protein in an enzyme to be damaged or inactive, so that the function and activity of enzyme are reduced. Until now, the effect of temperature on specific activity enzyme by enzyme Cr(VI) reduction has yet to be known. In order to determine the effect of temperature on specific activity enzyme by bacteria Bacillus cereus isolate AB13, the research was conducted as followed: rejuvenation and culture of isolate AB13, fractionation of cell-free media and cell-free extracts, measurement of enzyme protein content by the Bradford method and measurement of Cr(VI) reduction by chromate reductase by DPC method with an incubation temperature between 25°C-55°C. Specific enzyme activity is the number of units of enzyme activity per total of protein. Specific activity of enzyme shows the level of purity of an enzyme. The higher specific activity of an enzyme, the higher the purity of the enzyme. The results showed that the increase in specific enzyme activity occurred at temperatures from 30°C to 35°C. The optimum temperature was 35°C with specific enzyme activity of 0.0390 U/mg in cell-free culture media (S1 fraction) and 0.0445 U/mg in cell-free extracts (fraction S2). While at temperatures from 40°C to 55°C there was decreasing specific enzyme activity.