Degradation characteristics of methyl ethyl ketone and methyl isobutyl ketone by Pseudomonas putida KT-3

Methyl ethyl ketone (MEK) and methyl isobutyl ketone (MIBK) have been widely used as solvents in various industries. Biodegradation of MEK and MIBK by Pseudomonas putida KT-3, which could utilize MEK or MIBK as a sole carbon source, was characterized, and the cosubstrate interaction in MEK/MIBK mixture was also studied. Within the range of initial MEK concentration (from 0.5 to 5. 5 mM), an increased substrate concentration increased the specific degradation rate of MEK by P putida KT-3 (from 3.15 to 10.58 mmol/g DCW · h), but the rate sightly increased at 11.0 mM of initial MEK concentation (11.28 mmol/g DCW · h). The similar degradation rates of MIBK (4.69-4.92 mmol/g DCW · h) were obtained at more than 3.0 mM of initial MIBK concentation. Kinetic analysis on the degradation of MEK/MIBK mixture by P putida KT-3 showed that MEK or MIBK acted as a competitive inhibitor. Maximum degradation rate (V_max), saturation constant (K_m) and inhibition constant (K_I) were as follows: V_max,MEK = 12.94 mmol/g DCW · h; K_m,MEK = 1.72 mmol/L; K_I,MIBK = 1.30 mmol/L; V_max,MIBK = 5.00 mmol/g-DCW · h; K_m,MIBK = 0.42 mmol/L; K_I,MEK = 0.77 mmol/L.