Fig. 4

a IR spectrum of untreated with engine oil (control). b IR spectrum of the used engine oil acted upon by Bacillus cereus. c IR spectrum of the used engine oil acted upon by Lysinibacillus fusiformis. d IR spectrum of the used engine oil acted upon by Bacillus encimensis.e IR spectrum of the used engine oil acted upon by Paraclostridium benzoelyticum