Degradation of cyclohexane and cyclohexanone by Bacillus lentus strain LP32

Abstract

A Gram-positive bacterium, Bacillus lentus LP32, originally isolated on the basis of its ability to utilise pyrene as sole source of carbon was found to be able to grow luxuriantly on alicyclic compounds as sole substrates. It showed poor growth on anthracene, naphthalene, 1-naphthol and phenanthrene. Growth rate on cyclohexane was 1.32 d^-1, while doubling time was 0.76 d. The corresponding values for growth on cyclohexanone were 0.77 d^-1 and 1.29 d, respectively. Within 10 days, the amount of cyclohexane in culture reduced from 317.62 to 102.55 mgl^-1, then to 23.04 mgl^-1 on day 18. On cyclohexanone, substrate concentration decreased from 287.56 mgl^-1 to 101.66 mgl^-1 in 10 days before declining to 24.21 mgl^-1 on day 18. The rate of degradation when growing on cyclohexane was 23.50 mgl^-1d^-1 in the first 10 days and 9.93 mgl^-1d^-1 between day 10 and day 18, with 67.71% degradation in 10 days and overall percentage degradation of 92.43%. On cyclohexanone, the corresponding values were 18.59 and 9.68 mg l^-1d^-1 as well as 64.65 and 91.58%, respectively. This organism is a potential candidate for bioremediation purpose.

Keywords: Degradation, cyclohexane, cyclohexanone, alicyclic compounds.