Journal of Environmental Biology

Statistical optimisation for improvement of phenol degradation by Rhodococcus sp. NAM 81

Norazah Mohammad Nawawi^1,2, Siti Aqlima Ahmad¹*, Mohd Yunus Shukor¹, Mohd Arif Syed¹,

Khalilah Abdul Khalil³, Nor Arina Ab Rahman¹, Farrah Aini Dahalan⁴ and Abdul Latif Ibrahim²

¹Department of Biochemistry, Faculty of Biotechnology and Biomolecular Sciences, Universiti Putra Malaysia, UPM 43400

Serdang, Selangor, Malaysia

²Institute of Bio-IT Selangor, Universiti Selangor, Jalan Zirkon A7/A, Seksyen 7, 40000 Shah Alam, Selangor, Malaysia

³Department of Biomolecular Sciences, Faculty of Applied Sciences, Universiti Teknologi MARA, Seksyen 2, 40150

Shah Alam, Selangor, Malaysia

⁴The School of Environmental Engineering, Universiti Malaysia Perlis, Kompleks Pengajian Jejawi 3, 02600 Arau, Malaysia

*Corresponding Author E-mail: aqlimaahmad@gmail.com, aqlima@upm.edu.my

Publication Data

Paper received:

16 February 2015

Revised received:

29 August 2015

Re-revised received:

05 October 2015

Accepted:

31 October 2015

Abstract

Phenol is an important compound widely used in formulation of dyes, pesticides, in fabrication of plastics, as well as being generated in several industrial effluent other industries. In the present study, ability of phenol-degrading bacteria Rhodococcus sp. NAM 81 was characterised by optimising the important parameters that were able to support phenol degradation abilities using two-step statistical. Fractional factorial design (FFD) was applied to select significant variables (temperature, pH, phenol concentration, ammonium sulphate concentration, sodium chloride concentration, incubation time) that affects percentage of phenol degradation. pH (B), phenol concentration (C), sodium chloride (E) and incubation time (F) were observed to be significant (p<0.05), which was further optimised for phenol degradation and cell growth, using response surface methodology (RSM) based on central composite design (CCD). From the optimisation by CCD, pH 7.25, 0.74 g l^-1 of phenol with 0.06 g l^-1 of NaCl concentration in 23 hrs of incubation time is the best condition for phenol degradation. Meanwhile, Rhodococcus sp. NAM 81 grow best in pH 7.72, 0.85 g l^-1 of phenol, 0.06 g l^-1 of NaCl for 24 hrs incubation time were the best condition predicted to produce 0.867 g l^-1 of Rhodococcus sp. NAM 81 cells. Verification of experiment indicated no significant different between the predicted and experimental data (P>0.05) for phenol degraded performance, as well as Rhodococcus growth. Under optimum conditions, the proposed method was successfully applied to improve 1.2 fold of phenol degradation and 1.3 for cell growth as compared to non-optimal cultivation.? ??

 Key words

Central composite design, Fractional factorial design, Phenol degradation, Response surface methodology, Rhodococcus sp.

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