Sains Malaysiana 42(5)(2013): 615–623


Screening and Optimization of Biosurfactant Production by the Hydrocarbon-Degrading Bacteria

(Penyaringan dan Pengoptimuman Biosurfaktan yang Dihasilkan oleh Bakteria Pendegradasi-Hidrokarbon)


Ainon Hamzah*, Noramiza Sabturani & Shahidan Radiman

School of Biosciences and Biotechnology, Faculty of Science and Technology

Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor D.E. Malaysia


Received: 13 July 2011/Accepted: 24 October 2012



Biosurfactants are amphiphilic compounds produced by microorganisms as secondary metabolite. The unique properties of biosurfactants make them possible to replace or to be added to synthetic surfactants which are mainly used in food, cosmetics and pharmaceutical industries and in environmental applications. In this study twenty hydrocarbon-degrading bacteria were screened for biosurfactant production. All of the bacterial isolates were grown in mineral salt medium (MSM) with addition of 1% (v/v) Tapis crude oil as carbon source. The presence of biosurfactant was determined by the drop-collapse test, microplate analysis, oil spreading technique, emulsification index (%EI24) and surface tension measurement. Only one isolate, Pseudomonas aeruginosa UKMP14T, was found to be positive for all the qualitative tests and reducing the surface tension of the medium to 49.5 dynes/cm with emulsification index of 25.29%. This isolate produced biosurfactant optimally at pH9.0 and incubation temperature of 37°C. Furthermore, P. aeruginosa UKMP14T when grown in MSM with addition of 1% (v/v) glycerol and 1.3 g/L ammonium sulphate with C/N ratio 14:1 produced biosurfactant with percentage of surface tension reduction at 55% or 30.6 dynes/cm with %EI24 of 43%. This percentage of surface tension reduction represents an increasing reduction in surface tension of medium by 39% over the value before optimization. This study showed that P. aeruginosa UKMP14T has the ability to biodegrade hydrocarbon and concurrently produce biosurfactant.


Keywords: Biosurfactant; hydrocarbon-degrading bacteria; optimization; surface tension



Biosurfaktan adalah sebatian ampifilik yang dihasilkan oleh mikroorganisma sebagai metabolit sekunder. Ciri-ciri biosurfaktan yang unik membolehkan mereka menggantikan atau ditambahkan kepada surfaktan sintetik yang kebanyakannya digunakan dalam industri makanan, kosmetik dan farmaseutikal dan diaplikasi dalam sekitaran. Dalam kajian ini sebanyak 20 pencilan bakteria-pencurai hidrokarbon disaring untuk penghasilan biosurfaktan. Kesemua pencilan bakteria dihidupkan di dalam medium garam mineral (MSM) yang ditambah dengan 1% (i/i) minyak mentah Tapis sebagai sumber karbon. Kehadiran biosurfaktan ditentukan dengan ujian titisan-runtuh, analisis mikroplat, teknik sebaran minyak, indeks emulsifikasi (%EI24) dan pengukuran ketegangan permukaan. Hanya satu pencilan iaitu Pseudomonas aeruginosa UKMP14T yang memberikan hasil positif ke atas semua ujian kualitatif dan mengurangkan ketegangan permukaan medium sehingga 49.5 dynes/cm dengan indeks emulsifikasi 25.29%. Pencilan ini menghasilkan biosurfaktan yang optimum pada pH9.0 dan suhu eraman 37°C. Selain itu, apabila P. aeruginosa UKMP14T dihidupkan di dalam MSM dengan penambahan 1% (i/i) gliserol dan 1.3 g/L ammonium sulfat dengan nisbah C/N 14:1, ia menghasilkan biosurfaktan dengan peratus pengurangan ketegangan permukaan sebanyak 55% atau 30.6 dynes/cm dengan %EI24, 43%. Peratus pengurangan ketegangan permukaan ini mewakili peningkatan pengurangan dalam ketegangan permukaan medium sebanyak 39% jika dibandingkan sebelum pengoptimuman. Kajian ini menunjukkan bahawa P. aeruginosa UKMP14T mempunyai keupayaan untuk biodegradasi hidrokarbon serta menghasilkan biosurfaktan.


Kata kunci: Bakteria pencurai-hidrokarbon; biosurfaktan; ketegangan permukaan; pengoptimuman


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