Sains Malaysiana 40(9)(2011): 1043–1048

Surface Activity of Surfactin Recovered and Purified from Fermentation

Broth Using a Two-Step Ultrafiltration (Uf) Process

(Aktiviti Permukaan Surfaktin yang diekstrak dan ditulenkan daripada Pati Farmentasi

Menggunakan Teknik Dua-Pringkat Ultrafiltrasi)

Mohd Hafez Mohd Isa*

Faculty of Science and Technology, Universiti Sains Islam Malaysia (USIM)

Bandar Baru Nilai, 71800 Nilai, Negeri Sembilan

A. Richard Frazier & Paula Jauregi

Department of Food Biosciences, Universiti of Reading, Whiteknights, P.O. Box 226 Reading

RG6 6AP, United Kingdom

Diserahkan: 16 Jun 2010 / Diterima: 26 Januari 2011

ABSTRACT

B. subtilis under certain types of media and fermentation conditions can produce surfactin, a biosurfactant which belongs to the lipopeptide class. Surfactin has exceptional surfactant activity, and exhibits some interesting biological characteristics such as antibacterial activity, antitumoral activity against ascites carcinoma cells, and a hypocholesterolemic activity that inhibits cAMP phosphodiesterase, as well as having anti-HIV properties. A cost effective recovery and purification of surfactin from fermentation broth using a two-step ultrafiltration (UF) process has been developed in order to reduce the cost of surfactin production. In this study, competitive adsorption of surfactin and proteins at the air-water interface was studied using surface pressure measurements. Small volumes of bovine serum albumin (BSA) and β-casein solutions were added to the air-water interface on a Langmuir trough and allowed to stabilise before the addition of surfactin to the subphase. Contrasting interfacial behaviour of proteins was observed with β-casein showing faster initial adsorption compared to BSA. On introduction of surfactin both proteins were displaced but a longer time were taken to displace β-casein. Overall the results showed surfactin were highly surface-active by forming a β-sheet structure at the air-water interface after reaching its critical micelle concentration (CMC) and were effective in removing both protein films, which can be explained following the orogenic mechanism. Results showed that the two-step UF process was effective to achieve high purity and fully functional surfactin.

Keywords: Beta casein (β-casein); bovine serum albumin (BSA); critical micelle concentration (CMC); surfactin

ABSTRAK

B. subtilis melalui beberapa jenis media dan keadaan fermentasi tertentu dapat menghasilkan surfactin, sejenis biosurfaktan yang tergolong di dalam kategori lipopeptide. Surfaktin memiliki aktiviti surfaktan yang luar biasa dan menunjukkan beberapa ciri biologi yang menarik seperti aktiviti anti-bakteria, aktiviti anti-tumor terhadap sel kanser ascites, dan aktiviti hipoklesterolemik yang dapat menghalang pertumbuhan cAMP phosphodiesterase, serta memiliki sifat anti-HIV. Sejenis kaedah yang kos-efektif untuk ekstraksi dan penulenan surfaktin daripada pati fermentasi menggunakan teknik dua-peringkat ultrafiltrasi (UF) telah dibangunkan untuk mengurangkan kos pengeluaran surfaktin. Dalam kajian ini, jerapan kompetitif di antara surfactin dan protein di permukaan udara-air dikaji dengan menggunakan pengukuran tekanan permukaan. Kuantiti kecil serum albumin lembu (BSA) dan β-kasein ditambahkan ke permukaan udara-air di palung Langmuir dan dibiarkan menstabil sehingga membentuk lapisan di permukaan sebelum diikuti dengan penambahan surfaktin melalui sub-fasa. Perbezaan sifat di permukaan ditunjukkan oleh protein, dengan β-kasein menunjukkan jerapan awal yang lebih cepat berbanding BSA. Selepas penambahan surfaktin melalui sub-fasa, kedua-dua lapisan protein di permukaan udara-air digantikan oleh surfaktin, walaupun masa yang lebih lama diperlukan untuk β-kasein. Secara keseluruhannya, hasil kajian menunjukkan surfaktin memiliki sifat yang amat aktif di permukaan dengan membentuk struktur helaian-β di permukaan udara-air apabila mencapai kepekatan kritikal misel (CMC). Surfaktin amat berkesan untuk menggantikan kedua-dua lapisan protein di permukaan, dan fenomena ini boleh dijelaskan melalui mekanisme orogenik. Selain daripada itu, hasil kajian juga menunjukkan teknik dua-peringkat UF amat berkesan untuk mendapatkan surfaktin dengan ketulenan yang tinggi dan dapat berfungsi sepenuhnya.

Kata kunci: Beta kasein (β-kasein); kepekatan kritikal misel (CMC); serum albumin lembu (BSA); surfaktin

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*Pengarang untuk surat-menyurat; email: m.hafez@usim.edu.my