Kajian Potensial Listrik Bakteri Amonifikasi Indigenous (Xanthomonas sp) Melalui Teknologi Microbial Fuel Cell (MFC)

Mahasiswa: Reny Maria Angraeni Tesis (2009), Program Studi Magister Bioteknologi SITH, email: rereazzahra@students.itb.ac.id Pembimbing: Dr. I Nyoman Pugeg Aryantha

SITH-ITB, email: nyoman@sith.itb.ac.id Gelar: Magister Sains (M.Si), Wisuda Juli 2009

Abstrak

Krisis energi yang terjadi pada kurun waktu sekarang ini menuntut dikembangkannya sumber energi alternatif yang terbarukan, ekonomis, dan berlimpah. Salah satu upaya yang dilakukan dalam pemenuhan energi listrik adalah pengkajian bakteri sebagai biokatalis melalui Teknologi MFC. Teknologi tersebut memungkinkan terjadinya konversi energi kimia di dalam substrat menjadi energi listrik dengan bantuan kerja enzim dari bakteri. Kajian yang dilakukan dalam penelitian ini menganalisa interaksi faktor-faktor terkait dari bakteri amonifikasi lokal dalam sistem MFC untuk menghasilkan potensial listrik yang tinggi. Sampel diambil dari beberapa tempat seperti limbah peternakan, endapan lumpur, dan danau di Pulau Jawa, Sumatera, dan Sulawesi. Dari hasil isolasi awal menggunakan medium TSB didapatkan sebanyak 24 isolat. Kemudian isolat tersebut dipilah kembali menggunakan sistem MFC dan didapatkan bakteri Xanthomonas sp sebagai penghasil nilai potensial tertinggi yaitu 805 mV. Sistem MFC yang dipakai mempunyai volume 500 mL yang terdiri atas dua ruang yaitu anoda yang berisikan Xanthomonas sp dengan medium komponen protein dan katoda yang berisikan K3(FeCN)6 di dalam larutan buffer K2HPO4. Kedua chamber dipisahkan oleh cation exchange membrane yang luasnya berukuran 7,069 X 10-4 cm2 dan dihubungkan dengan multimeter yang mempunyai panjang kabel 3.00 x 10-1 m. Optimasi dilakukan terhadap medium dengan menggunakan komposisi yang mengacu pada medium TSB, dengan sumber N yang diambil dari berbagai senyawa seperti, asam amino, sumber N-anorganik, dan protein kompleks. Optimasi pH awal dilakukan pada tingkat asam, basa, dan netral yaitu 6, 7, dan 8. Sedangkan optimasi jumlah inokulum dilakukan pada tingkat 5%, 10%, dan 15%. Hasil optimasi yang menghasilkan nilai potensial terbaik adalah medium mengandung asam amino trypton & pepton dengan jumlah inokulum 5% dalam keadaan pH awal netral yakni sebesar 850 mV. Dari hasil optimasi itu lalu dilakukan pengukuran secara simultan produktivitas interaksi faktor – faktor terkait bakteri Xanthomonas sp dalam menghasilkan nilai potensial listrik yang tinggi. Pola pertumbuhan bakteri menunjukkan jumlah biomassa 9,49 x 106 CFU/mL dengan aktivitas enzimatik (hidrolisis FDA) sebesar 7,08 unit/mL (1 unit = µg fluorescein/menit) pada waktu t4 = 25 jam yang bisa memberikan nilai potensial terbaik (890 mV) dengan kadar ammonium yang dihasilkan 191,30 mg/L dan pH medium berada pada nilai 7,30. Kemampuan bakteri Xanthomonas sp dalam menghasilkan potensial listrik yang tinggi mempunyai potensi yang besar, sehingga pemanfaatan dalam skala aplikasi dapat digunakan di masa datang.

Keywords : Microbial Fuel Cell, Amonifikasi, Xanthomonas sp, cation exchange membrane, FDA method.

The Study of Electrical Potential Production Through Microbial Fuel Cell (MFC) Systems by Indigenous Ammonification Bacteria (Xanthomonas sp)

Student: Reny Maria Angraeni Thesis (2008), Master’s program In Biotechnology, School of Life Sciences and Technology-ITB, email: rereazzahra@students.itb.ac.id Advisors: Dr. I Nyoman Pugeg Aryantha School of Life Sciences and Technology ITB, email: nyoman@sith.itb.ac.id Degree: Magister Sains (M.Si), Conferred July 2009

Abstract

The use of an alternative renewable energy to face energy crisis becomes a critical thing. It was assumed that bacterial as natural resources can be used to produce electrical energy. A Microbial Fuel Cell (MFC) technology converts chemical energy, available in a bio-convertible substrate, directly into electricity. To achieve this, bacteria were used as a catalyst to convert substrate into electrons. This study aimed to analyze the interaction between factors that influenced the productivity of Ammonification bacteria in term of the ability to produce electrical voltage through MFC systems. Ammonification bacteria sample has been isolated from cattle wastewater, mud and lake sediment in Java, Sumatera, and Sulawesi islands. Isolation of Ammonification bacteria using basalt medium (TSB) found 24 isolates. Each isolate were then screened for the best ability to produce electrical voltage with MFC systems. The chosen bacterium with the best electrical potential observed of 805 mV were identified as Xanthomonas sp. An MFC system of 500 mL chamber was set up with Basalt medium inoculated with Xanthomonas sp as anode component while K3Fe(CN)6 in K2HPO4 buffer as cathode component. Both chambers were separated by a cation exchange membrane area (7.069 x 10-4 m2). Electron which flew through graphite (1.1 x 10-3 m2) produced electric voltage were then measured by multimeter (connected with 3.00 x 10-1 m cable). Chosen bacterial strain which generate the best electrical potential was further optimized for the growth medium. Composition of Nitrogen in the optimization medium was made so that it contains the same amount as the defined medium basalt (TSB). Nitrogen source used in this research are amino acids, an-organic source of Nitrogen, and complex protein respectively. Further optimization were then conducted for pH value and starting inoculums. Optimizations were conducted on an acid, neutral pH, and alkaline pH value. Optimizations of starting inoculums were conducted for starting inoculums of 5%, 10% and 15% respectively. Therefore the result of each optimization for medium, pH value, and starting inoculums were combined. The result of the combination shows tryptone and peptone as a Nitrogen source with neutral pH and starting inoculums of 5%, give an electric potential of 850 mV. On the final step, optimum condition were then measured based on interaction factors between Xanthomonas sp in MFC systems. The growth pattern based on FDA method showed the best electrical voltage of 890 mV in the t4 = 25 hours. The number of biomass were 9,49 X 106 CFU/mL with FDA hydrolytic enzymatic were 7,08 unit/mL (1 unit = µg fluorescein/minute)

and ammonium productivity 191,30 mg/L. The ability of Xanthomonas sp bacteria to produce a high electrical voltage has a great future prospect. These results will be used in further research optimization on application scale.

Keywords : Microbial Fuel Cell, Ammonification, Xanthomonas sp, cation exchange membrane, FDA method.