Mikrobiyal Yakıt Hücrelerinde Kullanılan Antibiyotik Ve Hormonların Elektrik Üretimi Üzerine Etkileri
Mikrobiyal Yakıt Hücrelerinde Kullanılan Antibiyotik Ve Hormonların Elektrik Üretimi Üzerine Etkileri
Dosyalar
Tarih
2012-08-16
Yazarlar
Aktan, Sevil
Süreli Yayın başlığı
Süreli Yayın ISSN
Cilt Başlığı
Yayınevi
Fen Bilimleri Enstitüsü
Institute of Science and Technology
Institute of Science and Technology
Özet
Mikrobiyal yakıt hücreleri (MYH) oksijensiz ortamda mikroorganizmaları katalizör olarak kullanarak organik maddelerin oksidasyonu sonucu oluşan kimyasal enerjiyi doğrudan elektrik enerjisine çeviren sistemlerdir. Son yıllarda fermentasyon ürünlerini ve çeşitli atıksuları kullanarak elektrik üretimi araştırmacıların ilgisini çektiğinden bu konuda pek çok çalışma yapılmıştır. Elektrik üretiminin yanında bu sistemler atıksuyu arıttığından gelecekte pratik kullanımlar için potansiyel taşımaktadır. Mikrobiyal yakıt hücrelerinin diğer bir kullanım alanı ise biosensör olarak çalıştırılmalarıdır. Bu sistemlerin bugüne kadar yapılan araştırmalar sonucu elde edilen elektrik verimleri ticari olarak kullanımdan oldukça uzaktır. Kullanılabilir ve düşük maliyetli teknolojilerin geliştirilmesi için önümüzdeki yıllarda birçok temel araştırmalar yapılmalıdır. Bu çalışma temel olarak iki kısımdan oluşmaktadır. Birincisi iki hazneli microbiyal yakıt hücresinde saf kültür Shewanella putrefaciens kullanılarak farklı organik maddelerden elektrik üretimi olup, optimizasyon çalışmalarından sonra kültür edilmiş hücreler iki hazneli MYH’ne transfer edilmiştir. Shewanella putrefaciens elektrokimyasal olarak aktif, anot yüzeyine biyofilm yapabilme özelliğine sahip olup organik maddelerden elde edilen elektronları anot yüzeyine aracı bir medyatör kullanmadan verme özelliğine sahiptir. Böylece sentetik medyatörlerin toksik etkisi ve yenilenme gereği ortadan kaldırılmıştır. Deneyler sonunda elde edilen düşük güç yoğunluğu sebebiyle (0.8 mW/m2) çalışmaya karışık kültür bakteriler ile devam edilmiştir. Çalışmanın ikinci kısmında, tek hazneli mikrobiyal yakıt hücresinde aklime edilmiş karışık kültür mikroorganizmalar kullanılarak sodyum asetat ile beslenen sistem için elektrik üretimi, KOİ giderimi, Colombus verimliliği bulunmuştur. Sodyum asetat ile beslenen tek hazneli microbiyal yakıt hücresi ile elektrik üretimi üzerine farklı konsantrasyonlarda dört farklı hormon (estrone, 17β-estradiol, estriol ve 17α-ethinylestradiol) ile üç farklı antibiyotik (erythromycin, sulfamethoxazole, tetracycline) maddesi eklenerek bu maddelerin olası inhibisyon etkileri araştırılmıştır. Antibiyotikler 50, 100 ve 200 mg/L konsantrasyonlarında hazırlanıp asetat ile beraber sisteme verilmiştir. Öte yandan hormonlar ise 0,1, 0,5 ve 1 mg/L konsantrasyonlarda uygulanmıştır. Bu setlerin her biri sadece asetat kullanılan setlerle karşılaştırılmış ve akım, colombus verimliliği ve KOİ gideriminde farklılıklar değerlendirilmiştir. Böylece MYH sistemi bir nevi biyosensör olarak kullanılmıştır. Literatürde bu inhibitor maddelerin elektrojen (elektrik üreten) bakteriler üzerine etkisini gösteren benzer çalışmalara rastlamak pek mümkün olmadığından kıyaslama yapılamamakla beraber çalışmamızın orjinalliği açısından önem taşımaktadır. İncelenen antibiyotikler dünyada ve ülkemizde en fazla tüketilen ana gruplardan olması nedeniyle seçilmiştir. Sentetik hormonlar da son yıllarda yoğun kullanımı ile canlılar üzerinde olumsuz etkileri araştırmacılar tarafından gözlemlendiğinden bu çalışmada bakteriler üzerinde elektrik üretimi açısından değerlendirilmesi yapılmıştır.
A microbial fuel cell (MFC) is a bioreactor that directly converts chemical energy occurring as a result of oxidation of organic compounds to electrical energy through catalytic reactions of microorganisms under anaerobic conditions. In recent years, since electricity generation from a microbial fuel cell by using fermentation products and different wastewaters as fuel draws researchers’ attention, lots of investigations have been made and well documented. Apart from electricity generation, these systems have a great potential for practical applications in the future due to wastewater treatment. The other purpose of MFC usage is a biosensor. The electricity efficiencies obtained recently in MFCs are far away from those required for commercial application and lots of fundamental works have to be done in order to develop usable technologies with low cost. This thesis consists of two stages in general. Firstly, it is purposed to generate electricity from different organic compounds by using two chambered MFC and pure culture Shewanella putrefaciens. After optimization experiments, cultivated cells are transferred to the two chambered MFC. Shewanella putrefaciens is bioelectrochemically active and can form a biofilm on the anode surface and transfer electrons directly (without mediator) by conductance through the membrane. When they are used, the anode acts as the final electron acceptor in the dissimilatory respiratory chain of the microbes in the biofilm. Thus, it is avoided from toxicity and instability of synthetic mediators. Because of poor power density of the system (0.8 mW/m2), it is continued with mixed culture. In the second phase of this study, by using acclimated mixed culture microorganisms in single chambered MFC, electricity generation, current, chemical oxygen demand (COD) removal, coulombic efficiency (CE) values were measured for the system fed with sodium acetate as carbon source. In single chambered MFC, 4 different estrogens (hormones) which are estrone, 17β-estradiol, estriol ve 17α-ethinylestradiol and 3 different antibiotics (erythromycin, sulfamethoxazole, tetracycline) are used. It is investigated inhibition responses of these matters in MFC system. During antibiotic experiments, one cycle is only acetate, following cycle is antibiotic plus acetate and it continues in this way. When the values of current and CE change after antibiotic plus acetate, the system is fed with only acetate repeatedly to recover to its original value. The concentrations of antibiotics are 50, 100 ve 200 mg/L and they are given to the system together with acetate. On the other hand, the concentrations of hormones are 0,1, 0,5 ve 1 mg/L and the same procedure is carried out. Each set is compared with only the sets in which acetate is used and differences in the current, CE and COD removal values are observed. Therefore, the MFC system is used in a way as a biosensor in this study. In literature, studies that show the effects of inhibitory matters on electrogen microorganisms are too limited. Thus, making a comparison is not quite possible and also the originality of our study gains an importance. Erythromycin (ERY), sulfamethoxazole (SMX) and tetracycline (TC) are chosen because they are widely used in Turkey and around the world. On the other hand, since it is observed by the researchers that widely usage of synthetic hormones in recent times has negative effects on fish, it is proved in this study that they show diversity in terms of electricity current of electrogen bacteria.
A microbial fuel cell (MFC) is a bioreactor that directly converts chemical energy occurring as a result of oxidation of organic compounds to electrical energy through catalytic reactions of microorganisms under anaerobic conditions. In recent years, since electricity generation from a microbial fuel cell by using fermentation products and different wastewaters as fuel draws researchers’ attention, lots of investigations have been made and well documented. Apart from electricity generation, these systems have a great potential for practical applications in the future due to wastewater treatment. The other purpose of MFC usage is a biosensor. The electricity efficiencies obtained recently in MFCs are far away from those required for commercial application and lots of fundamental works have to be done in order to develop usable technologies with low cost. This thesis consists of two stages in general. Firstly, it is purposed to generate electricity from different organic compounds by using two chambered MFC and pure culture Shewanella putrefaciens. After optimization experiments, cultivated cells are transferred to the two chambered MFC. Shewanella putrefaciens is bioelectrochemically active and can form a biofilm on the anode surface and transfer electrons directly (without mediator) by conductance through the membrane. When they are used, the anode acts as the final electron acceptor in the dissimilatory respiratory chain of the microbes in the biofilm. Thus, it is avoided from toxicity and instability of synthetic mediators. Because of poor power density of the system (0.8 mW/m2), it is continued with mixed culture. In the second phase of this study, by using acclimated mixed culture microorganisms in single chambered MFC, electricity generation, current, chemical oxygen demand (COD) removal, coulombic efficiency (CE) values were measured for the system fed with sodium acetate as carbon source. In single chambered MFC, 4 different estrogens (hormones) which are estrone, 17β-estradiol, estriol ve 17α-ethinylestradiol and 3 different antibiotics (erythromycin, sulfamethoxazole, tetracycline) are used. It is investigated inhibition responses of these matters in MFC system. During antibiotic experiments, one cycle is only acetate, following cycle is antibiotic plus acetate and it continues in this way. When the values of current and CE change after antibiotic plus acetate, the system is fed with only acetate repeatedly to recover to its original value. The concentrations of antibiotics are 50, 100 ve 200 mg/L and they are given to the system together with acetate. On the other hand, the concentrations of hormones are 0,1, 0,5 ve 1 mg/L and the same procedure is carried out. Each set is compared with only the sets in which acetate is used and differences in the current, CE and COD removal values are observed. Therefore, the MFC system is used in a way as a biosensor in this study. In literature, studies that show the effects of inhibitory matters on electrogen microorganisms are too limited. Thus, making a comparison is not quite possible and also the originality of our study gains an importance. Erythromycin (ERY), sulfamethoxazole (SMX) and tetracycline (TC) are chosen because they are widely used in Turkey and around the world. On the other hand, since it is observed by the researchers that widely usage of synthetic hormones in recent times has negative effects on fish, it is proved in this study that they show diversity in terms of electricity current of electrogen bacteria.
Açıklama
Tez (Doktora) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2011
Thesis (PhD) -- İstanbul Technical University, Institute of Science and Technology, 2011
Thesis (PhD) -- İstanbul Technical University, Institute of Science and Technology, 2011
Anahtar kelimeler
Microbiyal yakıt hücresi,
Shewanella putrefaciens,
Elektrik,
Antibiyotik,
Hormon,
Microbial fuel cell,
Shewanella putrefaciens,
Electricity,
Antibiotic,
Hormon