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Öğe Biyokütleden biyohidrojen üretimi(2012) Kars, GökhanDünya’nın enerji ihtiyacı sürekli artmakta buna karşın fosil kökenli enerji kaynakları hızla tükenmektedir. Bu nedenle yenilenebilir ve sürdürülebilir alternatif enerji kaynakları arayışları artmış bu konulardaki araştırmalar çok önem kazanmıştır. Alternatif enerji taşıyıcısı olarak biyohidrojen, biyokütle gibi yenilenebilir enerji kaynaklarının kullanılmasıyla karanlık fermentasyon veya fotofermentasyon ile üretilebilmektedir. Karanlık fermentasyonda kullanılan glikoz ancak 2-3 karbonlu organik asitlere kadar parçalanabilmektedir. Buna karşın, karanlık fermentasyon ve fotofermentasyon proseslerinin ard arda yürütülmesi ile oluşan iki basamaklı biyoproses ile, karanlık fermentasyonda oluşan organik asitler fotofermentasyon aşamasında kullanılıp karbondioksite kadar parçalanmakta ve böylece tüm süreç maliyet ve enerji açısından daha uygun ve verimli olmaktadır. Biyokütle olarak şeker pancarı melası kullanılarak, termofilik bakterilerin kullanıldığı karanlık fermentasyon ve devamında fotosentetik bakterilerin kullanıldığı fotofermentasyon ile iki basamaklı hidrojen üretim biyoprosesi geliştirilebilmektedir. Böylece, kolaylıkla ve düşük maliyetle temin edilebilen melas kullanılarak hidrojen üretimi gerçekleştirilebilir, melasın en iyi şekilde değerlendirilmesi sağlanır ve Türkiye’nin enerji ihtiyacının bir kısmı yenilenebilir ve sürdürülebilir bir enerji kaynağından sağlanmış olunur. Bu çalışmada Türkiye’de üretilen şeker pancarı melasından biyohidrojen üretim potansiyeli incelenmiştir. Ayrıca, üretilen hidrojenin Proton Değişim Zarlı Yakıt Pilinde (PEMFC) elektriğe dönüştürülmesiyle oluşabilecek enerji potansiyeli de değerlendirilmiştir. Buna göre Türkiye’de 2010 yılında üretilen melasdan iki basamaklı biyohidrojen üretimi neticesinde 14 362 073 011.98 mol H2 ve 446 804 091.40 kWh elektrik enerjisi elde edilebilir.Öğe Heterologous expression of glutamyl-tRNA reductase gene in Rhodobacter sphaeroides O.U.001 to enhance 5-aminolevulinic acid production(TAYLOR & FRANCIS LTD, 2014) Kars, Gökhan; Alparslan, ÜmmühanThe pathways for synthesis of 5-aminolevulinic acid (5-ALA) use either succinyl-CoA and glycine (C-4 pathway), or glutamate (C-5 pathway). Although Rhodobacter sphaeroides synthesizes 5-ALA through the C-4 pathway, it also has the genes coding for the enzymes of the C-5 pathway, except for glutamyl-tRNA reductase. The glutamyl-tRNA reductase gene was cloned from Rhodospirillum rubrum and expressed in R. sphaeroides; thus, the C-5 pathway was enabled to function upon assembling all the required genes. Consequently, a new and unique bacterial strain producing more 5-ALA was developed. Biohydrogen was also produced in the same bioprocess within a biorefinery approach using sugar beet molasses as substrate. The amount of 5-ALA produced by the modified strain was 25.9mg/g dry cell weight (DCW), whereas the wild-type strain produced 12.4mg/g DCW. In addition, the amount of H-2 generated by the modified and wild-type cells, respectively, was 0.92 L/L culture and 1.05 L/L culture.Öğe Hydrogen Generation by Rhodobacter Sphaeroides O.U.001 Using Pretreated Waste Barley(2019) Kars, Gökhan; Emsen, AyçaIn the present study, valorization of waste barley by producing hydrogen (H2) and 5-aminolevulinic acid (5-ALA) using Rhodobacter sphaeroides O.U.001 was aimed. Firstly, 3 % (w/v) waste barley hydrolysate was prepared by treating 3 g of powdered waste barley with H2SO4 in a total volume of 100 mL mixture and then autoclaving this mixture at 121 ºC for 30 min. Upon generation of fermentable simple sugars by pretreatment and analytical examination of the hydrolysate in terms of ammonium content, element composition and light transmittance, various types of growth media containing various concentrations of sugar (5 - 6 - 7 - 8 g/L) were prepared. The cells were cultivated in these media under photo-heterotrophic conditions which favor H2 and 5-ALA generations. pH changes, growth, H2 production and 5-ALA generation were monitored in the media. The results showed that all the media prepared from 3 % (w/v) waste barley hydrolysate sustained the cell growth appreciably. The highest OD value (OD660: 1.71) was attained when using 8 g/L sugar. Furthermore, biological H2 evolution was seen in each bioreactor. In particular, the highest hydrogen accumulation (0.29 L H2/L) was achieved in 6 g/L sugar-containing medium. However, 5-ALA was not detected in any of the media. To conclude, considerable cell growth and biological hydrogen production was achieved using 3 % (w/v) waste barley hydrolysate under the conditions tested but there was no detectable 5-ALA generation.Öğe Valorization of sugar beet molasses for the production of biohydrogen and 5-aminolevulinic acid by Rhodobacter sphaeroides OU001 in a biorefinery concept(PERGAMON-ELSEVIER SCIENCE LTD, 2013) Kars, Gökhan; Alparslan, ÜmmühanThe production of biohydrogen and 5-aminolevulinic acid (5-ALA) from sugar beet molasses was investigated within a biorefinery framework. A purple non-sulfur photosynthetic bacterium, Rhodobacter sphaeroides O.U.001, was used for this purpose. The suitability of the molasses for biohydrogen and 5-ALA production was assessed in certain aspects and then five different culture media with various sugar contents (3 g/L, 7 g/L, 14 g/L, 21 g/L and 28 g/L) were prepared. Results have shown that molasses is a promising substrate for the production of biohydrogen and 5-ALA in a biorefinery concept and increasing sugar content results in enhanced product accumulation. Specifically, the highest amount of biohydrogen and 5-ALA was observed in 28 g/L sugar-containing medium (1.01 L H-2/L culture, 23,337 mu M). In conclusion, this paper presents the new findings about the enhanced accumulation of biohydrogen and 5-ALA within a biorefinery context. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
