Hava kaldırmalı reaktörde yarrowia lipolytica ile lipid üretimi
Lipide production with yarrowia lipolytica in air-lift reactor
Yazar: ATA EGE ÖZKAN
Danışman: DOÇ. DR. MAHMUT ALTINBAŞ
İstanbul Teknik Üniversitesi / Lisansüstü Eğitim Enstitüsü / Çevre Mühendisliği Ana Bilim Dalı / Çevre Bilimleri ve Mühendisliği Bilim Dalı
Derece: Yüksek Lisans, 2022
Konu: Mikrobiyoloji = Microbiology ; Çevre Mühendisliği = Environmental Engineering
Dizin: Analitik yöntem = Analytical method ; Lipidler = Lipids ; Reaktörler = Reactors

Özet:
Günümüzde, petrol, kömür ve doğal gaz gibi fosil yakıtların hızla büyüyen sanayi sektörlerinde yaygın bir şekilde kullanımı sonucu global düzeyde enerji tüketiminin artması ve enerji ihtiyaçlarının gelecekte de artacağı tahmini, fosil yakıt rezervlerinin giderek azalması, küresel iklim değişikliği ve artan çevre kirliliği nedenleri ile alternatif enerji kaynağı oluşturmak; enerji sistemlerinin sürdürülebilirliğini sağlamak açısından acil bir ihtiyaçtır. Biyodizel, global enerji ihtiyaçlarını karşılayabilecek ve petrole alternatif olabilecek bir enerji kaynağı olarak düşünülebilir. Biyodizel, biyokütlenin hücre içi yüksek oranda lipit depolama özelliği sonucu oluşan Tek Hücre Yağlarının (THY) transesterifikasyon gibi uygun dönüşüm teknikleri uygulanması sonucu üretilebilir. Ancak biyodizel kullanımının sürdürülebilir olması için, kalite ve ekonomi açısından petrolle kıyaslanabilir olması gerekmektedir. Bu şartları sağlamak için, THY üretim proseslerinin optimize edilmesi gerekmektedir. Bu kapsamda, yağlı maya türü olan Y. lipolytica'nın, yarı kesikli ve kesikli biyoreaktör işletme stratejileriyle, YPD besiyeri beslenmesi sonucundaki çoğalma ve lipit üretim veriminin optimizasyonu ve farklı atıklarla karşılaştırılması; projenin asıl amacını oluşturmaktadır.
THY'nin lipit üretim veriminin optimize edilmesi ile maliyetin azaltılması ve böylece ticari ürün olarak piyasada yer alması beklenmektedir. THY üretiminin işletim maliyeti büyük oranda hammadde temininden ve reaktör işletiminden kaynaklanmaktadır. Atık ve atıksu akımları yüksek nütrient içeriğinden dolayı yağlı mayaların beslenmesi için ucuz ve uygulanabilir bir çözümdür. Atık ve atıksu akımlarının geri kazanılabilir değerli bileşim içeriğine rağmen, heterojen yapısından dolayı stabil olmaması biyokütle büyümesi sırasında istenmeyen bir durum olacaktır. Bu nedenle, atık çözünürlüğünü arttırmak ve proses stabilizasyonunu sağlamak için, karanlık fermentasyon (karbonhidratların, ışık yokluğunda anaerobik olarak ayrıştırılarak büyük oranda asetat ve bütirat salınımı) ve ön arıtma işlemleri (termal olarak, kimyasal olarak ve mikrodalga ile) uygulanmıştır.
Bu tez çalışmasında, Y. lipolytica ile kullanılan akım sentetik YPD medyasıdır ve kentsel organik atık (karbonhidrat içeriği yüksek), zeytin karasuyu, sızıntı suyu (karbon ve azot içeriği yüksek) ve melas akımlarının gerekli parametlerini ön görmek amacıyla kullanılmıştır. İntraselüler olarak lipit üretiminin optimizasyonu yapılırken, biyodizel üretimi düşünülerek depolanan lipitin miktarını arttırmak amacıyla farklı parametreler, laboratuvar ölçekli hava kaldırmalı reaktör kurularak, farklı işletme koşullarına denenmiştir ve lipit üretim verimleri incelenmiştir, bunlara ek olarak fizibilite analizi ile sistemin pilot ölçekli kullanımı irdelenmiştir.

Abstract:
SUMMARY
Today, academics in the plan of basic budgets for developed and developing world research, development studies, and for fuel based  studies on energy sources such as, hydroelectric, wind, solar, tidal, geothermal and biomass; they can be considered as an alternative to fossil fuels and affordable as a globally increasing energy potential, and they can predict the forecasts correctly.
Although there are many different renewable alternative environmental energy sources such as hydroelectric, wind, solar, tidal and geothermal, technical advances are required to make them generally usable due to the storage problem of the produced energy. On the other hand, unlike other energy sources, biomass energy is the most likely alternative environmentalist energy candidate in the light of today's technology, since it eliminates the problem of storing energy. 
For these reasons, studies on biomass and biofuels that can be obtained from various biomass sources are emphasized. Biofuels are fuels produced from biological materials. They are produced by using raw materials produced in many different sectors such as forestry or agriculture as a resource. There are many different types of biofuels such as biodiesel, bioethanol, bioether, biogas, syngas, and each one has different uses and properties.
Biomass can be converted into fuels such as ethanol, methanol, methane, hydrogen and diesel as a result of biological applications, which considered as the future of energy sources. Today's R&D studies are focused on bioethanol and biodiesel production. Biodiesel is a biofuel with a high potential to be used in various existing diesel engines and heating systems, thanks to its similar properties to diesel, which is a petroleum-derived fuel. At the same time, biodiesel is a type of fuel that does not increase the atmospheric carbon dioxide level and can be considered an environmentally friendly fuel as it does not contribute to global climate change. Since it is a clean technology product, it can be considered as a decomposable, non-toxic sustainable energy alternative. Because of these, biodiesel production attracts the attention of researchers.
Also, as a result of the widespread use of fossil fuels such as oil, coal and natural gas in rapidly growing industrial sectors, the increase in energy consumption at the global level and the forecast that energy needs will increase in the future, the gradual decrease of fossil fuel reserves, global climate change and increasing environmental pollution. Creation of the resource; is an urgent need to ensure the sustainability of energy systems. Biodiesel can be considered as an energy source that can meet global energy needs and be an alternative to oil.  

Biofuels can be examined in 4 different groups according to their production sources and producer types. The first type of biofuels is the type of biofuel produced by the use of the plants themselves, which are produced and harvested by conventional agriculture, or by using the remaining biomass after processing. The second type of biofuels are fuels produced by the conversion of difficult-to-degrade biomass into biofuel by special microorganisms, which cannot be used by commonly used microorganisms. Wastes with high lignocellulosic content, such as frying oil waste, olive black water and solid wastes from landfills can be given as examples of raw material sources used to produce the second type of biofuels. The third type of biofuels are biofuels produced using autotrophic organisms, without using any organic carbon source. The fourth type of biofuels are biofuels produced using genetically modified microorganisms.
Many different biofuels can be produced using the different types of biofuel production sources/methods mentioned. Biodiesel, which is one of these different fuels, draws attention due to its ability to be produced by different methods, wide usage area and relatively easier/economical production. While biodiesel has a higher energy content than ethanol in terms of energy content per unit mass, it is much easier to store and use than biogas and biohydrogen. In addition, biodiesel can be used directly in existing diesel engines without any modification.
According to the predictions and calculations, it is possible to obtain biodiesel equivalent to the consumption of fossil fuels by using a 2nd or 3rd type of biofuel production method. Moreover, biodiesel production in this way is in no way competitive with food production such as in 1st type of biofuel production method. Also, there are currently no technological barriers to producing biodiesel using a type 2 or type 3 biofuel production method. However, despite the studies for many years, cost-effective biodiesel production could not be realized as much as fossil fuels. 
Biodiesel is chemically defined as a fatty acid alkyl ester. Its production occurs when a fatty acid, which can be of different chain length, reacts with an alcohol in the presence of a suitable catalyst and forms an ester.
Biodiesel can be produced as a result of the application of appropriate conversion techniques such as transesterification of Single Cell Oils (SCO), which is formed as a result of the high intracellular lipid storage feature of biomass. However, for the use of biodiesel to be sustainable, it must be comparable to petroleum in terms of quality and economy. To meet these requirements, SCO manufacturing processes need to be optimized. 
By optimizing the lipid production efficiency of SCO, it is expected that the cost will be reduced and thus it will be available in the market as a commercial product. The operating cost of THY production is largely due to raw material supply and reactor operation. Waste and wastewater streams are an inexpensive and viable solution for feeding oily yeasts due to their high nutrient content. Despite the valuable recoverable composition content of wastewater and wastewater streams, instability due to its heterogeneous structure will be an undesirable situation during biomass growth. 
Therefore, in literature dark fermentation (largely acetate and butyrate release by anaerobically decomposition of carbohydrates in the absence of light) and  
pretreatment processes (thermally, chemically and by microwave) have been applied to increase waste solubility and provide process stabilization.
Oil production from fatty yeasts has been a slow research topic. Of about 600 yeast species, more than 30 genera are known as fatty. The most prominent among them are Yarrowia, Candida, Cryptococcus, Rhodotorula, Rhodosporidium, Rhizopus, Trichosporon and Lipomyces species. Some oily yeast strains can contain up to 70% of their dry cell weight in fat.
Yarrowia lipolytica (Y. lipolytica) is a high-fat yeast, which can contain up to 70% of their dry cell weight. On the other hand, Y. lipolytica is a type of oily yeast that can grow rapidly and use hydrophobic substances that are difficult to break down/remove. For this reason, it is a suitable strain to produce biodiesel within the scope of the biorefinery concept. 
In this thesis, the stream used with Y. lipolytica is synthetic YPD media and was used to predict the necessary parameters of urban organic waste (high carbohydrate content), olive black water, leachate (high carbon and nitrogen content) and molasses streams. While optimizing intracellular lipid production, in order to increase the amount of stored lipid by considering biodiesel production, different parameters were tested in different operating conditions by establishing a laboratory-scale air-lift reactor, and lipid production efficiencies were examined. In addition, the feasibility analysis and pilot-scale use of the system were examined.