Esra Imamoglu

Influences of different stress media and high light intensities on accumulation of astaxanthin in the green alga Haematococcus pluvialis

Haematococcus pluvialis Flotow is used in the aquaculture, pharmaceutical and cosmetic industries. The aim of this study was to compare the effect of various stress media and high light intensities on astaxanthin accumulation. The experimental design was achieved by four different stress media and two different light intensities for 14 days of induction period. The astaxanthin concentrations of 29.62 mg g(-1) and 30.07 mg g(-1) were obtained in distilled water with CO(2) and N-free medium, respectively, with no significant difference between them at 546 micromol photons m(-2)s(-1). Because of the morphological changes of H. pluvialis, microscopic observation was considered during the induction period to facilitate the selection of stress medium. It was clear that the rate of astaxanthin accumulation was much faster in distilled water with the addition of CO(2). The main point is that, this medium is more economical than others, especially for the large-scale productions.

Scale-up and kinetic modeling for bioethanol production

Bioethanol was produced from acidic hydrolysate of rice hulls using recombinant Escherichia coli KO11. Two different issues (scale-up and kinetic modeling) were evaluated simultaneously and concomitantly for bioethanol production. During the step-wise scale-up process from 100 mL shaken flask to 10 L stirred-tank bioreactor, the constant Reynolds number and the constant impeller tip speed were evaluated as scale-up methodologies under laboratory conditions. It was determined that the volumetric bioethanol productivity was 88% higher in 10 L bioreactor in comparison to the value of 0.21 g L(-1) h(-1) in shaken flask. The modified Monod and Luedeking-Piret models provided an accurate approach for the modeling of the experimental data. Ethanol concentration reached the maximum level of 29.03 g/L, which was 5% higher than the value of model prediction in 10 L bioreactor. The findings of this research could contribute to the industrial scale productions especially from lignocellulosic raw materials.

Large-scale bioprospecting of cyanobacteria, micro- and macroalgae from the Aegean Sea

Marine organisms constitute approximately one-half of the total global biodiversity, being rich reservoirs of structurally diverse biofunctional components. The potential of cyanobacteria, micro- and macroalgae as sources of antimicrobial, antitumoral, anti-inflammatory, and anticoagulant compounds has been reported extensively. Nonetheless, biological activities of marine fauna and flora of the Aegean Sea have remained poorly studied when in comparison to other areas of the Mediterranean Sea. In this study, we screened the antimicrobial, antifouling, anti-inflammatory and anticancer potential of in total 98 specimens collected from the Aegean Sea. Ethanol extract of diatom Amphora cf capitellata showed the most promising antimicrobial results against Candida albicans while the extract of diatom Nitzschia communis showed effective results against Gram-positive bacterium, S. aureus. Extracts from the red alga Laurencia papillosa and from three Cystoseira species exhibited selective antiproliferative activity against cancer cell lines and an extract from the brown alga Dilophus fasciola showed the highest anti-inflammatory activity as measured in primary microglial and astrocyte cell cultures as well as by the reduction of proinflammatory cytokines. In summary, our study demonstrates that the Aegean Sea is a rich source of species that possess interesting potential for developing industrial applications.

Process optimization and modeling for the cultivation of Nannochloropsis sp. and Tetraselmis striata via response surface methodology.

The aim of this study was to determine the optimal physical process conditions for the cultivation of locally isolated strains of Nannochloropsis sp. and Tetraselmis striata to achieve maximum growth rate. It was essential to evaluate biomass production at different agitation rates, light intensities, and temperature levels. Central composite design and response surface methodology were applied to design the experiments and optimize the cultivation process for Nannochloropsis sp. and T. striata. The specific growth rate of 0.250 d−1 was obtained for Nannochloropsis sp. cells under the light intensity of 54 μmol photons · m−2 · s−1, at the agitation rate of 151 rpm in 24.5°C. The optimal physical process conditions for T. striata were obtained under the light intensity of 56 μmol photons · m−2 · s−1 in 25.5°C at the agitation rate of 151 rpm in 25.5°C, resulting in a specific growth rate of 0.226 d−1. The predicted values were justified by the verification tests. Good agreement between the predicted values and the experimental values confirmed the validity of the models for the cultivation of microalgal strains. In this article, the noteworthy result was that temperature was a dominant factor in obtaining high chl‐a content for Nannochloropsis sp., whereas the growth of T. striata strongly depended on light exposure.

Trends in red biotechnology: Microalgae for pharmaceutical applications

Abstract This chapter introduces the pharmaceutical applications of microalgae with respect to their potential properties. It overviews the previous and recent studies on antioxidant, antiinflammatory, antitumor, anticancer, antimicrobial, antiviral and antiallergic activities of microalgal bioactive molecules. It explains the potential mechanism underlying the effects of these molecules with the related pathways. By the end of the chapter the future prospects on the red biotechnology, including the developments in research and industry are explained. A full discussion of recent examples is included to raise the possibility of microalgal resources to become a promising compound in various types of industrial areas with the key concept of potential usage.

Evaluation of scale-up parameters of bioethanol production from Escherichia coli KO11 / [Escherichia coli KO11 suşundan biyoetanol üretimi için ölçek büyütme parametrelerinin değerlendirilmesi]

Abstract Objective: In recent years, increased attention has been devoted to the conversion of biomass into fuel ethanol, as one of the cleanest liquid fuel alternatives to fossil fuels. However, industrial production of bioethanol is related with successful scaling-up studies. Methods: In this study, the experimental designs of scale-up procedures based on constant mixing time, impeller tip speed and oxygen mass transfer coefficient were performed in 8 L stirred tank reactor and were compared in terms of product yield and productivity with those obtained from 2 L stirred tank reactor using quince pomace as a substrate for bioethanol production by Escherichia coli KO11. Results: Scale-up based on constant mixing time yielded a maximum ethanol concentration of 23.42 g/L which corresponded to 0.4 g ethanol/ g reduced sugar in 8 L stirred tank reactor. Moreover, shear stress increased only 1.1 fold which resulted in low cell damage and high cell viability. Conclusion: Constant mixing time was identified as the most important key parameter especially for scaling-up of viscous fermentation broths of bioethanol production due to the significance of the homogeneity. Özet Amaç: Son yıllarda fosil yakıtlara alternatiflerden biri olarak biyokütlenin dönüşümüyle etanol eldesi çok önem kazanmıştır. Endüstriyel ölçekte biyoetanol üretimi, başarılı bir ölçek büyütmeye bağlıdır. Metod: Bu çalışmada, 8 L karıştırmalı tank reaktörde sabit karışma süresi, sabit bıçak ucu hızı ve sabit oksijen kütle transfer katsayısına göre ölçek büyütme prosedürleri gerçekleştirilmiştir. Sonuçlar, Escherichia coli KO11 suşundan ayva posası ile 2 L reaktörde elde edilen sonuçlarla ürün verimi ve verimliliği bakımından karşılaştırılmıştır. Bulgular: 8 L karıştırmalı tank reaktörde maksimum etanol konsantrasyonu (23.42 g/L), 0.4 g etanol/g indirgen şeker verimiyle sabit karışma süresine göre yapılan ölçek büyütmede elde edilmiştir. Ayrıca, kayma gerilimi sadece 1.1 kat artmıştır ve bu durum düşük hücre hasarı ve yüksek hücre canlılığıyla sonuçlanmıştır. Sonuç: Sabit karışma süresi, biyoetanol üretiminde homojenitenin önemi açısından özellikle viskoz fermentasyon sıvıları için en önemli parameter olarak tanımlanmıştır.

Determination of Superoxide Dismutase Activities in Different Cyanobacteria for Scavenging of Reactive Oxygen Species

Abstract There is considerable interest in cyanobacteria as sources of antioxidant pigments, antiinflammatory substances, enzymes such as superoxide dismutase (SOD) and vitamins. Antioxidant enzymes have significant role in the removal of reactive oxygen species produced during visible and ultraviolet irradiance stress in cyanobacteria. One of the most ubiquitous protective enzyme is superoxide dismutase (SOD). Most of cyanobacteria are known to have both FeSOD and MnSOD which are associated with photosystem I and II. These enzymes are responsible for scavenging superoxide radicals.Spirulina platensis and Synechococcus nidulans are widely used cyanobacteria as food supplement and cosmetic due to their bioactive compounds. Although the chemical composition of S.platensis has been investigated by many researchers, research on the relationship between protein content and comparison of SOD activity with other cyanobacteria is limited.Among several SOD producing cyanobacteria, the most promising organisms were investigate in terms of SOD activities in this study. The aim of the present work was to investigate and compare the SOD activities of different cyanobacteria including S. platensis, Pseudanabeana sp., S. nidulans and associate with protein contents. SOD activities of these cyanobacteria were determined by xanthine/xanthineoxidase method.Modified Lowry method was used for protein determination. The analysis results showed that the maximum specific SOD activity obtained was 50.4 U/mg from S.nidulans and the minimum specific SOD activity was 18.4 U/mg from Pseudanabeana sp. Total protein amount of S. nidulans, S. platensis, Pseudanabeana sp. was determined as 0.25 mg/ml, 0.27 mg/ml and 0.43 mg/ml respectively. As a result, Synechococcus nidulans was more efficient at scavenging peroxide radicals than Pseudanabeana sp.

Screening of fatty acid composition in Nitzschia sp.

Abstract Introduction: The main target of this study was to compare the effects of nitrogen limitation and light intensities on cell growth, lipid content and fatty acid profile of Nitzschia sp. Methods: F/2 medium and N-free F/2 medium were both tested at two different light intensities of 11 and 56 μEm−2s−1 in the internal loop air-lift photobioreactor for Nitzschiasp. Results: The presence of nitrogen led to more cells grown efficiently. Furthermore, the increase in chlorophyll content went parallel to the increase in dry weight. The most abundant saturated and monounsaturated fatty acids were pentadecanoic acid (C15:0) and palmitoleic acid (C16:1) which constituted 17%–42% and 15%–48% of total fatty acids for all growth conditions, respectively. It was recorded that palmitoleic acid was present at higher concentrations than palmitic acid. Discussion and conclusion: The noteworthy finding was that the lipid content increased with increasing the growth rate of Nitzschia sp. under phototrophic conditions.

Effects of geometrical configurations of photobioreactors on the growth of marine benthic diatom Cylindrotheca closterium / Fotobiyoreaktörlerin geometrik konfigürasyonlarının sucul bentik diatom Cylindrotheca closterium üremesi üzerine etkisi

Abstract Objective: For algal biotechnology, the primary barrier is the developing of cost effective photobioreactor operating in a high-efficiency. In this study, the effects of three different types of photobioreactors (bag, flat plate and bubble column) on the growth and sugar production of the diatom Cylindrotheca closterium were simultaneously investigated for 7 days of batch cultivation period. Methods: The photobioreactors were incubated at 21±2°C under the light intensity of 50 μmol photons m-2s-1 with a 12: 12 h light: dark cycle photoperiod at the air flow rate of 2 L min-1 for 7 days of batch productions. The turbidity (optical density), chlorophyll-a, exopolysaccharide (EPS) content and reducing sugar concentration were measured. Results: The maximum specific growth rate of 0.29 day−1, which corresponded to the doubling time of 2.40 day, was obtained in the bag photobioreactor cultivation of C. closterium. It was found that the polyethylene bag photobioreactors are suitable for the production of diatoms as a closed photobioreactor. Conclusion: The key is not only the selection of geometrical configuration of photobioreactor, but also the determination of the light penetration path for cost effective photobioreactor design operating in high efficiency related to the algal productions. Özet Amaç: Algal biyoteknoloji icin birincil engel, yuksek verimlilikte calışan duşuk maliyetli fotobiyoreaktor tasarımıdır. Bu calışmada, uc farklı fotobiyoreaktorde (torba, kabarcık kolon ve panel) diatom Cylindrotheca closterium icin ureme ve şeker uretimi 7 gun boyunca incelenmiştir. Metod: Fotobiyoreaktorlerde 21±2°C sıcaklıkta, 50 μmol photons m-2s-1 ışık şiddeti altında 12: 12 saat aydınlık: karanlık dongusu ile 2 L dak-1 akış hızında 7 gunluk uretimler gercekleştirilmiştir. Optik yoğunluk, klorofil-a, ekzopolisakkarit ve indirgen şeker konsantrasyonları olculmuştur. Bulgular: C. closterium’un torba fotobiyoreaktorde uretiminde 0.29 gun-1 olarak maksimum buyume hızına ve 2.4 gun olarak ikilenme suresine ulaşılmıştır. Polietilen torba fotobiyoreaktorlerin diatom uretimlerinde daha elverişli olduğu bulunmuştur. Sonuç: Algal uretimlerde yuksek verimlilikte calışan duşuk maliyetli fotobiyoreaktor tasarımı icin hem fotobiyoreaktorun geometrik konfigurasyon secimi hem de ışık emilim yolunun belirlenmesi onemlidir.

COMPARISON OF ASTAXANTHIN EXTRACTABILITY YIELDS FOR DISRUPTED HAEMATOCOCCUS CYSTS

This comprehensive study focusing on the extractability of astaxanthin from Haematococcus cysts was carried out to compare the effectiveness of the cell disruption procedures. Both single step and combined cell disruption procedures were evaluated. A physical, chemical, enzymatic or mechanical disruption process was applied prior to mechanical disruption (bead vortex homogenizer or tissue homogenizer) for the combined cell disruption procedures. In this study the best result was obtained with the consecutive mechanical disruption processes using the combined procedure of tissue homogenizer and bead vortex homogenizer, yielding 68.32 mg Ast/g DW which was 31% higher than that obtained with the single step bead vortex homogenizer treatment. It was concluded that the combined disruption procedures were more effective than the single step disruption procedures with respect to the extractability of astaxanthin from Haematococcus cysts.