Zeliha Demirel

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.

BİYOKÜTLE İÇİN MİKROALG VE SİYANOBAKTERİ’NİN BÜYÜK ÖLÇEKLİ ÜRETİMİ

Mikroalgler ve siyanobakteriler, binlerce yildir ilac, gida ve su urunleri yetistiriciligi endustrisi icin yuksek degerli bilesiklerin dogal bir kaynagi olarak kullanilmaktadir ve buyuk olcekli mikroalg yetistirilmesi, yarim yuzyili askin bir suredir yapilmaktadir. Yakin zamanda yeni mikroalg ve siyanobakteri turleri tanimlanmis ve cesitli urunler icin algal biyokutle yetistiriciligi ticari olcekli sistemlere gecilmistir. Ilk olarak, steril sisede (2L, 5L ve 10L) laboratuvar kosullarinda yetistirilen Arthrospira (Spirulina) platensis ve Phaeodactylum tricornutum kulturlerinin spesifik buyume hizlari ve klorofil-a analizleri yapilmistir. Ardindan ticari uygulama icin buyuk olcekli siyanobakterler ve mikroalg biyokutlesi uretimi icin acik ve kapali sistemler kuruldu. Alg biyokutlesi uretimi icin cevresel kosullar altinda bir acik karistirma tanki ve iki farkli tipte kapali-kultur sistemi veya fotobiyoteraktor (polipropilen torbalar ve plexiglas tupleri) kullanildi. Bununla birlikte, P. tricornutum , dusuk sicakliga karsi iyi direnc gostermis ve dusuk isik siddeti kosullarinda bile buyuyebilmistir. Acik havuz sistemlerinin performansi karsilastirildiginda, entegre sicaklik duzenlemesine sahip dis mekan sistemlerinin, daha iyi iklim kosullarina sahip bolgelerdeki acik havuzlarda yetistirilen kulturlere benzer bir biyokutle uretimi elde edildigi gosterilmistir. Ulkemizde yetistirilen mikroalg ve siyanobakterilerin biyokutle verimliliginin arttirmasi, ileri teknikle tasarlanan ve dusuk maliyetli teknolojilerle gelistirilen fotobiyoreaktor ile saglanabilir.

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.