Identification of Optimal Conditions for Growth and Pigment Production in indegenous Dunaliella salina strain Using Central Composite Design Method

Öz

Microalgae are widely used in biotechnological applications due to their natural compounds such as protein, lipid and colored pigments. Dunaliella salina, a green algae tolerant to high salt concentrations, is a natural source of beta-carotene, and therefore it is one of the microalgae species that is prominent in biotechnological productions. Beta-carotene accumulation occurs in D. salina cells under stress conditions such as high salinity, high temperature, intense light or nutrient scarcity, but these conditions also negatively affects the cell growth. A two-phase production system is usually applied to the cultures in which the cell growth is first promoted and then the pigment production is increased by applying the stress condition. In this study, it was aimed to determine the culture conditions that would simultaneously promote biomass growth and intracellular carotenoid accumulation without the need for two phase production by using the central composite design method for a Dunaliella salina strain isolated from local sources. Two media components that cause carotenoid accumulation in the cell; salt (NaCl) and nitrate (KNO3) were selected as the factors to be used for experimental design. As a result of the experiments carried out at three different levels of factors, it was determined that the amount of salt in the medium was the primary factor in terms of both biomass increase and carotenoid accumulation. For D. salina cells, culture medium containing 1.75 M NaCl and 1.2 mM KNO3 was determined as the optimum condition for both increasing the amount of biomass and pigment accumulation in parallel. Carotenoid deposition was significantly affected by salt concentration, while the amount of nitrate used in the media was found to have a lower effect in the selected range.

Anahtar Kelimeler

• Biomass
• Carotenoids
• Central Composite Design
• Dunaliella salina

Yerli Dunaliella salina suşunda Büyüme ve Pigment Üretimi için Optimal Koşulların Merkezi Kompozit Tasarım Yöntemi Kullanılarak Belirlenmesi

Öz

Mikroalgler, sahip oldukları protein, lipid ve renkli pigmentler gibi doğal bileşikler sebebi ile biyoteknolojik uygulamalarda geniş bir kullanım alanı bulmaktadır. Yeşil algler sınıfına dahil olan ve yüksek tuz toleransı gösterebilen Dunaliella salina türü, doğal bir beta-karoten kaynağı olması sebebi ile biyoteknolojik üretimlerde öne çıkan mikroalg türleri arasındadır. Yüksek tuzluluk, yüksek sıcaklık, yoğun ışık miktarı ya da besin kıtlığı gibi stres koşulları altında D. salina hücrelerinde beta-karoten birikimi gerçekleşmekte, ancak bu durum hücre büyümesini olumsuz etkilemektedir. Bu sebeple genellikle hazırlanan kültürlerde önce hücre büyümesinin teşvik edildiği, ardından stres koşulu uygulanarak pigment üretiminin artırıldığı iki fazlı üretim sistemi benimsenmiştir. Bu çalışmada yerel kaynaklardan izole edilen bir D. salina suşu için merkezi kompozit tasarım yönteminden faydalanılarak biyokütle artışı ve hücre içi karotenoid birikimini, iki fazlı üretime gerek olmaksızın, eş zamanlı olarak teşvik edecek ortam koşullarının belirlenmesi amaçlanmıştır. Hücre içinde karotenoid birikimine sebep olan iki ortam bileşeni; tuz (NaCl) ve nitrat (KNO3), deney tasarımı için kullanılacak faktörler olarak seçilmiştir. Faktörlerin üç farklı düzeyinde gerçekleştirilen denemeler sonucunda ortamdaki tuz miktarının hem biyokütle artışı hem de karotenoid birikimi açısından birincil etmen olduğu belirlenmiştir. D. salina hücreleri için 1,75 M NaCl ve 1,2 mM KNO3 içeren kültür ortamında biyokütlenin, ve paralel olarak hücre içi pigment miktarının artışı için optimum koşul olarak belirlenmiştir. Karotenoid birikimi, tuz konsantrasyonu açısından önemli ölçüde etkilenirken, kullanılan nitrat miktarının seçilen aralıkta daha düşük etki gösterdiği görülmüştür.

Anahtar Kelimeler

• Biyokütle
• Karotenoidler
• Merkezi Kompozit Tasarım
• Dunaliella salina

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