Nazime MERCAN, Belma ASLIM, Z. Nur YÜKSEKDAĞ, Yavuz BEYATLI

Production of poly-$beta$-hydroxybutyrate (PHB) by some Rhizobium bacteria

Bu çalışmada, 1 adet Rhizobium japonicum, 6 adet Rhizobium cicer, 8 adet Rhizobium spp. ve Bradyrhizobiumjaponicum USDA 110 susunda PHB üretimi tespit edilmiştir. Suşların PHB içerikleri 0.01-0.5 g/l ve PHB verimleri de hücre kuru ağırlığına göre %1.36-40.0 arasında bulunmuştur. Çalışmamızda, suşlar arasından PHB üretimi en yüksek olan Rhizobium spp. 2426 ile orta verimliliğe sahip olan Rhizobium spp. 640 suşları seçilerek, farklı karbon ve azot kaynaklarının PHB üretimine etkisi test edilmiştir. Suşlar farklı karbon ve azot kaynağı içeren YEM sıvı besiyerinde düşük miktarda PHB üretirken, yüksek PHB üretimi L-Sistein ve Glisin içeren besi ortamında elde edilmiştir. Bu besi ortamında (L-Sistein ve Glisin) %PHB verimi Rhizobium spp. 640 suşunun sırasıyla %13.40 ve %56.67 olarak tespit edilirken, aynı azot kaynaklarında bu oran Rhizobium spp. 2426 susunda sırasıyla %70.0 ve %61.43 olarak tespit edilmiştir. Rhizobium spp. 2426'nm, L-Sisteinli YEM sıvı besiyerinde farklı zamanlardaki PHB üretme yeteneği araştırılmıştır. Bu susun en iyi PHB üretim ve yüzde verimi 48. saatte belirlenmiş, PHB üretimi 0.285 g/l ve yüzde verimi ise %74.03 olarak tespit edilmiştir. Bu saatten sonra PHB üretiminde düşüş olmuştur.

Bazı Rhizobium bakterilerin poli-$beta$-hidroksibütirat (PHB) üretimleri

In this study, the production of Poly-b-hydroxybutyrate (PHB) was determined in 1 Rhizobium japonicum, 6 Rhizobium cicer, 8 Rhizobium spp. and Bradyrhizobium japonicum USDA 110. The content of according to dry cell weight was determined to be 1.38-40.0%. In our study, Rhizobium spp. 2426, which produced the highest percentage yield of PHB, and Rhizobium spp. 640, which produced the intermediate percentage yield of PHB, were first selected among all the strains, and the the effect of different carbon and nitrogen sources on PHB production in these strains was tested. While the strains produced less PHB in yeast extract mannitol (YEM) broth media with different carbon and nitrogen sources, the highest level of PHB accumulation was observed in the media with L-cysteine and glycine. In this YEM medium with L-cysteine and glycine the percentage of PHB yield of Rhizobium spp. 640 was respectively determined to be 13.40% and 56.67%, while in the same nitrogen sources this percentage in Rhizobium spp. 2426 was determined to be 70% and 61.43%. The Rhizobium spp. 2426 strain capable of PHB accumulation was investigated in YEM with L-cystein at different incubation times (between 24 h and 120 h). The best PHB production and percentage yield of this strain was determined. The PHB production was 0.285 g/l and the percentage yield was 74.03% after 48 h. After this time there was a decrease in PHB yield.

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