simultaneous polyhydroxyalkanoates and rhamnolipids production by thermus thermophilus hb8同时polyhydroxyalkanoates栖热菌属和鼠李糖脂生产的酸奶hb8.pdfVIP

Pantazaki et al. AMB Express 2011, 1:17 /content/1/1/17 ORIGINAL Open Access Simultaneous polyhydroxyalkanoates and rhamnolipids production by Thermus thermophilus HB8 Anastasia A Pantazaki1*, Christos P Papaneophytou1 and Dimitra A Lambropoulou2 Abstract The ability of Thermus thermophilus HB8 to produce simultaneously two environmentally-friendly biodegradable products, polyhydroxyalkanoates (PHAs) and rhamnolipids (RLs), using either sodium gluconate or glucose as sole carbon source, was demonstrated. The utilization of sodium gluconate resulted in higher levels of PHAs and RLs production than when glucose was used as sole carbon source. The initial phosphate concentration (as PO43-) influences both PHAs and RLs productions that were increased during cultivation time. PHAs accumulation was enhanced ( 300 mg/L) after 72 h of cultivation in an initial [PO43-] of 25 mM, while RLs production ( 200 mg/L) was started after 35 h and continued until 72 h of cultivation, in a phosphate-limited medium containing initially 5 mM of [PO43-]. In addition, the combine effect of initial [PO43-] and cultivation time on biomass, PHAs and RLs production was evaluated from 2D contour plots. The results revealed that low initial phosphate concentrations (up to 5 mM) and long incubation time (72 h) promoted RLs biosynthesis while higher initial phosphate concentrations (up to 25 mM) where favorable for biomass and PHAs production. The molecular composition of the produced bio-products was identified. The accumulated PHAs were co-polymers which mainly consisted of 3- hydroxydecanoate (3HD) as resulted by gas chromatography (GC) analysis. The secreted RLs were extracted and their total mixture contained both mono- and di- RLs identified by thin-layer chromatography (TLC). Moreover, the molecular composition of the produce