Optimizing emulsan production of <Emphasis Type="Italic">A. venetianus</Emphasis> RAG-1 using response surface methodology

Statistical experimental design was used to optimize medium constituents for emulsan production by Acinetobacter venetianus RAG-1 in batch cultivation. The factors affecting emulsan production were screened by a two-level factorial design, and the optimal concentration of medium constituents for emulsan production were determined by the method of steepest path ascent and central composite experimental design. Experimental results showed that the optimal medium constituents were 9.16 g/L ethanol, 8.2 g/L KH₂PO₄, 23.32 g/L K₂HPO₄, 5.77 g/L (NH₄)₂SO₄ and 0.354 g/L MgSO₄•7H₂O. Under this optimal composition, the predicted emulsan production was 72.198 mg/L, and experimental value was 73.312 mg/L for 80 h culture in the shake flasks, and the emulsan yield by A. venetianus RAG-1 was enhanced nearly 1.48-fold (from 49.5 to 73.312 mg/L). Based on the results, we identify the optimal medium constituents for emulsan production and could take advantage of strategy for scale up the fermentation of emulsan production.