Optimizing rhamnolipid production by Pseudomonas aeruginosa ATCC 9027 grown on waste frying oil using response surface method and batch-fed fermentation

LUO Zhi(罗致)^1,2, YUAN Xing-zhong(袁兴中)^1,2, Zhong Hua(钟华)^1,2, Zeng Guang-ming(曾光明)^1,2, Liu Zhi-feng(刘智峰)^1,2, Ma Xiao-ling(马小

(1 College of Environmental Science and Engineering, Hunan University, Changsha 410082, China;
2 Key Laboratory of Environmental Biology and Pollution Control of Ministry of Education (Hunan University), Changsha 410082, China)

Abstract:Rhamnolipid production by Pseudomonas aeruginosa ATCC 9027 with waste frying oil as sole carbon source was studied using response surface method. Cultures were incubated in shaking flask with temperature, NO^3- and Mg²⁺ concentrations as the variables. Meanwhile, fed-batch fermentation experiments were conducted. The results show that the three variables are closely related to rhamnolipid production. The optimal cultivation conditions are of 6.4 g/L NaNO₃, 3.1 g/L MgSO₄ at 32 °C, with the maximum rhamnolipid production of 6.6 g/L. The results of fed-batch fermentation experiments show that feeding the oil in two batches can enhance rhamnolipid production. The best time interval is 72 h with the maximum rhamnolipid production of 8.5 g/L. The data are potentially useful for mass production of rhamnolipid on oil waste with this bacterium.

Key words:Pseudomonas aeruginosa; rhamnolipid; waste frying oil; response surface method; fed-batch