Microbial Production of 1, 3-Propanediol by a Newly Isolated Citrobacter freundii Strain CF-5

Microorganisms tolerant to 1, 3-propanediol (1, 3-PDO) were screened out from various environmental samples, and isolate CF-5 was found to produce 2.8 g/L 1, 3-PDO with glycerol as carbon source. Based on 16S rRNA gene sequence analysis, CF-5 was identified as a Citrobacter freundii strain. The fermentation conditions of strain CF-5 were analyzed. Higher biomass production was obtained in the medium supplemented with limited amount of glucose without repression of conversion efficiency of glycerol to 1, 3-PDO. Under the combined aerobic and oxygen limited incubation conditions, higher yield of 1, 3-PDO was reached. The fed-batch fermentation was performed in a 5 L bioreactor, 1, 3-PDO was found mainly produced in exponential growth phase cells of C. freundii CF-5 with the highest productivity 0.63 g/L*h, and the overall yield of 1, 3-PDO fermentation was 11.8 g/L within 36 h fermentation.