Effects of oxygen-vectors on the synthesis of epsilon-poly-lysine and the metabolic characterization of Streptomyces albulus PD-1

The production of epsilon-poly-lysine (ε-PL) was enhanced by adding oxygen-vectors to the culture broth of Streptomyces albulus PD-1. ε-PL concentration reached a maximum of 30.8±0.46g/L and the dry cell weight was 33.8±0.29g/L when 0.5% n-dodecane was added to fed-batch fermentation. This improvement in ε-PL production and cell mass production can be related to 0.5% n-dodecane that could maintain dissolved oxygen concentration >32% saturation throughout the course of the ε-PL production phase. The transcription level of key genes and enzyme activities were analyzed. Results showed that the metabolic pathway responsible for ε-PL synthesis was strengthened when n-dodecane was added. The change in intracellular nucleotide levels was also investigated. Higher ATP level and a lower NADH/NAD⁺ ratio were obtained with 0.5% n-dodecane in broth, thereby providing more energy for ε-PL synthesis. These results indicated that ε-PL synthesis was strengthened from carbon metabolism and energy metabolism with 0.5% n-dodecane in broth.