LAUSR

OBJECTIVES When citrate and pyruvate were utilized to strengthen ATP generation for high cAMP production, oxidative stress became more severe in cells resulting in lower cell viability and cAMP formation at the late fermentation phase. To further improve cAMP biosynthesis, the effects of polyphosphate on cAMP fermentation performance together with intracellular ATP and oxidation levels were investigated under high oxidative stress condition and then high efficient cAMP fermentation process based on polyphosphate and salvage synthesis was developed and studied. RESULTS With 2 g/L-broth sodium hexametaphosphate added at 24 h was determined as the optimal condition for cAMP production by Arthrobacter sp. CCTCC 2013431 in shake flasks. Under high oxidative stress condition caused by adding 15 mg/L-broth menadione, cAMP contents and cell viability were improved greatly due to hexametaphosphate addition and also exceeded those of control (without hexametaphosphate and menadione added) when fermentations were conducted in a 7 L bioreactor. Meanwhile, ATP levels and antioxidant capacity were improved obviously by hexametaphosphate as well. Moreover, a fermentation process with hexametaphosphate and hypoxanthine coupling added was developed by which cAMP concentration reached 7.25 g/L with an increment of 87.1% when compared with only hypoxanthine added batch and the high ROS contents generated from salvage synthesis were reduced significantly. CONCLUSION Polyphosphate could improve intracellular ATP levels and antioxidant capacity significantly under high oxidative stress condition resulting in enhanced cell viability and cAMP fermentation production no matter by de novo synthesis or salvage synthesis.