Maximum Production of 1,4-Dihydroxy-2-Naphthoic Acid by Fed-Batch and Anaerobic/Aerobic Culture of Propionibacterium freudenreichii ET-3

Maximum production strategy of 1,4-dihydroxy-2-naphthoic acid (DHNA) was investigated using a fed-batch and anaerobic/aerobic culture of Propionibacterium freudenreichii ET-3. DHNA is a precursor of menaquinone (MK) and the cell produces DHNA and MK in the molar ratio of 3:2 by consuming lactose in skim milk powder medium under normal anaerobic condition. We found that in anaerobic fed-batch culture, which limited lactose concentration, the cell stopped producing MK. As a result, DHNA concentration in fed-batch culture increased as lactose feeding rate decreased, and the maximum DHNA concentration in fed-batch culture was 0.40 mM, which is 3.3-fold that in anaerobic batch culture. However, propionate accumulation inhibited and then stopped DHNA production in anaerobic fed-batch culture. Our previous study showed that the cell could consume propionate under aerobic condition and this knowledge based on metabolic flux distribution for DHNA production was applied here. The cell produced DHNA continuously by switching from anaerobic condition to aerobic condition after lactose feeding. DHNA concentration in the optimal condition was 0.51 mM, which is 4.2-fold that in anaerobic batch culture.