Efficient production of high-molecular-weight hyaluronic acid with a two-stage fermentation

In this paper, the production pattern of hyaluronic acid (HA) was revealed: the chain growth of HA mainly occurred in the first half of fermentation while the product accumulated throughout the fermentation period. Attempts were made to develop a two-stage fermentation process which provided high-level synthesis in both product titer and molecular weight. The pH was kept at 8.0 with a temperature of 31 °C in the first fermentation stage (0-10 h) to promote the growth of weight-average molecular weight (M _w), and the pH and temperature were maintained at 7.0 and 37 °C, respectively, in the following fermentation stage to facilitate HA accumulation. In addition, constant rates of aeration (1 vvm) and agitation (600 rpm) were adopted. The two-stage fermentation provided a balanced result in which a product titer of 4.75 g L^-1 and a M _w of 2.36 × 10⁶ Da were achieved under optimized conditions. The process introduces an effective way to produce HA considering the effect of segmented control strategy.