Optimization Of The Clavulanic Acid Fermentation Process

The effects of working volume, carbon source, nitrogen source, surfactant, and inorganic salt on the cell growth and clavulanic acid (CA) biosynthesis were investigated in shake flasks. The results showed that, when the working volume of culture was50mL in500mL Erlenmeyer flasks,4497mg/L CA was reached, which was43.5%higher than that obtaind in25mL culture. Streptomyces clavuligerus could not grow in the medium with glucose as the sole carbon source, but starch or modified starch did.In50L fermentator, with the modified starch as supplement carbon source6047mg/L CA was obtained, which was similar level to that of the processes using glycerol as the carbon source (6363mg/L).The effects of different nitrogen sources on the production of CA were studied. The results showed that the cottonseed protein was the best nitrogen source for the biosysthesis of CA among the11nitrogen sources, and4348mg/L CA was achieved. Cluster analysis method was used to analysis the effect of amino acid composition of different nitrogen sources on the CA biosynthesis. It was found that aspartate, glutamic acid, threonine, lysine and methionine had great influence on the biosynthesis of CA. When1.0%of aspartate, glutamic acid, threonine, or lysine was supplemented in the culture, CA production increased by22.3%、39.3%、16.3%or6.3%, respectively, while adding1.0%of methionine, the CA production reduecd by23.29%.Trition X-100and low concentration of CTAB were of benefit to the biosynthesis of CA, while SDS had a strong inhibitory effect. When adding1.00%of Trition X-100or0.1%CTAB to the medium at60h, the concentration of CA increased by24.24%and11.9%, respectively.Agitation rate had obvious effects on cell growth, viscosity of broth, dissolved oxygen, and productivity of CA. When the specific air flow rate was1.0vvm and the stirrer speed was kept constant at700rpm, the final titer of CA was68%higher than that in the conditions of1.0vvm and500rpm. At the same time, we studied the effects of two different combination of impeller on the fluid dynamics of the broth in the120m3fermentator. The results showed that in the fermentor with Rushton combination, the consistency index K was19.7%higher than that with Mix combination. While the gas holdup distribution in the fermentor with Mix combination was25%higher than that with Rushton combination.