Study on L-Malic acid production by submerged fermentation

Aspergillus wentti F-891,which had been treated with 60Co,was screened as the strain to convert fumaric acid to L-malic acid in 1000 L fermentor by submerged fermentation.The fermentation conditions such as the variations of air velocity,temperature,pH and rotation speed,which could affect the conversion rate of fumaric acid and production of L-malic acid,were investigated.The result showed the average conversion rate of fumaric acid and the average L-malic acid yield were 82.18% and 107.39 g/L,respectively,under the optimum conditions:concentration of fumaric acid 11%;air velocity (v/v/m) 1:1.08 (0-48 h) and 1:1.20 (48-108 h);temperature 30℃ (0-48 h) and 25℃ (48-108 h);original pH 6.0-6.2;fermentation period 96-108 h;rotation speed 200 rpm.