Author(s): Madihah Md Salleh
The effect of different methanol concentrations (1-6 percent v/v) in growth medium on kojic acid production by Aspergillus flavus Link was studied using shake flask experiments. A slight growth inhibition of A. flavus in medium containing methanol at concentrations of up to 4 percent (v/v) was observed; however, kojic acid production was greatly enhanced. Both growth and kojic acid production were greaty inhibited when methanol concentration of above 5 percent (v/v) was used. The highest kojic acid production (40.7-41.7 g/L) was obtained in medium with 3-4 percent (v/v) methanol, which gave the yield based on glucose consumed and overall productivity of about 0.47 g/g and 0.072 g/L.h, respectively. In comparison to fermentation with no methanol, the improvement of kojic acid production in terms of maximum concentration, yield based on glucose consumed and overall productivity was 2, 4.6 and 1.7 times higher, respectively. The average size of the pellets depended on the concentration of methanol added to the medium. A linear inverse relationship between kojic acid production and pellet size was observed, suggesting that kojic acid production depends on the oxygen transfer rate.