초록
<P>Citric acid (CA) is the most important commercial product which is produced by using various sugar substrates in the terrestrial environment. The present study made an attempt to produce citric acid by the fungal strain Aspergillus niger from red seaweed Gelidiella acerosa is the best alternative to sugar substrate in the marine environment. In this study three types of production media were prepared including control (sucrose) by following standard fermentation conditions. The acid production was indicated by the reduction of pH levels. The control medium gave the highest yield of 80?g/l at pH 1.5 and the medium containing crude seaweed powder and other compositions gave the yield of 30?g/l at pH 3.5 whereas the medium containing crude seaweed and 10% sucrose gave the yield of 50?g/l at pH 3.0. When calculating the benefit cost ratio, crude seaweed powder and 10% sucrose yielded 50?g of citric acid at the lower cost of Rs. 35, whereas the other two media gave the yield of 80 and 30?g respectively with the cost of Rs. 77 and 28. In economic point of view, the medium containing seaweed and 10% sucrose showed more benefit with lower cost.</P>