สภาวะที่เหมาะสมสำหรับการผลิตกรดมะนาวในถังหมักขนาด 5 ลิตรโดยเชื้อ Aspergillus niger A185 / สนธวรรณ สุภัทรประทีป = Optimal conditions for the production of citric acid in A 5-l Fermenter by Aspergillus niger A185 / Sonthawon Supattaraprateep
Production of citric acid by Aspergillus niger A185 was carried out by cultivation in a suitable medium consisting of 200 g (solid content) of hydrolyzed starch with dextrose equivalent of not less than 94%; ammonium sulfate, 2.5 g; potassium dihydrogen phosphate, 0.4 g; dipotassium hydrogen phosphate, 0.4 g; magnesium sulfate, 0.3 g; copper ion (as copper sulfate), 0.5 mg; and methyl alcohol, 3% (v/v) in one litre of medium with initial pH of 6.5. Optimal conditions for shake flask culture was carried out by using 48 hours inoculums culture, at 30 ℃ and rotary shaking at 250 r.p.m. By shake flask cultivation, citric acid production of 125.6 g/l was obtained within 240 hours. The production of citric acid by 5-L fermenter was investigated using the same medium compositions as above with an initial culture volume of 3.5 litre, at 30℃, agitation speed at 500 r.p.m., and aeration rate at 1.0 v.v.m. with no pH controlled. In batch culture, 115.3 g/l of citric acid was obtained after 204 hours of cultivation while the maximum yield of 147.9 g/l was produced in fed-batch culture after 192 hours of cultivation, in which C and N sources were added at suitable time. Under fed-batch fermentation, citric acid productions were increased to 17.8% and 28.3%, higher than that by shake flask and by batch culture, respectively.