Arachidonic acid (AA) production by Mortierella alpina 1S-4 was investigated using a 50-L fermentor. In order to optimize the dissolved oxygen (DO) concentration and to investigate the effect of DO on morphology, cultivation was carried out under constant DO at various levels in the range of 3-50 ppm. To maintain a DO concentration above 7 ppm, two methods, i.e., the oxygen-enrichment (OE) method (experimental range, 25-90% oxygen gas supplied) and the pressurization (PR) method (experimental range, 180-380 kPa headspace pressure), were used. As a result, the optimum DO concentration range was found to be 10-15 ppm. In this optimum DO concentration range, the AA yield was enhanced about 1.6-fold compared to that obtained at 7 ppm DO, and there was no difference in the AA productivity between the OE and PR methods. When the DO concentration was maintained at 20-50 ppm using the OE method, the morphology changed from filaments to pellets, and the AA yield decreased drastically because of stress due to the limited mass transfer through the pellet wall. When the DO concentration was maintained at 15-20 ppm using the PR method, the morphology did not change, and the AA yield decreased gradually.

No abstract

No abstract

Carbon and nitrogen sources were investigated for improving peroxidase production by Arthromyces ramosus, a hyperproducer of peroxidase. Glucose as carbon source and a mixture of yeast extract and polypeptone at the ratio of 3 to 5 as nitrogen source in a production medium were shown to give the highest peroxidase activity. During the culture amino acids such as alanine, arginine, methionine, leucine, tyrosine and tryptophan were depleted. Therefore, glucose supplemented nitrogen source fed-batch culture was carried out and a peroxidase activity of 73 U/ml was obtained. This activity was 1.7 times higher than that of glucose fed-batch culture. This indicates that an adequate nitrogen source supply during the culture is effective for improving the peroxidase production by A.ramosus.

No abstract