Perfusion culture of the diatom Nitzschia laevis for ultra-high yield of eicosapentaenoic acid

Abstract

In the development of high yield of eicosapentaenoic acid (EPA) by the diatom Nitzschia laevis, substrate limitation and toxic metabolite inhibition were the two principal obstacles. In the present study, a perfusion culture was developed to eliminate substrate (glucose) limitation and by-product inhibition simultaneously. Using an exponential feed strategy and manipulating glucose supply rate and by-product removal rate, the optimal glucose concentration in the feed medium was determined to be 50 g l-1. With this feed glucose concentration (S0 = 50 g l-1), the perfusion culture resulted to a cell dry weight concentration of 40 g l-1. Such a high cell density led to an EPA yield of 1112 mg l-1, which is the highest ever reported in microalgal cultures. In addition, the perfusion culture (at S0 = 50 g l-1) greatly reduced the amount of wastewater (broth) during cultures. Considering the simple set-up and operation, the proposed perfusion culture is potentially useful for large scale EPA production by N. laevis. © 2002 Elsevier Science Ltd. All rights reserved.