Abstract
A red-pigmented bacterial strain NS-17 was isolated from soil, and physiological and biochemical characteristics and 16S rDNA analysis established this organism as a strain of Serratia marcescens. The red pigment isolated from cells of NS-17 was identified as prodigiosin. By analyzing factors affecting the production of prodigiosin, modified medium and culture conditions were set up, and a continuous fermentation method was carried out to take advantage of the mass production of foam during fermentation. Continuous fermentation was achieved in the following conditions: 32℃, 1:1 ventilation ratio, and medium with a nutrient concentration 5-fold higher than that of the fermentation medium (with half the inorganic salt concentration) supplied as a feed medium at a flow rate of 8 mL/min. For the first time of continuous fermentation of Serratia marcescens coupling with foam flotation, a high yield of prodigiosin was obtained. After 56 h of culturing, the total harvest of cells was enhanced 2.33-fold compared to that of batch fermentation, the total amount of prodigiosin was enhanced 2.70-fold compared to that of batch fermentation, and cells and prodigiosin were concentrated in the efflux broth automatically.
Highlights
A red-pigmented bacterial strain NS-17 was isolated from soil, and physiological and biochemical characteristics and 16S rDNA analysis established this organism as a strain of Serratia marcescens
For the first time of continuous fermentation of Serratia marcescens coupling with foam flotation, a high yield of prodigiosin was obtained
The traditional production of PG was by batch fermentation, but the yield was not sufficiently high, and because the fermentation process produces considerable foam, operators must add a large amount of defoamer, which is not conducive to downstream extraction and purification
Summary
Prodigiosin (PG) is a family of natural red pigments extracted from some species of Streptomyces, Serratia, Pseudomonas and other genera [1] [2]; these pigments are a kind of typical alkaloid compound produced as a secondary metabolite. Some members of this pigment family have shown a variety of drug activities, such as antibacterial [3], antifungal [4], antimalarial [5] [6], antialgal [7] [8], immunomodulating [9] [10] and antitumor [11] [12] activities, displaying important medicinal properties. To improve the yield of PG and to avoid requiring defoamer, the S. marcescens cells were continuously separated from the broth by the foam produced during fermentation, and the efflux broth was collected
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