The Study Of Technology On Fermentation Coupling With Foam Fractionation

Fermentation coupling with separation processes, which is also known as in situproduct removel (ISPR) is a technolgy. This technology selects a suitable separationmethod while ferment is going. By this, the product or byproducts which have toxic effectsor inhibition effect on cell or biological reactions will be removed promptly from the cells,surrounding. This paper investigated fermentation coupling with separation to produce nisinand polymyxin E. Those products accumulation will cause feedback inhibition to theirbacteria, which will also limit the production. Since the two kinds of antibiotics are bothsurface active substances, this paper chose foam fractionation coupled with fermentation toimprove the yield of the products.Nisin is a polypeptide bacteriocin produced by certain Lactococcus lactis. Nisin iswidely used as an effective non-toxic natural preservative in food industry. In this paper,Lactococcus lactis subsp. lactis was used to produce nisin. In order to improve the yield ofnisin, based on previous works in our research group, this paper studied on the process offermentation coupling with foam fractionation and membrane module for nisin production.First, we improved the bioreactor which was designed for recovery of nisin fromfermentation broth by foam fractionation and membrane module. A foam fractionationcolumn installed in the bioreactor was perforated at its wall at the lower part and the poreswere covered by membrane (0.45m in pore size), thereby to provide an anaerobicfermentation conditions, and also prevent the cells are brought out of the fermenter by thefoams. After verifying the feasibility of the new coupling bioreactor, we used thisbioreactor to produce nisin. The effects of air flow rate, the initial aeration time and intervaltime on the performance of the technology were studied to increase the yield of nisin. Theresults showed that under the optimal conditions of air flow rate60mL/min, the initialaeration time of the fourth hour and regular30-min interval, the total nisin titer reached3946IU/mL, increased by24.2%, compared with the control group (3177IU/mL).Polymyxin E, an antimicrobial peptide produced by fermentation using certain strainsof Paenibacillus polymyxa, with the advantages of heat-resisting, gastrointestinal easyabsorption, excretion rapid, low toxicity, no side effects, hard to produce drug-resistantstrains, is considered to be one of the safest animal growth promotion antibiotics. Becauseof the Bacillus polymyxa is an aerobic bacterium, this paper aerated directly into thefermenter in situ removal of the product to production polymyxin E. First, we investigatedthe effect of air flow rate on the fermentation coupling with foam fractionation. Based onthe problem of poor foamability of polymyxin E, we propose to add a certain amount ofSDS in the coupling operation. We investigated the effect of different concentrations of SDS and the methods for adding on the total titer of polymyxin E. The results showed thatunder the optimal conditions of air flow rate100mL/min, added0.002g/L SDS disposablythe total polymyxin E yield reached8.00×106U, increased by32%, compared with thecontrol group (6.03×106U).