Study On The Breeding And Fermentation For Gellan Production

This study was carried out in an attempt to address the technical problems associated with the process of gellan fermentation production. We use the Sphingomonas elodea JLJ as the fermentation strains. Then VHb gene was expressed in Sphingomonas elodea JLJ to improve oxygen uptake and utilization. It enhanced the growth of the strains in the hypoxic environment, and increased gellan yield.First, combined with the feature of morphological, physiological, the biochemical characteristics and16S rDNA sequence analysis, to determine the strain JLJ is the Sphingomonas elodea JLJ. Secondly, we cloned the vgb and its native promotor from the Vitreoscilla, transformed into the JLJ and got the transformant JLJ-VHb+. Biochemical activity of expressed VHb was confirmed by PCR, SDS-PAGE and the CO-difference spectra analysis which exhibited a characteristic absorption maximum near420nm. The results showed that the expression of VHb could enhanced cell growth. The composition of fermentation medium and the physical conditions of cultivations were investigated. The optimum medium were consist of: Sucrose3%, Soybean meal0.5%, NaNO30.1%, KH2PO40.1%, K2HPO40.15%, MgSO40.06%. The optimum fermentation conditions were confirmed:pH6.0, seed age16h, inoculum volume10%,200r/min,30℃, and the maximum gellan yield of VHb+recombinant was1.713%±0.02%after cultivated72h,42%higher than that of the parental strain.VHb exhibited positive effect on cell growth and optimize gellan yield. The results provided potential applications of VHb in other industrially important strains to solve the increasing demand of aerobic processes in polysaccharides production.