Optimization Of Erythromycin Cultivation Process And Scale-up From 50L To 132m~3 Scale For Improving Production With Recombinant Strain

Improving production and component were the vital problems for erythromycin industry. In our previous work,several recombinant strains were obtained by metabolic engineering of industrial Saccharopolyspora erythraea, in which the expression of eryG and eryK were enhanced. In this study, on the purpose of achieving the industrialization of recombinant strains, we first studied the time course of physiological parameters and components in 50L fermenter, and then the cultivation process were optimized with the medium components (carbon, nitrogen and phosphate, trace elements) for improving erythromycin A purity.The process were also studied to cofirm the best conditions in 25 m3 fermenter. Based the characteristics of the cell metabolism combinated with the rheological characteristics of fermentation broth, erythromycin production was successfully scaled up to an industrial scale (132 m3).The physiology study of recombinant strains revealed that there was no apparent difference between HL3168 and its recombinant derivative in 50L fermenter. The genetic modification strategy was comfirmed effective. The purity of ErA were improved from 59.93%to 68.50%, the ErB was decreased significantly from 3.28%to 0.25%and the ErC was decreased significantly from 9.08%to 1.66%. With the enhancement of activity of EryK, the ratio of ErE and ErF, which are the other two impurities of erythromycin,were increased by 47.0%and 48.6% respectively.The experiments showed that adding dextrin with increasing the ratio of corn steep liquor or ammonium sulfate, was beneficial for the microbial metabolism of recombinant strain.The quality of soy bean flour had an obvious effect on the erythromycin production.The ratio of ErC was decreased significantly with adding 0.036g/L CuCl2-2H2O or 0.1%betaine in the basal medium,or feeding ammonium sulfate in erythromycin biosynthesis phase.While adding 0.04g/L CoCl2·6H2O in the medium,the erythromycin titer reached 11851 U/ml at 186h,which was 12.4% higher than that of the control, and the ratio of ErE and ErF were decreased significantly. The glucose metabolism and the metabolic flux of erythromycin biosynthesis were enhanced markedly by adding 0.04g/L CoCl2·6H2O from the changes of intracellular and extracellular organic acids.The components advantage of recombinant strains was verified in 25 m3 fermenter. The ErA production was 7883 U/ml at 191h, which was was close to that in 50L fermenter.The high viscosity of the fermentation broth and high quantity of feeding sugar during the cultivation process were the two problems encounted while further scaling-up to 132 m3 scale. Based the characteristics of the cell metabolism combinated with the rheological characteristics of fermentation broth, the quality of seed and the fermentation process were further optimized.With these efforts, the high viscosity of the fermentation broth was decreased significantly, and the production of ErA was 6856 U/ml at 166h, which was close to that in 50L fermenter.