High Thro?ghput Screening Of High-yield Cephalosporin C Producing Stain And Measurement Of The Oil Contents Of Bioprocesses Using Low-field NMR

Due to the discovery of low toxic and broad-spectrum antimicrobial property,the global market for Cephalosporins is growing rapidly,which also attracts a great deal of attentions on industrial production of the common precursor,cephalosporin C(CPC).In this study,CPC fermentation process by Acremonium chrysogenum was optimized by multi-levels integration of strain and equipment as well as process technique,including selection of high-yield strain,application of advanced instrument,and simulation of field characteristic in shake flask.It has been generally believed that strain mutation and selection can improve the fermentation performance of industrial strain efficiently.In order to obtain a cephalosporin C(CPC)high-yield strain,atmospheric and room temperature plasma(ARTP)was employed as mutation mode,and subsequently,all the mutants with equal screening chance by a mixture culture method combined with a high-thro?ghput screening bioassay was adopted.As a result,the high-yield and stable strains 1A-1?6G-2?6G-3?6G-5 was successfully screened out and the CPC titer of 6G-2 was nearly 20.39%higher than that of the parental strain W-6 in the shake flask.Oil,as one of the carbon sources in CPC production,plays a vital role on bioprocess regulation.Tho?gh Low-field NMR(LF-NMR)analysis technology has been applied to detect oil concentration in our previous works;Carr-Purcell-Meiboom-Gill(CPMG)experiments were conducted to construct the transverse relaxation time(T2)distribution curves,and the excellent results were achieved,with correlation coefficient of 0.9998 for the oil mass and the relative peak area in the fermentation broth for the T2 distribution curve.Therefore,it could be concluded that LF-NMR had a great potential to monitor oil level in bioprocesses.After optimization of measurement conditions,LF-NMR analysis technology was successfully applied to the oil contents determination for CPC fermentation process.On the other hand,oxygen supply and mixing are commonly considered to be important for cell growth and metabolism in CPC production.A systematic study to elaborate the effects of baffles on physiological characteristics of A.chrysogenum was investigated.Computational fluid dynamics(CFD)technique was used to simulate and calculate the oxygen transfer related parameters in baffled flask,showing that the baffled flask was superior to unbaffled flask on both mass transfer capacity and mixing.Furthermore,thro?gh the analyses of CPC titer and KLa value in baffled flask with different filling volumes,the CPC titer in baffled flask was nearly 50%higher than that of unbaffled flask under the filling volumes of 30mL.The results demonstrated that significant improvement of CPC production could be achieved by adopting suitable working volume.