Study On Mutation Of Natamycin Producing Strains And Optimization On Their Fermentation Conditions

Natamycin is a polyene macrolide antibiotics, It can be restrained effectivelybacterium and yeast, natamycin has the characteristic of strong inhibition, safe,non-toxic, using broadly, good stability and so on. It have been used for food transport,processing and storage. Because the strain selection and fermentation technologyresearch start later at home, leading to the natamycin yield had relatively low yield,high cost of production, limited to the development and use of natamycin, the study ofselection of natamycin-producing strain and the optimization fermentation conditionis particularly important. In this project, study on mutation of natamycin-producingstrains and the optimization of its fermentation condition, in order to improve thenatamycin yield, reduction in production cost of natamycin, it will further expand thescope of its application areas.The full wavelength was made for Natamycin standard sample, the result showedthe optimal determination wavelength was303nm. The natamycin standard samplewas measured by HPLC and UV respectively. The optimal HPLC conditions ofnatamycin were as follows: the ratio of mobile Phase was methanol,water and glacialacetic acid was60:40:5,C18column (250mm×4.6mm),flow speed was1mL/min,injection volume was20μl(Based on GB/T21915-2008).After calculation we got thelinear regression equations were Y=42332x-5768,R~2=0.9997and Y=0.1077x-3E-05,R~2=0.9999. In order to reduce culture medium affect the result during thedetermination processing, the fermentation liquid was treated as follows：oscillatorshocking for1min,then ultrasonic treating for30min,and then centrifugal for15minat4℃,diluted the supernatant with methanol and used it as the sample whichwould bemeasured.CS11was mutanted with ion implantation and chemical mutation, three mutantswas obtained by streptomycin sulphate resistance screening. The natamycin yield wasup to1.86g/L, which was increased by0.8times over the original strain. the resultwere obtained through conical flask culture fermentation test: six continuous fermenting,the decrease of production less than11%,the results showed that a mutantwith inheritable qualities.The culture medium composition and the fermentation condition of strain wereoptimized, this method to get the strains on the good growth state and to the highestyield of natamycin. In this paper, glucose was the sole carbon source, the peptone wasnitrogen sources were found to be most suitable ones for fermentation process ofnatamycin by single factor experiment. The effects of initial pH value on fermentationwere studied. The optimal formula of medium through the response surfaceexperimentation was that glucose48.5g/L,peptone25g/L, yeast extract Powder7.5g/Land orginal pH value6.5, The optimum fermentation conditions were6%inoculumsvolum,medium volume was40mL/250mL, fermentation temperature was28℃.Base on the above optimum condition of fermentation in conical flask, the batchfermentation was performed in10-liter fermentor, and the dissolved oxygen conditionof fermentor were optimized in this dissertation, Base on the dissolved oxygenexperiment,it have been finished for the study of the added sugar in the process offermentation. The results show that when the inoculum concentration is6%,ventilatory capacity was4L/min, rotational speeds was550r/min, dissolvesoxygen not be lower than30%,sugar concentration was maintained above10%,fermentation period120h, The yield of natamycin from4.038g/L to5.476g/L,whichis increased by35%.