| Pullulan,a kind of exopolysaccharides produced by Aureobasidium pullulans,has a number of favorable performances such as film-forming,high adhesion,low digestibility,nontoxicity and other characters and is used widely in food ,pharmaceutical,chemical industry.petrochemical and light industries etc. It is even drawing more and more attentions. In this paper.production of pullulan with apure culture of Aureobasidium pullulansAs3.3894 was investigated and fermentation was conducted on cane molasses,which was used as as carbon source.We also systematically studied the feasibility of fermention on cane molasses.the growth curve of As3.3894,the conditions for pullulan production on cane molasses.the dynamic processes of fermention.the SEM structure of pullulan film and the application of the film in mango fruit preservation.Cane molasses is full of fermentable components such as carbon and nitrogen source, which can be used as produce pullulan, but the fermentation conditions should be optimiazed. The tolerable test showed that concentration of cane molasses below 200g/L was feasible for A. pullulansAs3.3984 to grow and produce pullulan. The growth curve of A. pullulansAs3.3984 indicateed that its exponential phase is 12-18h after vaccinated.The anthranone method used as pullulan assay was studied, and this method had an average relative error of 0.6%.The effect of molasses, nitrogen source, salt and the optimum initial pH value of medium on pullulan production of A. pullulansAs3.3984 were studied. Based on biomass and yield of polysaccharide, the suitability of fermatable medium was obtained, Compositions of the initial medium were as following:canemolasses, 120g/L;(NH4)SO40.4g/L;MgSO4,1.0g/L;MoCl2.0.4g/L, and pH,5.5.Exopolysaccharides production was studied when As3.3984 was growing in of fermatable medium and the fermenting conditions were suitable.the best culture conditions for A. pullulansAs3.3984 to synthesis pullulan were that inoculation amount is 15% of cultures ,with fermentation at30 and adequated oxygen for 144h.Constant pH method for exopolysaccharides produced by A. pullulansAS3.398 was studied .It was showed that the method could both increase yield of exopolysaccharides and deduce the fermentation time, and the maximum yield of pullulan was 25.09g/L and fermention time was J20h.The pullulan production by batch fermentation of A.pullulansAs3.398 as well as the kinetics of fermention process were studied Based on Logistic equation and Luedeking-piret,the dynamic equation describing the pullulan production , biomass substrate (cane molasses ) consumption were obtained .At the same time the experimental data and the model values were tested .veified and compared.The structure of pulluan was studied by applying Fourier transform infrared(FTIR) techniques. The FTIR spectra of pullulan showed that the structure of pullulan sample from the fermention process was the same as the standard.the surface tructure of pullulan film was observed by applying Sanning Electron Microscopy (SEM), it showed that the surface of mango fruit was coated by the film and its widpipe was sealed.Respiration kinetic of mango fruit before and after being coated were studied, and dynamics equations among respiratory intensity (Rco2), coefficient of penetrating(Pg), temperture(T), the carbon dioxide concentration(Y), time(t) and etc. were established .the dynamice equations were as follows: Rco2=0.331/y1.9112 (uncoated) and RCO2=6.15 10-2/y2.2723 (coated). The preserving effects to mango of pullulan film were analysed.The experimental results showed that the sense and internal quality mango fruit were influced by pullualn film working in coordination with PE film, Excellent quality and the best presreving effect were obtained. when mango fruit was coated by 3%pullulan film... |
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