Mutation Of Gellan Gum Strain And Fermentation Optimization

Gellan gum as a kind of industrially useful exopolysaccharides fermented by Sphingomonas paucimobilis was acknowledged in recent years.It has a wide range of applications in the food industry,pharmaceutical industry,chemical industry.The function of gellan gum mainly focus on thickening agent,suspending agent,emulsifying agent,and stabilizer.The characteristic of low dosage,high transparency,strong aroma release support gellan gum become second largest exopolysaccharides except xanthan gum and has favourable market prospects.In this paper,Sphingomonas sp.WZW002 as original strain was selected with rifampicin,meanwhile different nitrogen source was applied to improve gellan production.Our works about this thesis included as follows:(1)Based on the principle of ribosome engineering,3-5 times rifampicin of minimum inhibitory concentration(MIC)2.0 mg/L was used for isolating gellan strain of high yield.According to the theory of identifyingmicroorganism by infrared spectrum(FTIR)and analysis method of lambert beer law,we established a high-throughput screening method.The gellan production of mutant strain was 17.2g/L and increased by 5.8% compared with original strain.(2)Feasibility of utilizing cottonseed meal(CSM)as nitrogen source to improve gellan production was investigated.The optimization of fermentation process showed that concentration of CSM was 0.6%,particle size to select 60 mesh,loaded liquid of fermentation was 60 ml,under these conditions,gellan production could reach at 20.4g/L.At the same time enlarged fermentation with 5L mechanical agitation tank,gellan production could be improved to 23.6g/L with CSM as nitrogen source,much better than that with soybean meal(SBM).(3)Amino acid composition and element composition analysis of CSM was studied to explain mechanism of high yield.The research showed glutamic acid,2.0% Na H2PO4 and low-dose gossypol could improve gellan production.The following experiment confirmed CSM as a delayed nitrogen source had great influence on gellan production.Structure analysis,molecular weight and gossypol determination ensured the reliability and security of gellan gum fermented by CSM.