Studies On The Mutation Breeding And Fermentation Process For Bacteria Producing Gellan

The characteristics of gellan gum producing strains,breeding process of the strain and fermentation process of a new species were studied in this articl.Eventually,we won a yellow-pigment-free and antibiotics-resistant mutant strain.The yield of gellan gum was improved.The physiological and biochemical Properties was researched about the gellan gum producing strain,to determine the strain belongs to Sphingomonas paucimobilis.At the same time,its culture and fermentation conditionsits have been more suited,and the optimal conditions were listed as follows:sucrose 50g/L,soybean powder 6g/L,CaCO3 1.5g/L,MgSO40.8 g/L,pH 7.0.Finally arrive at the conclusions of the high concentration of carbon source and the ratio of carbon and nitrogen in favor of the gellan gum accumulation in the fermentation process.After the basic conditions of culturing and fermenting were studied to this strain,the breeding of the strains were studied.First,we irradiated bacteria using UV.The separating tablet of containing ampicillin was used.Ultimately,the production of gellan gum was increased by 23%.Then,the strain was again treated with ethylmethane sulfonate,the double resistance separating plate of ampicillin and rifampicin was used to select.Finally,the final double drug-resistant strain was received,especially a yellow-pigment-free and antibiotics-resistant mutant strain,the yield increased by 39%.The amplification process was researched using mutant strains,.As a result of the multi-stage amplification,the gellan was producted in 30L fermenter,but also the production fermenter plastic rate from 1.2%to 1.43%.We established the fermentation kinetics model in 30L fermenter using Logistic,Luedeking-Piret and Luedeking-Piret-Like.Obtained the mathematical fitting model of bacteria growth,gellan gum synthesis and sucrose consumption.The fermentation process can be described accurately to gellan gum,this model provides a theoretical basis for fermentation control.Furthermore,the change trend was studied in the fermentation process to molecular weight and acylation degree of gellan gum.We found that the molecular weight of the gellan gum smaller,the acylation degree does not with the extension of the fermentation time.The Plackett-Burman design and response surface methodology were used to optimize the fermentation conditions of the yellow-pigment-free and antibiotics-resistant mutant strain for gellan gum production.The optimal conditions were listed as follows:CaCO3 2.00g/L,glutamic sodium 0.54g/L,sucrose 40.50g/L,soybean flour 5.05g/L.Under optimized fermentation conditions,the yield achieve 16.78g/L,the gellan gum production was increased by 33%.The highest gellan production 16.59g/L,and between the model predictions closer to the experiment value.The description of the model has a better fit.The results from the 5L fermentor indicated that the yield of crude gellan gum reached 16.70 g/L and the viscosity of its fermentation broth was 10500mPa.s.Finally,the study of fermenting process was researched about high sugar concentration in the 5L fermentor.After,we concluded the best condition that the use of the 7%sucrose concentration.Ultimately make the rubber producing rate to 2.6%.