Study On The Fermentation Conditions Of Pullulan By Potato Syrup

Pullulan,an extracelluler polysaccharide produced by Aureobasidium Pullulans, in the process of fermentation.The pullulan is water-soluble,no-gelation,no-aging, without toxicity,easy machine-shaping and so on.It can be applied in many fields including pharmaceutical and cosmetic industry,food packaging,refreshing of fruits and seafood,tobacco manufacturing,protection of seeds and industrial sewage disposal etc.This paper used potato as its raw material,the potato starch syrup of different DE values which liquefacted byα-amylase was used as the carbon source of the mutant strain Aureobasidium pullulans D1-11.The influence of different saccharification enzymes(SNase303 glucoamylase orβ-amylas) and treatment methods(decolor and desalt treatment) were studied by the rotational composite design of quadratic regression experiments.Polysaccharide yield,biomass,pigment content are the detection index in this study.There are three different experiment designs such as the orthogonal experiment design and the uniform design used to studied the effects of fermentation conditions and nutritional conditions on pullulan fermentation, fermentation conditions include liquid volume in flask,pH,inoculum size, fermentation temperature,nutritional conditions include the carbon source and divalent cation.The results showed that:1.The optimal formulation was obtained by the single factor screening test and the L₉(3⁴) orthogonal experiment design,that was 25%liquid volume in flask,pH6.5, fermentation temperature 30℃,fermented with 8%inoculum size,the proper order of influential factors is liquid volume in flask,temperature,the inoculum size,pH,the yeild of pullulan can reach 19.71g/L under this fermentation process.2.The liquefication technology of potato syrup by medium temperatureα-amylase was obtained by single factor screening,that was 25%concentration of potato,10u/g dosage of medium temperatureα-amylase,50 min of liquefaction.3.Based on the single factor screening test for the saccharification process,a second-order model was obtained with a correlation coefficient 0.9831(a＜0.05), through multiple regression analysis.Analysis of the response surface showed that dextrose equivalent(DE) 20-60%were prepared at 60℃,pH3.8-4.5 by altering the amount ofβ-amylase(30-90u/g),digested time(3-5h) and the dextrose equivalent (DE) of liquefication(15%-19%).The carbon resource was made from potato starch, which could meet standard requirement.The results had the capability of providing the basis for pullulan in the next step.The proper order of factors influent saccharification liquid was digested time,the amount ofβ-amylase,the dextrose equivalent(DE) of liquefication.4.Based on the single factor screening test for the saccharification process,a second-order model was obtained with a correlation co-efficient 0.9823(a＜0.05) through multiple regression analysis.Analysis of the response surface showed that dextrose equivalent(DE) 20-60%were prepared at 60℃,pH3.8-4.5 by altering the amount of glucoamylase(150-250u/g),digested time(3-5h) and the dextrose equivalent(DE) of liquefication(15%-19%).The carbon resource was made from potato,which could meet standard requirement for pullulan.The proper order of factors influent saccharification liquid was digested time,the dextrose equivalent(DE) of liquefication,the amount of glucoamylase.5.The single factor screening test including the carbon source and divalent cations,the syrup maded byβ-amylase and decolor and desalt treatment was superior to SNase303 glucoamylase.The best result was the potato syrup byβ-amylase in DE 50%80 g/L,CaCO₃ 0.1 g/L,the yield of pullulan was 21.98 g/L,21.11 g/L.6.The optimal formulation was obtained by the uniform design,that was:CaCO₃ 0.06 g/L,β-amylase in DE 50%82.25g/L,26.62%liquid volume in flask,fermented with 11.99%inoculum size,pH 7.5,the production of pullulan can reach 28.90 g/L under this fermentation process;an analysis of variable was indicated that the carbon source was the most influential factor.