Studies On The Technology Of ε-poly-L-Lysine Production By Streptomyces Albulus

In order to enhanceε-poly-L-Lysine(ε-PL) production by Streptomyces albulusfermentation, the fermentation conditions and extraction technology ofε-PL fromculture broth were inverstigated as following:①explored the conditions ofε-PLfermentation in shake flask;②optimization of batch fermentation conditions ofε-PLproduction in 50 L autocontrol fermentor;③compare of different fed-batch methods;④the primarily study of the sepatation and extraction ofε-PL from culture broth.The effects of temperature, pH and culture medium amount onε-PL productionin shake flask were studied, it was a foundation work for optimization of batchfermentation in 50 L fermentor. The results indicated that the suitable temperature forS. albulus growth andε-PL polymerization is 30℃, the situation at 28℃wassimilar to 30℃, but the accumulation ofε-PL was lowest at 32℃; The productionofε-PL with pH control was enhanced to 1.59 g/L from 0.89 g/L without pH control;The culture medium volume of 100 mL in 500 mL shake flask was favorable for thegrowth of cells and synthesis ofε-PL.The researches showed that temperature, pH and stirrer speed played importantroles on the batch fermentation ofε-PL in 50 L autocontrol fermentation jar. Theoptimal temperature for S. albulus growth andε-PL synthesis was 30℃, the same asin shake flask, the low yield ofε-PL was accompanied by the low rate of cells growthat 32℃; The residual glucose concentration was still 20.1 g/L at pH3.0, low pHwould benefit neither cells growth norε-PL synthesis, the high accumulation(3.05 g/L)ofε-PL was achieved at pH4.0, and the high dry cell weight(12.88 g/L) wasobtained at pH5.0, however, when pH shifts to 5.0 or higher, the accumulatedε-PLwas depolymerized; High stirrer speed accompanying high dissolved oxygen wouldimprove the growth of cells and synthesis ofε-PL, and the dissolved oxygen wassufficient to meet the requirement of cells growth at 200 rpm, however over highstirrer speed such as 400 rpm would damage the mycelium so as to decreaseε-PLproduction.Under the optimized condition: 30℃, initial pH6.8, aeration 1 200 L/h, stirrer speed 200 rpm at prophase of culture, at anaphase, stirrer speed 300 rpm, pHcontrolled at 4.0, after 84.5 h culture, the yield and productivity ofε-PL was 3.21 g/Land 0.065 g.ε-PL/g.sub respectively, the yield ofε-PL was increased by 310% from0.78 g/L.Two different kinds of fed-batch culture were investigated, the results showedthat fed-batch culture was fitter forε-PL production with S.albulus than batch culture.In addition, pH control and variable speed fed-batch culture was superior to glucoseconcentration control and span fed-batch culture, both the yield and productivity ofε-PL with former tactic were higher than the latter, they were 7.36 g/L and 6.53 g/L,0.072 g.ε-PL/g.sub and 0.068 g.ε-PL/g.sub, respectively. The reason was likelyattributed to that the latter fed-batch culture way would bring a tremendous change ofculture system due to the addition of great volume nutriment with high concentration,and lead to the disorder of metabolism, but the former way could keep a continual andstabile condition for cells growth andε-PL synthesis.Then, the separation and extraction ofε-PL from broth was pilot studied. In theprocess of broth pretreatment, filtration was likely to leadε-PL losing; The weak acidcation-exchange resin D152 was choosed to separateε-PL from pretreated broth, theeluent was 0.1 N hydrochloric acid, velocity of flow was 2.5 mL/min, theconcentration ofε-PL was condensed by 229%, coefficient of recovery reached78.83%; decolorized with activated charcoal could decrease the loss ofε-PL.