Study On Fermentation Kinetics And Extraction Technology Of ε-poly-l-lysine

Natural preservation is a kind of food preservation with broad prospects for development. Natural preservation has become the hotspots of research in recent years. ε-poly-L-lysine(ε-PL) is a kind of polypeptide compounded synthesized by Streptomyces albulus. It is composed of 25~30 lysine residues and it is a kind of natural food preservation with high safety performance, excellent anticorrosion performance and tremendous commercial potentials. In this paper, Streptomyces albulus were used as a strain, the fermentation kinetics pattern was studied and extraction technology of ε-PL was optimized. The main results obtained as follows:(1) Batch fermentation for ε-PL by S. albulus was carried in 25 L fermentor, the rules of biomass, ε-PL yield and sugar consumption in the process of fermentation was analyzed. According to these rules, ε-PL synthesis was believed as part growth associated type. After the test data were fitted by Logitstic equation、Leudeking-Piret equation and similar Leudeking-Piret equation, the batch fermentation kinetics model was established wih high R2 value and adj-R2 value.(2) The adsorption conditions of ε-PL by ion exchange resin were studied by the single factor tests and response surface analysis and adsorption rate as indexed. The maximum adsorption rate of ε-PL by HZD-3B resin(97.69%) was obtained at pH 8.5, the initial ε-PL concentration 40g/L, the resin amount 150g/L, and adsorption time 13 h. Under the optimal condition, the was; The maximum adsorption rate of ε-PL by D155 resin was obtained at pH 8.0, the initial ε-PL concentration 40g/L, the resin amount 150g/L, and adsorption time 14 h. The adsotprion data were better fitted by Freundlich equation and pseudo-second order kinetics equation.(3) The desorption rate of ε-PL was used as the index to optimize desorption condition ε-PL adsorpted into two resins. The maximum desorption rate(87.98%) from HZD-3B resin was obtained at 0.4mol/L HCl, desorption time 8h, and desorption temperature 30 oC. The total recovery yield of ε-PL was 85.95% using HZD-3B resin. The maximum desorption rate(97.57%) from HZD-3B resin was obtained at 0.4mol/L HCl, desorption time 10 h, and desorption temperature 30 oC. The total recovery yield of ε-PL was 94.49% using HZD-3B resin. According to these results, the D155 resin was selected to isolate ε-PL.(4) Extraction process of ε-PL of fermentation was preliminary established by the conditions optimization of three key opration process including fermentation liquor pretreatment 、 ionexchange and decoloring. After fermented liquor was hot-pretreated at pH 3.0 and 70 oC for 30 min, the loss rate of ε-PL less than 5%, protein remove rate with 84%~86% was obtained. The infrared spectrum analysis and scanning electron microscope showed that D155 is mainly adsorbed loosely on the surface of resin and interior hole of resin; HZD-3B is mainly adsorded tighly on the surface of resin. The maximum decolorization rate(87.85%) using active carbon as decolorizing agent was obtained at 3%(W/V) active charcoal LT-720, pH4.0, 90 oC for 90 min. The recovery rate ε-PL reached 93.01%.(5) Analysis of HPLC、FTIR、SRD indicated that spectrograms of ε-PL sample are perfectly consistent with those of standard of ε-PL. The high purity ε-PL products could be obtained by the optimization process.