Screening For High Lysozyme-Yielding Strains And The Studies On Fermentation Of Producing Lysozyme

Systematic study on the screening of lysozyme-yielding strains,liquid fermentation of lactase high producing strain S2-6b and enzyme properties were carried out in this paper. The main results were as following:Screening of high-yielding lysozyme strains,the method of the primary screening has three standards,lyric zone on the double layer plates,lyric zone of liquid fermentation, identifying the ferment product,respectively,the second screening was enzyme activity assay.Then we obtained a bacterium named S2-6b from the orchard soil sample from Agricultural University of Hebei.It included that we can find the high-yielding lysozyme strains by the optimal method.The strain S2-6b was identified.Through optic microscope and scanning electron microscope,the S2-6b's modality,size wsa observed.Modality,size and colour of colony both on broth agar culture medium were described.Through the traditional physiological and biochemical test,together with the 16SrDNA sequence and phylogenetic analysis,the strain S2-6b was finally ascertained to be Lysobacter(Lysobacter S2-6b).The fermentation conditions of Lysobacter S2-6b,including carbon source,nitrogen source,inorganic salt,surfactant,temperature,formation time,pH value and so on,were investigated in shake flask level.The orthogonal test of the three factors showed that the optimized culture medium was soluble starch 1.5%,meat-extract 2.5%,corn steep 0.5%, Tween-80 0.1%.Through shake flask experiments,the optimum fermentation conditions for S2-6 strain were 28℃incubation,inoculum's level 3.0%(V/V),volume ratio 40mL/300mL,shake speed 200rpm formation time 40 h and initial pH 7.5.The maximal activity was 6 167 U/mL under the optimum conditions,which was about 3 times of the initial strain.The test of crude enzyme indicated that optimal temperature of Lysobacter S2-6b was 75℃,the half life of reaction temperature was 17.3 min.Optimal pH was 7.0 and it was stable at pH 3.0-11.0 at room temperature.The metal irons and reagent Mg²⁺,Mn²⁺,Cu²⁺, Al³⁺,Ca²⁺,SDS have inhibited on lysozyme.EDTA has activation on lysozyme.Compared with chicken lysozyme,the Lysobacter S2-6b lysozyme has more widely antimicrobial spectrum.Lysobacter S2-6b lysozyme has different effect on experimented bacterium.