产黄原胶降解酶放线菌筛选及发酵工艺研究

Actinomycetes Strains Screening for Xanthan-degrading and Study on Ferment Conditions for Enzyme Producing

【目的】黄原胶是植物致病菌野油菜黄单胞菌所分泌的胞外多糖,其主链类似纤维素很难降解,可作为生物胶用于增稠剂、悬浮剂、乳化剂和稳定剂,还能引起十字花科植物黑腐病。筛选分离对黄原胶有显著降解作用的放线菌,以生物方法降解黄原胶,降解产物黄原胶寡糖可有效防治黑腐病,具有开发为生物农药的潜力。【方法】从自然土壤样品中进行分离筛选、纯化、16S rRNA鉴定及诱变选育,获得高效降解黄原胶放线菌菌株,通过发酵工艺研究,确定最适产酶条件。【结果】优化产酶培养基配方为:蔗糖3%,(NH4)2SO40.5%,KNO31%,酵母膏0.1%。菌株发酵产酶培养条件为:发酵温度28℃,pH 7.5,500 mL瓶装量为150 mL,底物浓度0.5%,接种量为5%。【结论】获得一株高效降解黄原胶的链霉菌(Streptomycessp.),优化其产黄原胶降解酶的摇瓶培养基及培养条件,发酵液黄原胶降解酶的酶活达到200 IU/L。

【Objective】Xanthan is a kind of extracellular polysaccharose（EPS） produced by a plant pathogen of Xanthomonas campestris.It has a main chain structure similar to cellulose and is difficult to degrade,and can be widely used for thickening agent,suspending agent,emulsifying agent and stabilizing agent as biogel with its special physical properties.However,it can also cause black rotten disease for crucifer.The purpose of this program is to obtain oligosaccharide produced by biodegradation of xanthan which used for biochemical to control black rotten disease by screening actinomycetes strains for xanthan-degrading.【Method】The program was carried out by screening actinomycetes strains from natural soil based on xanthan-degrading ability,identifying by 16S rRNA analysis,selecting mutants by ultraviolet mutation for higher enzyme activity,and studying on ferment conditions for enzyme producing by one factor and orthogonal tests.【Result】A strain of Streptomyces sp has been obtained,and the xanthan-degrading enzyme activity of its fermentation liquid reached 200 IU/L after culture medium and ferment conditions optimization.