碳氮比对固氮菌株WN-F合成胞外多糖的影响

摘要

The aim of this study is to isolate a nitrogen-fixing strain of producing high-yield polysaccharide from the cultivated maize soil samples around the Long-term Positioning Experiment Station of Brown Soil in Shenyang Agricultural University,and to study the strain identification,the optimization of culture conditions,and the relationship between nitrogen fixation and sugar production.The identification of the strain was carried out by morphological observation and molecular biology.The growth and culture conditions of the strain were determined by analyzing microbial hiomass via enzyme mark instrument.The relationship between nitrogen fixation and sugar production was analyzed by measuring OD60o and polysaccharide yield.Results showed that the strain was Bacillus aryabhattai and named as WN-F.WN-F strain reached its highest growth at 37 ℃ and 180 r/min for 12 h.The medium was optimized as the formula (L-1):sucrose 20 g,beef extract 2 g,KH2PO4 0.4 g,MgSO4 · 7H2O 0.4 g,NaCl 0.4 g,CaSO4 · 2H2O 0.4 g and CaCO3 2 g.The polysaccharide yield of strain WN-F showed a parabolic relationship with the increase of initial nitrogen concentration,and the proper carbon nitrogen ratio promoted the synthesis of extracellular polysaccharide.B.aryabhattai WN-F is a dominant strain in maize soil for long-term positioning experiment.High-yield extracellular polysaccharide has a nitrogen fixation effect,thus,it is a candidate strain for applying combined nitrogen fixation of maize and reducing fertilizer application.%从沈阳农业大学棕壤长期定位试验站的栽培玉米土壤样品中分离筛选到高产多糖固氮菌株WN-F,从菌株鉴定、培养条件优化和固氮与产糖关系进行初步研究.对其进行形态学观察和分子生物学鉴定,酶标仪分析菌体生物量法确定菌株的生长培养条件,并分析其固氮与产糖之间的关系.结果表明,该菌株为阿氏芽孢杆菌,并命名为Bacillus aryabhattai WN-F.WN-F菌株在37℃,180 r/min情况下12h时生长量达最高值.其培养基优化配方为(L-1):蔗糖20.0 g,牛肉膏2.0 g,KH2PO40.4 g、MgSO4·7H2O 0.4 g、NaCl0.4 g、CaSO4·2H2O 0.4 g和CaCO3 2.0 g.菌株WN-F的产糖情况随着初始氮浓度的增加,呈现出抛物线关系,适宜碳氮比促进菌体合成胞外多糖.Bacillus aryabhattai WN-F是长期定位试验玉米土壤中的优势菌株,高产胞外多糖且有固氮作用,是发挥玉米联合固氮作用,减少化肥施用的候选菌株.