微生物多糖胶质高产菌株的筛选与鉴定

通过观察多糖胶质性状及以多糖胶质产量为指标进行初筛，从22 株可产多糖胶质的菌株中筛选获得一株多糖胶质的高产菌，多糖胶质产量为8.65 g/L；通过16S rDNA序列的同源性分析鉴定为地毯草黄单胞菌（Xanthomonas axonopodis）FJAT-10151。通过形态学观察、生理生化实验、革兰氏染色法鉴定该菌株为革兰氏阴性菌株，菌落较小、圆形、淡黄色、表面光滑且湿润、微隆、边缘整齐、不透明、具有迁移性。通过水提醇沉法从其发酵液中提取多糖胶质，利用苯酚-硫酸法、咔唑法、考马斯亮蓝法测定多糖胶质中中性糖、酸性糖、蛋白质的含量，分别为36.81%、8.90%、15.27%。所产的粗多糖胶质经Sevag法除蛋白，通过完全酸水解、糖腈乙酸酯衍生化以及气相色谱-质谱联用（gas chromatography-mass spectrometer，GC-MS）研究分析表明，该多糖胶质的单糖组分含葡萄糖和甘露糖，物质的量比为1∶1.12。通过红外光谱、紫外光谱、GC-MS等手段初步鉴定该多糖胶质为黄原胶。通过黏度及质构剖面分析法（texture profile analysis，TPA）对该多糖胶质的凝胶特性进行研究，1 g/100 mL多糖胶质溶液在60 r/min条件下的黏度为408 mPa·s。TPA测试结果表明，与购买的结冷胶、黄原胶相比，本研究得到的黄原胶硬度小，弹性和黏着性较好，胶黏性和咀嚼性最好。研究表明该株地毯草黄单胞菌具有较大的潜在应用价值。

Screening and Identification of Bacteria for Enhanced Production of Polysaccharide Gum

For the purpose of increasing the production of microbial polysaccharide gum, strain FJAT-10151, which showed
a productivity of 8.65 g/L, was screened from 22 bacterial isolates conserved in our laboratory, which have been reported
for the production of polysaccharide gum. The selected isolated was identified as Xanthomonas axonopodis by 16S rDNA
sequence analysis. By morphology observation, physiological and biochemical tests and Gram staining, it was further
identified as a Gram negative strain, and its colonies were small, round, yellowish, opaque and mobile, having a smooth,
moist and slightly bulge surface and regular edge. Polysaccharide gum was isolated from the fermentation broth of the
strain in water extraction and alcohol precipitated. As determined by phenol-sulfuric acid method, carbazole method and
Coomassie brilliant blue method, the contents of neutral saccharide, acidic saccharide and protein in the exopolysaccharide
gum were 36.81%, 8.90% and 15.27%, respectively. The polysaccharide gum was deproteinized by the Sevage method
and then completely hydrolyzed for gas chromatography-mass spectrometry (GC-MS) analysis after derivatization to
aldononitrile acetates. The analysis indicated that it mainly consisted of glucose and mannose at a molar ratio of 1:1.12.
It was identified by FTIR, UV spectroscopy and GC-MS as a xanthan. Gelation properties of the polysaccharide gum
were tested by viscosity and texture profile analysis (TPA). The viscosity of 1 g/100 mL polysaccharide gum solution was
408 mPa·s at 60 r/min. The TPA results indicated that the polysaccharide gum extracted from Xanthomonas axonopodis
FJAT-10151 had excellent gel properties with the smallest hardness, better elasticity and stickiness, and the best
adhesiveness and chewiness compared with commercial gellan and xanthan. In conclusion, this Xanthomonas axonopodis
strain has potential applications.