常压室温等离子体诱变选育黄原胶生产菌

Breeding of xanthan gum producing bacteria byatmospheric room temperature plasma mutagenesis

以野油菜黄单胞菌为出发菌株,进行常压室温等离子体(ARTP)诱变,筛选产黄原胶的优良菌株。研究结果表明:以菌落直径为初筛指标,共获得5株诱变菌株;进一步以黄原胶产量和黏度为复筛指标,获得1株优良菌株X20。其黄原胶产量与黏度分别为3.52 g/L和77.30 mPa·s,比出发菌株分别提高77.78%和40.03%。经过10次传代培养,诱变菌X20具有较好的遗传稳定性。不同环境因子都会影响X20的发酵性能。以谷氨酸为氮源时,黄原胶产量及黏度均最高,分别为7.30 g/L和495.50 mPa·s,比出发菌分别提高43.27%和22.29%。高质量浓度谷氨酸(大于1 g/L)会显著抑制出发菌株和X20的发酵液黏度,4 g/L谷氨酸使其黏度分别降低至21.8 mPa·s和25.93 mPa·s。不同初始pH条件下X20的黄原胶黏度均高于出发菌株,且X20更适应pH 6.5的发酵环境,黏度可达546.5 mPa·s。随着盐度增加,诱变菌株的黄原胶产量增加、黏度下降,且都高于出发菌株。当盐度为8 g/L时,X20的黄原胶产量和黏度分别为12.19 g/L和331.23 mPa·s,比出发菌株分别高23.05%和109%。X20的发酵液黏度在不同温度(20℃~80℃)及高矿化度(28.90 g/L)条件下均保持稳定,且始终优于出发菌株,具有一定的工业应用潜力。

Xanthomonas campestris was used as the starting strain for the screening of xanthan gum-producing strain by atmospheric room temperature plasma(ARTP)mutagenesis.The results showed that five mutated strains were obtained based on the diameter of colony on primary screening plate.Then,one excellent strain X20 was found by evaluating the yield and viscosity of xanthan gum for further secondary screening.The xanthan gum yield and viscosity of strain X20 were 3.52 g/L and 77.30 mPa·s,which were 77.78%and 40.03%higher than that of the starting strain,respectively.After 10 generations of cultivation,strain X20 exhibited good genetic stability.Different environmental factors affecting the fermentation performance of strain X20 were studied.When glutamic acid was used as the nitrogen source,the highest xanthan gum production and viscosity were 7.30 g/L and 495.50 mPa·s,respectively,which were 43.27%and 22.29%higher than those of the starting bacteria.High concentration of glutamic acid(>1 g/L)significantly suppressed the fermentation culture viscosity of the starting strain and X20,which reduced to 21.8 mPa·s and 25.93 mPa·s at 4 g/L glutamic acid,respectively.Xanthan gum viscosity of strain X20 was higher than that of the starting strain under different initial pH conditions.Moreover,strain X20 was more adapted to the fermentation environment of pH 6.5(with viscosity of 546.5 mPa·s).With the increase of salinity,the xanthan gum yield of strain X20 increased while its viscosity decreased,but all of them were higher than those of the starting strain.When the salinity was 8 g/L,the xanthan gum yield and viscosity of X20 were 12.19 g/L and 331.23 mPa·s,which were 23.05%and 109%higher than those of the starting strain,respectively.The viscosity of X20 remained stable at different temperatures(20℃-80℃)and high mineralization(28.90 g/L),and was always better than that of the starting strain,showing some potential for industrial application.