The Research On Characteristics,Improvement And Preliminary Application Of Thermophilic Bacillus Licheniformis

Xanthan gum,that is of good rheology,emulsion stability,suspension property,compatibility and tackability,is as an important work in oil drilling fluid thickener.And it canenhance the productivity of oil in drilling,completion,profile control and water sealing and tertiary oil recovery Actually using the xanthan gum is to increase the difficulties of handling followed process.So degrading the xanthan gum effectively at high temperature oil field is an important step in oil exploration.Basing on ThermopHilic bacillus licheniformis HT-1 by identifing before,the experiment admeasure compound mutagenesis strain temperature tolerance,pH tolerance and degradation ability of xanthan gum that it is composite mutagenesis of rultraviolet and microwave,and compare the composite mutagenesis with the original strains.Finally,we explore preliminarily the application of composite strain The main resuLts are as follows:The optimal growth temperature is 50? of the wild type strain of HT-1,pH is 7.5,0.1%of xanthan gum,1%of glucose(carbon source),1%of the yeast powder(nitrogen source);Optimum conditions of xanthan degradation is 0.3%of xanthan gum.As the sole carbon source and nitrogen source,the temperature is 50?,pH is 7.5.On this basis of this,the ultraviolet mutagenesis of wild type strain of HT-1 is to get HT1UV-3 induced strain,its viscosity rate is reached to 35.79%to xanthan gum,the viscosity rate increased by 14.42%compared with original strains.Then we did the microwave mutagenesis to the HT1UV-3 mutant strain,end up with 5 mutant strains,named HT1UM3-1?HT1UM3-2?HT1UM3-3?HT1UM3-4?HT1UM3-5.In terms of the temperature tolerance,the optimum growth temperature of the HT1UM3-3 strain is 55 ?;In regard to the pH tolerance,the original strains changed little dealt with uv mutagenesis and microwave compound mutation;In terms of xanthan gum degradation research,maximum viscosity rate of HT1UM3-5 strain reaches to 42.02%,it increases by 20.70%compared with the original strain.Finally,we explorated the survival rate and the degradation ability to the 5 improved strains in the environment of crude oil.Results showed that wether wild type or mutant,degree of tolerance of the thermopHilic bacillus licheniformis for crude oil is not high,and the half mortality rate is 0.5 g/L.In the crude oil environment,xanthan gum degradation ability test of the strain showed that the viscosity reduction rate of original strains is 0%,but mutant strains is below 7.5%in the 0.5 g/L concentration of crude oil.We use different strains to test the degradation ability to the three gum of guar gum,sesbania gum,,carrageenan.The result shows that the degradation ability to guar gum is relatively weak,and the maximum viscosity reduction rate are not more than 4%;In the sesbania gum,the degradation of HT1UM3-1,HT1UM3-2,HT1UM3-4,HT1UM3-5 is better than original strains that their viscosity reduction rate is 5%-8%.In the degradation of carrageenan,the degradation ability of composite strain is far superior to original strains that their viscosity reduction rate is 5%-8%,and it is higher 60%.