Effect Of Agar Concentration On Bacterial Cellulose Synthesis In Static Culture

Bacterial cellulose(BC)has great application prospects in biomedicine,tissue engineering,electronic materials and other fields due to its unique properties.Studies have shown that,the shaking culture method is used to obtain BC that has poor mechanical performance.And the static culture method is used to obtain BC that has low yield,whether the reason is due to the influence of environmental mass transfer remains to be further clarified.In this paper,the Gluconacetobacter xylinus(G.xylinus)and the engineering strain(Gluconacetobacter xylinus-vhb+,G.xylinus-vgb+)obtained by gene recombination with Gxylinus were studied by adding different concentrations of agar,investigated the effects of the two strains on the synthesis of BC.Taking G.xylinus as the research object,by adding different concentrations of agar to the liquid medium of synthetising BC,a certain mass transfer resistance of glucose was formed,to study the fermentation synthesis process of BC.The results showed that with the increase of agar concentration,the utilization rate of glucose,the cell number and the BC yield were gradually decreased.Compared with the control group(without agar),the utilization rate of glucose,the cell number and the BC yield were reduced by 40.64%and 70.31%,49.95%and 82.05%,49.95%and79.24%,respectively.In addition,when the glucose concentration in different parts of the liquid medium was homogenous and when the agar concentration was 0.3%and 0.6%,the gradient of glucose concentration in different parts of the culture medium showed a gradient distribution,indicating that the BC synthesis process was affected by the mass transfer resistance of glucose.In the BC synthesis process,effective supply of oxygen is required.Therefore,it has been examined whether or not the utilization rate of glucose can be improved by increasing the utilization efficiency of oxygen.we used G.xylinus-vgb+(Expression of VHb encoding gene vgb on G.xylinus by pBla-VHb-122 plasmid)as the research object,By comparing the the fermentation parameters of G.xylinus-vgb+ and G.xylinus,we known that:Under the same culture conditions,compared with the original strain G.xylinus,G.xylinus-vgb+ was more powerful of using glucose,had high conversion rate,good cell growth,high BC synthesis.In the control group and the agar concentration of 0.3%of the medium,the utilization rate of glucose increased by 12.09%and 54.55%,respectively;at the same time,compared with the amount of cells,the amount of cells of G.xylinus-vgb+ in the liquid,at agar concentrations of 0.3%and 0.6%,was increased by 8.52%,15.06%,and 17.14%,respectively;the BC production also increased by 12.95%,47.98%,and 15.63%,respectively.The results showed that the effective supply of oxygen could improve the utilization rate of glucose,and then increased the BC production.In addition,the physicochemical properties of BC membranes obtained under different culture conditions were studied.FTIR results showed that the BC membranes obtained under different culture conditions had the same transmission peaks,so,they have the same chemical structure.The XRD pattern,TG and DTG curves showed that the thermal stability and crystallinity of BC synthesized at different agar concentrations were approximately the same.