Study Of Engineering Basison Xanthan Gum Synthesis By XG-101 Xanthomonas Campestris Fermentation

The viscosity of fermentation broth increased rapidly in the latter part of Xanthan gum fermentation process with the xanthan gum concentration increasing, and the fermentation broth is regarded as a pseudo-plastic fluid. So there are some difficulties in fermentation process such as serious decline of mass transfer efficiency and heat transfer efficiency, as well as the existence of dead-mixing zones. These affect the xanthan gum yield and product quality, and improve the cost of the fermentation and separation, which hinders the xanthan gum production technology to develop. These critical factors must be resolved. In addition, the most domestic processes of xanthan gum production currently have utilized batch fermentation mode. The different requirements on substrate of cell proliferation and synthesis of xanthan gum in two stages of the process haven't been considered. These also bring about a negative impact on product yield and quality.Response to the above, we study the xanthan gum fermentation process in the 30 L bio-mechanical stirring reactor from the following three aspects in this paper:Firstly, we used the two types of new impellers (first type: the upper - double-folded blade downflow disc turbine, and the lower - six blade Brumajin impeller; and second type: the single Maxblend impeller), which be applied separately in xanthan gum fermentation experiments. These types of new impellers were developed by cold model test in our laboratory. Separately studied the two types of new impellers used in xanthan gum fermentation process and product impact of each parameter. And the experimental results with conventional six flat-bladed disc turbines were compared from the parameters as follows: OD, xanthan gum concentration, viscosity, the average molecular weight, pyruvic acid functional groups, as well as the determination of residual sugar. It could be found from the study that the new impellers possess a comprehensive superior to the traditional impeller in the various mixing parameters, the product yield and quality have been markedly improved, and the Maxblend impeller shows more excellent performance. Secondly, on the basis of the above experiment, Maxblend impeller is applied on xanthan gum fermentation to take further study. The kinetics of growth and xanthan production by Xanthomonas campestris XG-101 in batch culture were studied under pH control. Fermentations were carried out over a range of stirrer speeds (140 r/min~260 r/min) and the pyruvic acid functional groups content, as well as the molecular weight of the product were estimated. Increased agitation levels resulted in higher kinetics parameters of the xanthan fermentation respectively, while product formation in this fermentation appeared to be some associated with cell growth. In addition, a new gas distributor influence on the xanthan fermentation was carried out in this study.Thirdly, on the end stage of logarithmic phase in the fermentation of xanthan gum, a fed-batch fermentation was studied and compared with batch fermentation. The results show fed-batch fermentation which can adjust to the requirements of cell proliferation and synthesis of xanthan gum, and supply corresponding growth substrate in two stages, the quality of products has corresponding improvement in the fed-batch fermentation compared to the batch fermentation.