Kuttuva S G, Restrepo A S, Ju L-K
Department of Chemical Engineering, The University of Akron, Akron, OH 44325-3906, USA.
Appl Microbiol Biotechnol. 2004 Apr;64(3):340-5. doi: 10.1007/s00253-003-1461-x. Epub 2003 Oct 16.
Water-in-oil (W/O) fermentation technology has the potential for overcoming the problems related with high broth viscosity in xanthan fermentations. By dispersing the aqueous broth in a continuous organic phase, the broth-thickening mechanisms are confined within the aqueous droplets without significantly increasing the overall viscosity. In this study, xanthan fermentations were made with perfluorocarbon (PFC) or vegetable oil as the organic phase. The results were compared with those obtained previously using n-hexadecane as the organic phase, to evaluate the effects of various properties. PFC provided easy phase separation at the end of fermentation but required higher power input for agitation, a direct result of its high density. The aqueous droplets formed were large (400-450 microm), limiting the cell concentration employable due to the occurrence of oxygen starvation in the inner core. One main advantage of using vegetable oil was its low cost. In addition, vegetable oil provided much finer droplets (<120 microm) and produced high xanthan concentrations (>100 g l(-1)). However, complete phase separation for product recovery was difficult to achieve. Fermentations in both organic phases were terminated by the occurrence of phase inversion to highly viscous O/W dispersions at aqueous-phase volume fractions of 0.53-0.56. The initial fraction was 0.3 but changed due to base addition for pH adjustment and nutrient addition for prolonged production.
油包水（W/O）发酵技术有潜力克服黄原胶发酵中与高发酵液粘度相关的问题。通过将水相发酵液分散在连续有机相中，发酵液增稠机制被限制在水滴内，而不会显著增加总体粘度。在本研究中，以全氟化碳（PFC）或植物油作为有机相进行黄原胶发酵。将结果与之前使用正十六烷作为有机相所获得的结果进行比较，以评估各种性质的影响。PFC在发酵结束时提供了易于分离的相，但由于其高密度，搅拌需要更高的功率输入。形成的水滴较大（400 - 450微米），由于内核中出现氧气饥饿，限制了可采用的细胞浓度。使用植物油的一个主要优点是成本低。此外，植物油提供了更细的液滴（<120微米），并产生了高黄原胶浓度（>100 g l(-1)）。然而，产品回收的完全相分离很难实现。在水相体积分数为0.53 - 0.56时，两种有机相中的发酵都因发生相转变为高粘性的水包油（O/W）分散体而终止。初始分数为0.3，但由于添加碱进行pH调节和添加营养物以延长生产而发生了变化。
