Evaluation of different organic phases for water-in-oil xanthan fermentation

Abstract

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.

A bioprocess for the production of high concentrations of R-(+)-α-terpineol from R-(+)-limonene

“…In this study, the feasibility of the replacement of n-hexadecane, an organic phase exhibiting a high solubility and thus enabling high transfer rates of oxygen [33], by vegetable oils, where oxygen solubility is much lower [34,35], was considered. This system was used to provide a convenient way to have two different oxygenation conditions for the aqueous medium, the organic solvent enabling the best oxygen supply to this layer.…”

Enhancement of Oxygen Mass Transfer and Gas Holdup Using Palm Oil in Stirred Tank Bioreactors with Xanthan Solutions as Simulated Viscous Fermentation Broths

“…In order to calculate the k L a value, (5) was used: $\begin{array}{c}\frac{d{C}_L}{dt}=k_{L}a\left(C_L^{\ast }-C_L\right)\end{array}$ which on integration yielded $\begin{array}{c}\ln \left(\mathrm{1}-\frac{C}{C^{\ast }}\right)=-k_{L}a·t.\end{array}$ The k L a value was determined from the slope of plot ln⁡(1 − C L / C L *) versus t where C L * is the equilibrium dissolved oxygen concentration. The effect of the probe response was neglected as the time required for the oxygen transfer 1/ k L a was high compared to the dynamic response of the probe (1/ k L a ≫ 10 τ r ) [12]. However, in case of the slower response, the dynamic response of the probe must be taken into account for the calculation of k L a [15–17].…”

“…This method also was applied in xanthan gum fermentation by Ju and Zhao [11] and Kuttuva et al [12]. They postulated that this method has the ability to solve the viscosity problem and indirectly enhance the oxygen transfer.…”

Hydrogen peroxide (H2O2) supply significantly improves xanthan gum production mediated by Xanthomonas campestris in vitro

“…Organic compounds, such as hydrocarbons [20], fluorocarbons [5], and soybean oil [9], can be used as oxygen vectors to intensify oxygen supply. Another technology (water-in-oil fermentation technology) has been developed to enhance the performance of highly viscous fermentation processes [12]. However, the cost of the consumed oil is high, and the cost of recovery increases.…”