Oil/water and pre‐emulsified oil/water (PIT) dispersions in a stirred vessel: Implications for fermentations

Abstract

This study examines dispersions of rapeseed oil (RSO) in water by mechanical agitation under conditions mimicking those found in certain antibiotic fermentations; for example, in the presence of air, antifoam, and finely divided CaCO(3) particles. A problem with residual oil has been reported for such fermentations, and it has been suggested that the use of pre-emulsified oil can reduce this problem. Hence, the dispersion of a pre-emulsified oil produced by the "phase inversion temperature (PIT) method" has been evaluated. In both cases, the volume fraction of oil was 2%. For the RSO systems, a relatively high agitation speed was required to disperse the oil, especially in the presence of the particles and, when the agitation was stopped, separation occurred rapidly. The Sauter mean drop diameters depended on the system, being at an average energy dissipation rate of approximately 0.9 W kg(-1), 180 microm for RSO/water, 130 microm for RSO/water(antifoam)/air, 580 microm for RSO/water/CaCO(3), and 850 microm for RSO/water(antifoam)/air/CaCO(3). For the same four systems, the PIT emulsion, once dispersed, was very stable and the drop size was essentially independent of the operating conditions, with a Sauter mean diameter of approximately 0.3 microm. The implications of these findings for fermentations in which oil is used as a carbon source are assessed.

The Use of Phase Inversion Temperature (PIT) Microemulsion Technology to Enhance Oil Utilisation during Streptomyces rimosus Fed-batch Fermentations to Produce Oxytetracycline

“…Above the phase inversion temperature range the oil-in-water dispersion changes to a water-in-oil dispersion and as the temperature falls again a fine stable micro-emulsion is formed with very small oil-in-water droplets (diameter, $0.2 lm). This size is significantly smaller than that obtained ($200 to $800 lm) by dispersing RSO by agitation, the actual size depending on the stage of the fermentation (Erler et al 2003). These latter studies also showed that the drop size ($0.3 lm) in the PIT-RSO emulsion (the same as used here) was unaffected by addition to the broth and remained the same throughout the different stages of the fermentation.…”

“…Therefore, further process optimisation will be necessary if the predicted benefits from the use of PIT technology during such fermentation processes are to be realised. However, since the properties of the PIT emulsions are largely independent of scale of operation (Erler et al 2003), depending only on the type of surfactant and fermentation process used, it is suggested that the development of optimal feeding regimes for PIT emulsions during laboratory and production scale could lead to a decrease in final residual oil concentration with higher oxytetracycline titres. Further, that by carefully choosing the emulsification mixture so that the surfactants can be metabolised by the microorganism, then subsequent problems in downstream processing could be avoided.…”

“…control fermentations) and PIT-RSO being fed constantly from the beginning of the fermentation. The PIT-RSO microemulsion consisted of 44% (w/w) deionised water, 40% (w/w) rapeseed oil (from the same batch as the control RSO), and 16% (w/w) surfactant (Erler et al 2003). The feeding rates are commercially confidential and as such are not reported here except that the quantity of RSO fed into each process was the same on a weight basis.…”

Study rheological behavior of refined rapeseed oil

“…Lost of researches had focused on the processing and utilization of rapeseed oil, especially on the deep refining and industrial application in recent years. However, they din's analyze the liquid rheological characteristic of rapeseed oil to elucidate the instruction for the technology parameters of industrial operation [16,17].…”