Open cultivation of microorganisms in water‐in‐oil Pickering emulsions stabilized by stearate microparticles

Abstract

AbstractWe report a long‐term open cultivation of model microorganisms in water‐in‐oil (W/O) Pickering emulsions stabilized by food‐grade calcium stearate microparticles without contamination. W/O Pickering emulsions were successfully prepared using calcium stearate microparticles in tetradecane. Effect of microparticle concentration on the emulsion's Sauter mean diameter was investigated at various hold‐ups. As a result, the smaller the hold‐up, the smaller was the change in Sauter mean diameter due to the microparticle concentration. It was found that Sauter mean diameter of the emulsions was almost constant for 2 months. Model microorganisms Escherichia coli and Bacillus subtilis solubilized in the emulsion were stationary cultivated in the air‐exposed state. The viable cell ratio temporarily decreased at the beginning of cultivation but then increased continuously with cultivation time after 28 days. Furthermore, there were no contamination for 28 days in the air‐exposed state of the emulsion solution containing a culture medium without microorganisms. It was also shown that the growth rate of the microorganisms in the emulsion system is significantly lower than those in conventional cultivation systems. Thus, the calcium stearate Pickering W/O emulsion system is suitable for a long‐term “open” cultivation of microorganisms without the use of any special equipment such as a jar‐fermenter.