Liquid-core capsule composed of calcium carbonate (CaCO3) and carboxyl methyl cellulose (CMC) as inner liquid-core surrounded by a cross-linked alginate membrane was prepared in this study. Liquid-core capsules have been widely used in various industrial applications. The performance of fermentation medium is affected by the accumulation of product(s) in the medium which will reduce the pH that may inhibit the growth of the fermenting microbes. The use of liquid-core capsules to control pH of fermentation medium is a new approach. The objectives of this research were to analyse the effect of liquid-core capsule properties (i.e. diameter, membrane thickness) on the efficiency of pH control, and process variables (i.e. calcium carbonate loading, capsule to solution volume ratio, capsule reusability, and medium viscosity) on the efficiency of the capsules to control pH of fermentation medium. Lastly, to evaluate the effect of liquid core capsules properties on the fermentation kinetics of lactic acid bacteria (LAB). The results showed the smallest and thinnest capsules (diameter 3.18mm and membrane thickness 0.49mm) could achieve pH 6.92 which is higher than that (only reached pH 6.72) of the largest and thickest capsules (diameter 8.35mm and membrane thickness 1.99mm) after 24 hours. Therefore, 40% (w/v) of CaCO3 loading and 1:3 ratio to LA solution volume was selected for LAB fermentation study. Then, the capsule reusability test showed the capsule was can used up to two runs with the pH above 4. The effect of capsule in the medium viscosity (up to 1090cP.s) was capable to control the pH at the desired pH range (> pH 4). In LAB fermentation, pH of fermentation was well controlled by the capsule and the results were comparable to those of free CaCO3. Then, the viable cell concentration was well maintained by the capsule. Similar results were obtained when the large scale fermentation was conducted. In short, the pH regulator capsules were capable to control the pH of the tested solutions at the desired level. In order to improve the viable cell concentration and lactic acid production at the end of the LAB fermentation.
