Lactic acid (LA) is the most widely used multifunctional organic acid and approximately 50% of it is produced by biotechnological process. Immobilizing microbial cells not only improves cell retention but also protects cells from harsh environment conditions during LA production. A great amount of whey is produced as byproduct worldwide in the manufacture of cheese or casein and its disposal has been an issue of environmental pollution. The objectives of this research were therefore to develop a simple method to encapsulate (immobilize) Lactobacillus reuteri for the continuous production of LA and to evaluate LA production in the whey based medium compare with MRS and modified MRS media using free and immobilized L. reuteri. Five strains of L. reuteri grown in lactobacillus MRS broth at 37ºC for 24 h were washed in peptone water and suspended in 2% sodium alginate solution. Encapsulation of cells was performed by dripping the mixture of sodium alginate and culture into ice-cold (2°C) 0.4 M calcium chloride solution using a separator funnel. The beads were then subjected to each of 500 ml MRS, modified MRS and whey-based broth and then incubated at 37°C for 12 h. Samples were withdrawn at 2 h intervals during incubation period and analyzed for LA as represented in pH. Results show that the developed method is a rapid and simple microbial encapsulation procedure for the continuous production of LA. The efficacy of LA production as measured in pH was not significantly different in all tested media. At the end of fermentation process, pH of whey medium containing conventional (free) and encapsulated cells reached to 4.20 and 3.85, respectively. This indicates that higher amount of acid is yielded with encapsulated cells than free cells. In addition, immobilized cell strain MM2-3 produced the highest lactic acid (pH3.5) while free cell strain SD2112 produced the lowest lactic acid (pH 4.05). Hence, results from this study suggest that we were able to develop a simple and rapid method for the encapsulation of L. reuteri.