Development of a Low-cost Culture Medium for Lactobacillus Cultivation

De Man, Rogosa and Sharpe (MRS) medium is generally used for the cultivation of the whole group of lactic acid bacteria. However, this medium is expensive and not applicable for large-scale production. Therefore, a low-cost culture medium used whey as the main ingredient was developed. Two lactobacilli, Lactobacillus brevis and Lactobacillus plantarum, from Department Culture Collection were chosen for this study. At first, only 7% whey powder in distilled water was used. The lactobacilli were grown at 37  C for 24 hours. The growth was followed by spread-plate method on MRS agar containing 0.5% CaCO3. It appeared that only Lactobacillus brevis can grow in whey water with the growth lower than in MRS broth. They grew from 5.03 and 5.17 log CFU/mL at 0 h to 7.4 and 9.1 log CFU/mL at 24 h, respectively. Then, five medium formulas were developed: 7% whey in Luria-Bertani broth (WLB), WLB + 0.5% glucose, WLB modified (using sodium acetate instead of sodium chloride, WLBM), WLBM + 0.5% glucose (WLBMG) and WLBM + glucose + 0.2% K2HPO4 (WLBMGK). The results showed that the growth of L. brevis in WLBMG was nearly equivalent to that in MRS broth for 24-hour cultivation. They grew from 5.36±0.01 and 5.33±0.04 log CFU/mL at 0 h to 7.95±0.04 and 8.09±0.02 log CFU/mL at 24 h, respectively. However, the amount of lactic acid equivalent (LAE, assayed by titration method) was about a half of that produced in MRS broth (0.20±0.01% LAE in WLBMG and 0.53±0.05 % LAE in MRS). When these media were used for the cultivation of Lactobacillus plantarum, it appeared that the growth of L. plantarum in WLBMGK was comparable with the growth in MRS broth. They grew from 5.66±0.11 and 5.69±0.11 log CFU/mL at 0 h to 8.12±0.02 and 8.18±0.03 log CFU/mL at 24 h, respectively. Nevertheless, the amount of lactic acid equivalent was nearly a half of that produced in MRS (0.68±0.006% and 1.45±0.067%, respectively). Meanwhile, the cost per liter of WLBMG and WLBMGK (87 and 90 baht) are about 75 % the cost of MRS (118 baht).