Evaluating the efficiency of utilizing alternative nitrogen sources in sweet potato-based medium on the growth of Lactobacillus sp.

The traditional nitrogen sources used in lactic acid bacteria growth media are expensive and can contribute significantly to the overall cost of the media. In addition, some of these nitrogen sources are derived from animal sources that are unsuitable for certain applications, particularly with regard to vegan products. Sweet potato (Ipomoea batatas) is a readily available and nutrient-rich crop product that has shown potential as an alternative growth medium for cultivating Lactobacillus sp. In the present study, we investigated the feasibility and efficiency of alternative nitrogen sources in sweet potato-based medium with regard to supporting the growth of Lactobacillus sp. The high carbohydrate content of sweet potatoes, along with their essential vitamins and minerals, provides an ideal environment for the proliferation of bacteria. Baking and soaking treatments that release fermentable sugars and other nutrients enabled the sweet potato-based medium to support substantial bacterial growth. The medium was supplemented with different combinations of nitrogen sources 2, 8, or 14 g/L of X-Seed Nucleo Max, X-Seed KAT, and NuCel 780 MG to form SPM1, SPM2, and SPM3. Seven Lactobacillus sp. strains were used in the present study. At least two of the sweet potato medium compositions- SPM2, which contained 2 g/L X-Seed Nucleo Max, 3 g/L X-Seed KAT, and 3 g/L NuCel 780 MG and SPM3, which contained 2 g/L X-Seed Nucleo Max, 6 g/L X-Seed KAT, and 6 g/L NuCel 780 MG were sufficient to grow Lactobacillus sp. strains in a manner sufficiently similar or superior to that of MRS. At 12 h of incubation, the average population of Lactobacillus sp. strains for SPM2 and SPM3 were higher than that in MRS and reached an average of 7.94 ± 0.11, 7.15 ± 0.13, 8.38 ± 0.11, and 8.57 ± 0.12 log CFU/mL for MRS, SPM1 SPM2, and SPM3, respectively. Moreover, the buffering capacity of SPM2 and SPM3 with values of 12.42 ± 0.11 and 11.78 ± 0.08 g/L, respectively, were significantly (p ≤ 0.05) higher than that in MRS which had a value of 10.75 ± 0.12 g/L. The findings thus demonstrated that sweet potato based medium SPM2 is suitable for the growth of Lactobacillus sp. strains and could be used as an alternative to the standard media.