Nitrogen Sources Effect on Lactobacillus reuteri Growth and Performance Cultivated in Date Palm (Phoenix dactylifera L.) By-Products

摘要

Lactic acid bacteria (LAB) are fastidious microorganisms that have specific nutritional requirements. The de Man, Rogosa, and Sharpe (MRS) is an expensive standard growth medium for LAB to produce lactic acid, and the industry is always looking for an alternative low-cost medium. The date palm (Phoenix dactylifera L.) is naturally full of essential nutrients that lead to stimulate or promote the growth of Lactobacillus spp. The date fruit industries generate a large amount of unwanted date by-product. Thus, the objective of this study was to examine the effect of different nitrogen sources on the growth of Lactobacillus reuteri grown in a date base medium. In this study, date palm fruit was pressed, and the fiber was blended with distilled water, centrifuged, and the supernatant was autoclaved to obtain date palm extract (DPE). The date palm medium (DPM) was formed by mixing the DPE with buffer solution. The DPM was then supplemented with different concentrations of different nitrogen sources. Lactobacilli MRS was used as a standard growth medium. Three different L. reuteri strains were individually inoculated into batches of MRS and DPMs at an initial inoculum 2.5 Log CFU/mL, and then incubated at 37°C for 18 h. Bacterial growth was monitored by measuring the optical density readings (O.D 610 nm) for up to 18 h. At the end of the incubation period, final populations of each individual strain were verified by enumeration of the MRS agar. Our results showed that the bacterial population in DPM (control; without nitrogen), reached 3.55±0.5 Log CFU/mL. However, the bacterial populations that reached 7.03±0.1Log CFU/mL in the DPM medium were supplemented with 0.8% phytone peptone, compared to the MRS 7.90±0.24 Log CFU/mL. Our findings thus suggest that date by-products could be used as a low-cost alternative for the LAB growth medium.