Activa

The changes in the pH of culture medium during the cultivation were quickly checked with a microvolume of the medium using a Compact pH meter LAQUAtwin-pH-22 (Horiba Scientific, Kyoto, Japan), as described previously [20 (link)]. The growth of bacteria was monitored through the optical density of the culture media at 600 nm (OD₆₀₀) using a Spectro UV–Vis Double PC 8 Auto Cell Scanning Spectrophotometer (UV–Vis Double Beam Model UVD-3200, Labomed Inc., Los Angeles, CA, USA). The sample with OD₆₀₀ value higher than 0.8 abs should be diluted, such that the recorded value was in the range of 0.3–0.8 abs. The medium supernatant harvested via centrifugation to remove cells and precipitate was filtered through a 0.2 µm syringe filter (Minisart, Gottingen, Germany) and diluted at an appropriate concentration for analyzing dissolved Mn concentration using inductively coupled plasma–atomic emission spectroscopy (ICP-AES; Activa, JY Horiba, Kyoto, France).

The pH of the cucumber extract samples was measured using a compact pH meter (LAQUAtwin-pH-22, Horiba Scientific, Kyoto, Japan). The organic acid and sugar contents of the cucumber extract were determined by high-performance liquid chromatography (HPLC) using a Dionex Ultimate3000 high-performance liquid chromatography (ThermoFisher Scientific Inc., Waltham, MA, USA). The conditions of the HPLC are summarized in Table 1. Before subjected to HPLC, all samples were centrifuged at 10,000 rpm for 5 min to remove biomass and then filtrated through a 0.2-µm syringe filter and serially diluted at the appropriate concentration for determination.
Inorganic elements, such as Mg, Na, Ca, K, Fe, V, Ni, Al, B, As, Pb, S, were analyzed using an inductively coupled plasma–atomic emission spectroscopy (ICP-AES; Activa, JY Horiba, France) at the Busan Center of the Korea Basic Science Institute (KBSI). The samples were serially diluted at an appropriate concentration before analysis.

Regular rat chow (Teklad Global 18% Protein Rodent diet (Harlan Teklad, WI)) was used as the control diet. Energy composition of rat chow diet was 58% as carbohydrate, 18% as fat, and 24% as protein. Sea salt was from the Jeonnam Sinan region and the refined salt was from the Hanju region of Korea. Feed was made from the powdered form of the chow using the facilities located at the Korea Food Research Institute. Both salts were added to the rat chow on the basis of weight. General composition analysis and mineral contents of the salts was performed based on CODEX STAN 150–1985 and ICP-AES (Activa, HORIBA Jobin-Yvon, Longjumeau, France), respectively. Based on our analysis, on a weight basis the sea salt contained 85.7% NaCl whereas the refined salt contained 99.9% NaCl. In addition to NaCl, the sea salt contained 1.5 mg/g of calcium, 2.9 mg/g of potassium and 3.9 mg/g of magnesium as well as trace amounts of iron, manganese and zinc. Refined salt did not contain any measurable amounts of any other mineral.