Determination of Growth by Optical Density (OD560 nm)

The quantifying of the total number of cells for each strain (R1, L1, L2, L3, and L4) was made using a turbidimetric method. The OD_560 nm of the bacterial suspension includes living cells, dead cells, and noncellular material that absorbs/scatters the light and indicates de total mass achieved. The wavelength of the spectrophotometer (UV-Vis Spectrofotometer Pharmacia LKB Biochrom Limited, Ultrospect III, Cambridge, England) was set at 560 nm. One milliliter of the sterile broth which was used to grow bacteria (LAPTg or MRS) was used to calibrate the equipment to zero absorbance and 1 mL of each sample was used to measure the OD_560 nm.