The change in the density spectrum of the batch culture Arthrospira (Spirulina) platensis was investigated. The two-beam spectrophotometer Lambda 365 Double Beam UV-Visible was used. The spectrophotometer was equipped with an integrating sphere (IS). The peculiarity of the IS design is that it collects only the past light and the main part of the light scattered in the straight direction. By measuring the absorption spectra of the sample near and at a distance of 1 cm from the integrating sphere, the absorption spectrum compensated for scattering is calculated. With the standard location of the cell (close to the IS), the optical density in the range of 750-800 nm was not take zero values. The optical density increased monotonously with increasing distance between the cell and the IS. This is due to selective (in pigments) and non-selective (in microalgae cells) scattering. The light attenuation coefficient is determined as the average value of all L in the range of 750-800 nm. In our case, this value was about 1.61. Based on the obtained true absorption spectra, it is shown that in the process of growth of the batch culture, the ratio between the pigments did not change. The ratios of chl a/car (1.36) and chl a/C-Phy (1.06) are considered.
spirulina, attenuation spectra, integrating sphere, light attenuation coefficient, true absorption spectrum
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