Changes in nutritive value of Pavlova sp. collected from different population growth phases in batch style culture assessed from cell ultra-structure

Abstract

In this study, the efficiency of ultra-structural observations was shown to enable estimation of the nutritive value and activity of Pavlova sp. as a food organism, in addition to the nutritive analysis of cells. Batch style culture of the alga using 10-L carboys was carried out for 30 days, and cells were collected at day 10, day 20 and day 30 after inoculation. These collections corresponded to the exponentially growth phase, stationary phase and death phase, respectively. Nutritive Pavlova cells containing high levels of EPA and DHA have a large developed chloroplast and few small oil droplets. Following change from the exponentially growth phase to death phase, the fatty acid content decreased conspicuously. In parallel with the nutritive change, the chloroplast shrank and many oil droplets accumulated in cells. Thus, a large quantity of these fatty acids seems to be contained in chloroplast membranes. Active swimming Pavlova sp. in the exponentially growth phase had two flagella. Moreover, the results of the feeding experiment to pearl oyster spats showed that the nutritive value of the exponentially growth phase Pavlova sp. was higher than those of other phases. From the results of this study, Pavlova sp. collected during the exponentially growth phase is recommended to be used as food.