Autolysis in combination with bead-milling Results

Yeast extract is mostly obtained by autolysis [1]. In autolysis cells digest their own cell compounds with their own enzymes [2]. The idea was to transfer this commonly used principal on algae. Therefore, C. vulgaris and C. sorokiniana were heated to 50 °C in alkaline or acidic environment for 41 h. To further crack the cell wall, both algae were treated with bead-milling afterwards. To quantify the success of cell wall disruption free amino acids were measured with rFAN-assay.

The yield of free amino acids was set into relation with the amount of biomass used in the experiment (figure 1).

Figure 1 -Autolysis and subsequent bead-milling of algae C. vulgaris and C. sorokiniana. The percentage of free amino acids [%] relates to the biomass used in the experiment.

The highest amounts of free amino acids were reached with yeast at pH 12 with 4.85 %. Both algae showed very low yield in free amino acids. The best results showed C. sorokiniana at pH 12. It is possible, that the amount of glass beads and the size of the glass beads were to little, which led to less cell wall disruption. Therefore, amino acids would have been retained within the cells. This would explain the little amounts of free amino acids achieved with this method. Also, C. vulgaris and C. sorokinia have a cell wall, in contrast to yeast [3]. Cell walls are harder to break, than a plasma membrane. This could explain the difference between the yeast samples and the algae samples. Due to the low yield in free amino acids, it was decided to investigate other methods for cell extraction of algae.