## 3 Results
### Storage Experiment 2--Lipid and Chlorophyll Analysis  
Although the odor of the samples of storage experiment 1 was not assessed in a standardized way, it is noteworthy that a pungent off-odor was perceived for all 20 \({}^{\circ}\)C stored samples but not for 4 \({}^{\circ}\)C and 8 \({}^{\circ}\)C stored samples. Therefore, and because of the high levels of malodorous compounds in these samples, the 20 \({}^{\circ}\)C storage conditions were omitted in the set-up of the subsequent test. The lipid level of the initial biomass was \(17.3\pm 0.2\%\) on a dry matter (dm) basis and remained fairly stable during storage (Table 1). Despite the limited differences, factorial ANOVA analysis indicated that the three storage factors had a statistically significant impact (i.e., temperature, temperature \(\times\) closing type and closing type \(\times\) storage time, Supplementary Materials Table S1), and the highest lipid levels were observed for algae stored at 8 \({}^{\circ}\)C in open tubes (Table 1). FFA constituted \(2.3\pm 0.4\%\) of the lipids of the initial biomass. Although three storage factors affected FFA levels (storage time, closing type and temperature \(\times\) storage time, Supplementary Materials Table S1), differences were small and FFA levels stayed within a limited range (1.5% to 2.3% of the lipid mass) for algae stored without added acetic acid (Table 1). However, the FFA level increased to \(21.6\pm 3.7\%\) of the lipids after 17 days of storage at 8 \({}^{\circ}\)C in open tubes when acetic acid was added. Such an increase was not observed when algae were stored under similar conditions but without acetic acid addition. The chlorophyll concentration was initially \(19.7\pm 0.8\) mg/g dm and was affected by storage temperature (\(p=0.011\)) and the way of closing the storage tubes (\(p<0.001\)) when no acetic acid was added. Chlorophyll levels were generally higher after 8 \({}^{\circ}\)C storage than after 4 \({}^{\circ}\)C storage, and were also higher after storage in open tubes than after closed tube storage (Table 1). Again, a large \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Storage Condition** & **Storage Time (Days)** & **Lipid (\% dm)** & **FFA (\% Lipid)** & **Chlorophyll (mg/g dm)** \\ \hline t\({}_{0}\) & 0 & \(17.3\pm 0.2\) & \(2.3\pm 0.4\) & \(19.7\pm 0.8\) \\
4 \({}^{\circ}\)C, open & 7 & \(17.2\pm 0.1\) & \(2.0\pm 0.2\) & \(23.2\pm 2.7\) \\  & 17 & \(18.0\pm 0.3\) & \(1.8\pm 0.1\) & \(24.5\pm 3.6\) \\
4 \({}^{\circ}\)C, closed & 7 & \(17.2\pm 0.1\) & \(1.9\pm 0.1\) & \(17.2\pm 2.5\) \\  & 17 & \(16.7\pm 1.0\) & \(1.9\pm 0.2\) & \(19.1\pm 2.3\) \\
8 \({}^{\circ}\)C, open & 7 & \(18.2\pm 0.2\) & \(1.5\pm 0.1\) & \(27.0\pm 2.0\) \\  & 17 & \(19.0\pm 0.3\) & \(2.1\pm 0.1\) & \(29.1\pm 1.7\) \\
8 \({}^{\circ}\)C, closed & 7 & \(16.6\pm 0.3\) & \(1.8\pm 0.1\) & \(20.6\pm 0.3\) \\  & 17 & \(17.0\pm 0.2\) & \(2.3\pm 0.1\) & \(19.4\pm 0.6\) \\
8 \({}^{\circ}\)C open + acetic acid & 7 & \(18.0\pm 0.4\) & \(2.9\pm 0.2\) & \(25.8\pm 1.4\) \\  & 17 & \(17.2\pm 0.1\) & \(21.6\pm 3.7\) & \(10.5\pm 0.6\) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Results of storage experiment 2. Concentrations are given as averages \(\pm\) standard deviations. The results of an ANOVA analysis can be found in Supplementary Materials Tables S1 and S2. Figure 5: Impact of acetic acid addition for 8 \({}^{\circ}\)C storage in open tubes—storage experiment 1. Lowercase letters (a, b, c) denote significant differences. Propionic acid values that are not labelled by the same letter are significantly different. Because there was no significant interaction between the effect of preservation time and acetic acid addition on butyric acid levels (\(p=0.17\)), no post-hoc analysis was performed, and no letter labels were added for butyric acid in the figure. change was seen when acetic acid was supplemented. In that case, chlorophyll levels decreased to 10.5 \(\pm\) 0.6 mg/g dm after 17 days of storage at 8 \({}^{\circ}\)C in open tubes, while this decrease was not seen when no acetic acid was added.