# Effects of Caprolactam Wastewater on Algal Growth and Nutrients Removal by _Arthrospira platensis_
## 3 Results and Discussion
### Fed-Batch Supply of WCP Decreasing the Impact on A. platensis
#### 3.3.3 Effect of WCP Supply Modes on Biochemical Composition of _A. platensis_  
Table 4 shows the effect of the WCP supply mode on the biochemical composition of _A. platensis_. Compared with the control, WCP significantly reduced the protein content of _A. platensis_, whereas the batch mode had the greatest impact. The protein content in fed-batch mode 1 was 65.36%, 67.82%, 63.44%, and 58.54% on days 4, 8, 12, and 16, respectively. The protein content in fed-batch mode 2 was almost the same as that of fed-batch mode 1. The protein content in the batch mode, which was 55.11%, 59.70%, 58.01%, and 57.98% on days 4, 8, 12, and 16, respectively, was significantly lower than that of fed-batch mode 1. The results indicated that supplying WCP to _Arthospira_ culture in a fed-batch manner could reduce the negative effects of WCP on protein synthesis. Similar results were also observed in other studies. For example, it was found that the fed-batch process can reduce the toxic or inhibitory compound loadings in wastewater and improve the algal tolerance to high substrate concentrations [23,42]. The protein content in fed-batch mode 1 ranged from 58.54% to 67.28%, which was higher than that recorded in other reports. For example, _Spirulina subsalsa_ had a protein \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Culture Time** & **WCP Supplying Modes** & **Protein (\%)** & **Cabohydrate (\%)** & **Lipid (\%)** \\ \hline \multirow{4}{*}{Day 4} & Control & 71.24 \(\pm\) 0.31 a & 12.96 \(\pm\) 1.19 c & 15.48 \(\pm\) 4.00 a \\  & Fed-batch mode 1 & 65.36 \(\pm\) 0.46 b & 18.80 \(\pm\) 0.22 b & 13.76 \(\pm\) 2.24 a \\  & Fed-batch mode 2 & 65.89 \(\pm\) 0.79 b & 20.43 \(\pm\) 0.63 b & 14.26 \(\pm\) 2.80 a \\  & Batch mode & 55.11 \(\pm\) 1.34 c & 30.37 \(\pm\) 2.78 a & 13.25 \(\pm\) 1.44 a \\ \hline \multirow{4}{*}{Day 8} & Control & 73.95 \(\pm\) 0.74 a & 9.91 \(\pm\) 0.22 c & 14.10 \(\pm\) 2.54 a \\  & Fed-batch mode 1 & 67.28 \(\pm\) 1.77 b & 15.02 \(\pm\) 1.91 b & 15.50 \(\pm\) 1.10 a \\  & Fed-batch mode 2 & 64.88 \(\pm\) 1.44 c & 15.26 \(\pm\) 2.70 b & 15.37 \(\pm\) 0.45 a \\  & Batch mode & 59.70 \(\pm\) 1.36 d & 22.94 \(\pm\) 2.64 a & 14.99 \(\pm\) 2.69 a \\ \hline \multirow{4}{*}{Day 12} & Control & 69.29 \(\pm\) 0.70 a & 11.82 \(\pm\) 1.28 c & 14.19 \(\pm\) 2.85 a \\  & Fed-batch mode 1 & 63.44 \(\pm\) 2.93 b & 16.65 \(\pm\) 1.29 b & 12.74 \(\pm\) 0.50 a \\ \cline{1-1}  & Fed-batch mode 2 & 60.19 \(\pm\) 1.77 bc & 18.45 \(\pm\) 1.44 ab & 14.86 \(\pm\) 0.55 a \\ \cline{1-1}  & Batch mode & 58.01 \(\pm\) 2.75 c & 20.22 \(\pm\) 1.63 a & 15.53 \(\pm\) 3.13 a \\ \hline \multirow{4}{*}{Day 16} & Control & 67.32 \(\pm\) 0.27 a & 7.10 \(\pm\) 0.86 a & 15.02 \(\pm\) 2.24 a \\ \cline{1-1}  & Fed-batch mode 1 & 58.54 \(\pm\) 2.84 b & 13.51 \(\pm\) 2.49 b & 14.59 \(\pm\) 1.32 a \\ \cline{1-1}  & Fed-batch mode 2 & 56.63 \(\pm\) 2.58 b & 11.80 \(\pm\) 0.92 b & 14.73 \(\pm\) 0.50 a \\ \cline{1-1}  & Batch mode & 57.98 \(\pm\) 1.55 b & 11.92 \(\pm\) 0.95 b & 14.60 \(\pm\) 0.40 a \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Main biochemical components content of _Arthospira platensis_ as affected by the caprolactam wastewater supply modes. Data with different letters indicate significant differences (\(p<\) 0.05) between the control and treatments.