Simulation design for microalgal protein optimization

Figures & data

Table 1. Experimental range and levels of the independent variables

		Coded Levels
Independent Variables	Symbol Coded	−α	−1	0	+1	+α
Light intensity (μmol photons m^−2s^−1)	X1	30	40	55	70	80
Temperature (°C)	X2	20	22	25	28	30
Agitation rate (rpm)	X3	100	120	150	180	200

Table 2. Experimental simulation design matrix and the results for Tetraselmis striata

Standard order	Variables in non-coded levels			Tetraselmis striata Protein (μg/ 100 μL)
Runs	X1	X2	X3	Actual value	Predicted value
1	30	25	150	3.532±0.196	9.558
2	55	25	150	20.282±0.501	24.252
3	40	22	120	1.444±0.112	7.385
4	70	22	120	5.932±0.224	8.275
5	55	25	150	19.337±0.446	24.254
6	40	28	180	7.944±0.243	15.991
7	55	20	150	18.063±0.425	23.309
8	70	28	120	10.357±0.459	12.543
9	40	22	180	12.500±0.386	20.811
10	70	22	180	12.341±0.652	18.744
11	55	25	200	2.325±0.135	17.374
12	70	28	180	9.968±0.682	14.373
13	55	25	100	4.901±0.248	4.662
14	80	25	150	2.214±0.168	8.951
15	55	30	150	14.802±0.701	22.850
16	55	25	150	19.008±0.813	24.254
17	40	28	120	7.171±0.682	11.205
18	55	25	150	15.393±0.436	24.254

Table 3. Analysis of variance (ANOVA) of the model for protein amount of Tetraselmis striata

Source	Sum of squares	Degree of freedom	Mean square	F-value	p > F
Model	622.68	9	69.19	8.31	0.0033
X1: Light intensity	3.93	1	3.93	0.47	0.5116
X2:Temperature	0.37	1	0.37	0.045	0.8373
X3: Agitation	13.38	1	13.38	1.61	0.2405
X1X2	0.097	1	0.097	0.012	0.9167
X1X3	4.22	1	4.22	0.51	0.4968
X2X3	36.47	1	36.47	4.38	0.0697
${\displaystyle X_1^2}$	342.96	1	342.96	41.21	0.0002
${\displaystyle X_2^2}$	2.16	1	2.16	0.26	0.6244
${\displaystyle X_3^2}$	309.36	1	309.36	37.17	0.0003
Residual	66.58	8	8.32
Lack of fit	52.80	5	10.56	2.30	0.2626
Pure error	13.79	3	4.60
Cor. total	689.27	17
Std. dev.	2.88	R-squared	0.9034
Mean	10.42	Adj. R-squared	0.7947
C.V.%	27.69	Pred. R-squared	0.3795
Press	427.72	Adeq. precision	7.279

Figure 1. The relationship between the predicted values and actual values for protein amount of T. striata.

Figure 2. 3D response surface plot of central composite design showing the mutual effects of light intensity and temperature on protein amount (μg/100 μL) of T. striata.

Figure 3. 3D response surface plot of central composite design showing the mutual effects of light intensity and agitation rate on protein amount (μg/100 μL) of T. striata.

Figure 4. 3D response surface plot of central composite design showing the mutual effects of temperature and agitation rate on protein amount (μg/100 μL) of T. striata.

Figure 5. Growth profile of T. striata under optimized conditions: protein (▴), cell count (□).