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Table 2 Central composite design: factor (Xi), response variable (Y) and residual

From: Optimization of enzymatic esterification of dihydrocaffeic acid with hexanol in ionic liquid using response surface methodology

Run Concentration of hexanola (mM × 10−4) Enzyme amountb (%) Reaction time (h) Reaction temperature (°C) Conversion (%) Predicted (%) Residual
X1 X2 X3 X4 Y Y0 Y − Y0
12c 5.5 (0) 25.0 (0) 48.0 (0) 50.0 (0) 65.131 62.222 2.909
11 8.8 (+1) 35.0 (+1) 24.0 (−1) 60.0 (+1) 25.054 28.459 −3.404
4 2.2 (−1) 15.0 (−1) 24.0 (−1) 60.0 (+1) 17.151 23.714 −6.563
23 2.2 (−1) 15.0 (−1) 72.0 (+1) 40.0 (−1) 12.597 16.561 −3.964
5 2.2 (−1) 35.0 (+1) 24.0 (−1) 40.0 (−1) 18.375 9.751 8.623
26 8.8 (+1) 15.0 (−1) 72.0 (+1) 60.0 (+1) 29.213 36.068 −6.855
3 8.8 (+1) 35.0 (+1) 72.0 (+1) 40.0 (−1) 81.140 78.966 2.174
14c 5.5 (0) 25.0 (0) 48.0 (0) 50.0 (0) 64.554 62.222 2.332
1 2.2 (−1) 35.0 (+1) 72.0 (+1) 60.0 (+1) 19.431 24.580 −5.149
19 8.8 (+1) 15.0 (−1) 24.0 (−1) 40.0 (−1) 21.519 11.621 9.897
6 5.5 (0) 25.0 (0) 8.0 (−1.66) 50.0 (0) 17.720 25.369 −7.649
25 11.0 (1.66) 25.0 (0) 48.0 (0) 50.0 (0) 35.044 34.562 0.482
13c 5.5 (0) 25.0 (0) 48.0 (0) 50.0 (0) 62.571 60.415 2.156
28c 5 (0) 25.0 (0) 48.0 (0) 50.0 (0) 60.401 60.415 −0.014
22 5.5 (0) 8.3 (−1.66) 48.0 (0) 50.0 (0) 35.341 34.698 0.643
7 5.5 (0) 25.0 (0) 87.9 (1.66) 50.0 (0) 66.911 59.798 7.113
20 5.5 (0) 41.6 (1.66) 48.0 (0) 50.0 (0) 55.932 57.111 −1.179
15 5.5 (0) 25.0 (0) 48.0 (0) 66.6 (1.66) 45.865 41.460 4.405
27 0.0 (−1.66) 25.0 (0) 48.0 (0) 50.0 (0) 0.000 1.018 −1.018
9 5.5 (0) 25.0 (0) 48.0 (0) 33.3 (−1.66) 38.220 43.160 −4.94
30 2.2 (−1) 35.0 (+1) 24.0 (−1) 60.0 (+1) 21.574 20.005 1.569
2 8.8 (+1) 15.0 (−1) 72.0 (+1) 40.0 (−1) 42.416 48.361 −5.945
18 8.8 (+1) 35.0 (+1) 72.0 (+1) 60.0 (+1) 69.420 65.198 4.222
10 8.8 (+1) 15.0 (−1) 24.0 (−1) 60.0 (+1) 15.065 13.174 1.891
29c 5.5 (0) 25.0 (0) 48.0 (0) 50.0 (0) 66.363 69.144 −2.781
16 2.2 (−1) 35.0 (+1) 72.0 (+1) 40.0 (−1) 24.885 28.172 −3.287
8 2.2 (−1) 15.0 (−1) 24.0 (−1) 40.0 (−1) 15.505 11.986 3.519
24 2.2 (−1) 15.0 (−1) 72.0 (+1) 60.0 (+1) 49.382 42.135 7.247
17 8.8 (+1) 35.0 (+1) 24.0 (−1) 40.0 (−1) 53.586 56.072 −2.486
21c 5.5 (0) 25.0 (0) 48.0 (0) 50.0 (0) 65.196 69.144 −3.948
  1. aSubstrate molar ratio was selected correspondingly to 0.5 − 2(2.2–8.8 × 10−4 mM) hexanol to dihydrocaffeic acid (4.4 × 10−4 mM)
  2. b15–35% relative to the total weight of substrates
  3. c Center point