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Table 4 Levels of independent variables established according to central composite design for enzymatic esterification of hexyl dihydrocaffeate condition level (coded and, un coded)

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

Independent variable Independent variable level
Low (−1) Medium (0) High (+1) Axial (−1.66) Axial (+1.66)
Reaction timea 24 48 72 8.0 88.0
Reaction Tempb 40 50 60 33.3 66.7
Conc. of hexanolc 2.2 5.5 8.8 0.0 11.0
Enzyme amountd 15 25 35 8.3 41.6
  1. aReaction time (h)
  2. bReaction temperature (°C)
  3. cConcentration of hexanol (substrate molar ratio was selected correspondingly to 0.5 − 2((2.2–8.8) × 10−4 mM) of hexanol to dihydrocaffeic acid (4.4 × 10−4 mM)
  4. d15–35% relative to the total weight of substrates