Research Article

Production of Monomeric Aromatic Compounds from Oil Palm Empty Fruit Bunch Fiber Lignin by Chemical and Enzymatic Methods

Table 1

Effect of pH, solid content, enzyme concentration, time, and temperature on oxidation products yield from enzyme cutinase hydrolysis on lignin (; ).
(a) pH

CompoundspH 7pH 8pH 10pH 12
YieldRecoveryYieldRecoveryYieldRecoveryYieldRecovery

Hydroxybenzoic acid153.14 ± 3.077.66 ± 0.15165.30 ± 2.518.27 ± 0.13162.72 ± 4.138.14 ± 0.21156.14 ± 4.037.81 ± 0.20
Syringaldehyde13.89 ± 0.220.70 ± 0.0114.94 ± 0.360.75 ± 0.0213.93 ± 0.900.70 ± 0.052.71 ± 0.600.14 ± 0.03
Vanillin 3.33 ± 0.580.17 ± 0.038.02 ± 0.320.40 ± 0.028.49 ± 0.090.42 ± 0.019.55 ± 0.530.48 ± 0.03
p-Coumaric acid7.04 ± 0.210.35 ± 0.017.72 ± 0.200.39 ± 0.018.22 ± 1.180.41 ± 0.066.83 ± 0.450.34 ± 0.02
Ferulic acid13.80 ± 0.630.69 ± 0.0314.06 ± 0.130.70 ± 0.0713.68 ± 0.380.68 ± 0.027.78 ± 0.390.39 ± 0.02

Note.
Different alphabets in the same row indicated that there are significant differences () between the yields from different pH.
Different alphabets in the same row indicated that there are significant differences () between the recoveries from different pH.
(b) Lignin concentration

Compounds2% wt.5% wt.8% wt.10% wt.
YieldRecoveryYieldRecoveryYieldRecoveryYieldRecovery

Hydroxybenzoic acid165.30 ± 2.518.27 ± 0.13454.14 ± 11.669.08 ± 0.23642.83 ± 14.458.04 ± 0.18733.19 ± 26.687.33 ± 0.27
Syringaldehyde14.94 ± 0.360.75 ± 0.0249.70 ± 2.880.99 ± 0.0670.19 ± 3.310.88 ± 0.0477.78 ± 3.780.79 ± 0.04
Vanillin 8.02 ± 0.320.40 ± 0.0216.65 ± 1.070.33 ± 0.0222.80 ± 1.040.29 ± 0.0125.39 ± 0.780.25 ± 0.08
p-Coumaric acid7.72 ± 0.200.39 ± 0.0119.07 ± 0.670.38 ± 0.0127.06 ± 1.200.34 ± 0.0229.13 ± 2.720.29 ± 0.03
Ferulic acid14.06 ± 0.130.70 ± 0.0739.02 ± 1.420.78 ± 0.0350.19 ± 1.230.63 ± 0.0256.95 ± 2.520.57 ± 0.03

Note.
Different alphabets in the same row indicated that there are significant differences () between the yields from different lignin concentration.
Different alphabets in the same row indicated that there are significant differences () between the recoveries from different lignin concentration.
(c) Enzyme concentration

Compounds0.625 mL cutinase g−1 lignin 1.25 mL cutinase g−1 lignin 1.875 mL cutinase g−1 lignin 2.5 mL cutinase g−1 lignin
YieldRecoveryYieldRecoveryYieldRecoveryYieldRecovery

Hydroxybenzoic acid642.83 ± 14.458.04 ± 0.18557.80 ± 12.766.97 ± 0.16569.66 ± 11.487.12 ± 0.14542.94 ± 27.886.79 ± 0.35
Syringaldehyde70.19 ± 3.310.88 ± 0.0453.94 ± 1.200.67 ± 0.0254.09 ± 3.000.68 ± 0.0454.94 ± 4.670.69 ± 0.06
Vanillin 22.80 ± 1.040.29 ± 0.0121.68 ± 0.480.27 ± 0.0121.87 ± 0.710.27 ± 0.0120.77 ± 1.120.26 ± 0.01
p-Coumaric acid27.06 ± 1.200.34 ± 0.0222.81 ± 1.440.29 ± 0.0221.78 ± 0.650.27 ± 0.0119.69 ± 0.250.25 ± <0.00
Ferulic acid50.19 ± 1.230.63 ± 0.0246.94 ± 1.590.59 ± 0.0246.33 ± 3.560.58 ± 0.0446.93 ± 2.810.59 ± 0.04

Note.
Different alphabets in the same row indicated that there are significant differences () between the yields from different enzyme concentration.
Different alphabets in the same row indicated that there are significant differences () between the recoveries from different enzyme concentration.
(d) Time

Compounds24 hours48 hours72 hours
YieldRecoveryYieldRecoveryYieldRecovery

Hydroxybenzoic acid642.83 ± 14.458.04 ± 0.18592.59 ± 35.117.41 ± 0.44649.62 ± 21.358.12 ± 0.27
Syringaldehyde70.19 ± 3.310.88 ± 0.0428.23 ± 0.550.35 ± 0.0134.03 ± 2.010.43 ± 0.03
Vanillin 22.80 ± 1.040.29 ± 0.0126.61 ± 1.800.33 ± 0.0232.64 ± 2.350.41 ± 0.03
p-Coumaric acid27.06 ± 1.200.34 ± 0.0222.08 ± 0.590.28 ± 0.0123.76 ± 1.630.30 ± 0.02
Ferulic acid50.19 ± 2.230.63 ± 0.0241.77 ± 0.900.52 ± 0.0143.39 ± 1.100.54 ± 0.01

Note.
Different alphabets in the same row indicated that there are significant differences () between the yields from different time.
Different alphabets in the same row indicated that there are significant differences () between the recoveries from different time.
(e) Temperature

Compounds40°C55°C65°C
YieldRecoveryYieldRecoveryYieldRecovery

Hydroxybenzoic acid492.54 ± 38.896.16 ± 0.49557.80 ± 12.766.97 ± 0.16498.88 ± 42.356.24 ± 0.53
Syringaldehyde35.22 ± 2.010.44 ± 0.0353.94 ± 1.200.67 ± 0.0260.12 ± 4.260.75 ± 0.05
Vanillin15.99 ± 0.740.20 ± 0.0121.68 ± 0.500.27 ± 0.0123.44 ± 2.210.29 ± 0.03
p-Coumaric acid13.94 ± 1.290.17 ± 0.0222.81 ± 1.440.29 ± 0.0213.01 ± 2.150.16 ± 0.03
Ferulic acid37.81 ± 2.350.47 ± 0.0346.94 ± 1.590.59 ± 0.0231.74 ± 2.800.40 ± 0.04

Note.
Different alphabets in the same row indicated that there are significant differences () between the yields from different temperature.
Different alphabets in the same row indicated that there are significant differences () between the recoveries from different temperature.
Yield of oxidation products was expressed in unit part per million (ppm), while recovery of oxidation products from lignin was expressed in unit milligram per gram of lignin (mg g−1 lignin).