Hydrolysis pattern analysis of xylem tissues of woody plants pretreated with hydrogen peroxide and acetic acid: Rapid saccharification of softwood for economical bioconversion
Background: Woody plants with high glucose content are alternative bioresources for the production of biofuels and biochemicals. Various pretreatment methods may be used to reduce the effects of retardation factors such as lignin interference and cellulose structural recalcitrance on the degradation of the lignocellulose material of woody plants.
Results: A hydrogen peroxide-acetic acid (HPAC) pretreatment was used to reduce the lignin content of several types of woody plants, and the effect of the cellulose structural recalcitrance on the enzymatic hydrolysis was analyzed. The cellulose structural recalcitrance and the degradation patterns of the wood fibers in the xylem tissues of Quercus acutissima (hardwood) resulted in greater retardation in the enzymatic saccharification than those in the tracheids of Pinus densiflora (softwood). In addition to the HPAC pretreatment, the application of supplementary enzymes (7.5 FPU cellulase for 24 h) further increased the hydrolysis rate of P. densiflora from 61.42% to 91.94% whereas the same effect was not observed for Q. acutissima. It was also observed that endoxylanase synergism significantly affected the hydrolysis of P. densiflora. However, this synergistic effect was lower for other supplementary enzymes. The maximum concentration of the reducing sugars produced from 10% softwood was 89.17 g L-1 after 36 h of hydrolysis with 15 FPU cellulase and other supplementary enzymes. Approximately 80 mg mL-1 of reducing sugars was produced with the addition of 7.5 FPU cellulase and other supplementary enzymes after 36 hours, achieving rapid saccharification.
Conclusion: HPAC pretreatment removed the interference of lignin, reduced structural recalcitrance of cellulose in the P. densiflora, and enabled rapid saccharification of the woody plants including a high concentration of insoluble substrates with only low amounts of cellulase. HPAC pretreatment may be a viable alternative for the cost-efficient production of biofuels or biochemicals from softwood plant tissues.
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Additional file 1: Figure S1. The fragmentations of HPAC-pretreated softwood and hardwood. (A) P. densiflora; (B) Q. acutissima. Tracheids or wood fibers from P. densiflora and Q. acutissima were hydrolyzed with 7.5 FPU cellulase (50 μL mL-1) g biomass-1 in 1 mL of 0.1 M citrate buffer (pH 5.0) at 50 °C. a, 0 h; b, 3 h; c, 6 h.
Additional file 2: Figure S2. The comparison of end-product inhibition effect on various substrate concentrations of P. densiflora during enzymatic hydrolysis. The theoretical product of each concentration of the substrate was calculated from the concentration of reducing sugars when the hydrolysis of 1% HPAC-pretreated softwood was nearly complete. The reactions were performed with 15 FPU cellulase g biomass-1 at 50 °C for 36 h.
Posted 13 Jan, 2021
Received 06 Jan, 2021
On 04 Jan, 2021
On 04 Jan, 2021
Invitations sent on 03 Jan, 2021
On 29 Dec, 2020
On 29 Dec, 2020
On 29 Dec, 2020
Received 29 Nov, 2020
On 29 Nov, 2020
On 15 Nov, 2020
Received 23 Sep, 2020
On 18 Sep, 2020
Invitations sent on 10 Aug, 2020
On 10 Aug, 2020
On 07 Aug, 2020
On 07 Aug, 2020
On 06 Aug, 2020
On 06 Aug, 2020
Hydrolysis pattern analysis of xylem tissues of woody plants pretreated with hydrogen peroxide and acetic acid: Rapid saccharification of softwood for economical bioconversion
Posted 13 Jan, 2021
Received 06 Jan, 2021
On 04 Jan, 2021
On 04 Jan, 2021
Invitations sent on 03 Jan, 2021
On 29 Dec, 2020
On 29 Dec, 2020
On 29 Dec, 2020
Received 29 Nov, 2020
On 29 Nov, 2020
On 15 Nov, 2020
Received 23 Sep, 2020
On 18 Sep, 2020
Invitations sent on 10 Aug, 2020
On 10 Aug, 2020
On 07 Aug, 2020
On 07 Aug, 2020
On 06 Aug, 2020
On 06 Aug, 2020
Background: Woody plants with high glucose content are alternative bioresources for the production of biofuels and biochemicals. Various pretreatment methods may be used to reduce the effects of retardation factors such as lignin interference and cellulose structural recalcitrance on the degradation of the lignocellulose material of woody plants.
Results: A hydrogen peroxide-acetic acid (HPAC) pretreatment was used to reduce the lignin content of several types of woody plants, and the effect of the cellulose structural recalcitrance on the enzymatic hydrolysis was analyzed. The cellulose structural recalcitrance and the degradation patterns of the wood fibers in the xylem tissues of Quercus acutissima (hardwood) resulted in greater retardation in the enzymatic saccharification than those in the tracheids of Pinus densiflora (softwood). In addition to the HPAC pretreatment, the application of supplementary enzymes (7.5 FPU cellulase for 24 h) further increased the hydrolysis rate of P. densiflora from 61.42% to 91.94% whereas the same effect was not observed for Q. acutissima. It was also observed that endoxylanase synergism significantly affected the hydrolysis of P. densiflora. However, this synergistic effect was lower for other supplementary enzymes. The maximum concentration of the reducing sugars produced from 10% softwood was 89.17 g L-1 after 36 h of hydrolysis with 15 FPU cellulase and other supplementary enzymes. Approximately 80 mg mL-1 of reducing sugars was produced with the addition of 7.5 FPU cellulase and other supplementary enzymes after 36 hours, achieving rapid saccharification.
Conclusion: HPAC pretreatment removed the interference of lignin, reduced structural recalcitrance of cellulose in the P. densiflora, and enabled rapid saccharification of the woody plants including a high concentration of insoluble substrates with only low amounts of cellulase. HPAC pretreatment may be a viable alternative for the cost-efficient production of biofuels or biochemicals from softwood plant tissues.
Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
Figure 6