Effect of combined non-thermal plasma/Fenton treatment on lignocellulose degradation in corn stalks

Abstract

Corn is one of the world´s most commonly cultivated crops.A major part of the plant remaining after harvesting is the corn stalk.This corn residueis rich in carbohydrates and could be suitable for the fermentative production of numerous value-added products. The corn stalk’s complex structure, recalcitrance deriving from lignin, and high crystallinity and polymerization degree of cellulose prevent conventional pretreatment techniques to separate it efficiently into elementary fractions. Therefore, it is usually processed by burning directly on the ground or landfilling.It seldom can be used for composting or combusted for heat generation. In this study, different advanced oxidation processes were used for the treatment of corn stalks to enable more sustainable valorization of biomass by enzymatic hydrolysis. The effects of non-thermal plasma treatment, treatment with Fenton reagent, and combined non-thermal plasma/Fenton treatment on lignocellulose degradation and biomass digestibility were monitored. Treatment efficacy in terms of degradation was assessed by determininglignincontent. Structural and textural properties of treated biomass were analyzed using FTIR analysis and mercury intrusion porosimetry (MIP).The carbohydrate digestibility estimation was based on hexose and pentose content in hydrolyzed samples. Applied treatments showed success in breaking complex lignocellulose structures. The delignification rates for the non-thermal plasma treated sample, thesample treated only with the Fenton reagent, and the combined non-thermal plasma/Fenton treated sample were 19%, 28.7%, and 53%, respectively. Selectivity towards lignin increased with prolonging the non-thermal plasma treatmentorthe addition of the Fenton reagent.To achieve a delignification rateof 53% by using only non-thermal plasma, treatment should last at least 60 minutes. When the Fenton reagent is added, the same result is obtained with a halved duration of the plasma treatment. Under these conditions, pore size diameter in treated biomass increased, resulting in enhanced biomass digestibility with 2.25 times higher hexose yield compared to the untreated sample. This is a significant step forward in developing sustainable treatments for lignocellulosic biomass, which is especially important in biorefinery processes.