Removal of phenolic compounds through overliming for enhanced saccharification of wheat straw

Abstract

BACKGROUND The deactivation of cellulases by phenolics is considered to be the main bottleneck in the saccharification of agricultural by‐products for efficient bioethanol production on a large scale. The removal of these phenolic inhibitors, produced as a result of pretreatment, is essential for an efficient saccharification process. One such process is overliming that has been mostly studied for hydrolysates of agricultural by‐products. In the present study however, solid biomass was used whereby the detection of phenolic compounds and their effect on saccharification was studied. RESULTS The pretreated wheat straw showed 19% saccharification and total phenolic content (TPC) of 188 mg gallic acid equivalent g‐1 biomass dry weight. Detoxification of pretreated wheat straw applying different alkalis, i.e. NaOH, NH4OH and Ca(OH)2 was conducted. Overliming using Ca(OH)2 solution of pH 12, for 2 h at 80°C showed significant removal of 60% of phenolic compounds, which in turn enhanced the saccharification by 2.4‐fold. Scanning electron microscopy of pretreated and overlimed substrates also showed considerable change in structure, making it more accessible for enzymatic hydrolysis. CONCLUSION The elimination of phenolic compounds due to overliming has facilitated increased saccharification that in turn will help in substrate efficient biofuel production. © 2018 Society of Chemical Industry

Eurasian water milfoil: Composition, recovery of phenolics and anthocyanins, and saccharification

“…Alkalis are often used for biomass detoxification through removal of phenolic compounds, mainly lignin, in order to facilitate the subsequent saccharification. [39] In our case, due to the relatively low concentration used, NaOH only partially removed the lignin. [40] The TPH derived from the solid residue did not show any colour change in response to the change in pH, which means that anthocyanins were not recovered or were degraded in polymeric form.…”

From the culture broth to the erythritol crystals: an opportunity for circular economy

“…In the case of lignocellulosic biomass, it is necessary to overcome the recalcitrance of the raw material (Daza Serna et al 2016 ) and to enhance the sugar recovery (Weinwurm et al 2012 ) while minimizing the production of inhibitory compounds such as furfural and 5-(hydroxymethyl)furfural during pretreatment (Weinwurm et al 2017 ). Detoxification for removal of inhibitory compounds can be performed by membrane separation, overliming, electrocoagulation or adsorption (Zhou et al 2013 ; Haq et al 2018 ; Wang et al 2018 ; Jeong et al 2019 ).…”

Pilot Scale Elimination of Phenolic Cellulase Inhibitors From Alkali Pretreated Wheat Straw for Improved Cellulolytic Digestibility to Fermentable Saccharides

“…Pre-treatment of wheat straw and estimation of lignocellulosic content was carried out according to our previous report by Haq et al (2018). For pretreatment, 2.5% sodium hydroxide (NaOH) was used for 10 min at a steaming temperature of 200 • C in specialized boiler.…”

“…Recently we have demonstrated that the removal of these phenolic compounds can significantly increase the saccharification rate (Haq et al, 2018). However, application of this process at commercial level needs studies at pilot scale which will provide a better understanding of the process.…”