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

Abstract

Depleting supplies of fossil fuel, regular price hikes of gasoline and environmental deterioration have necessitated the search for economic and eco-benign alternatives of gasoline like lignocellulosic biomass. However, pre-treatment of such biomass results in development of some phenolic compounds which later hinder the depolymerisation of biomass by cellulases and seriously affect the cost effectiveness of the process. Dephenolification of biomass hydrolysate is well cited in literature. However, elimination of phenolic compounds from pretreated solid biomass is not well studied. The present study was aimed to optimize dephenoliphication of wheat straw using various alkalis i.e., Ca(OH)2 and NH3; acids i.e., H2O2, H2SO4, and H3PO4; combinations of NH3+ H3PO4 and H3PO4+ H2O2 at pilot scale to increase enzymatic saccharification yield. Among all the pretreatment strategies used, maximum reduction in phenolic content was observed as 66 mg Gallic Acid Equivalent/gram Dry Weight (GAE/g DW), compared to control having 210 mg GAE/g DW using 5% (v/v) combination of NH3+H3PO4. Upon subsequent saccharification of dephenoliphied substrate, the hydrolysis yield was recorded as 46.88%. Optimized conditions such as using 1%+5% concentration of NH3+ H3PO4, for 30 min at 110°C temperature reduced total phenolic content (TPC) to 48 mg GAE/g DW. This reduction in phenolic content helped cellulases to act more proficiently on the substrate and saccharification yield of 55.06% was obtained. The findings will result in less utilization of cellulases to get increased yield of saccharides by hydrolyzing wheat straw, thus, making the process economical. Furthermore, pilot scale investigations of current study will help in upgrading the novel process to industrial scale.

Valorization of Afzelia bella oilseeds cake in bioethanol production using 1-butyl-3-methyl-imidazolium chloride ionic liquid and dilute sulfuric acid pretreatment

“…Ionic liquids are environmentally friendly, reusable and reputedly very effective for the pretreatment of lignocellulosic biomasses (Rezania et al, 2020;Haq et al, 2021). 1-Butyl-3-methyl-imidazolium chloride was successfully synthesized according to the method described in the literature (Pinkert et al, 2009;Wei et al, 2012;Zhang et al, 2015).…”

“…However, these lignocellulosic substrates need to be pretreated to facilitate hydrolysis and subsequent bioethanol production (Sharma et al, 2021). There are several types of pretreatments, including chemical (acid or alkaline), physical and enzymatic (Saini et al, 2020;Rezania et al, 2020;Xu et al, 2020;Haq et al, 2021;Sharma et al, 2021). The latter pre-treatment is effective but very costly.…”

“…For this reason, the first two are more widely used, as they are less costly (Saini et al, 2020;Rezania et al, 2020;Haq et al, 2021). Nowadays, a variety of ionic liquids with imidazolium, pyridinium, ammomium and phosphonium cations coupled with various anions such as chloride, acetate and phosphonate have been used in the pretreatment of lignocellulosic biomasses because they improve saccharification efficiency by removing lignin from lignocellulosic biomasses and they also have high thermal stability, negligible vapor pressures; they do not release toxic or explosive gases when used (Saini et al, 2020;Rezania et al, 2020;Xu et al, 2020;Haq et al, 2021;Sharma et al, 2021). After this pre-treatment, the lignocellulosic substrate is hydrolyzed into fermentable simple sugars (glucose, fructose, galactose, etc.…”

Purification and Enzymatic Properties of a New Thermostable Endoglucanase From Aspergillus Oryzae HML366

“…Cellulose is a linear homopolysaccharide of 100-1000 D-glucose units, which are linked together by β-(1,4). )-Glycosidic bond (Himmel et al 2007;Yang et al 2021;Zhou et al 2021).…”

“…It can also increase the strength of pulp. Thus, endoglucanases have been widely used in pulp, textiles, bioethanol, washing, wine and beer, food processing, animal feed, agriculture, biomolecular chemical products and the pharmaceutical industry (Araújo et al 2021;Haq et al 2021;Aich and Datta 2020;Li et al 2021;Pereira et al 2021;Ibrahim et al 2021;Petrova et al 2009;Zhang et al 2021).…”