Performance Evaluation of Combined Hydrothermal-Mechanical Pretreatment of Lignocellulosic Biomass for Enzymatic Enhancement

Abstract

Pretreatment is a crucial process in a lignocellulosic biorefinery. Corncob is typically considered as a natural renewable carbon source to produce various bio-based products. This study aimed to evaluate the performance of the hydrothermal-mechanical pretreatment of corncob for biofuels and biochemical production. Corncob was first pretreated by liquid hot water (LHW) at different temperatures (140–180 °C) and duration (30, 60 min) and then subjected to centrifugal milling to produce bio-powders. To evaluate the performance of this combined pretreatment, the energy efficiency and waste generation were investigated. The results indicated that the maximum fermentable sugars (FS) were 0.488 g/g biomass obtained by LHW at 180 °C, 30 min. In order to evaluate the performance of this combined pretreatment, the energy efficiency and waste generation were 28.3 g of FS/kWh and 7.21 kg of waste/kg FS, respectively. These obtained results indicate that the combined hydrothermal-mechanical pretreatment was an effective pretreatment process to provide high energy efficiency and low waste generation to produce biofuels. In addition, the energy efficiency and waste generation will be useful indicators for process scaling-up into the industrial scale. This combined pretreatment could be a promising pretreatment technology for the production of biofuels and biochemicals from lignocellulosic valorization.

Surfactants, Biosurfactants, and Non-Catalytic Proteins as Key Molecules to Enhance Enzymatic Hydrolysis of Lignocellulosic Biomass

“…Many reagents have been used as catalysts in alkaline pretreatment technologies, such as calcium hydroxide, potassium hydroxide, aqueous ammonia solution, sodium hydroxide, and others, reducing the crystallinity of the biomass, separating structural bonds between lignin and carbohydrates, breaking the macromolecular structure, increasing the surface area of the biomass, and, hence, producing minimal inhibitory subproducts, and enhancing biomass enzymatic digestibility [ 11 ]. Nevertheless, pretreatments count for around 30–40% of the total cost of the process, so alternative strategies must be considered to make it viable [ 17 ]. In addition to pretreatments, an alternative approach is the use of additives (e.g., surfactants, biosurfactants, and non-catalytic proteins) to enhance the enzymatic process and valorize the lignocellulosic biomass in a biorefinery concept.…”

Thermodynamic and Kinetic Equilibrium for Adsorption of Cellulosic Xylose of Commercial Cation-Exchange Resins

“…The hydrothermal pretreatment is commonly a thermochemical conversion process, which operates by using water as medium to decompose the lignocellulosic structure, thereby providing a complex liquid fraction called hydrolysate . The chemical reaction taking place in the hydrothermal process is mostly hydrolysis by disrupting and solubilizing the hydroxyl groups of hemicellulose and some specific chemical bonds . The biomass hydrolysate consists typically of monosaccharides, organic acids, phenolic compounds, furfurals, inhibitors, and some other derivatives. , Monosaccharides are the major components contained in the hydrolysate, which could be useful for conversion into biofuels, biochemicals, food, and pharmaceutical ingredients .…”

Subcritical Water as Pretreatment Technique for Bioethanol Production from Brewer’s Spent Grain within a Biorefinery Concept

“…The use of subcritical water (subW) as an eco-friendly method for lignocellulose pretreatment avoiding chemicals addition was proposed in recent studies [ 8 , 9 , 10 , 11 ]. SubW is pressurized water in its liquid state in the temperature range from 100 °C to 374 °C.…”

“…During the subW pretreatment, the hemicelluloses fraction is mostly hydrolyzed/solubilized. This way, the sugars present in the hemicelluloses fraction are released (as oligomers and/or monomers), and the remaining solid is enriched in cellulose and lignin [ 8 , 11 , 13 ]. In addition, during subW pretreatment, different bioactive compounds can be released from the biomass, such as phenolic compounds, protein, and amino acids [ 7 ].…”

“…The cellulose-rich fraction remaining after the subW pretreatment can be subjected to enzymatic hydrolysis. This biopolymeric cellulosic fraction can feed bioethanol production [ 11 ], and different fermentation strategies can be employed, namely separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF). The main advantage of SHF is that the hydrolysis and the fermentation processes can be performed under their different optimal conditions, around 50 °C for the enzymatic hydrolysis and 28–30 °C for the yeast fermentation.…”