Properties important for solid-liquid separations change during the enzymatic hydrolysis of pretreated wheat straw

Innovation in lignocellulosics dewatering and drying for energy sustainability and enhanced utilization of forestry, agriculture, and marine resources - A review

Efficient utilization of forestry, agriculture, and marine resources in various manufacturing sectors requires optimizing fiber transformation, dewatering, and drying energy consumption. These processes play a crucial role in reducing the carbon footprint and boosting sustainability within the circular bioeconomy framework. Despite efforts made in the paper industry to enhance productivity while conserving resources and energy through lower grammage and higher machine speeds, reducing thermal energy consumption during papermaking remains a significant challenge. A key approach to address this challenge lies in increasing dewatering of the fiber web before entering the dryer section of the paper machine. Similarly, the production of high-value-added products derived from alternative lignocellulosic feedstocks, such as nanocellulose and microalgae, requires advanced dewatering techniques for techno-economic viability. This critical and systematic review aims to comprehensively explore the intricate interactions between water and lignocellulosic surfaces, as well as the leading technologies used to enhance dewatering and drying. Recent developments in technologies to reduce water content during papermaking, and advanced dewatering techniques for nanocellulosic and microalgal feedstocks are addressed. Existing research highlights several fundamental and technical challenges spanning from the nano- to macroscopic scales that must be addressed to make lignocellulosics a suitable feedstock option for industry. By identifying alternative strategies to improve water removal, this review intends to accelerate the widespread adoption of lignocellulosics as feasible manufacturing feedstocks. Moreover, this review aims to provide a fundamental understanding of the interactions, associations, and bonding mechanisms between water and cellulose fibers, nanocellulosic materials, and microalgal feedstocks. The findings of this review shed light on critical research directions necessary for advancing the efficient utilization of lignocellulosic resources and accelerating the transition towards sustainable manufacturing practices.

Statistical analysis of the crystallinity index of nanocellulose produced from Kraft pulp via controlled enzymatic hydrolysis

Enzymatic hydrolysis processes can change the physical characteristics of nanocellulose derived from Kraft pulp. Among these attributes are its crystallinity index and dimensions. In this study, we determined the optimal conditions under which nanocellulose could be produced enzymatically with the greatest increase of the crystallinity index relative to its initial state. Application of Central Composite Rotatable Design statistical analysis to the experiments was employed to direct an increase the crystallinity index in 10% at the 24-H hydrolysis time. Upon establishment of ideal levels of starting material and enzyme, reactions were carried out at hydrolysis times of 24, 48, and 72 H under these ideal parameters. The effectiveness of deagglomeration was demonstrated by measuring the hydrodynamic diameter of the particles by dynamic light scattering. Scanning electron microscopy was performed on four samples, the original material, kraft pulp, and hydrolyzed biomaterials at 72 H in the ideal parameters. The hydrolyzed material with the best statistical data, revealing a fiber diameter of 180 nm, disclosing to be biomaterial with nanocellulose dimensions.

Enhancement of Bacillus subtilis Growth and Sporulation by Two-Stage Solid-State Fermentation Strategy

Two-stage solid-state fermentation strategy was exploited and systematically optimized to enhance Bacillus subtilis growth and sporulation for increasing effective cell number in B. subtilis microbial ecological agents. The first stage focused on improving cell growth followed by the second stage aiming to enhance both cell growth and sporulation. The optimal fermentation condition was that temperature changed from 37 °C to 47 °C at a fermentation time of 48 h and Mn2+ content in medium was 4.9 mg MnSO4/g dry medium. Solid medium properties were improved by the optimal two-stage fermentation. HPLC results demonstrated that glucose utilization was facilitated and low-field nuclear magnetic resonance (LF-NMR) results showed that more active sites in medium for microbial cells were generated during the optimal two-stage fermentation. Moreover, microbial growth and sporulation were enhanced simultaneously during the second stage of fermentation through delaying microbial decline phase and increasing sporulation rate. As a result, effective cell number of B. subtilis reached 1.79 × 1010/g dry medium after fermentation for 72 h, which was 29.7% and 8.48% higher than that of conventional fermentation for 72 h and 48 h, respectively. Therefore, the optimal two-stage fermentation could increase the effective cell number of B. subtilis microbial ecological agents efficiently.

Effects of preheating on briquetting and subsequent hydrothermal pretreatment for enzymatic saccharification of wheat straw

Briquetting of plant biomass with low bulk density is an advantage for handling, transport, and storage of the material, and heating of the biomass prior to the briquetting facilitates the densification process and improves the physical properties of the briquettes. This study investigates the effects of preheating prior to briquetting of wheat straw (WS) on subsequent hydrothermal pretreatment and enzymatic conversion to fermentable sugars. WS (11% moisture content) was densified to briquettes under different conditions; without preheating or with preheating at 75 or 125°C for either 5 or 10 min. Subsequent hydrothermal pretreatment was done for both un-briquetted WS and for briquettes. Enzymatic saccharification was afterwards performed for all samples. The results showed that as expected, nonpretreated WS briquettes gave very low sugar yields (22-29% of the cellulose content), even though preheating at 125°C prior to briquetting (without pretreatment) improved sugar yields somewhat. When combined with pretreatment, briquetting with preheating showed neutral or negative effects on sugar yield. This result suggests that moderate preheating (75°C for 5 min) before briquetting improved bulk density and compressive resistance of briquettes without impeding subsequent enzymatic conversion. However, excessive preheating (75 or 125°C for 10 min) before briquetting may result in irreversible structural modifications that hinder the interaction between biomass and water during pretreatment, thereby decreasing the accessibility of cellulose to enzymatic saccharification.