Assessment of pure, mixed and diluted deep eutectic solvents on Napier grass (Cenchrus purpureus): Compositional and characterization studies of cellulose, hemicellulose and lignin.

Pretreatment with pure, mixed, and diluted deep eutectic solvents (DESs) was evaluated for its effect on Napier grass through compositional and characterization studies. The morphological changes of biomass caused by pretreatment were analyzed by FTIR and XRD. The cellulose and hemicellulose content after pretreatment using mixed DES increased and decreased 1.29- and 4.25-fold, respectively, when compared to untreated Napier grass. The crystallinity index (CrI. %) of mixed DES sample increased due to the maximum removal of hemicellulose (76 %) and delignification of 62 %. The material costs of ChCl/FA and ChCl/LA for a single run are ≈2.16 USD and ≈1.65 USD, respectively. Pure DES showed that ChCl/LA pretreatment enhanced delignification efficiency and that ChCl/FA increased hemicellulose removal. It was estimated that a single run using ChCl/LA:ChCl/FA to achieve maximum hemicellulose and lignin removal would cost approximately ≈1.89 USD. Future work will evaluate the effect of DES mixture on enzyme digestibility and ethanol production from Napier grass. HYPOTHESES: Deep eutectic solvent (DES) pretreatment studies on the fractionation of lignocellulosic biomass have grown exponentially. The use of pure and diluted DES has been reported to improve saccharification efficiency, delignification, and cellulose retention (Gundupalli et al., 2022). These studies have reported maximum lignin removal but also a lower effect on hemicellulose removal from lignocellulosic biomass. It was hypothesized that mixing two pure DESs could result in maximum removal of hemicellulose and lignin after pretreatment. To our knowledge, no studies have been performed to investigate the efficiency of pretreatment using a DES mixture and compared the outcome with pure and diluted DESs. Furthermore, it was hypothesized that using two pure DESs in a mixed form could lower the material cost for each experimental run. Process efficiency was determined by compositional, XRD, and FTIR analysis. Avenues for future research include determining glucose and ethanol yields during the enzymatic saccharification and fermentation processes.

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

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.

Improvement of Enzymatic Saccharification and Ethanol Production from Rice Straw Using Recycled Ionic Liquid: The Effect of Anti-Solvent Mixture.

One of the major concerns for utilizing ionic liquid on an industrial scale is the cost involved in the production. Despite its proven pretreatment efficiency, expenses involved in its usage hinder its utilization. A better way to tackle this limitation could be overcome by studying the recyclability of ionic liquid. The current study has applied the Box-Behnken design (BBD) to optimize the pretreatment condition of rice straw through the usage of 1-ethyl-3-methylimidazolium acetate (EMIM-Ac) as an ionic liquid. The model predicted the operation condition with 5% solid loading at 128.4 °C for 71.83 min as an optimum pretreatment condition. Under the optimized pretreatment condition, the necessity of the best anti-solvent was evaluated among water, acetone methanol, and their combinations. The study revealed that pure methanol is the suitable choice of anti-solvent, enhancing the highest sugar yield. Recyclability of EMIM-Ac coupled with anti-solvent was conducted up to five recycles following the predicted pretreatment condition. Fermentation studies evaluated the efficacy of recycled EMIM-Ac for ethanol production with 89% more ethanol production than the untreated rice straw even after five recycles. This study demonstrates the potential of recycled ionic liquid in ethanol production, thereby reducing the production cost at the industrial level.

Gelatin-bacterial cellulose composite sponges thermally cross-linked with glucose for tissue engineering applications.

Freeze-drying and thermal cross-linking techniques were used to prepare gelatin-bacterial cellulose (GB) composite sponges for potential application as scaffolds in tissue engineering. To avoid the use of toxic and costly cross-linking agents, glucose was used to cross-link the gelatin via the Maillard reaction. The effects of the weight ratio of gelatin to bacterial cellulose (BC) and the cross-linking conditions (temperature and duration) on the GB sponges were examined. An open and highly interconnected porous structure was attained for the GB sponge with a gelatin:BC weight ratio of 25:75 that was cross-linked at 140°C for 3h. Its high porosity, good swelling properties, good structural stability in water, non-toxicity and good biocompatibility against Vero cell are promising for its application as a scaffold for tissue engineering.

Structural modification and characterization of bacterial cellulose-alginate composite scaffolds for tissue engineering.

A novel bacterial cellulose-alginate composite scaffold (N-BCA) was fabricated by freeze drying and subsequent crosslinking with Ca(2+). The N-BCA then underwent a second freeze drying step to remove water without altering the physical structure. A stable structure of N-BCA with open and highly interconnected pores in the range of 90-160 µm was constructed. The N-BCA was stable in both water and PBS. The swelling ability of N-BCA in water was approximately 50 times its weight, which was about 6.5 times that of the freeze dried bacterial cellulose pellicles. N-BCA demonstrated no cytotoxicity against L929 mouse fibroblast cells. For long-term culture, N-BCA supported attachment, spreading, and proliferation of human gingival fibroblast (GF) on the surface. However, under static conditions, the cell migration and growth inside the scaffold were limited. Because of its biocompatibility and open macroporous structure, N-BCA could potentially be used as a scaffold for tissue engineering.

Applicability of Washburn capillary rise for determining contact angles of powders/porous materials.

The Washburn capillary rise (WCR) technique has been widely utilized for determining contact angles of powders or porous materials; however, there are concerns regarding powder size and powder packing, especially for materials that exhibit large contact angle hysteresis. In this paper, some of these concerns were addressed. Due to the large water contact angle hysteresis on flat nylon 6/6 films, these films were ground into powders of different sizes and then used as model packing materials. The powders were packed in glass tubes to result in various packing structures that affected the penetration (i.e. advancing) rate of the test liquids. While all advancing contact angles obtained from WCR were found to be overestimated, more reasonable values were resulted when relatively large powders (e.g. 500-2000 µm) were used to pack the tubes. With larger powders, the packing contained bigger voids and consequently lead to slower penetration rates of the liquids, hence a relatively smaller advancing contact angle. The smaller advancing contact angle obtained from the slower advancing rate was also observed by using the sessile drop method. To verify the applicability of using large powders (500-2000 µm) for contact angle determination by using WCR, the advancing water contact angles of a bacterial cellulose/alginate composite sponge (BCA) with and without UV/ozone treatment were measured. The results showed that by using relatively large powders, WCR could be applied to obtain a reasonable advancing contact angle and assess the wettability change of complex porous materials.