Effects of hydrochloric acid washing on the microstructure and pyrolysis bio-oil components of sweet sorghum bagasse

Enhanced Thermostability of an l-Rhamnose Isomerase for d-Allose Synthesis by Computation-Based Rational Redesign of Flexible Regions

d-Allose is a low-calorie rare sugar with great application potential in the food and pharmaceutical industries. The production of d-allose has been accomplished using l-rhamnose isomerase (L-RI), but concomitantly increasing the enzyme's stability and activity remains challenging. Here, we rationally engineered an L-RI from Clostridium stercorarium to enhance its stability by comprehensive computation-aided redesign of its flexible regions, which were successively identified using molecular dynamics simulations. The resulting combinatorial mutant M2-4 exhibited a 5.7-fold increased half-life at 75 °C while also exhibiting improved catalytic efficiency. Especially, by combining structure modeling and multiple sequence alignment, we identified an α0 region that was universal in the L-RI family and likely acted as a "helix-breaker". Truncating this region is crucial for improving the thermostability of related enzymes. Our work provides a significantly stable biocatalyst with potential for the industrial production of d-allose.

Conventional and microwave-assisted acid pretreatment of tea waste powder: analysis of functional groups using FTIR

Tea waste powder (TWP) is one of the potential biomass waste to recover valuable chemicals and materials. The prime objective of this work is to investigate the role of acid pretreatment on TWP. Diluted acids (HCl, H₃PO₄, CH₃COOH, and H₂SO₄) were used to soak the TWP to understand the role of acids on bond cleavage and chemicals formation. One gram of TWP was soaked in 100 mL of diluted acids for 24 h. The soaked samples were further subjected to a hot air oven (temperature: 80 °C, duration: 6 h), orbital shaking (shaking speed: 80-100 rpm, duration: 6 h), and microwave irradiation (microwave power: 100 W, duration: 10 min) to understand the synergistic effects of acids and mode of exposure. The pretreated solid samples and liquid samples were analyzed using FTIR to understand the presence of functional groups. The mass loss of TWP after treatment significantly varied with the type of acid and exposure mode used. In the orbital shaker, the mass loss was varied in the following order: H₂SO₄ (36%) > CH₃COOH (32%) > H₃PO₄ (22%) > HCl (15%). In hot air oven, high mass loss was observed compared to orbital shaking [HCl (48%) > CH₃COOH (37%) > H₂SO₄ (35%) > H₃PO₄ (33%)]. The mass loss in microwave irradiation is lower (19 to 25%) with all acids compared to orbital shaking. In the solid samples, O-H stretching, C-H stretching, C=O stretching, C=C stretching, -C-O-, and -C-OH- functional groups were noticed. Similarly, C=O and C=C peaks and C-O and -C-OH peaks were noticed in liquid samples. Interestingly, microwave irradiation showed promising results in 10 min of pretreatment, whereas orbital shaking and hot air oven pretreatments require 6 h to achieve the same result.

Cr/13X Zeolite and Zn/13X Zeolite Nanocatalysts Used in Pyrolysis of Pretreated Residual Biomass to Produce Bio-Oil with Improved Quality

By loading Cr and Zn on 13X zeolite, efficient nanocatalysts were prepared; they were characterized by different techniques and used for corn cobs pyrolysis to produce bio-oil. The corn cobs biomass (CCB) was washed with sulfuric acid 0.1 M, and the characteristics of the pretreated biomass (PTCCB) were analyzed. Pyrolysis was performed at different catalyst-to-biomass ratios (C/B), and the composition of the obtained bio-oil was determined. The results showed that the crystallinity of the nanocatalysts was slightly lower than that of the pattern 13X zeolite. The surface observation of the nanocatalysts showed the presence of pores and particles, which are quite evenly dispersed on the surface, and no difference was observed in the morphology of the Zn/13X zeolite and Cr /13X zeolite nanocatalysts. In comparison to 13X zeolite, the morphological changes, metal dispersion, and surface area decrease of both Zn/13X and Cr/13X zeolite nanocatalysts could be observed. Pyrolysis tests demonstrated that the use of Zn/13X zeolite and Cr/13X zeolite nanocatalysts could be very profitable to obtain a high conversion to hydrocarbons of the compounds containing oxygen, and consequently, the quality of the bio-oil was improved.

Conversion of Waste Corn Straw to Value-Added Fuel via Hydrothermal Carbonization after Acid Washing

To enhance the hydrothermal carbonization (HTC) process on biomass waste and improve the quality of biomass solid fuel. Corn straw was pretreated with acid washing and subsequently hydrothermally carbonized at 180–270 °C. The solid product obtained (hydrochars) was compared with the solid product produced from untreated hydrothermally carbonized straw. The results show that the acid pretreatment removed 7.9% of the ash from the straw. ICP and XRD analysis show that most of the alkali and alkaline earth metals have been removed. This addresses the defect of high ash content as the HTC temperature increases. The HHV of hydrochars produced by HTC after acid washing can reach 27.7 MJ/kg, which is nearly 10% higher than that of hydrochars prepared without acid washing pretreatment, and nearly 70% higher than that of straw raw materials. Elemental analysis and FTIR analysis show that the acid washing pretreatment changed the content and structure of the biomass components in the straw, resulting in a more complete HTC reaction and higher carbon sequestration. The decrease of H/C and O/C deepened the degree of coal-like transformation of hydrochars, with the lowest approaching the bituminous coal zone. The combustion characteristics of the hydrochars prepared after acid washing were significantly upgraded, the comprehensive combustion index and thermal stability of hydrochars both increased. Therefore, HTC after acid washing pretreatment is beneficial to further improve the high heating value and combustion characteristics of hydrochar.

Bio-Oil: The Next-Generation Source of Chemicals

Bio-oil, although rich in chemical species, is primarily used as fuel oil, due to its greater calorific power when compared to the biomass from which it is made. The incomplete understanding of how to explore its chemical potential as a source of value-added chemicals and, therefore, a supply of intermediary chemical species is due to the diverse composition of bio-oil. Being biomass-based, making it subject to composition changes, bio-oil is obtained via different processes, the two most common being fast pyrolysis and hydrothermal liquefaction. Different methods result in different bio-oil compositions even from the same original biomass. Understanding which biomass source and process results in a particular chemical makeup is of interest to those concerned with the refinement or direct application in chemical reactions of bio-oil. This paper presents a summary of published bio-oil production methods, origin biomass, and the resulting composition.

Torrefaction under mechanical pressure of 10-70 MPa at 250 °C and its effect on pyrolysis behaviours of leucaena wood

In this study, torrefaction under mechanical pressure of 10-70 MPa at 250 °C was proposed as a pretreatment method and its effect on pyrolysis behaviours of Leucaena (LC) was examined at 900 °C. It was found that the mechanical pressure applied during torrefaction could significantly increase the char yield at 900 °C. The char yield increased from 18.7% for Raw to 26.4% and 27.5% for MP40 and MP70, respectively. The %C of biochar prepared from MP40 (MP40-900) was 86.5%, whereas the %C of biochar prepared from raw (Raw-900) was 82.6%. From TG-MS analyses during the pyrolysis of MP, a large amount of oxygen was removed as H₂O and CO₂. The analyses of tars produced from MP showed higher fraction of acids and furans compared with tar produced from Raw. Furthermore, the mechanism of the pyrolysis of LC torrefied under mechanical pressure was discussed.

Synergy of Hydrothermal and Organic Acid Washing Treatments in Chinese Fir Wood Vinegar Preparation

Pretreatment is an effective method to change the pyrolysis behavior and improve the product properties of biomass. In this study, the effects of hydrothermal treatment (HTT) and hydrothermal treatment combined with organic acid washing (HTT-A) on Chinese fir waste (CF) pyrolysis and preparation of wood vinegar (WV) were investigated. The results indicated that HTT promoted the decomposition of hemicellulose and disrupted the chemical structure, while HTT-A partly removed the lignin as well as hemicellulose. HTT-A showed a more effective removal efficiency of alkali/alkaline earth metals (AAEMs) than HTT. Both HTT and HTT-A delayed the initial decomposition temperature but promoted the pyrolysis process. The yields of WVs increased after HTT and HTT-A, while the moisture contents reduced, obviously. HTT increased the relative contents of phenols from 47.04 to 59.85% but reduced the relative contents of acids from 24.31 to 18.38%, whereas HHT-A reduced the relative contents of phenols but increased those of aldehydes. In addition, HTT and HTT-A showed the different effects on chemical compositions of WVs, especially for phenolic and acid compounds. This study indicated that HTT and HTT-A were the efficient methods to produce WVs with target chemical components, which would be conducive to the efficient application of WVs.