Volume 15 Issue 3

Bioacetone, biobutanol, and bioethanol (BioABE) production is dependent on the fermentable sugars produced from lignocellulosic biomass and on the composition and initial pH of the medium. Understanding these process variables and their interconnectedness could enhance the BioABE product yield. Acacia mangium is available abundantly and it is a potential feedstock for BioABE production. In this study, BioABE was produced from fermentable sugars of A. mangium using Clostridium acetobutylicum YM1. Alkaline treated A. mangium (70 °C, 3 h, 5.50 %w/v NaOH) was further hydrolyzed via enzymatic hydrolysis using a multi-enzyme of white rot fungi to convert it into fermentable sugars. Approximately 15 g/L of fermentable sugars was produced from A. mangium (100 g/L) and was used for BioABE production in comparison with glucose. Initial findings showed that only 0.94 g/L of BioABE was produced in comparison with glucose (2.86 g/L) at a pH of 6.2. Decreasing the initial pH of the medium to 4.50 increased the BioABE (2.87 g/L), and after the medium was supplemented with tryptone-yeast-acetate (TYA), the BioABE yield increased by more than 100% to 6.84 g/L. This study discovered that BioABE produced from A. mangium was comparable to using commercial glucose, thus offering high potential as a low-cost feedstock.

Brewer’s grains (BG), a by-product of the beer industry, were first pretreated by sulfuric acid, sodium hydroxide, and white-rot fungus Coriolus versicolor for the preparation of bio-adsorbents BGPH, BGPOH, and BGPB, respectively. All bio-adsorbents were rich in hydroxyl groups and could adsorb Congo red dye from aqueous solution, and BGPOH worked better than the others. The order of maximum equilibrium adsorption capacity of bio-adsorbents for Congo red was BGPOH > BGPH > BGPB. The Langmuir, Freundlich, and Temkin adsorption isotherm models all fit well with the experimental data. The negative Gibbs free energy change meant that the adsorption was spontaneous, and lower temperature was useful for the adsorption of Congo red onto the bio-adsorbents. The pseudo first-order and second-order kinetics models fit well with the experimental data, and the second-order kinetics model fit better, which indicated the adsorption was controlled by diffusion phenomena. Brewer’s grains with the three pretreatments could be used as efficient adsorbents for the treatment of dye wastewater.

The flavor fingerprint of Eucommia ulmoides Oliv. bark (EUb) and its fermentation product were investigated, and volatile compounds were analyzed using headspace gas chromatography-ion mobility spectrometry (HS-GC-IMS) combined with partial least squares discrimination analysis (PLS-DA). A total of 71 peaks were identified, of which 51 target compounds were characterized, including alcohols, aldehydes, acids, and esters. The gallery plot contained 186 signal peaks. The results indicate there were significant differences in the volatile constituents of the three edible fungi. Furthermore, EUb also had its own unique composition of volatile components, and after fermentation with different edible fungi, the volatile components in the product changed significantly compared to the raw materials. A PLS-DA was performed based on the signal intensity of the target volatile compounds obtained; the results clearly showed that the samples (edible fungi, EUb, and different fermentation products) in a relatively independent space were well distinguished. This further illustrated that the composition and content of volatile components from EUb were significantly changed by microorganisms through bio-fermentation. Combining the signal intensity of the flavor substance, the difference between the different fermentation products was also clearly observed, and the flavor compound’s fingerprint was established by HS-GC-IMS and PLS-DA methods.

Bioactive edible films have the potential to be probiotic carriers. This innovative approach can replace plastic packaging and can benefit human health. This study demonstrated the incorporation of Lactobacillus rhamnosus GG (LGG) into whey protein isolate (WPI) and sodium caseinate (NaCas) edible films. Probiotic cells were directly incorporated into the film forming solutions, and the films were produced by the casting method. The physical, mechanical, and probiotic viability properties of the edible films were determined in the presence and absence of LGG. Furthermore, the viability of LGG was evaluated during the drying process and storage of 14 days at 4 °C and 25 °C, respectively. The results showed the incorporation of LGG increased the moisture content, puncture force, and lightness of both films. However, viability of LGG was lower in the WPI film regardless of storage temperature. At the end of storage days, both WPI and NaCas edible films maintained the LGG viability above the recommended levels when stored at 4 °C, which was 106 CFU/g. The findings of this study suggested that edible films made of WPI and NaCas showed feasibility to immobilize LGG with chilled storage at 4 ℃.

Ionic liquids (ILs) are effective solvents for lignocellulose pretreatment. Enzymatic saccharification converts pretreated lignocelluloses into valuable products, and IL-tolerant cellulase improves the enzymatic efficiency and the reuse of ILs. In this study, a fungal strain with a relatively high cellulase production was isolated and identified as Aspergillus aculeatus G1-3. The high production of β-glucosidase (1.943 U per mL), CMCase (1.303 U per mL), and FPase (0.165 U per mL) was obtained using corn stover as the carbon source and peptone as the nitrogen source. The results were obtained at pH 8.0 and 30 °C with an inoculation size of 3% (volume per volume) for 7 days. A mutant strain Aspergillus aculeatus P6 with β-glucosidase (7.023 U per mL), CMCase (1.543 U per mL), and FPase (0.098 U per mL) was obtained by 60Co-γ irradiation. The cellulase activity was measured at pH 5.0 and 60 °C for enzymatic hydrolysis. The cellulase from mutant strains was stable in different concentrations of 1-ethyl-3-methylimidazolium acetate. Enzymatic saccharification of the original corn stover and ILs-pretreated corn stover was successfully performed with high sugar yields. The mutant strains of Aspergillus aculeatus have great potential for their further application in the conversion of lignocellulosic biomass into biofuels.

To achieve a better understanding of the pyrolysis behavior of pre-oxidized β-ether-type lignin, three Cα=O type dimers with different substituent groups on the aromatic ring were synthesized and analyzed by a simultaneous thermal analysis instrument (STA), in-situ Fourier transform infrared spectroscopy (in-situ FTIR), and pyrolysis-gas chromatography/ mass spectrometry (Py-GC/MS). The results showed that major primary pyrolysis reactions of Cα=O type models normally occurred at 200 to 400 °C, and connecting bridge structures of models were completely destroyed, causing the emission of abundant volatiles. Substituent groups of aromatic rings played direct roles in thermal stability of models, volatiles emission, product characteristics, and secondary reaction pathways of major primary products. Particularly, the aryl–OCH3 group clearly enhanced the reactivity of intramolecular linkages and was an important active functional group for secondary reactions. As major primary products and intermediates, guaiacol and 2-methoxy-benzaldehyde were formed via the cleavage of Cα–O and Cα–Cβ bonds and could also be converted into phenol, benzaldehyde, and 2-methylphenol via rearrangement of aryl–OCH3 into an aryl–CH3 group or –OCH3 group removal. Oxidization of benzylic alcohol to benzylic ketone not only simplified depolymerization pathways, but also resulted in better selectivity of phenolic monomers and a predictable product distribution.

Warm compaction technology is an eco-friendly method to improve the added value of poplar. In this work, the wood powder was compacted in the mold between 120 °C to 200 °C, at 80 MPa for 30 min. The color change, chemical properties, and mechanical properties were evaluated. The color of the formed compaction darkened uniformly. The CIE lightness color coordinate (L*) and chroma coordinates a* and b* decreased with the increase of forming temperature. Fourier infrared spectral analysis showed degradation of carbohydrates, along with the formation of a new chemical structure of darker color. Mechanical properties including modulus of rupture (MOR) and modulus of elasticity (MOE) of compacted wood increased initially and then decreased. These results provide a reference for the surface color control of thermally forming materials.

The discoloration of uncoated wood surfaces in both outdoor and indoor use in non-heated spaces has become an increasing problem in European timber constructions due to the use of less toxic substances for protection and also changes in outdoor climate conditions, necessitating the use of protective coatings. To investigate the effect of methyl methacrylic (MMA) resin for the protection of wood from discoloration and mould growth, resin-treated wood surfaces were studied in a laboratory-scale mould test, as well as in an outdoor weathering test. Non-modified Scots pine and Norway spruce were used, and some of the test materials were also thermally modified. The resin suppressed mould growth for the laboratory-scale experiments. The protective effect was considerably reduced for outdoor tests. The MA resin did not effectively prevent the wood from greying from ultraviolet (UV) radiation exposure; there was some protective effect detected on the pine. The Fourier transform infrared (FTIR) spectra of weathered specimens showed a reduction of lignin-associated absorption bands for all treatments, which corresponded to the UV degradation and greying of the wood surface. It is suggested that MMA resin may provide adequate protection against mould growth on wood without direct exposure to rain and sunshine (e.g., attics, basements, etc).

Different biomass sources (bamboo, rape straw, lignin, and Yaupon holly) were liquefied using microwave energy to produce biopolyols, which were then used to prepare biofoams without any further separation process. The results indicated that the content of hydroxyl groups in biopolyols derived from different biomass sources was sorted in descending order as rape straw, Yaupon holly, bamboo, and lignin. The rheological analysis demonstrated that the biopolyols were pseudoplastic, and the yield stress of biopolyols was remarkably increased with increasing biomass content. The compressive strength of polyurethane (PU) foam was rendered smaller by introducing biomass sources. Nevertheless, the biofoam obtained from biomass sources with higher hydroxyl groups content had better PU performance. In addition, the termite resistance performance of PU foam increased with the introduction of Yaupon holly, rape straw, and bamboo sources. Accordingly, the biofoams derived from the liquefaction of rape straw performed better than those from other biomass sources.

Two slurries that consisted of precipitated calcium carbonate (CaCO3) nanoparticles and unbeaten hardwood bleached kraft pulp (HBKP) were prepared via ultrafine bubble and mixing methods. In the ultrafine bubble method, a CO2 gas flow was bubbled into a HBKP slurry that contained Ca(OH)2 to prepare a precipitated CaCO3/HBKP composite slurry. The HBKP/water and precipitated CaCO3/water slurries were prepared separately and mixed to prepare a precipitated CaCO3/HBKP mixture slurry. Each of the two CaCO3/HBKP slurries was separated into five fractions using a tube flow fractionation (TFF) system. The first and second fractions consisted of long HBKP fibers and fiber aggregates. The third fraction had the highest mass ratio of the components in the five fractions, and it had approximately 1-mm-long HBKP fibers. The fourth fraction contained primarily HBKP short fibers and CaCO3 aggregates. Thus, the CaCO3/HBKP components in the slurry were separated adequately by TFF, depending on their hydrodynamic sizes. The average width of each fraction in the CaCO3/HBKP composite slurry was always larger than that of the corresponding fraction from the CaCO3/HBKP mixture slurry, which indicated that precipitated CaCO3 nanoparticles and their aggregates attached stably to long and short pulp fiber surfaces in the composite slurry.