Research Articles

As one of the most abundant materials in nature, lignin has been used widely in co-generation operations and for fine chemicals and bio-fuels production. These uses, although important, are of relatively low value. Lignin contains many aromatic compounds with useful structures, and it is potentially more profitable to produce high-value fine chemicals from the low-molecular weight lignin fraction while using the high-molecular weight fraction for fuel or other applications. A transgenic P. putida bacterial strain PDHV85 was developed with the capability to convert vanillin, vanillic acid, and syringaldehyde to 2-pyrone-4,6-dicarboxylic acid (PDC), a novel platform chemical that can produce a variety of bio-based polymers. Initial testing with vanillin showed promise for lignin conversion. Testing for this, we used kraft lignin, Japanese cedar (Cryptomeria japonica), or birch (Betula platyphylla) to represent some of the most abundant industrial lignin sources from softwood and hardwood. Repeated manipulation of culture conditions and strain adaptation allowed conversion of these extracts to PDC by PDHV85, which has not previously been reported in a bacterial strain. No inhibition was observed at 0.14 mg/mL kraft lignin extract, 1.14 mg/mL Japanese cedar extract, nor 1.15 mg/mL birch extract when using the optimized growth conditions.

Activated carbons with large adsorption capacity and high mesopore fraction were obtained from rice straw by a combination of pre-pyrolysis and NaOH activation procedures. The experiments varied the pre-pyrolysis procedure, impregnation ratio of activating agent, and activation temperature. Samples were examined by inductively coupled plasma-mass spectrometry (ICP-MS), X-ray diffractometry (XRD), field-emission scanning-electronic microscopy (FE-SEM), thermogravimetric analysis (TGA), and N2-adsorption analysis. The surface area and pore characteristics of the activated carbons were investigated by the Brunauer, Emmett, Teller (BET) method, Dubinin-Raduch (DR) model, and the t-plot method. The surface area, pore volume, and iodine adsorption capacity of the samples increased with increasing activation temperature and the impregnation ratio of the activating agent. A maximum surface area of 2093 m2/g was obtained at the activation temperature of 900 °C. The pore structure in the one-stage activation procedure was mainly microporous. Two-stage activation procedure efficiently enhanced mesopore volume, and therefore further increased the adsorption capacity of activated carbons. NaOH acted as both the activating agent in the reaction and as the cleaner to remove the ash. The results of this experiment will be useful in developing resource recovery systems from agricultural biomass.

The purpose of this study was to investigate the effects of microwave power and additives on the microwave-assisted pyrolysis of cotton stalk. Pyrolysis temperature profiles, product yields, and bio-oil components were analyzed. The results indicated that as the microwave power increased, so did the final temperature and heating rate. When microwave power increased from 800 to 1200 W, the yield of the solid residue decreased and gas yield increased, but the maximum bio-oil yield of 26.7% was achieved under a microwave power of 1000 W. All three of the additives (NaOH, Na2CO3, and H3PO4) increased the yields of solid residue and gas, while the yield of the bio-oil decreased. Gas chromatography-mass spectrometry (GC-MS) analysis indicated that the main components of bio-oil from microwave-assisted pyrolysis of pure sample were acetol, furfural, 2-methoxy-phenol, and 4-methyl-2-methoxy-phenol. Sodium hydroxide and sodium carbonate (NaOH and Na2CO3) greatly favor the formation of acetol. Phosphoric acid (H3PO4) remarkably promoted the formation of furfural and 4-methyl-2-methoxy-phenol, while H3PO4 inhibited the formation of acetol.

A new method involving the non-covalent binding of Coomassie Brilliant Blue G-250 (CBBG) to alkali-soluble lignin was developed. The binding of the dye to alkali-soluble lignin caused an increase in visible absorption at the maximum wavelength of 630 nm or 640 nm. A linear correlation of the absorbance at their maximum absorbing peak with alkali-soluble lignin concentration was observed. Lignin estimation in black liquor showed that the result of the new method and the gravimetric methods after acidification were closer to quantitative information than that obtained from UV spectroscopy. The isothermal titration calorimetric experiments, and Fourier Transform Infrared (FTIR) spectroscopy comparative analysis of precipitates washed by water, 4% ethanol, and 95% ethanol indicated that CBBG was bound to alkali-soluble lignin, and the binding was non-covalent. This potential method is reproducible, rapid, and cheap, and there is little or no inference from carbohydrate degradation products.

A mathematical description was developed for production of saccharides and fermentation inhibitors during the hot-compressed water pretreatment of cassava residue. Pretreatment was conducted at 150 °C, 160 °C, 170 °C, and 180 °C, and reaction times ranged from 0 to 70 min. The formation of saccharides and four main inhibitors (furfural (F), hydroxymethylfurfural (HMF), acetic acid, and formic acid) were studied. A model for predicting the concentrations of F and HMF (CF and CHMF, respectively) as functions of H+ concentration was established. Furthermore, kinetic models were built after introducing the hydrogen ion concentration index mi. Hydrogen ion concentration had a dramatic effect on the dissolution of pentosan but did not greatly affect the dissolution of hexosan or the degradation of hexose or pentose. Additionally, the activation energies for the formation of pentose or hexose were lower than the degradation energies. The coefficients of determination (R2) of the kinetic models for predicting the yield of the four compounds (pentose, hexose, furfural, and HMF) were higher than 0.923. These kinetic models provided a theoretical foundation and technical support for controlling the production of the main carbohydrates and fermentation inhibitors.

This study describes the properties of thermoplastic polymer composites based on polyethylene (of low and high density) and ethylene-propylene copolymers using various types of conifer needles (pine, spruce, fir, and cedar) as fillers. For the needles, thermogravimetric analysis (TGA) and TGA/Fourier transform infrared spectroscopy (TGA/FTIR) were performed to investigate their structures and thermal resistance, as required for the composite processing methods. Moreover, structural differences were studied for the analyzed fillers and composite materials (FTIR). The results were compared with the values obtained for composites with conifer wood flour. Composites with conifer needles (pine) had increased water absorption and similar strength properties. However, irrespective of the degree of filling, composites with pine needles were positively characterized by the highest melt mass flow rate (MFR) values and showed a slightly better impact resistance than composites filled with other flours. Thus, shredded coniferous needles with sufficient thermal resistance could be successfully used as fillers in composites. This conclusion was based on thermoplastic polymers as an alternative and/or supplement to the wood flour used in the manufacture of wood-polymer composites.