Yuedong Zhang

Optimization of medium composition for butyric acid production by Clostridium thermobutyricum using response surface methodology

The optimal medium for butyric acid production by Clostridium thermobutyricum in a shake flask culture was studied using statistical experimental design and analysis. The optimal composition of the fermentation medium for maximum butyric acid yield, as determined on the basis of a three-level four-factor Box-Behnken design (BBD), was obtained by response surface methodology (RSM). The high correlation between the predicted and observed values indicated the validity of the model. A maximum butyric acid yield of 12.05 g/l was obtained at K(2)HPO(4) 7.2 g/l, 34.9 g/l glucose, 20 g/l yeast extract, and 15 g/l acetate, which compared well to the predicated production of 12.13 g/l.

Properties of nanocellulose isolated from corncob residue using sulfuric acid, formic acid, oxidative and mechanical methods

In this work, nanocellulose was extracted from bleached corncob residue (CCR), an underutilized lignocellulose waste from furfural industry, using four different methods (i.e. sulfuric acid hydrolysis, formic acid (FA) hydrolysis, 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-mediated oxidation, and pulp refining, respectively). The self-assembled structure, morphology, dimension, crystallinity, chemical structure and thermal stability of prepared nanocellulose were investigated. FA hydrolysis produced longer cellulose nanocrystals (CNCs) than the one obtained by sulfuric acid hydrolysis, and resulted in high crystallinity and thermal stability due to its preferential degradation of amorphous cellulose and lignin. The cellulose nanofibrils (CNFs) with fine and individualized structure could be isolated by TEMPO-mediated oxidation. In comparison with other nanocellulose products, the intensive pulp refining led to the CNFs with the longest length and the thickest diameter. This comparative study can help to provide an insight into the utilization of CCR as a potential source for nanocellulose production.

Hemicellulose isolation, characterization, and the production of xylo-oligosaccharides from the wastewater of a viscose fiber mill

Viscose fiber mills generate a lot of wastewater enriched with hemicelluloses. The structure of the hemicellulose in the wastewater was characterized and the hemicellulose was isolated to produce xylo-oligosaccharides (XOS). It was confirmed that the hemicellulose was mainly 4-O-methylglucuronoxylan with a small amount of glucomannan and xyloglucan. The 4-O-methylglucuronoxylan was completely de-acetylated and linear with a few 4-O-methyl glucuronic acid attached. After purified by the acid precipitation and washing, the hemicellulose was pretreated by dilute acid, and then subjected to xylanase hydrolysis. After the dilute H2SO4 pretreatment at pH 2.6 and 150°C for 30min and the followed xylanase hydrolysis (65IU/g xylan), the total XOS yield was improved from 0.215 to 0.578g/g xylan. The percentage of XOS in the final sugar product was 68.9%. These results demonstrated the potential economical and environmental benefits of the process to utilize the byproducts from viscose fiber mills.

Combined Deacetylation and PFI Refining Pretreatment of Corn Cob for the Improvement of a Two-Stage Enzymatic Hydrolysis

A combined deacetylation and PFI refining pretreatment was applied to corn cob for the improvement of a two-stage enzymatic hydrolysis. In stage 1, the pretreated corn cob was first hydrolyzed by xylanase to produce xylo-oligosaccharides (XOS). In stage 2, the solid residue isolated from stage 1 was further hydrolyzed by cellulase and β-glucosidase. NaOH, Na2CO3, and Ca(OH)2 were tested to remove acetyl groups in the process of deacetylation, and it was found that Ca(OH)2 could be the most suitable alkali for deacetylation in this work. After deacetylation using 0.8 mmol of Ca(OH)2/g of substrate and PFI refining, 50.5% xylan in the raw material could be hydrolyzed into XOS. The corresponding xylan yield of stage 1, the glucan yield of stage 2, and the total sugar yield (all sugars released in the hydrolyzate) after the two-stage enzymatic hydrolysis were 0.306, 0.305, and 0.661 g/g of corn cob, respectively.

Production of furfural from waste aqueous hemicellulose solution of hardwood over ZSM-5 zeolite

This study aimed to produce furfural from waste aqueous hemicellulose solution of a hardwood kraft-based dissolving pulp production processing in a green method. The maximum furfural yield of 82.4% and the xylose conversion of 96.8% were achieved at 463K, 1.0g ZSM-5, 1.05g NaCl and organic solvent-to-aqueous phase ratio of 30:15 (V/V) for 3h. The furfural yield was just 51.5% when the same concentration of pure xylose solution was used. Under the optimized condition, furfural yield was still up to 67.1% even after the fifth reused of catalyst. Catalyst recycling study showed that ZSM-5 has a certain stability and can be efficiently reused.

Quantitative characterization of the impact of pulp refining on enzymatic saccharification of the alkaline pretreated corn stover

In this work, corn stover was refined by a pulp refining instrument (PFI refiner) after NaOH pretreatment under varied conditions. The quantitative characterization of the influence of PFI refining on enzymatic hydrolysis was studied, and it was proved that the enhancement of enzymatic saccharification by PFI refining of the pretreated corn stover was largely due to the significant increment of porosity of substrates and the reduction of cellulose crystallinity. Furthermore, a linear relationship between beating degree and final total sugar yields was found, and a simple way to predict the final total sugar yields by easily testing the beating degree of PFI refined corn stover was established. Therefore, this paper provided the possibility and feasibility for easily monitoring the fermentable sugar production by the simple test of beating degree, and this will be of significant importance for the monitoring and controlling of industrial production in the future.

Tough and multi-responsive hydrogel based on the hemicellulose from the spent liquor of viscose process

The hemicellulose isolated from the spent liquor of a viscose process was successfully utilized to prepare hydrogels by the graft copolymerization of acrylic acid (AA) with hemicellulose. The hemicellulose and prepared hydrogel were characterized by Fourier-transform infrared (FT-IR), scanning electron microscopy (SEM), and solid-state nuclear magnetic resonance ((13)C NMR). Under the optimum preparation conditions, the highest compressive strength and strain at break of the resultant hydrogel were 105.1±12.9kPa and 34.8%, respectively. Furthermore, the maximum equilibrium swelling degree of prepared hydrogel was 192. Also, the hydrogel could rapidly respond to pH, salt and ethanol. Taken together, the prepared hydrogels had great mechanical and multi-responsive properties. Thus, the prepared hydrogels had a great potential application in drug release, water treatment and cell immobilization. In addition, the utilization of alkaline extracted hemicellulose from the viscose fiber factory has huge market potential and economic benefits.

Reflectance and biochemical responses of maize plants to drought and re-watering cycles: Reflectance and biochemical responses of maize to D-W cycles

The ability to recover from drought stress after re‐watering is an important feature that will enable plants to cope with the predicted increase in episodic drought. The effects of pre‐drought and re‐watering conditions on leaf spectral properties and their relationships with the biochemical processes that underlie the recovery from pre‐drought conditions should be better understood. The reflectance spectra, 10 spectral reflectance indices (SRIs) and biochemical characteristics of maize (Zea mays) leaves were monitored 7, 14, 21 and 28 days after the initiation of soil drought stress during two successive cycles of drought and re‐watering periods. The leaf reflectance of the two inbred maize lines increased under the drought stress, especially in the visible spectral range. In addition, an obvious recovery of the leaf reflectance was only observed in the first re‐watering period, and its value remained higher than that of the control plants during the second recovery period. A recovery lag in the pigment contents was also observed during the second cycle. The recovery variations in the pattern and magnitude of the SRIs and the total contents of C, N and P that were measured in response to the re‐watering during both cycles were diverse and complex; both full and partial recoveries were observed. The SRIs representing different physiological attributes of plant growth, including the water index, red edge position, photochemical reflectance index and near‐infrared reflectance at 800 nm, showed strong linear relationships (P < 0.01 or 0.05) with the growth and biochemical traits across the successive drought and re‐watering cycles. The results suggest that maize plants can adjust their leaf reflectance properties and employ growth and biochemical strategies to adapt to cyclic drought stress and recover from drought stress after re‐watering.