纤维素水解液厌氧发酵产丁二酸发酵液中有机酸和混合单糖的测定

对于以纤维素类原料(玉米皮)水解糖液作碳源厌氧发酵制备丁二酸的发酵液,利用Aminex HPX-87H(300 mm×7 8 mm i.d., 5 μm)离子排斥色谱柱及折光示差检测器检测,以0 005 mol/L H2SO4溶液(pH 2 0)作流动相,在流速为0 6 mL/min,柱温为55 ℃时对发酵液进行检测,16 min内能将发酵液中甲酸、乙酸、丁二酸、葡萄糖、木糖、阿拉伯糖完全分离定量.6种物质线性相关系数均大于0 999,方法的回收率为99 3%～102 1%;RSD为0 6%～1 6%.本方法能够简便、快速测定丁二酸发酵体系中有机酸及单糖的含量.     

Xylan hemicellulose improves chitosan hydrogel for bone tissue regeneration

The hemicellulose xylan, which has immunomodulatory effects, has been combined with chitosan to form a composite hydrogel to improve the healing of bone fractures. This thermally responsive and injectable hydrogel, which is liquid at room temperature and gels at physiological temperature, improves the response of animal host tissue compared with similar pure chitosan hydrogels in tissue engineering models. The composite hydrogel was placed in a subcutaneous model where the composite hydrogel is replaced by host tissue within 1 week, much earlier than chitosan hydrogels. A tibia fracture model in mice showed that the composite encourages major remodeling of the fracture callus in less than 4 weeks. A non‐union fracture model in rat femurs was used to demonstrate that the composite hydrogel allows bone regeneration and healing of defects that with no treatment are unhealed after 6 weeks. These results suggest that the xylan/chitosan composite hydrogel is a suitable bone graft substitute able to aid in the repair of large bone defects. Copyright © 2016 John Wiley & Sons, Ltd.     

Influence of hemicelluloses on the aggregation patterns of bacterial cellulose

Cellulose from the bacteriumAcetobacter xylinum was used as a model system for investigating the influence of other cell wall polysaccharides on the aggregation of cellulose. The patterns of aggregation of the bacterial cellulose were modified when the cellulose was produced in the presence of hemicellulose-like saccharides. The celluloses were found to be more like the I-type found in higher plant celluloses than the I-type in the control bacterial celluloses. The effects of isolation procedures on structure were also explored. It was found that the structures of isolated celluloses were influenced by the procedures used in isolation.Formerly The Institute of Paper Chemistry, Appleton, WI, USA.Retired     

Xylitol production from wood hydrolyzates by entrapped Debaryomyces hansenii and Candida guilliermondii cells

Debaryomyces hansenii cells were entrapped in Ca-alginate beads and used for producing xylitol from wood hydrolyzates. Batch experiments showed that bioconversion was severely hindered when Ca-alginate beads were hardened with Al³⁺ solutions. As an alternative to Al³⁺ hardening, the improvements in both mechanical stability of bioparticles and fermenting ability of the immobilized system derived from using increased concentrations of sodium alginate were assessed. The best results were obtained using a 4% (w/v) Na-alginate solution in the gelification step. This concentration was selected to perform continuous fermentations in a packed-bed reactor using raw or charcoal-treated hydrolyzates (15.5 g of xylose/L) with two different yeasts: Candida guilliermondii and Debaryomyces hansenii. With a final cell concentration of about 50 g of cells/L (0.075 g of cells/g of beads), the volumetric productivities reached with these yeasts in media made from charcoal-treated hydrolyzates were 0.58 and 0.91 g/L·h, respectively.     

Effects of hemicellulose and lignin on enzymatic hydrolysis of cellulose from dairy manure

This study focused on the effect of hemicellulose and lignin on enzymatic hydrolysis of dairy manure and hydrolysis process optimization to improve sugar yield. It was found that hemicellulose and lignin in dairy manure, similar to their role in other lignocellulosic material, were major resistive factors to enzymatic hydrolysis and that the removal of either of them, or for best performance, both of them, improved the enzymatic hydrolysis of manure cellulose. This result combined with scanning electron microscope (SEM) pictures further proved that the accessibility of cellulose to cellulase was the most important feature to the hydrolysis. Quantitatively, fed-batch enzymatic hydrolysis of fiber without lignin and hemicellulose had a high glucose yield of 52% with respect to the glucose concentration of 17 g/L at a total enzyme loading of 1300 FPU/L and reaction time of 160 h, which was better than corresponding batch enzymatic hydrolysis.     

Amino acid profiling and antimicrobial activity of Cucurbita moschata and Lagenaria siceraria seed protein hydrolysates

Cucurbita moschata and Lagenaria siceraria seed proteins were extracted and hydrolysed with trypsin in order to recover antibacterial peptides. Amino acid content and molecular weight distribution were estimated to justify their co-relationship with antimicrobial activity. Antimicrobial activities of C. moschata and L. siceraria seed protein hydrolysates against three Gram-negative bacteria and two Gram-positive bacteria were evaluated. Seed protein hydrolysates of both of these plants have significantly higher activity against Acinetobacter baumannii (p < 0.05). The lethal concentration (LC₅₀) values of L. siceraria hydrolysates (LSH) and C. moschata hydrolysates (CMH) were 70 ± 6.2 and 135.6 ± 4.5 μg/mL in viable count method and 73.2 ± 2.9 and 122.9 ± 3.2 μg/mL in turbidity method, respectively, against A. baumannii. Based on the above findings, seed protein hydrolysates of these plants may be considered as nutritional food and functional antimicrobial agents in food system.     

Production of ethanol from cellulosic biomass hydrolysates using genetically engineered saccharomyces yeast capable of cofermenting glucose and xylose

Recent studies have proven ethanol to be the idael liquid fuel for transportation, and renewable ligno cellulosic materials to be the attractive feed stocks for ethanol fuel production by fermentation. The major fermentable sugars from hydrolysis of most cellulosic biomass are D-glucose and D-xylose. The naturally occurring Saccharomyces yeasts that are used by industry to produce ethanol from starches and cane sugar cannot metabolize xylose. Our group at Purdue University succeded in developing genetically engineered Saccharomyces yeasts capable of effectively cofermenting glucose and xylose to ethanol, which was accomplished by cloning three xylose-metabolizing genes into the yeast. In this study, we demonstrated that our stable recombinant Sacharomyces yeast, 424A (LNH-ST), which contains the cloned xylose-metabolizing genes stably integrated into the yeast chromosome in high copy numbers, can efficiently ferment glucose and xylose present in hydrolysates from different cellulosic biomass to ethanol.     

Impact of fluid velocity on hot water only pretreatment of corn stover in a flowthrough reactor

Flowthrough pretreatment with hot water only offers many promising features for advanced pretreatment of biomass, and a better understanding of the mechanisms responsible for flowthrough behavior could allow researchers to capitalize on key attributes while overcoming limitations. In this study, the effect of fluid velocity on the fate of total mass, hemicellulose, and lignin was evaluated for hot water only pretreatment of corn stover in tubular flow through reactors. Increasing fluid velocity significantly accelerated solubilization of total mass, hemicellulose, and lignin at early times. For example, when fluid velocity was increased from 2.8 to 10.7 cm/min, xylan removal increased from 60 to 82% for hot water only pretreatment of corn stover at 200°C after 8 min. At the same time, lignin removal increased from 30 to 46%. Dissolved hemicellulose was almost all in oligomeric form, and solubilization of hemicellulose was always accompanied by lignin release. The increase in removal of xylan and lignin with velocity, especially in the early reaction stage, suggests that chemical reaction is not the only factor controlling hemicellulose hydrolysis and that mass transfer and other physical effects may also play an important trole in hemicellulose and lignin degradation and removal.     

Hydrolysis characteristics of tissue fractions resulting from mechanical separation of corn stover

Corn stover has potential as a resource for both fiber and chemical needs if separation strategies can be developed to deal with its heterogeneity. Relative hydrolysis characteristics were assessed for pith (sclerenchyma and parenchyma) and fiber (collenchyma) tissue fractions derived from mechanical separation of corn stover to determine whether classification by tissue type resulted in fractions with different hydrolysis response. The physical characteristics of the tissue fractions were analyzed. The hydrolysis behavior of the fractions was evaluated under both acidic and basic conditions. The results from the hydrolysis experiments are compared with previously reported compositional analysis for the tissue fractions.     

Allium carbohydrates. XV. Polysaccharides from Allium motor

The content of carbohydrates in Allium motor was studied as a function of vegetation period. The qualitative and quantitative compositions and physical chemical properties of sugars soluble in alcohol, water-soluble polysaccharides, pectinic substances, and hemicellulose were characterized. Galacturonan was produced by partial hydrolysis of the pectinic substances. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 409–411, September–October, 2006.