Clarification of a wheat straw‐derived medium with ion‐exchange resins for xylitol crystallization

BACKGROUND: Xylitol bioproduction from lignocellulosic residues comprises hydrolysis of the hemicellulose, detoxification of the hydrolysate, bioconversion of the xylose, and recovery of xylitol from the fermented hydrolysate. There are relatively few reports on xylitol recovery from fermented media. In the present study, ion‐exchange resins were used to clarify a fermented wheat straw hemicellulosic hydrolysate, which was then vacuum‐concentrated and submitted to cooling in the presence of ethanol for xylitol crystallization. RESULTS: Sequential adsorption into two anion‐exchange resins (A‐860S and A‐500PS) promoted considerable reductions in the content of soluble by‐products (up to 97.5%) and in medium coloration (99.5%). Vacuum concentration led to a dark‐colored viscous solution that inhibited xylitol crystallization. This inhibition could be overcome by mixing the concentrated medium with a commercial xylitol solution. Such a strategy led to xylitol crystals with up to 95.9% purity. The crystallization yield (43.5%) was close to that observed when using commercial xylitol solution (51.4%). CONCLUSION: The experimental data demonstrate the feasibility of using ion‐exchange resins followed by cooling in the presence of ethanol as a strategy to promote the fast recovery and purification of xylitol from hemicellulose‐derived fermentation media. Copyright © 2008 Society of Chemical Industry     

Emulsifying Capacity and Emulsion Stability of Soy Proteins Compared with Corn Germ Protein Flour

Both emulsifying capacity (EC) and emulsion stability (ES) increased with increasing concentrations from 0.4% to 0.8% of soy flour (SF), soy concentrate (SC), soy isolate (SI) and corn germ protein flour (CGPF) when studied by response surface methodology. EC and ES increased as pH increased from 6 to 8 in all samples. Increasing incubation temperatures of protein solutions from 20–70°C or from 4–20°C did not affect EC or ES, respectively. SF had the highest EC, followd by SI, SC, and CGPF.     

The microbiology of mixed salad containing raw and cooked ingredients without dressing

Growth of aerobic mesophilic bacteria in mixed salad without dressing, containing cooked sweet corn and raw endive, was similar to that of raw endive alone. At 9°C, sweet corn permitted the growth of the lactic acid bacterium Leuconostoc mesenteroides , whenever the bacterium was present on raw endive, whereas no growth of lactic acid bacteria was recorded on raw endive alone. Listeria monocytogenes , artificially inoculated in the samples, grew more in the mixed salad than in the raw endive alone, for products stored at 6°C and 9°C. Acidification of sweet corn to pH 5.0 was proposed to reduce the development of L. monocytogenes in the mixed salad to a level similar to that recorded in the raw endive alone. Acidification with citric acid reduced spoilage of sweet corn, whereas acetic acid caused necrosis on the leaves of raw endive.     

农作物秸秆增强氟石膏复合材料的微观结构研究

将玉米秸秆加入改性后的氟石膏中，研究改性剂、玉米秸秆对氟石膏复合材料结构性能的影响；并用苯丙乳液对玉米秸秆纤维进行表面处理，用以改善基体材料和增强材料的界面结合状况，由此显著提高制品性能。     

Structure-activity relationships for analogs of (+)-(E)-endo-Β-bergamoten-12-oic acid,an oviposition stimulant ofHelicoverpa zea (Boddie)

-Bergamotenoic acid, a compound previously shown to stimulate oviposition inH. zea, was converted into a set of bicyclic analogs and tested with a set of acyclic side chain analogs to ascertain the molecular structure that maximizes insect behavioral response. While changes in the bicyclic ring elicited no variation in response, alteration in the side chain structure of-bergamotenoic acid resulted in significant changes in moth preference. Free rotation about the C-C bond proximal to the carboxylic acid group appears to be an important structural factor, since saturation of the side chain double bond significantly increased activity. The carboxylic acid group seems to be required for strong oviposition stimulation, since analogs lacking the carboxylic acid group exhibited no significant oviposition activity. Oviposition preference ofH. zea was also influenced by the length of the hydrocarbon chain to which the carboxylic acid is attached. While hexanoic acid was found inactive, the ovipositional preference for the heptanoic and octanoic acids was greatest for the one 8-carbon tested. This and other work suggest that carboxylic acids of specific chain lengths influence the oviposition behavior of bothHelicoverpa andHeliothis species and may be associated with host-plant selection. The potential use of this information in designing integrated pest management strategies for control ofH. zea is discussed.     

Effects of α-Terthienyl on the midgut detoxification enzymes of the European corn borer,Ostrinia nubilalis

The biochemical basis for the tolerance of the European corn borer,Ostrinia nubilalis, to the phototoxin-terthienyl was investigated by measuring the midgut polysubstrate monooxygenases and glutathioneS-transferase activities.-Terthienyl administered in the diet to the corn borers increased the level of cytochromeb ₅, NADH-cytochromec reductase,O-demethylase, and glutathioneS-transferase activities. The induced detoxification enzyme activities should enable the corn borer to metabolize-terthienyl more efficiently and therefore render the corn borer highly tolerant to-terthienyl.     

我国玉米供需曲线估测与市场预测

通过两阶段最小二乘法估测了我国玉米供需曲线,并预测未来两年均衡价格和净进口量.研究发现影响我国玉米供给的因素有玉米价格、大豆价格、技术进步和成灾率,影响我国玉米需求的因素有玉米价格、小麦价格、人均国内生产总值和总人口;预测未来两年我国玉米价格和净进口量都将呈上升趋势,我国将成为玉米净进口国.     

微波在植物纤维漂白中的应用研究

采用微波辐射技术，建立了次氯酸钠漂白麦草浆工艺。影响微波辐射漂白纸浆的因素有三项：微波辐射时间、辐射功率和次氯酸钠用量。当微波辐射功率为352w，辐射时间为2min，次氯酸钠用量为10mL时，2g绝干浆的白度达77％ISO以上。此外，通过与水浴的对比实验，发现微波加热2min纸浆达到的白度相当于水浴加热40min，这对于能源的节省是非常有意义的。     

气相色谱法测定玉米须中邻苯二甲酸二丁酯

建立以气相色谱技术测定玉米须中环境激素邻苯二甲酸二丁酯（DBP）的含量,以了解玉米须中DBP的含量状况．玉米须样品用石油醚提取,采用气相色谱法进行分析检测玉米须中DBP的含量．DBP的标准曲线回归方程为Y=1857．7x＋720．63,相关系数为0．99995,平均回收率为102．17％,RSD为8．75％,n=5．该方法灵敏度较高,结果准确,适用于玉米须中DBP含量的检测,能够准确的反映玉米须中邻苯二甲酸二丁酯的含量．     

高水分玉米应用臭氧防霉综合治理试验研究

本文为臭氧防霉实验研究。25℃条件下,10～20ppm臭氧直接处理串珠镰刀菌、黄曲霉、黑曲霉、草酸青霉、圆弧青霉,每天处理8小时,明显抑制其生长发育,连续处理效果更佳。用臭氧保藏高水分玉米,接触臭氧玉米不霉变,但臭氧渗透差,必须辅以通风。20℃时向含水量23.42％玉米中通入10ppm臭氧,可向下渗透1米,1米处O_3为0.5ppm,交换次数约每5分钟一次,玉米保藏20天未发生霉变,加大O_3浓度,O_3可渗透至1.5米。2～10ppm臭氧25℃时处理水分21.05％的玉米,玉米过氧化值、脂肪酸值均无明显变化。较新鲜玉米香味略差,但仍较对照样品好。试验还证明受臭氧处理玉米发芽率略有降低。