Corn stover fractions and bioenergy

Information is presented on structure, composition, and response to enzymes of corn stover related to barriers for bioconversion to ethanol. Aromatic compounds occurred in most tissue cell walls. Ferulic acid esterase treatment before cellulase treatment significantly improved dry weight loss and release of phenolic acids and sugars in most fractions over cellulase alone. Leaf fractions were considerably higher in dry weight loss and released sugars with esterase treatment, but stem pith cells gave up the most phenolic acids. Results help identify plant fractions more appropriate for coproducts and bioconversion and those more suitable as residues for soil erosion control.     

Effect of aeration on lignin peroxidase production by Streptomyces viridosporus T7A

The effect of aeration on lignin peroxidase production by Streptomyces viridosporus T7A was studied in a bench-scale bioreactor using a previously optimized growth medium (0.65% yeast extract and 0.1% corn oil, pH7.0) at 37°C and natural pH. Airflow rates of 0.3, 1.0, and 1.5 vvm and a fixed agitation of 200 rpm were initially studied followed by 1.0 vvm and 200, 300, 400, and 500 rpm. The use of 1.0 vvm and 400 rpm increased enzyme concentration 1.8-fold (100–180 U/L) and process productivity 4.8-fold (1.4–6.7 U/[L·h]) in comparison with the use of 200 rpm and 0.3 vvm. The inexpensive corn oil, used as carbon source, besides its antifoam properties, proved to be nonrepressive for enzyme production.     

Catalytic nitrobenzene oxidation of lignins

Alkaline nitrobenzene oxidation of hardwood and softwood lignins in the presence of redox and phase-transfer catalysts was studied. The selectivity of oxidation of lignins increased by 1.7 to 1.9 times. A possible mechanism of catalysis is discussed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 3004–3007, December, 1996.     

Degradation of ²-O-4 lignin model and related compounds by the ascomyceteChrysonilia sitophila (TFB 27441 strain)

Growth of the ascomyceteChrysonilia sitophila during degradation of lignin model dimers and monomers was compared to a glucose control. An inhibition of growth by Cα-carbonyl monomers and stimulation by β-O-4 lignin model and vanillyl alcohol were observed. A comparison of the degradation by this ascomycete with the basidiomycetePhanerochaete chrysosoporium showed similarities in relation to the type of degradation caused.     

Electrochemical Response of Cobalt(II) in the Presence of Ammonia

The electrochemical oxidation of cobalt(II) at gold, boron‐doped diamond, basal and edge plane pyrolytic graphite, and highly oriented pyrolytic graphite electrodes in aqueous solutions containing NH₃ has been studied using cyclic voltammetry, with subsequent chemical and electrochemical processes explained in detail. Furthermore, the electro‐reduction of [Co(NH₃)₆]³⁺ in the presence of different electrolytes has also been studied to obtain a better understanding of the oxidation pathway of the Co(II)‐ammine complexes. In aqueous solution the mechanism can be described by the following scheme:     

Effects of cell-wall acetate,xylan backbone,and lignin on enzymatic hydrolysis of aspen wood

Aspen wood substrates with varying degrees of deacetylation, xylan, and lignin removal have been prepared and submitted to enzymatic hydrolysis with a cellulase/hemicellulase preparation for an extended constant period of hydrolysis. Controlled deacetylation has been achieved by treating wood with various alkali metal hydroxide solutions, at various alkali/wood ratios. It has been found that samples with the same extent of deacetylation produce the same sugar yields upon enzymatic hydrolysis. Increased degree of deacetylation increases the yield of sugars obtained from enzymatic hydrolysis, all other compositional parameters held constant. The acetyl group removal is proportional to the stoichiometric relation between added base and wood acetyl content, i.e., the same number of milliequivalents of base/weight of wood remove the same extent of acetyl groups, regardless of the concentration of the base solution. No cation effects are found among Li, Na, and K alkali hydroxide solutions, suggesting that swelling is not as important a parameter as is the removal of the acetyl groups from the xylan backbone in determining the extent of hydrolyzability of the resulting sample.     

木质素磺酸镁接枝丙烯酰胺的影响因素

天然高分子化合物木质素是木材水解工业和造纸工业的副产物。早期人们在研究纤维素同甲基丙烯酸甲酯、丙烯腈的接枝反应中时发现了木质素的接枝反应活性[1],Meisterh和Patil[2]则实现了将—CONH2接枝于木质素的设想,雷中方[3]等研究了木质素同具有较好吸附能力的—CONH2的接枝改性,并讨论了改性产物的水处理性能,他们所用的木质素是采用酸析法从碱法草浆黑液中提取的。本文以酸法制浆的红液 木素磺酸镁为原料,合成了木质素 丙烯酸胺接枝共聚物,并对接枝聚合过程中的引发体系、引发剂浓度、反应温度、木素与单体用量比、固液比等影…     

石墨炉原子吸收法中热解涂层石墨管在无标准分析法测定环境样品中铬的应用

本文探讨了热解涂层石墨管测定铬的最佳实验条件,研究了各种酸和干扰物质的基体效应,提出用浓氨水为基体改进剂克服高氯酸的干扰。比较了各原子化温度时的理论和实验特征量。使热解涂层石墨管有可能用于无标准分析法测定各种环境样品中的铬。     

Strategies to enhance the enzymatic hydrolysis of pretreated softwood with high residual lignin content

Pretreatment of Douglas-fir by steam explosion produces a substrate containing approx 43% lignin. Two strategies were investigated for reducing the effect of this residual lignin on enzymatic hydrolysis of cellulose: mild alkali extraction and protein addition. Extraction with cold 1% NaOH reduced the lignin content by only approx 7%, but cellulose to glucose conversion was enhanced by about 30%. Before alkali extraction, addition of exogenous protein resulted in a significant improvement in cellulose hydrolysis, but this protein effect was substantially diminished after alkali treatment. Lignin appears to reduce cellulose hydrolysis by two distinct mechanisms: by forming a physical barrier that prevents enzyme access and by non-productively binding cellulolytic enzymes. Cold alkali appears to selectively remove a fraction of lignin from steam-exploded Douglas-fir with high affinity for protein. Corresponding data for mixed softwood pretreated by organosolv extraction indicates that the relative importance of the two mechanisms by which residual lignin affects hydrolysis is different according to the pre- and post-treatment method used.     

Mechanism and potential applications of bio-ligninolytic systems in a CELSS

A large amount of inedible plant material, generated as a result of plant growth in a Controlled Ecological Life Support System (CELSS), should be pretreated and converted into forms that can be recycled on earth as well as in space. The main portion of the inedible biomass is lignocellulosic material. Enzymatic hydrolysis of this cellulose would provide sugars for many other uses by recycling carbon, hydrogen, oxygen, and nitrogen through formation of carbon dioxide, heat, and sugars, which are potential foodstuffs. To obtain monosaccharides from cellulose, the protective effect of lignin should be removed. White-rot fungi degrade lignin more extensively and rapidly than other microorganisms.Pleurotus ostreatus degrades lignin effectively, and produces edible and flavorful mushrooms that increase the quality and nutritional value of the diet. This mushroom is also capable of metabolizing hemicellulose, thereby providing a food use of this pentose containing polysaccharide. This study presents the current knowledge of physiology and biochemistry of primary and secondary metabolisms of basidiomycetes, and degradation mechanism of lignin. A better understanding of the ligninolytic activity of white-rot fungi will impact the CELSS Program by providing insights on how edible fungi might be used to recycle the inedible portions of the crops.