Auxin-induced changes in the molecular weight of hemicellulosic polysaccharides of the Avena coleoptile cell wall

The average molecular weight of the water soluble hemicelluloses(hemicellulose B) of the Avena coleoptile cell wall was determinedby gel permeation chromatography (GPC) and viscometry. Analysisof the neutral sugar composition of henucellulose B eluted froma GPC column (Sepharose 4B) indicated that it consists of ß-glucanwith a high molecular weight and arabinoxylan with a low molecularweight. A kinetic study of the effect of auxin on the moleculardistribution of henucellulose B demonstrated that auxin decreasedthe ß-glucan content of the hemicellulose as earlyas the first hour incubation, but not the arabinoxylan content,when it stimulated the extension of the coleoptile segments.Calculation of the weight-average molecular weight from thechromatograms suggested that auxin decreased the molecular weightof hemicellulose B; this was also confirmed by viscometry. Thus,auxin may cause cell wall loosening, leading to cell extension,through its effect on ß-glucan degradation or throughthe decrease in the molecular weight of hemicellulose B. (Received July 16, 1979; )     

Composition of sugar cane,energy cane,and sweet sorghum suitable for ethanol production at Louisiana sugar mills

A challenge facing the biofuel industry is to develop an economically viable and sustainable biorefinery. The existing potential biorefineries in Louisiana, raw sugar mills, operate only 3 months of the year. For year-round operation, they must adopt other feedstocks, besides sugar cane, as supplemental feedstocks. Energy cane and sweet sorghum have different harvest times, but can be processed for bio-ethanol using the same equipment. Juice of energy cane contains 9.8% fermentable sugars and that of sweet sorghum, 11.8%. Chemical composition of sugar cane bagasse was determined to be 42% cellulose, 25% hemicellulose, and 20% lignin, and that of energy cane was 43% cellulose, 24% hemicellulose, and 22% lignin. Sweet sorghum was 45% cellulose, 27% hemicellulose, and 21% lignin. Theoretical ethanol yields would be 3,609 kg per ha from sugar cane, 12,938 kg per ha from energy cane, and 5,804 kg per ha from sweet sorghum.     

利用蔗渣半纤维素水解液产油酵母的筛选、鉴定及发酵实验

对已分离到的产油酵母通过木糖摇瓶发酵,从中筛选到2株H2-1和J2-2利用蔗渣半纤维素水解液高产油脂酵母,其利用蔗渣半纤维素水解液油脂得率系数分别为13.49和10.28,均显示出对蔗渣半纤维素水解液的高转化率.根据常规生理生化特征和26S rDNA序列分析结果,确认H2-1为小红酵母(Rhodotorula minuta),J2-2为粘红酵母(Rhodotorula glutinis).     

Cell wall invertases from apex and callus tissues of sugar cane

Calluses were obtained from the stalk apex of sugar cane. Boththe stalk apex and callus tissues possessed firmly bound cellwall invertases. The invertases of each tissue were characterizedon the basis of their Km, optimum pH and the action of variousinhibitors. According to this characterization, the two tissuespossess different isoenzymes. Taking into account the presentisoenzymes and the known cell wall invertases from stalk tissue,we postulated a different pattern of isoenzymes for each organof the sugar cane. These differences suggest that the cell wallinvertases might be used as markers in studies of tissue differentiation. (Received May 27, 1980; )     

Effects of hypergravity on growth and cell wall properties of cress hypocotyls

Elongation growth of etiolated hypocotyls of cress (Lepidiumsativum L.) was suppressed when they were exposed to basipetalhypergravity at 35 g and above. Acceleration at 135 g causeda decrease in the mechanical extensibility and an increase inthe minimum stress-relaxation time of the cell wall. Such changesin the mechanical properties of the cell wall were prominentin the lower regions of hypocotyls. The amounts of cell wallpolysaccharides per unit length of hypocotyls increased underthe hypergravity condition and, in particular, the increasein the amount of cellulose in the lower regions was conspicuous.Hypergravity did not influence the neutral sugar compositionof either the pectin or the hemicellulose fraction. The amountof lignin was also increased by hypergravity treatment, althoughthe level was low. The data suggest that hypergravity modifiesthe metabolism of cell wall components and thus makes the cellwall thick and rigid, thereby inhibiting elongation growth ofcress hypocotyls. These changes may contribute to the plants'ability to sustain their structures against hypergravity. Key words: Cell wall extensibility, cellulose, hypergravity, Lepidium sativum L., lignin     

Cell wall invertases from apex and callus tissues of sugar cane

Calluses were obtained from the stalk apex of sugar cane. Boththe stalk apex and callus tissues possessed firmly bound cellwall invertases. The invertases of each tissue were characterizedon the basis of their Km, optimum pH and the action of variousinhibitors. According to this characterization, the two tissuespossess different isoenzymes. Taking into account the presentisoenzymes and the known cell wall invertases from stalk tissue,we postulated a different pattern of isoenzymes for each organof the sugar cane. These differences suggest that the cell wallinvertases might be used as markers in studies of tissue differentiation. (Received May 27, 1980; )     

Infection of sugar cane by the nitrogen-fixing bacterium Acetobacter diazotrophicus

Significant nitrogen fixation has recently been demonstratedin Brazilian sugar cane (Saccharum officinarum) cultivars knownto form associations with a number of diazotrophs, includingAcetobacter diazotrophicus, an acid-tolerant endophytic bacteriumwhich grows best on a sucrose-rich medium. In a series of experiments,aseptically-grown sugar cane plantlets were rooted in a liquidmedium and inoculated with A. diazotrophicus originally isolatedfrom field-grown sugar cane. After 4, 7, 9, and 15 d, plantswere examined under light, scanning and transmission electronmicroscopes and the presence of A. diazotrophicus on and withinplant tissues was confirmed by immunogold labelling. By 15 d,external bacterial colonization was seen on roots and lowerstems, particularly at cavities in lateral root junctions. Theloose cells of the root cap at root tips were a site of entryof the bacteria into root tissues. Both at lateral root junctionsand root tips, bacteria were also seen in enlarged, apparentlyintact, epidermal cells. After 15 d, bacteria were present inxylem vessels at the base of the stem, many connected via mucusto spiral secondary thickening. There was no obvious pathogenicreaction to the bacteria within the xylem. From these observations,it is proposed that, under experimental conditions, A. diazotrophicusfirstly colonized the root and lower stem epidermal surfacesand then used root tips and lateral root junctions to enterthe sugar cane plant where it was distributed around the plantin the transpiration stream. It is further suggested that thexylem vessels in the dense shoots of mature plants are alsoa possible site of N₂-fixation by diazotrophs as they providethe low pO₂ and energy as sucrose necessary for nitrogenaseactivity. Key words: Acetobacter diazotrophicus, endophyte, infection, nitrogen fixation, sugar cane.     

Studies on the cell wall of Chlorella I. Quantitative changes in cell wall polysaccharides during the cell cycle of Chlorella ellipsoidea

1. 1. The cell wall of Chlorella ellipsoidea was fractionated intotwo components, alkali-soluble hemicellulose and alkali-insoluble"rigid wall". The former was composed of several neutral sugars,i.e. rhamnose, xylose, arabinose, mannose and galactose, andthe latter had glucosamine as a main constituent sugar.
2. 2.Quantitative changes in both hemicellulose and "rigid wall"contents during the cell cycle were followed using synchronouslygrown cells. The two cell wall components showed markedly differentchanges. Hemicellulose increased in proportion to the enlargementof the cell surface area in the growing phase, while the "rigidwall" remained almost constant in this phase. The "rigid wall"increased only in the reproduction phase—the time of autosporeformation.

(Received September 26, 1977; )     

Genotypic Variations in Non-Structural Carbohydrate and Cell-Wall Components of the Stem in Rice,Sorghum, and Sugar Vane

We evaluated genetic variations in the non-structural carbohydrate (NSC) and the cell-wall components of stem in rice, sorghum, and sugar cane to assess the potential suitability of these gramineous crops for bioethanol production. For NSC, the maximum soluble sugar concentration was highest in sugar cane, followed by sorghum with sucrose. The major NSC in rice was starch, but there were wide variations in the starch to soluble sugar ratios among the cultivars. The total concentration of cell-wall components was negatively correlated with the NSC concentration, indicating competition for carbon sources. Among the cell-wall components, lignin was relatively stable within each group. The major sugar species composing hemicellulose was xylose in all crop groups, but there were differences in composition, with a higher fraction of arabinose and glucose in rice as compared to the other crops. In rice, there was less lignin than in sorghum or sugar cane; this might be advantageous for the efficient saccharification of cellulose.     

Genotypic variations in non-structural carbohydrate and cell-wall components of the stem in rice, sorghum, and sugar vane

We evaluated genetic variations in the non-structural carbohydrate (NSC) and the cell-wall components of stem in rice, sorghum, and sugar cane to assess the potential suitability of these gramineous crops for bioethanol production. For NSC, the maximum soluble sugar concentration was highest in sugar cane, followed by sorghum with sucrose. The major NSC in rice was starch, but there were wide variations in the starch to soluble sugar ratios among the cultivars. The total concentration of cell-wall components was negatively correlated with the NSC concentration, indicating competition for carbon sources. Among the cell-wall components, lignin was relatively stable within each group. The major sugar species composing hemicellulose was xylose in all crop groups, but there were differences in composition, with a higher fraction of arabinose and glucose in rice as compared to the other crops. In rice, there was less lignin than in sorghum or sugar cane; this might be advantageous for the efficient saccharification of cellulose.     

The glycosidases of Cellulomonas

Summary A Cellulomonas strain, with potential for saccharification of sugar cane bagasse, has been found to possess a range of glycosidase activities which could be necessary for effective hydrolysis of the hemicellulose fraction of the bagasse.     

Regulation of lettuce hypocotyl elongation by gibberellic acid. Correlation between cell elongation, stress-relaxation properties of the cell wall and wall polysaccharide content

Lettuce hypocotyl elongation caused by gibberellic acid wasstrongly inhibited by coumarin and dichlobenil, known inhibitorsof cellulose biosyndiesis. Stress-relaxation analysis of thecell wall revealed that gibberellic acid induces a decreasein both minimum relaxation time (To) and relaxation rate (b)and an increase in maximum relaxation time (Tm), when gibberellicacid stimulates hypocotyl elongation. Both coumarin and dichlobenilnullified the effect of gibberellic acid on changes in To, Tmand b values. The content of pectic, hemicellulosic and cellulosic substancesin the cell wall increased per hypocotyl but decreased per unithypocotyl length, in response to gibberellic acid treatment.Particularly, gibberellic acid caused a substantial increasein cellulose content per hypocotyl but a decrease per unit length.A good correlation existed between the decrease in To and thedecrease in hemicellulose content per unit lengdi of the cellwall. The increase in Tm was correlated with the decrease incellulose content per unit length of the cell wall. The decreasein b was correlated with the decrease in the content of bothcellulose and hemicellulose per unit length. Based on these results, we discuss the role of polysaccharidemetabolism of the cell wall in gibberellic acid-induced lettucehypocotyl elongation and the nature of gibberellic acid-inducedbiochemical modifications of the cell wall, which are representedby changes in stress-relaxation properties of the cell wall. ¹Present address: Department of Anatomy, Aichi Medical University,Nagakutecho, Aichigun, Aichi 480-11, Japan. (Received September 22, 1975; )     

Evaluation of holocellulase production by plant-degrading fungi grown on agro-industrial residues

Agaricus brasiliensis CS1, Pleurotus ostreatus H1 and Aspergillus flavus produced holocellulases when grown in solid and submerged liquid cultures containing agro-industrial residues, including sugar cane bagasse and dirty cotton residue, as substrates. These isolates proved to be efficient producers of holocellulases under the conditions used in this screening. Bromatological analysis of agro-industrial residues showed differences in protein, fiber, hemicellulose, cellulose and lignin content. Maximal holocellulase activity (hemicellulase, cellulase and pectinase) was obtained using solid-state cultivation with 10% substrate concentration. In this case, remarkably high levels of xylanase and polygalacturonase activity (4,008 and 4,548 IU/l, respectively) were produced by A. flavus when grown in media containing corn residue, followed by P. ostreatus H1 with IU/l values of 1,900 and 3,965 when cultivated on 5% and 10% sugar cane bagasse, respectively. A. brasiliensis CS1 showed the highest reducing sugar yield (11.640 mg/ml) when grown on medium containing sugar cane bagasse. A. brasiliensis was also the most efficient producer of protein, except when cultivated on dirty cotton residue, which induced maximal production in A. flavus. Comparison of enzymatic hydrolysis of sugar cane bagasse and dirty cotton residue by crude extracts of A. brasiliensis CS1, P. ostreatus H1 and A. flavus showed that the best reducing sugar yield was achieved using sugar cane bagasse as a substrate.     

甘蔗雌雄蕊的解剖学研究

甘蔗雄蕊花药的壁由四层细胞构成,药室内壁在花药成熟时才发育。花粉母细胞减数分裂属连续型,四分体正常发育为小孢子,但当开花时,只有少数进一步发育为成熟的花粉粒。甘蔗雌蕊柱头是分枝的,每一柱头毛是由数个细胞质浓密的细胞,呈不规则的纵列而组成。倒生胚珠一个,着生于子房室的内侧;内、外珠被均由两层细胞构成,外珠被上侧未能生长到珠孔,内珠被的内层细胞在胚珠发育中不断增大体积。石蜡制片是以樟油为透明剂的。     

酵母发酵蔗渣半纤维素水解物生产木糖酶

采用二次正交旋转组合设计研究了蔗渣半纤维素水解过程中硫酸浓度与液 固比对木糖收率的影响。回归分析表明 ,这两个因素与木糖的收率之间存在显著的回归关系。通过回归方程优化水解条件 ,当硫酸浓度 2 .4g L ,液 固 =6 .2 ,在蒸汽压力 2 .5× 10 4Pa的条件下水解 2 .5h ,10 0g蔗渣可水解生成木糖约 2 4g。大孔树脂吸附层析处理蔗渣半纤维素水解物 ,能有效地减少其中的酵母生长抑制物含量 ,显著改善水解物的发酵性能。用大孔树脂在pH 2条件下处理过的蔗渣半纤维素水解物作基质 ,含木糖 2 0 0g L ,产木糖醇酵母菌株CandidatropicalisAS2 .1776发酵 110h耗完基质中的木糖 ,生成木糖醇 12 7g L ,产物转化率 0 .6 4(木糖醇g 木糖g) ,产物生成速率 1.15g L·h .     

Pyrolysis of olive residue and sugar cane bagasse: non-isothermal thermogravimetric kinetic analysis

Thermal degradation and kinetics for olive residue and sugar cane bagasse have been evaluated under dynamic conditions in the presence of nitrogen atmosphere, using a non-isothermal thermogravimetric method (TGA). The effect of heating rate was evaluated in the range of 2-50 K min(-1) providing significant parameters for the fingerprinting of the biomass. The DTG plot for the olive residue and sugar cane bagasse clearly shows that the bagasse begins to degrade at 473 K and exhibits two major peaks. The initial mass-loss was associated with hemicellulose pyrolysis and responsible for the first peak (538-543 K) whereas cellulose pyrolysis was initiated at higher temperatures and responsible for the second peak (600-607 K). The two biomass mainly devolatilized around 473-673 K, with total volatile yield of about 70-75%. The char in final residue was about 19-26%. Mass loss and mass loss rates were strongly affected by heating rate. It was found that an increase in heating rate resulted in a shift of thermograms to higher temperatures. Ozawa-Flynn-Wall and Vyazovkin methods were applied to determine apparent activation energy to the olive residue and sugar cane bagasse. Two different steps were detected with apparent activation energies in the 10-40% conversion range have a value of 153-162 kJ mol(-1) and 168-180 kJ mol(-1) for the hemicellulose degradation of olive residue and sugar cane bagasse, respectively. In the 50-80% conversion range, this value is 204-215 kJ mol(-1) and 231-240 kJ mol(-1) for the cellulose degradation of olive residue and sugar cane bagasse, respectively.     

Radiation and fermentation treatment of cellulosic wastes

The effect of radiation pasteurization of sugar cane bagasse and rice straw and fermentation using various strains of fungi were studied for upgrading of cellulosic wastes. The initial contamination by fungi and aerobic bacteria both in bagasse and straw was high. The doses of 30 kGy for sterilization and 8 kGy for elimination of fungi were required. Irradiation effect showed that rice straw contained comparatively radioresistant microorganisms. It was observed that all the fungi (Hericium erinacium, Pleurotus djamor, Ganoderma lucidum, Auricularia auricula, Lentinus sajor-caju, Coriolus versicolor, Polyporus arcularius, Coprinus cinereus) grow extending over the entire substrates during one month after inoculation in irradiated bagasse and rice straw with 3% rice bran and 65% moisture content incubated at 30°C. Initially, sugar cane bagasse and rice straw substrates contained 39.4% and 25.9% of cellulose, 22.9% and 26.9% of hemicellulose, and 19.6% and 13.9% of lignin + cutin, respectively. Neutral detergent fibre (NDF) values decreased significantly in sugar cane bagasse fermented byG. lucidum, A. auricula andP. arcularius, and in rice straw fermented by all the 8 strains of fungi. Acid detergent fibre (ADF) values also decreased in bagasse and rice straw fermented by all the fungi.P. arcularius, H. erinacium, G. lucidum andC. cinereus were found to be the most effective strains for delignification of sugar cane bagasse.     

Glycanases Associated with Cell Walls of Cicer arietinum L: Arabinogalactan Degradation

The proteins extracted from Cicer arietinum cell walls showedendo-glycanase activity against the water-soluble hemicellulosicpolysaccharides extracted with 4% KOH. Such endo-glycanase activitywas able to shift the molecular mass distribution of the arabinogalactancausing a decrease in its average molecular mass, as well asto release small oligosaccharides constituted exclusively ofarabinose. Exo-glycanase activities such as glucosidase andgalactosidase were also present. Key words: Arabinogalactan, cell wall, Cicer arietinum, glycanase, hemicellulose     

Sugar Composition and Molecular Weight Distribution of Cell Wall Polysaccharides in Outer and Inner Tissues from Segments of Dark Grown Squash (Cucurbita maxima Duch.) Hypocotyls

The elongation growth of stem segments is determined by the outer cell layers (epidermis and collenchyma). We measured the sugar composition and molecular weight distribution of pectin and hemicellulose fractions obtained from inner and outer tissues of squash (Cucurbita maxima Duch.) hypocotyls. In addition, we studied the changes in these parameters after a 9 hour period of incubation of the segments. The results show that outer tissues have higher molecular weight pectin and hemicellulose compared to inner tissues (2-3 times higher). Incubation results in a 13 to 25% decrease in the amount of pectin and hemicellulose in inner tissues and an increase of 11 to 32% in the outer tissues. This increase in the outer tissues is accompanied by a decrease in the molecular weight of some of the components. These results clearly show that cell wall metabolism during elongation growth differs markedly in inner and outer tissues, and that future studies on the effect of auxin need to take these differences into account.     

Changes of Cell Wall Composition and Polymer Size in Primary Roots of Cotton Seedlings Under High Salinity

The aim of this study was to investigate changes in cell wallchemical composition and polymer size in the root tip of intactcotton seedlings (Gossypium hirsutum L. cv. Acala SJ-2) grownin saline environments, in order to relate the interaction betweenhigh salinity and root growth to possible changes in cell wallmetabolism. Cotton seedlings were grown in modified Hoagland nutrient solutionwith various combinations of NaCl and CaCl₂. Cell walls werefractionated into four fractions (pectin, hemicellulose 1 and2, cellulose), and analysed for their total sugar content, neutralsugar composition and size of polysaccharides. At 1 mol m^–3Ca, 150 mol m^–3 NaCl resulted in a significant increasein the cell wall uronic acid content, but a reduction in cellulosecontent on a per unit dry weight basis. Supplemental Ca overcamethe inhibitory effect of high Na on cellulose content. The neutralsugar composition of the cell wall fractions showed no majorchanges caused by varied Na/Ca ratios. Determinations of polysaccharidepolymer size showed that high Na at 1 mol m^–3 Ca led toan increase in the amount of polysaccharides of intermediatemolecular size and a decrease in that of small size in the hemicellulose1 fraction, indicating a possible inhibition of polysaccharidedegradation by high Na. This change was not observed in the10 mol m^–3 Ca treatments. The results reveal a relationshipbetween the effects of high salinity on root growth and cellwall metabolism, particularly in regard to cellulose biosynthesis Key words: Gossypium hirsutum, salinity, root, cell wall