Effects of ionic conduction on hydrothermal hydrolysis of corn starch and crystalline cellulose induced by microwave irradiation.

This study investigated the effects of ionic conduction of electrolytes under microwave field to facilitate hydrothermal hydrolysis of corn starch and crystalline cellulose (Avicel), typical model biomass substrates. Addition of 0.1M NaCl was effective to improve reducing sugar yield by 1.61-fold at unit energy (kJ) level. Although Avicel cellulose was highly recalcitrant to hydrothermal hydrolysis, addition of 0.1M MgCl2 improved reducing sugar yield by 6.94-fold at unit energy (kJ). Dielectric measurement of the mixture of corn starch/water/electrolyte revealed that ionic conduction of electrolytes were strongly involved in facilitating hydrothermal hydrolysis of polysaccharides.

In situ detection and identification of hesperidin crystals in satsuma mandarin (Citrus unshiu) peel cells.

INTRODUCTION: Hesperidin, a flavonoid known to have important pharmacological effects, accumulates particularly in the peels of satsuma mandarin (Citrus unshiu). Although histochemical studies have suggested that hesperidin forms crystals in some tissues of the Rutaceae and Umbelliferae, there has been no rigorous in situ detection or identification of hesperidin crystals in C. unshiu. OBJECTIVE: To characterise the chemical component of the crystals found in C. unshiu peels using Raman microscopy. METHODS: Sections of C. unshiu peels were made. The distribution and morphology of crystals in the sections were analysed microscopically. Raman microscopy was used to detect hesperidin in the sections directly. RESULTS: The crystals were more abundant in immature peel and were observed particularly in areas surrounding vascular bundles, around the border between the flavedo and albedo layers and just below the epidermal cells. In the morphological analysis by scanning electron microscopy, needle-shaped crystals aggregated and formed clusters of spherical crystals. Spectra obtained by Raman microscopy of the crystals in the peel sections were consistent with those of the hesperidin standard. CONCLUSION: This study showed the detailed distribution of crystals in C. unshiu peels and their main component was identified using Raman microscopy to be hesperidin for the first time.

Molecular cloning and characterization of a geranyl diphosphate-specific aromatic prenyltransferase from lemon.

Prenyl residues confer divergent biological activities such as antipathogenic and antiherbivorous activities on phenolic compounds, including flavonoids, coumarins, and xanthones. To date, about 1,000 prenylated phenolics have been isolated, with these compounds containing various prenyl residues. However, all currently described plant prenyltransferases (PTs) have been shown specific for dimethylallyl diphosphate as the prenyl donor, while most of the complementary DNAs encoding these genes have been isolated from the Leguminosae. In this study, we describe the identification of a novel PT gene from lemon (Citrus limon), ClPT1, belonging to the homogentisate PT family. This gene encodes a PT that differs from other known PTs, including flavonoid-specific PTs, in polypeptide sequence. This membrane-bound enzyme was specific for geranyl diphosphate as the prenyl donor and coumarin as the prenyl acceptor. Moreover, the gene product was targeted to plastid in plant cells. To our knowledge, this is the novel aromatic PT specific to geranyl diphosphate from citrus species.

Selective isolation of ß-glucan from corn pericarp hemicelluloses by affinity chromatography on cellulose column.

A combination of anion-exchange chromatography and affinity chromatography on a cellulose column was found to be effective for the isolation of ß-(1,3;1,4)-glucan (BG) from corn pericarp hemicelluloses (CPHs). CPHs containing 6.6% BG were extracted from corn pericarp with 6M urea-2 wt% NaOH solution and initially fractionated into neutral and acidic parts by anion exchange chromatography to remove acidic arabinoxylan consisting of arabinose (35.6%) and xylose (50.9%). The neutral fraction (yield; 10.1% on the basis of CPHs) consisting of 1.0% arabinose, 10.1% xylose and 80.3% glucose containing 28.4% BG was then applied to a cellulose column of Whatman CF-11. BG could be recovered from the adsorbed fraction on the cellulose column by elution with 2% NaOH in a yield of 2.6% on the basis of CPHs with a purity of 84.7%. The chemical structure of the isolated corn pericarp BG was confirmed by (13)C NMR spectroscopic, methylation and lichenase treatment analyses. The results indicate that the ratios of (1,4)/(1,3) linkage and cellotriosyl/cellotetraosyl segments of the BG were 2.60 and 2.5, respectively.

Cuticular membrane of Fuyu persimmon fruit is strengthened by triterpenoid nano-fillers.

The mechanical defensive performance of fruit cuticular membranes (CMs) is largely dependent on the molecular arrangement of their constituents. Here, we elucidated nano-sized interactions between cutin and triterpenoids in the cuticular matrix of Fuyu persimmon fruits (Diospyroskaki Thunb. cv. Fuyu), focusing on the mechanical properties using a combination of polymer analyses. The fruit CMs of Fuyu were primarily composed of wax (34.7%), which was predominantly triterpenoids followed by higher aliphatic compounds, and cutin (48.4%), primarily consisting of 9,10-epoxy-18-hydroxyoctadecanoic acid and 9,10,18-trihydroxyoctadecanoic acid. Based on the tensile tests of the CM, the removal of wax lead to a considerable decrease in the maximum stress and elastic modulus accompanied by an increase in the maximum strain, indicating that wax is of significant importance for maintaining the mechanical strength of the CM. Wide-angle X-ray diffraction and relaxation time measurements using solid-state (13)C nuclear magnetic resonance indicated that the triterpenoids in the cuticular matrix construct a nanocomposite at a mixing scale below 20-24 nm; however, the higher aliphatic compounds did not exhibit clear interactions with cutin. The results indicated that the triterpenoids in the cuticular matrix endow toughness to the CM by functioning as a nanofiller.

Microwave-assisted hydrolysis of polysaccharides over polyoxometalate clusters.

Polyoxometalate (POM) clusters were utilized as recyclable acid catalysts and microwave-absorbing agents for the microwave-assisted hydrolysis of corn starch and crystalline cellulose. Phosphotungstic (PW) and silicotungstic (SiW) acids showed high hydrolyzing activity, while phosphomolybdic acid (PMo) showed lower glucose stability. The PW catalyst could be recycled by ether extraction at least 4 times without changing its catalytic activity. The addition of PW could reduce the energy demand required for running the hydrolysis by 17-23%. The dielectric property of the aqueous PW solution was important for increasing the microwave-absorption capability of the reaction system and reducing the energy consumption.

Comparative decomposition kinetics of neutral monosaccharides by microwave and induction heating treatments.

The stabilities of five neutral monosaccharides (glucose, galactose, mannose, arabinose, and xylose) were kinetically compared after the molecules were submitted to microwave heating (internal heating) and induction heating (external heating) under completely identical thermal histories by employing PID (proportional, integral, and derivative) temperature controlled ovens and homogeneous mixing. By heating in water at 200°C, the rate constants for the decomposition reactions varied from 2.13×10(-4) to 3.87×10(-4)s(-1) for microwave heating; however, the values increased by 1.1- to 1.5-fold for induction heating. Similarly, in a dilute (0.8%) sulfuric acid solution, the decomposition rate constants varied from 0.61×10(-3) to 2.00×10(-3)s(-1) for microwave heating; however, the values increased by 1.5- to 2.2-fold for induction heating. The results show that microwave heating imparts greater stability to neutral monosaccharides than does induction heating. The undesirable decomposition of monosaccharides at the surface boundary of reactor walls may have increased the probability of monosaccharide decomposition during induction heating.

Two cytosolic aldolases show different expression patterns during shoot elongation in Moso bamboo, Phyllostachys pubescens Mazel.

In fast-growing Moso bamboo (Phyllostachys pubescens Mazel), cytosolic fructose 1,6-bisphosphate aldolase (aldolase; EC 4.2.2.13) was more highly active in elongating tissues than in tissues that had already finished elongating. It is well known that the removal of the culm sheath prevents bamboo from elongating. When the sheath was removed from the culm, the aldolase activity was gradually reduced over time. Two isozyme genes for aldolase, PpAldC1 and PpAldC2, were cloned from the elongating tissues of Moso bamboo. Gene expression analysis using a semi-quantitative reverse transcriptase-polymerase chain reaction revealed that PpAldC1 was highly expressed in elongating tissues but was hardly detected in elongated internodes, while PpAldC2 seemed to be expressed constitutively in both elongating and elongated tissues. Promoter analysis revealed that the expression of PpAldC1 was induced by gibberellin. These results indicated that the two genes for cytosolic aldolase in Moso bamboo showed different expression patterns and that one of them was involved in shoot elongation.

Total fractionation of green tea residue by microwave-assisted alkaline pretreatment and enzymatic hydrolysis.

Total refinery of constituents of green tea residue was achieved by combination of microwave-assisted alkaline pretreatment and enzymatic hydrolysis. Alkaline pretreatment was effective at separating pectic polysaccharides, protein, phenolic compounds and aliphatic compounds (probably originating from cuticular components), and the solubilization rate was attained 64­74% by heating at 120­200 °C. The higher heating value (HHV) of alkali-soluble fraction attained 20.1 MJ/kg, indicating its usability as black-liquor-like biofuel. Successive cellulolytic enzymatic hydrolysis mainly converted cellulose into glucose and attained the maximum solubilization rate of 89%. Final residue was predominantly composed of aliphatic cuticular components with high proportion in 9,10,18-trihydroxyoctadecanoic acid (30.1­48.6%). These cuticular components are potential alternative feedstock for aliphatic compounds commonly found in oil plants.

Compositional analysis of leaf cuticular membranes isolated from tea plants (Camellia sinensis L.).

Chemical constituents of cuticular membranes (CMs) isolated from three tea cultivars (Camellia sinensis (L.) O. Kuntze cvs. Yabukita, Samidori and Gokou) were compared. All CMs from the adaxial side of the leaves showed higher accumulation of wax, cutin and polysaccharide, while those from the abaxial side were abundant in cutan, showing the adaptation of the adaxial side to abiotic stresses, such as wind and rain, in contrast to the abaxial side, which provides defence against pathogens. Yabukita, a major tea cultivar in Japan, developed thick CMs while Samidori and Gokou, shade-cultivated tea cultivars, had lighter CMs, reflecting their thin and soft leaves. CMs rapidly accumulated 9,10-epoxy-18-hydroxyoctadecanoic acid at a very early stage of leaf development. Additionally, shade treatment did not influence cutin biosynthesis in CMs, reflecting high adaptation of tea leaves under low light levels.

Microwave-assisted hydrothermal hydrolysis of cellobiose and effects of additions of halide salts.

Microwave irradiation was compared with induction heating for hydrothermal hydrolysis of cellobiose. Microwave heating improved glucose selectivity and resulted in a pH of the hydrolyzates that was ⩽0.57 units lower than those from conventional heating, which suggests that fewer side-reactions occurred. Halide salts of alkali and alkali earth metals improved microwave-assisted hydrothermal saccharification of cellobiose at lower reaction severity by around 0.3 of logR(0). NaCl addition of ⩾10mM reduced the required microwave output to 58.6-66.2% as compared to conventional microwave-hydrothermal hydrolysis without halide salts. Kinetic analyses revealed that the addition of salt increased the hydrolysis rate by increasing the frequency factor of the reaction. The results showed that microwave irradiation in the presence of microwave-absorbing salts is effective for hydrothermal hydrolysis of carbohydrates.

Characterization of coumarin-specific prenyltransferase activities in Citrus limon peel.

Coumarins, a large group of polyphenols, play important roles in the defense mechanisms of plants, and they also exhibit various biological activities beneficial to human health, often enhanced by prenylation. Despite the high abundance of prenylated coumarins in citrus fruits, there has been no report on coumarin-specific prenyltransferase activity in citrus. In this study, we detected both O- and C-prenyltransferase activities of coumarin substrates in a microsome fraction prepared from lemon (Citrus limon) peel, where large amounts of prenylated coumarins accumulate. Bergaptol was the most preferred substrate out of various coumarin derivatives tested, and geranyl diphosphate (GPP) was accepted exclusively as prenyl donor substrate. Further enzymatic characterization of bergaptol 5-O-geranyltransferase activity revealed its unique properties: apparent K(m) values for GPP (9 µM) and bergaptol (140 µM) and a broad divalent cation requirement. These findings provide information towards the discovery of a yet unidentified coumarin-specific prenyltransferase gene.

Growth-dependent chemical and mechanical properties of cuticular membranes from leaves of Sonneratia alba.

Chemical and mechanical properties of the leaf cuticular membranes (CMs) of a mangrove, Sonneratia alba J. Smith, were analysed at various leaf development stages to evaluate their tolerance to environmental stress. Our analyses demonstrate that the CMs from leaves of S. alba at different growth stages are generally rich in wax (21.5-25.7%) and cutin (52.4-63.4%) which rapidly accumulate at the early stages of leaf growth, while cutan (4.3-10.3%) and polysaccharide (2.3-7.7%) continuously accumulate throughout growth. Immature CMs are physically weak and highly viscoelastic. However, CMs become strengthened and stiffened during leaf expansion and maturation (by factors of about 1.5 and 2.4, respectively) while their flexibility decreases (68-83% decrease). Finally, the CMs lose their strength at the senescent stage (30-43% decreasement). Correlation analysis between chemical composition and mechanical properties revealed that the cutin matrix is mainly responsible for the high viscoelastic properties of CMs, while wax, cutan and polysaccharide contributed to their elasticity. Wax also affected the strength of the CMs, whereas cutan and polysaccharide showed rigidizing effect. Rapid accumulation of wax and cutin in the CMs after bud burst followed by the mechanical supports of cutan and polysaccharide in an isolateral manner contributed to the remarkable environmental tolerance of S. alba.

Improvement of microwave-assisted hydrolysis of cassava pulp and tapioca flour by addition of activated carbon.

The superior effects of addition of activated carbon were evidenced for microwave assisted hydrolysis of starches in cassava pulp and tapioca flour under hydrothermal conditions varying irradiation temperature (160-230°C at 5min), duration of heating time (5-18min at 210°C) and amount of activated carbon at 0.5-2.0:1:20 of activated carbon:solid:liquid ratio. The presence of 1.0g/g in microwave-assisted hydrolysis gave much improved glucose yields (44.49% for cassava pulp and 71.93% for tapioca flour) at lower heating temperature (220°C and 200°C, each for 5min) with suppressed formation of secondary decomposed compounds than those without addition of activated carbon (32.41% in cassava pulp at 230°C and 55.11% in tapioca flour at 240°C, each for 5min). The highest glucose yield from cassava pulp (52.27%) was obtained after heating at 210°C for 15min.

A novel saccharification method of starch using microwave irradiation with addition of activated carbon.

Activated carbons were investigated for their heat catalytic effects to improve saccharification of starch by autohydrolysis in water under microwave electromagnetic field, and the results were compared with graphite and carbon nanotubes. The activated carbons with low adsorptive capacity of maltose showed high saccharification rate, while those with high adsorptive capacity exhibited low saccharification. In addition, the former activated carbons decreased the saccharification temperature by 10-30°C. Maltooligosaccharides produced in the presence of the latter activated carbons were recovered by desorption with 50% aqueous ethanol. The results indicated that both adsorptive capacities of maltooligosaccharides and catalytic effects of hot spots arisen from the uneven surface structure of activated carbons might contribute to the improvement in starch saccharification.

Optimization of microwave-assisted extraction of carbohydrates from industrial waste of corn starch production using response surface methodology.

Microwave-assisted extraction (MAE) was applied for production of carbohydrates mainly consisting of arabinoxylan from corn pericarp which is an industrial waste of corn starch production by using hot compressed water as a solvent. The solubilization rate increased with increase in heating temperature and reached 75.2% at 220 °C. The main extracted materials were carbohydrates consist of glucose, xylose and arabinose indicating solubilization of starch and hemicellulose, while residues were composed of cellulose. Four independent variables (heating temperature, come-up time, heating time and solid to liquid ratio) were optimized for maximizing the carbohydrates yield using the response surface methodology including fractional factorial design, the path of steepest ascent and central composite design. The optimized condition was as follows; heating temperature 176.5 °C, come-up time 2 min, heating time 16 min and solid to liquid ratio 1/20 (g/mL), respectively. The maximal yield attained 70.8% of carbohydrates with predominant production of xylo-oligosaccharides.

Microwave heating of tea residue yields polysaccharides, polyphenols, and plant biopolyester.

Microwave heating was used to produce aqueous-soluble components from green, oolong, and black tea residues. Heating at 200-230 degrees C for 2 min extracted 40-50% of polysaccharides and 60-70% of the polyphenols. Solubilization of arabinose and galactose by autohydrolysis occurred with heating above 170 degrees C, whereas heating above 200 degrees C was necessary to solubilize xylose. Catechins were soluble in water by heating at low temperature (110 degrees C); however, new polyphenols having strong antioxidant activity were produced above 200 degrees C. The amount of solubilized materials and antioxidant activity increased with increased fermentation of harvested tea leaves (green tea < oolong tea < black tea). Cutin, a plant biopolyester, remained in the residue after heating as did cellulose and lignin/tannin. The predominant cutin monomer that was recovered was 9,10-epoxy-18-hydroxyoctadecanoic acid, followed by dihydroxyhexadecanoic acid and 9,10,18-trihydroxyoctadecanoic acid.

Changes in stable isotopes, lignin-derived phenols, and fossil pigments in sediments of Lake Biwa, Japan: implications for anthropogenic effects over the last 100 years.

We measured stable nitrogen (N) and carbon (C) isotope ratios, lignin-derived phenols, and fossil pigments in sediments of known ages to elucidate the historical changes in the ecosystem status of Lake Biwa, Japan, over the last 100 years. Stable N isotope ratios and algal pigments in the sediments increased rapidly from the early 1960s to the 1980s, and then remained relatively constant, indicating that eutrophication occurred in the early 1960s but ceased in the 1980s. Stable C isotope ratios of the sediment increased from the 1960s, but decreased after the 1980s to the present. This decrease in stable C isotope ratios after the 1980s could not be explained by annual changes in either terrestrial input or algal production. However, when the C isotope ratios were corrected for the Suess effect, the shift to more negative isotopic value in atmospheric CO(2) by fossil fuel burning, the isotopic value showed a trend, which is consistent with the other biomarkers and the monitoring data. The trend was also mirrored by the relative abundance of lignin-derived phenols, a unique organic tracer of material that originated from terrestrial plants, which decreased in the early 1960s and recovered to some degree in the 1980s. We detected no notable difference in the composition of lignin phenols, suggesting that the terrestrial plant composition did not change markedly. However, we found that lignin accumulation rate increased around the 1980s. These results suggest that although eutrophication has stabilized since the 1980s, allochthonous organic matter input has changed in Lake Biwa over the past 25 years.

Complete nucleotide sequence of the cotton (Gossypium barbadense L.) chloroplast genome with a comparative analysis of sequences among 9 dicot plants.

Recently, the complete chloroplast genome sequences of many important crop plants were determined, and this can be considered a major step forward toward exploiting the usefulness of chloroplast genetic engineering technology. Economically, cotton is one of the most important crop plants for many countries. To further our understanding of this important crop, we determined the complete nucleotide sequence of the chloroplast genome from cotton (Gossypium barbadense L.). The chloroplast genome of cotton is 160,317 base pairs (bp) in length, and is composed of a large single copy (LSC) of 88,841 bp, a small single copy (SSC) of 20,294 bp, and two identical inverted repeat (IR) regions of 25,591 bp each. The genome contains 114 unique genes, of which 17 genes are duplicated in the IRs. In addition, many open reading frames (ORFs) and hypothetical chloroplast reading frames (ycfs) with unknown functions were deduced. Compared to the chloroplast genomes from 8 other dicot plants, the cotton chloroplast genome showed a high degree of similarity of the overall structure, gene organization, and gene content. Furthermore, the sequences of the genes showed high degrees of identity at the DNA and amino acid levels. The cotton chloroplast genome was somewhat longer than the chloroplast genomes of most of the other dicot plants compared here. However, this elongation of the cotton chloroplast genome was found to be due mainly to expansions of the intergenic regions and introns (non-coding DNA). Moreover, these expansions occurred predominantly in the LSC and SSC regions.

Transposon-mediated insertional mutagenesis revealed the functions of animal cellulose synthase in the ascidian Ciona intestinalis.

Tunicates are the only animals that perform cellulose biosynthesis. The tunicate gene for cellulose synthase, Ci-CesA, was likely acquired by horizontal transfer from bacteria and was a key innovation in the evolution of tunicates. Transposon-based mutagenesis in an ascidian, Ciona intestinalis, has generated a mutant, swimming juvenile (sj). Ci-CesA is the gene responsible for the sj mutant, in which a drastic reduction in cellulose was observed in the tunic. Furthermore, during metamorphosis, which in ascidians convert the vertebrate-like larva into a sessile filter feeder, sj showed abnormalities in the order of metamorphic events. In normal larvae, the metamorphic events in the trunk region are initiated after tail resorption. In contrast, sj mutant larvae initiated the metamorphic events in the trunk without tail resorption. Thus, sj larvae show a "swimming juvenile" phenotype, the juvenile-like trunk structure with a complete tail and the ability to swim. It is likely that ascidian cellulose synthase is required for the coordination of the metamorphic events in the trunk and tail in addition to cellulose biosynthesis.