Renewable bio ionic liquids‐water mixtures‐mediated selective removal of lignin from rice straw: Visualization of changes in composition and cell wall structure

Pretreatment of rice straw by using renewable cholinium amino acids ionic liquids ([Ch][AA] ILs)‐water mixtures and the subsequent enzymatic hydrolysis of the residues were conducted in the present work. Of the eight mixtures composed of ILs and water, most were found to be effective for rice straw pretreatment. After pretreatment with 50% ILs‐water mixtures, the enzymatic digestion of the lignocellulosic biomass was enhanced significantly, thus leading to satisfactory sugar yields of >80% for glucose and approximately 50% for xylose. To better understand the ILs pretreatment mechanism, confocal laser scanning microscopy combined with immunolabeling and transmission electron microscopy were used to visualize changes in the contents and distribution of two major components—lignin and xylan. The results coupled with changes in chemical structures (infrared spectra) of the substrates indicated occurrence of extensive delignification, especially in cell corner and compound middle lumen of cell walls, which made polysaccharides more accessible to enzymes. This pretreatment process is promising for large‐scale application because of the high sugar yields, easy handling, being environmentally benign and highly tolerant to moisture, and significantly reduced cost and energy consumption. Biotechnol. Bioeng. 2013; 110: 1895–1902. © 2013 Wiley Periodicals, Inc.     

Evaluation of pretreatment methods for lignocellulosic ethanol production from energy cane variety L 79-1002

Approximately half of the 80 billion tons of crop produced annually around the world remains as residue that could serve as a renewable resource to produce valuable products such as ethanol and butanol. Ethanol produced from lignocellulosic biomass is a promising renewable alternative to diminishing oil and gas liquid fuels. Sugarcane is an important industry in Louisiana. The recently released variety of “energy cane” has great potential to sustain a competitive sugarcane industry. It has been demonstrated that fuel-grade ethanol can be produced from post harvest sugarcane residue in the past, but optimized ethanol production was not achieved. Optimization of the fermentation process requires efficient pretreatment to release cellulose and hemicellulose from lignocellulosic complex of plant fiber. Determining optimal pretreatment techniques for fermentation is essential for the success of lignocellulosic ethanol production process. The purpose of this study was to evaluate three pretreatment methods for the energy cane variety L 79-1002 for maximum lignocellulosic ethanol production. The pretreatments include alkaline pretreatment, dilute acid hydrolysis, and solid-state fungal pretreatment process using brown rot and white rot fungi. Pretreated biomass was enzymatically saccharified and subjected to fermentation using a recombinant Escherichia coli FBR5. The results revealed that all pretreatment processes produced ethanol. However, the best result was observed in dilute acid hydrolysis followed by alkaline pretreatment and solid-state fungal pretreatment.     

Structure of Ovarian Asterosaponin-1 in the Starfish Asterias amurensis

Cultured crown gall cells of Catharanthus roseus Don (Vinca rosea L.) was found to contain brassinosteroids. These were identified as brassinolide and castasterone by GC/MS. This is the first conclusive identification of endogenous brassinosteroids in cultured cells.     

Stereochemical Difference in Secoisolariciresinol Formation between Cell-free Extracts from Petioles and from Ripening Seeds of Arctium lappa L.

Cell-free extracts from ripening seeds of Arctium lappa L. catalyzed the enantioselective formation of (-)-pinoresinol, (-)-lariciresinol and (-)-secoisolariciresinol from achiral coniferyl alcohol in the presence of NADPH and H₂O₂. The enantioselectivity of the lignan formation was opposite to that of the (+)-secoisolariciresinol formation catalyzed by cell-free extracts from petioles of the same plant species.     

Nitrogen Fixation and Allantoin Formation in Soybean Plants

The activity of nitrogenase and the concentration of ammonia and allantoin (+ allantoic acid) in root nodules were measured throughout the growth period of soybean plants. Nitrogenase activity measured by acetylene reduction increased with plant growth and reached a maximum level at the flowering period. The level of ammonia and allantoin concentration in nodules was parallel with increased nitrogenase activity. At the late reproductive stage (pod-forming period), nitrogenase activity showed a marked decrease, but the ammonia and allantoin in the nodules remained at a constant level. Detached nodules from 56 day-old soybean plants were exposed to ¹⁵N₂ gas, and the distribution of ¹⁵N among nitrogen compounds was investigated. Enrichment of ¹⁵N in allantoin and allantoic acid reached a fairly high level after 90 min of nitrogen fixation; ca. 22% of ¹⁵N in acid-soluble nitrogen compounds was incorporated into allantoin + allantoic acid. In contrast, enrichment of ¹⁵N in amide nitrogen was relatively low. No significant ¹⁵N was detected in the RNA fraction. The data suggested that ureide formation in nitrogen-fixing root nodules did not take place through the breakdown of nucleic acids, but directly associated with the assimilating system of biologically fixed nitrogen.     

Production of Acetone and Butanol Using Immobilized Growing-cells of Clostridium acetobutylicum

The biosynthetic route for chloromonilicin, an antifungal substance from cherry rot fungus, was investigated using deuterium-labeled precursors. The incorporation of synthetic deuterium-labeled moniliphenone into chloromonilicin and into its xanthone precursor, 4-chloropinselin, was confirmed by ’H-NMR spectrometry.     

Constitutional Studies on the Mucilage of “Yamanoimo,” Dioscorea batatas Decne,forma Tsukune

All four stereoisomers of 10,14-dimethyloctadec-1-ene, a sex pheromone component of the apple leafminer (Lyonetia prunifoliella: Lepidoptera), were synthesized starting from (R)- and (S)-propylene oxide by applying stereospecific inversion of chiral secondary tosylates as a key step. Field evaluation showed that male moths of the Japanese population were selectively attracted by the (10S,14S)-isomer and that the activity was not inhibited by the enantiomer.     

Dextranase from Arthrobacter oxydans KQ11-1 inhibits biofilm formation by polysaccharide hydrolysis

Dental plaque is a biofilm of water-soluble and water-insoluble polysaccharides, produced primarily by Streptococcus mutans. Dextranase can inhibit biofilm formation. Here, a dextranase gene from the marine microorganism Arthrobacter oxydans KQ11-1 is described, and cloned and expressed using E. coli DH5α competent cells. The recombinant enzyme was then purified and its properties were characterized. The optimal temperature and pH were determined to be 60°C and 6.5, respectively. High-performance liquid chromatography data show that the final hydrolysis products were glucose, maltose, maltotriose, and maltotetraose. Thus, dextranase can inhibit the adhesive ability of S. mutans. The minimum biofilm inhibition and reduction concentrations (MBIC₅₀ and MBRC₅₀) of dextranase were 2 U ml^?1 and 5 U ml^?1, respectively. Scanning electron microscopy and confocal laser scanning microscope (CLSM) observations confirmed that dextranase inhibited biofilm formation and removed previously formed biofilms.     

Synthesis of the (9R,13R)-isomer of LDS1, a flower-inducing oxylipin isolated from Lemna paucicostata

The first synthesis of the (9R,13R)-stereoisomer of LDS1, a flower-inducing oxylipin isolated from Lemna paucicostata, has been achieved from a known allylic alcohol by a seven-step sequence that involves the Horner–Wadsworth–Emmons olefination to construct its full carbon framework and an enzymatic hydrolysis of a penultimate methyl ester intermediate to provide the target molecule.