应用高电压脉冲电场辅助快速提取虾壳壳聚糖

为提高虾壳的综合利用效果,该文以虾壳为原料,将高电压脉冲电场（PEF）技术用于壳聚糖的提取研究。与常规加热法和微波法进行了对比试验,并通过单因素试验和三元二次回归旋转组合设计确定最佳制备工艺。结果表明：该技术与传统加热和微波法方法相比,具有非热、反应速度快,脱乙酰度高的特点。建立了脉冲数、场强、NaOH质量浓度对脱乙酰度影响的数学模型,确定了最佳工艺参数：脉冲数10,电场强度20.48 kV/cm,NaOH质量分数48.64%,该条件下脱乙酰度达到最大92.32%。因此,利用高电压脉冲电场技术可以快速制备虾壳中的壳聚糖。     

One-solvent extraction of astaxanthin from lactic acid fermented shrimp wastes

Free astaxanthin one-solvent extractions with ethanol, acetone, and liquid 1,1,1,2-tetrafluoroethane from raw and lactic acid fermented (ensilaged) shrimp residues were investigated. The total carotenoid recovery from ensilaged shrimp wastes was higher than that from non-ensilaged ones as assessed by HPLC analyses. Acetone gave the highest extraction yields of free astaxanthin with up to 115 microg/g of material. Moreover, liquid tetrafluoroethane is reported for the first time in a successful one-solvent extraction of carotenoids from shrimp.     

Physicochemical properties and bioactivity of fungal chitin and chitosan

Chitinous material was extracted from mycelia of Aspergillus niger and Mucor rouxii grown in yeast peptone dextrose broth for 15 and 21 days, respectively. The extracted material was characterized for purity, degree of acetylation, and crystallinity and tested for antibacterial and eliciting properties. The maximum glucosamine level determined in the mycelium of A. niger was 11.10% dw and in the mycelium of M. rouxii was 20.13% dw. On the basis of the stepwise extraction of freeze-dried mycelia, it appeared that M. rouxii mycelia contained both chitin and chitosan, whereas A. niger contained only chitin. The yields of crude chitin from A. niger and M. rouxii were 24.01 and 13.25%, respectively, and the yield of chitosan from M. rouxii was 12.49%. Significant amounts (7.42-39.81%) of glucan were associated with chitinous compounds from both species and could not be eliminated by the extraction method used. The degrees of acetylation were determined to be 76.53 and 50.07% for chitin from A. niger and M. rouxii, respectively, and 19.5% for M. rouxii chitosan. The crystallinity of fungal chitin and chitosan was estimated to be less intense than in corresponding materials from shrimp shells. The extracted chitin and chitosan in a concentration of 0.1% reduced Salmonella Typhimurium DT104 2576 counts by 0.5-1.5 logs during a 4 day incubation in tryptic soy broth at 25 degrees C. Furthermore, all tested chitinous materials from fungal sources significantly reduced lesions caused by Botrytis cinerea and Penicillium expansum in harvested apples.     

Extraction, isolation, and characterization of globulin proteins from Lupinus albus

Lupin has recently been added to the list of allergens requiring mandatory advisory labeling on foodstuffs sold in the European Union, and since December 2008, all products containing even trace amounts of lupin must be labeled correctly. Lupin globulins consist of two major globulins called α-conglutin (11S and "legumin-like") and β-conglutin (7S and "vicilin-like") and another additional two globulins, γ-conglutin and δ-conglutin, which are present in lower amounts. We report on a methodology to facilitate the extraction of each of these proteins using centrifugation and isolation by anion-exchange chromatography followed by size-exclusion chromatography. The isolated subunits were characterized using reducing and non-reducing polyacrylamide gel electrophoresis, western blotting, and peptide mass fingerprinting, all of which revealed that the individual protein subunits are highly pure and can be used as immunogens for the production of antibodies specific for each of the conglutin fractions, as well as standards, and the extraction protocol can be used for the selective extraction of each of the subunits from foodstuffs, thus facilitating a highly accurate determination of the lupin concentration. Furthermore, the subunits can be used to elucidate information regarding the toxicity of each of the subunits, by looking at their interaction with the IgE antibodies found in the serum of individuals allergic to lupin, providing critical information for the definition of the requirements of analytical assays for the detection of lupin in foodstuffs.     

Presence and dehydration of ikaite, calcium carbonate hexahydrate, in frozen shrimp shell.

Ikaite, calcium carbonate hexahydrate, has by means of X-ray diffraction analyses of frozen samples been identified as the mineral component of the white spots formed in the shell of frozen shrimp during storage. When the shrimp thaw and the shell material is dried and kept at room temperature, ikaite rapidly transforms into a mixture of anhydrous calcium carbonate forms. X-ray diffraction analyses and Raman spectra of synthetic ikaite as well as the dehydration product confirm the assignments, and the rate constant for dehydration is approximately 7 x 10(-)(4) s(-)(1) at ambient temperature. Differential scanning calorimetry showed that dehydration of synthetic ikaite is an entropy-driven, athermal process and confirms that a single first-order reaction is rate-determining. Ikaite is found to be stable in aqueous solution at temperatures below 5 degrees C and in the shell of frozen shrimps but decomposes on thawing to form anhydrous calcium carbonates.     

Mosquitocidal, nematicidal, and antifungal compounds from Apium graveolens L. seeds

The methanolic extract of Apium graveolens seeds was investigated for bioactive compounds and resulted in the isolation and characterization of mosquitocidal, nematicidal, and antifungal compounds sedanolide (1), senkyunolide-N (2), and senkyunolide-J (3). Their structures were determined by 1H and 13C NMR spectral methods. Compounds 1-3 gave 100% mortality at 25, 100, and 100 microg mL(-1), respectively, on the nematode, Panagrellus redivivus. Compound 1 showed 100% mortality at 50 microg mL(-1) on nematode, Caenorhabditis elegans, and fourth-instar mosquito larvae, Aedes aegyptii. Also, it inhibited the growth of Candida albicans and Candida parapsilasis at 100 microg mL(-1). Compounds 2 and 3 were isolated for the first time from A. graveolens. This is the first report of the mosquitocidal, nematicidal, and antifungal activities of compounds 1-3.     

Biochar derived from agricultural wastes and wood residues for sustainable agricultural and environmental applications

Lignocellulosic biomass can be circulated to produce many materials and products, including biochar. This study analyzed five different types of biochar produced from agricultural wastes and wood residues. The raw materials included three agricultural by-products: corncob, cassava rhizome, rice husk, and two types of wood residues: rain tree (Samanea saman (Jacq.) Merr.) and krachid (Streblus ilicifolius (Vidal) Corner.). The biochar were made in patented retorts with locally-appropriated technology at a temperature range of 450–500°C. This research focuses on the primary physicochemical properties and biochar components, allowing biochar to become a vital material to support sustainable agriculture and the environment. Biochar properties used for agriculture consist of specific surface area, total pore volume, average pore diameter, pH, electrical conductivity (EC), and cation exchange capacity (CEC). The properties that benefit the environmental purposes are the element: carbon (C), hydrogen (H), nitrogen (N), oxygen (O), and the molar ratio of H/C, O/C, and C/N. The study found that all five types of biochar contained suitable properties for soil amendment and carbon sequestration. However, significant differences were shown in specific surface area, average pore diameter, pH, CEC, and EC of various biochar. Based on O/C and H/C ratios, all five types of biochar persisted in soil from 100 to over 1,000 years.     

Enzymatic grafting of peptides from casein hydrolysate to chitosan. Potential for value-added byproducts from food-processing wastes

Tyrosinase was used to initiate the grafting of peptides onto the amine-containing polysaccharide chitosan. Chemical evidence for covalent grafting was obtained from electrospray mass spectrometry for products formed from reactions with glucosamine (the monomeric unit of chitosan) and the model dipeptide Tyr-Ala. When this model dipeptide was incubated with tyrosinase and chitosan, there was a marked increase in the viscosity of the solution. This viscosity increase provides physical evidence that tyrosinase can initiate peptide grafting onto the chitosan backbone. A peptide-modified chitosan derivative was generated by reacting chitosan (0.32 w/v%) with acid-hydrolyzed casein (0.5 w/v %) using tyrosinase. After reaction, the peptide-modified chitosan was partially purified and dissolved in an aqueous acetic acid solution. Low concentrations of this peptide-modified chitosan were observed to confer viscoelastic properties to the solutions. Specifically they conferred high viscosities and shear thinning properties to the solutions, and solutions containing only 1 w/w % of the peptide-modified chitosan behaved as weak gels. Thus, tyrosinase provides a simple and safe way to convert food-processing byproducts into environmentally friendly products that offer useful functional properties. The selectivity of tyrosinase and the relatively high reactivity of chitosan's amines allow grafting to be performed with uncharacterized peptide mixtures present in crude hydrolysates.     

Synthesis,rheological characterization,and constitutive modeling of polyhydroxy triglycerides derived from milkweed oil

Asclepias syriaca L., the common milkweed, is a new industrial crop. The seed contains about 20-30 wt % of a highly unsaturated oil having unusual fatty acids. Exploring value-added products from the oil, milkweed triglycerides have been oxidized by in situ performic acid to the polyoxirane and polyhydroxy triglycerides (PHTG). The rheological properties of milkweed PHTG were characterized in various shear flows. Milkweed PHTG displayed nonlinear viscoelastic behavior at applied strains greater than 1%. Milkweed PHTG was found to obey time-strain separability. A nonlinear Wagner constitutive model was used successfully to qualitatively predict the behavior of milkweed PHTG in both start-up and cessation of steady-state shear flow.     

An efficient method for the purification and characterization of nematicidal azadirachtins A,B, and H,using MPLC and ESIMS

Azadirachtin A enriched concentrate containing 60% active ingredient (a.i.) was prepared from the methanolic extract of the de-fatted neem (Azadirachta indica A. Juss) seed kernels. Azadirachtins A, B, and H, the three major bioactive constituents of neem seed kernel, were purified from this methanolic concentrate by employing reverse phase medium-pressure liquid chromatography (MPLC), using methanol-water solvent system as an eluant. The three pure azadirachtin congeners thus obtained were characterized by their unique mass spectral fragmentation, using electrospray probe in positive ion mode (ESI). All three azadirachtins exhibited nematicidal and antifungal activities. Azadirachtin B was the most effective against the reniform nematode Rotylenchulus reniformis (EC(50) 96.6 ppm), followed by Azadirachtin A (119.1 ppm) and H (141.2 ppm). At 200-ppm concentration, the test compounds caused 50-65% mortality of Caenorhabditis elegans nematode. Azadirachtin H showed the highest activity against the phytophagous fungi Rhizoctonia solani (EC(50) 63.7 ppm) and Sclerotium rolfsii (EC(50) 43.9 ppm), followed by B and A. The isolation of pure azadirachtins A, B, and H directly by MPLC purification from its concentrate and their characterization by ESIMS are unique and less time-consuming.     

Phenoloxidase activity of hemocyanin in whiteleg shrimp Penaeus vannamei: conversion, characterization of catalytic properties, and role in postmortem melanosis

Latent phenoloxidase activity of hemocyanin (Hc) in whiteleg shrimp Penaeus vannamei was assayed to determine its potential involvement in postmortem melanosis. Conversion of pure 12-mer, but not 6-mer, hemocyanin to phenoloxidase by endogenous (serine proteinases) and exogenous (SDS) effectors demonstrated the need of complex aggregation for displaying enzyme activity. Because Hc was converted to Hc-phenoloxidase (HcPO) by hemocytes extracts, the mechanism of conversion seems to be the same for polyphenoloxidases. HcPO has similar biochemical and kinetic properties as real polyphenoloxidases and uses mono- and diphenols as substrates. The kinetics of hydroxygenation of monophenols has a lag phase, typical for tyrosinases, contrary to oxidation of diphenols. Regardless of the structure of the substrate, melanin is finally formed. Because of the abundance, distribution, and resistance of Hc to freezing-thawing, involvement of Hc in black spot formation postmortem is suggested. This has important implications for commercialization of shrimp and related seafood.     

Purification and characterization of an antimicrobial chitinase extracellularly produced by Monascus purpureus CCRC31499 in a shrimp and crab shell powder medium

Monascus purpureus CCRC31499 produced an antimicrobial chitinase when it was grown in a medium containing shrimp and crab shell powder (SCSP) of marine wastes. An extracellular antimicrobial chitinase was purified from the culture supernatant to homology. The chitinase had a molecular weight of approximately 81,000 and a pI of 5.4. The optimal pH, optimum temperature, and pH stability of the chitinase were pH 7, 40 degrees C, and pH 6-8, respectively. The activity of the chitinase was activated by Fe(2+) and strongly inhibited by Hg(2+). The unique characteristics of the purified chitinase include high molecular weight, nearly neutral optimum pH, protease activity, and antimicrobial activity with bacteria and fungal phytopathogens. This is also the first report of isolation of a chitinase from a Monascus species.     

Evaluation and identification of potential organic nematicidal volatiles from soil bacteria

Naturally occurring volatile compounds with nematicidal activities (NAs) are of significant economical importance in agriculture and forestry. In this study, volatile organic compounds (VOCs) produced by 200 isolates of soil bacterial were evaluated in in vitro experiments. Our results identified that among the 200 bacterial isolates, 149 (74.5%) and 165 (82.5%) exhibited a greater than 20% NA against the free-living nematode Panagrellus redivivus and the pinewood nematode Bursaphelenchus xylophilus, respectively. Among them, 22 isolates showed 100% NA against P. redivivus and seven isolates showed 100% NA against B. xylophilus. When exposed to nematicidal volatiles, nematodes gradually reduced their movements within 1-12 h after treatment, and most stopped moving completely after 24 h. Our analysis indicated significant variation in nematicidal capability of the VOCs not only among bacterial species but also among isolates of the same species. Volatiles of representative isolates were extracted using solid-phase micro-extraction (SPME) and their structures identified using gas chromatography-mass spectrometry (GC-MS). The detected so volatile compounds included alcohols, aldehydes, ketones, alkenes and ethers. Of the 20 VOCs with strong NA (?80%), nine (phenol, 2-octanol, benzaldehyde, benzeneacetaldehyde, decanal, 2-nonanone, 2-undecanone, cyclohexene and dimethyl disulfide) displayed 100% NA to both model nematodes. Furthermore, five compounds (terpineol, benzeneethanol, propanone, phenyl ethanone and nonane) showed different NA to B. xylophilus (75-100%) and P. redivivus (17.02-100%).     

Purification and characterization of two antifungal chitinases extracellularly produced by Bacillus amyloliquefaciens V656 in a shrimp and crab shell powder medium

A Gram-positive bacterium with antagonistic activity was isolated from the soil. It has been identified as Bacillus amyloliquefaciens strain V656 on the basis of 16S ribosomal DNA analysis and standard bacteriological tests. B. amyloliquefaciens V656 produced antifungal enzymes when it was grown in a medium containing shrimp and crab shell powder (SCSP) of marine waste. The antifungal enzymes displayed chitinase activities. Two extracellular antifungal chitinases (FI and FII) were purified and characterized, and their molecular weights, isoelectric points, pH and thermal stabilities, and antifungal activities were determined. The characteristics of V656 chitinases are similar to those of the known bacterial chitinases in terms of their isoelectric points, thermal instabilities, and lack of lysozyme activity. In contrast to other known bacterial chitinases, the unique characteristics of V656 chitinases include extremely low molecular weights and nearly neutral optimum pH. Furthermore, this is the first report of the isolation of chitinases from B. amyloliquefaciens that are active against fungi.     

Isolation, characterization, and biological activity of naphthoquinones from Calceolaria andina L

Two compounds recognized as responsible for the insecticidal activity of extracts of Calceolaria andina L. (Scrophulariaceae) have been isolated and characterized as 2-(1, 1-dimethylprop-2-enyl)-3-hydroxy-1,4-naphthoquinone and the corresponding acetate, 2-acetoxy-3-(1,1-dimethylprop-2-enyl)-1, 4-naphthoquinone. Their activities against 29 pest species and 9 beneficial species of arthropod from a total of 11 orders have been determined. Activities against homopteran and acarine species are of the same order as those of established pesticides, and, significantly, no cross-resistance is observed for strains resistant to established classes of insecticide. Mammalian toxicities are low.     

燕麦生物碱的提取及其抗氧化活性研究

采用正交试验设计对麸皮中燕麦生物碱（AV）的提取条件进行优化,提取物经大孔吸附树脂纯化,并利用活性氧和DPPH自由基的清除率研究其抗氧化活性。结果表明：最佳提取参数为温度60℃,提取时间2h,溶剂为乙醇/水/冰醋酸（80/19.9/0.1）,料液比1︰8,此条件下得率为5.29%,经树脂纯化后粗提物中生物碱纯度达19.2%,且纯化后的燕麦生物碱表现出较强的清除OH·,O2-·和有机自由基DPPH的体外抗氧化活性,其清除能力分别是α-生育酚的79.4%、82.2%和78.0%。     

Suppression of soil-borne pathogens of tomato by composts derived from agro-industrial wastes abundant in Mediterranean regions

We studied nine composts derived from wastes and by-products of the olive oil, wine, and Agaricus mushroom agro-industries. They were mixed with peat at 1:3 w w ⁻¹ ratios and comparatively evaluated in pot experiments to assess suppressiveness against soil-borne and foliar pathogens of tomato. All compost amendments demonstrated high levels of suppressiveness against Phytophthora nicotianae Breda de Haan in tomato, when they were applied directly after curing (T0) indicating the occurrence of a “general suppression phenomenon” (81–100% decrease in plant disease incidence). They were, however, relatively less effective when applied 9 months after curing (T1, 55–100% disease decrease). Suppressiveness against Fusarium oxysporum f.sp. radicis-lycopersici Jarvis & Shoemaker was relatively lower and varied widely among composts (8–95% and 22–87% decrease in plant disease incidence for T0 and T1, respectively). Three of the composts conferred induced systemic resistance against the foliar pathogen Septoria lycopersici Speg. Biotic properties were determined, including respiration, fluorescein diacetate hydrolysis, and β-glucosidase activity of composts. The comparative evaluation of the nine composts revealed no shared critical biotic or abiotic characteristics indicative of their suppressive effects on the soil-borne and foliar pathogens. The complex origin of compost suppressiveness is discussed and the implementation of individual evaluation of each compost product for a specific use is advocated.     

Extraction and characterization of original lignin and hemicelluloses from wheat straw

Original lignin and hemicelluloses were sequentially extracted with high yield/purity, using acidic dioxane/water solution and dimethyl sulfoxide, from ball-milled wheat straw. The acidic dioxane lignin fraction is distinguished by high beta-O-4' structures and by low amounts of condensed units (beta-5', 5-5', and beta-1'). Hemicelluloses contain arabinoxylans as the major polysaccharides, which are substituted by alpha-l-arabinofuranose, 4-O-methylglucuronic acid, acetyl group (DS = 0.1), and xylose at O-3 and/or O-2 of xylans. It was found that arabinoxylans form cross-links with lignins through ferulates via ether bonds, glucuronic acid via ester bonds, and arbinose/xylose via both ether and glycosidic bonds, respectively, in the cell walls of wheat straw. Diferulates are also incorporated into cross-links between lignin and hemicelluloses as well as lignification of wheat straw cell walls. The guaiacyl unit is considered to be a significant condensed structural constructor in extracted lignin and a connector between lignin and carbohydrates.     

Effect of chitosan and chitin on the separation of membranes from proteins solubilized by pH shifts using cod (Gadus morhua)

Studies with isolated membranes and isolated membranes suspended in muscle proteins solubilized at pH 3 showed that mixing chitosan and membranes at this low pH followed by a pH adjustment to 10.5 could sediment membranes effectively at 4000 g. In the solubilized muscle homogenate, the effectiveness of membrane removal by chitosan at 4000 g for 15 min was molecular weight dependent. About 80% of the phospholipids and 28% of proteins were sedimented from solubilized muscle homogenate by mixing muscle homogenate (10 g of muscle tissue homogenized with 90 mL of distilled water) with 10 mL of MW 310-375 k chitosan (10 mg/mL in 0.1 N HCl) before solubilizing it at pH 10.5, whereas 55% of the phospholipids and 12% of proteins were sedimented by mixing muscle homogenate with the MW 310-375 k chitosan before solubilizing the homogenate at pH 3. Low molecular weight chitosans (at MW 1k or 33k) showed little effect on membrane sedimentation under the same conditions. Chitin was not useful for removing membranes at either pH 3 or 10.5, whether added before or after pH adjustment.     

Antioxidant activity of a catechol derived from abietic acid

The demand for novel effective antioxidant-based drugs has led to the synthesis and evaluation of the antioxidant potential in several molecules derived from natural compounds. In this work the in vitro antioxidant activity of an abietic acid-derived catechol (methyl 11,12-dihydroxyabietate-8,11,13-trien-18-oate, MDTO) was evaluated. This substance, possessing important biological properties, is similar to carnosic acid, a natural antioxidant from rosemary or sage leaves. Aiming to understand the antioxidant activity of MDTO, the energetics of its O-H bond, using time-resolved photoacoustic calorimetry (TR-PAC), was investigated. On energetic grounds it is predicted that MDTO is a good free radical scavenger, although its activity is lower than that of quercetin, a very effective antioxidant, which was used for comparison. In agreement with these predictions, the DPPH(*) and ABTS(*+) radical scavenging activities are lower than those of quercetin. In addition, MDTO also reacts with HOCl, a powerful proinflammatory oxidant produced by activated neutrophils, and protects liposomes against iron-ascorbate-induced oxidation. The discussion of these results foresees potential applications of MDTO as an antioxidant.