Paul Ki-souk Nam

Comprehensive profiling of isoflavones, phytosterols, tocopherols, minerals, crude protein, lipid, and sugar during soybean (Glycine max) germination.

Isoflavone, phytosterol, tocopherol, mineral, protein, lipid, and sugar contents of soybeans were analyzed during 7-day germination with or without exposure to light. The levels of phytosterols and tocopherols increased significantly during the 3 day germination. Although malonyl glycosides were the predominant forms of isoflavones in soybean seeds, 77% of malonyl daidzin and 30% of malonyl genistin were converted to corresponding daidzin, daidzein, genistin, and genistein during the germination period. Slight decreases in malonal glycidin and malonyl glycidin concentrations were also observed while the total molar concentration of isoflavones remained constant. An increase of approximately 4% in the protein level was accompanied by a 5-6% reduction in the carbohydrate and lipid contents after the 7-day germination. Mineral (Ca, Cr, Fe, Zn Cu, K, Mg, Mn) levels did not vary much during germination, and the presence of light during germination had only a little, if any, effect on the levels of the micro- and macronutrients in soybeans.

Solvent extraction and tandem dechlorination for decontamination of soil

The United States Environmental Protection Agency (US EPA) guidelines allow removal of polychlorinated biphenyls (PCBs) from soils via solvent extraction. This option holds promise for removal of other recalcitrant organic contaminants as well. A study was undertaken to evaluate the effectiveness of solvent extraction with two tandem degradation techniques. The degradation techniques were chemical dehalogenation with immobilized reagents and gamma-ray irradiation. The integrated approach was evaluated with contaminated soils from wood treatment and electric power substation sites. Evaluations were carried out on a bench scale in the laboratory and on a semi-pilot scale at a contaminated site. Binary solvent mixture of alkanes and alcohols yielded the highest extraction efficiencies. Extraction efficiencies in excess of 90% were obtained for PCBs, polychlorinated dibenzo-p-dioxins (PCDDs) and polynuclear aromatic hydrocarbons (PAHs). Extracted PCBs were rapidly degraded through chemical dehalogenation or with high doses of the gamma-ray irradiation. The residual organics in the solvent mixture were removed with activated carbon, and the solvent was recycled for subsequent soil extractions. Contaminants adsorbed on the activated carbon were destroyed with a counter flow oxidation process.

Isolation and screening of microalgae from natural habitats in the midwestern United States of America for biomass and biodiesel sources.

Native species of microalgae were isolated from natural water bodies in the Midwestern United States of America and were screened for the ultimate goal of mass cultivation in Missouri and the surrounding states, and for their potential as biomass and biodiesel sources. A number of different nutrient media recipes were utilized to isolate the maximum number of colonies from each field samples. These nutrient recipes were modified in order to optimize the isolation and growth dynamics of specific colonies. All of the isolates were categorized based on the morphological appearance of the culture and the microscopic cellular appearance of the isolated colonies. Isolates included many common green microalgae and cyanobacteria. Lipid content was determined for selected strains that demonstrated relatively quick growth. Scenedesmus sp. that demonstrated the high growth rate, resistance to invasion, and contained sufficient amounts of lipid was investigated for its potential as a sustainable biomass and biodiesel feedstocks.

Cellular oxidative damage is more sensitive to biosynthetic rate than to metabolic rate: A test of the theoretical model on hornworms (Manduca sexta larvae).

We develop a theoretical model from an energetic viewpoint for unraveling the entangled effects of metabolic and biosynthetic rates on oxidative cellular damage accumulation during animals growth, and test the model by experiments in hornworms. The theoretical consideration suggests that most of the cellular damages caused by the oxidative metabolism can be repaired by the efficient maintenance mechanisms, if the energy required by repair is unlimited. However, during growth a considerable amount of energy is allocated to the biosynthesis, which entails tradeoffs with the requirements of repair. Thus, the model predicts that cellular damage is more influenced by the biosynthetic rate than the metabolic rate. To test the prediction, we induced broad variations in metabolic and biosynthetic rates in hornworms, and assayed the lipid peroxidation and protein carbonyl. We found that the increase in the cellular damage was mainly caused by the increase in biosynthetic rate, and the variations in metabolic rate had negligible effect. The oxidative stress hypothesis of aging suggests that high metabolism leads to high cellular damage and short lifespan. However, some empirical studies showed that varying biosynthetic rate, rather than metabolic rate, changes animals lifespan. The conflicts between the empirical evidence and the hypothesis are reconciled by this study.

A High Efficiency All Glass Sampling and Concentration Device for Adsorptive Semivolatile Organics

A low-volume, inert sampling and enrichment device for semivolatile organic vapors is described. The device consists of two concentric fused silica capillaries. A small portion of the inter-capillary volume, cooled with a burst of compressed carbon dioxide, serves as a trap for the semivolatile organics. The low mass of the trap permits rapid sampling and desorption cycles suitable for applications requiring fast monitoring of semivolatile chemicals. The device is devoid of switching valves in the sampling train and consequently does not suffer from analyte loss due to irreversible adsorption or interference resulting from cross contamination. The device was successfully used for sampling low concentrations of highly adsorptive nitroaromatic compounds and is applicable for polychlorinated dibenzo-p-dioxins (PCDDs) and polyaromatic hydrocarbons (PAHs).

Flue-gas-influenced heavy metal bioaccumulation by the indigenous microalgae Desmodesmus communis LUCC 002

Desmodesmus communis LUCC 002 was cultivated using flue gas originating from a coal-fired power plant as a carbon dioxide (CO2) source. The flue gas contains various heavy metals. For investigating the fate of flue-gas-introduced metals on the cultivation system, bioaccumulation was measured in the microalgal biomass and milieu. The accumulated biomass was found to contain eight heavy metals: arsenic, chromium, barium, lead, selenium, silver, cadmium, and mercury. High heavy metal accumulations were also found in the control group of algae grown without the addition of flue gas at the same location. Further testing revealed that some of the heavy metals originated from well water used in the cultivation. The flue-gas-influenced bioaccumulation pattern of different heavy metals was observed. The responses of individual heavy metals and the influence of well water microbial flora on the algal growth were investigated, this study showed that hormesis was developed by the D. communis LUCC 002.

Efficacy of L-Cysteine as an Anti-Oxidant in Papain Catalyzed Synthesis ofOligopeptides in Organic Solvent System

Enzymatic peptide synthesis has drawn considerable attention for synthesis of high by-pass oligopeptide feed supplements in animal nutrition. A hardy protease, (papain) with a cysteine moiety at the active site requires the presence of an anti-oxidant in the reaction medium to ensure that the thiol group remains intact. Free cysteine has been the antioxidant of choice for papain-catalyzed synthesis of oligopeptides in aqueous systems. However, due to limited solubility of cysteine in organic solvents, it is generally not a suitable antioxidant for the synthesis of oligopeptides in biphasic solvent systems; instead, mercaptoethanol is often used. Lysine and Methionine is couple of well-known limiting amino acids that find application in cattle feed and poultry. Synthesis of co-oligopeptides of Lysine and Methionine has generally been attempted in bi-phasic solvent systems with Mercaptoethanol as an anti-oxidant. The inherent toxicity of mercaptoethanol when present even in trace amounts make its use undesirable during synthesis of oligopeptides to be used as feed supplements. Use of non-toxic antioxidants such as Cysteine would make the end product more amenable as a nutritional supplement for animal feed. Therefore efficacy of L-cysteine as an anti-oxidant was investigated during papain catalyzed oligomerization of Lys, Arg, Glu and Asp in two organic systems: a three phase micro-aqueous media consisting of n-octane, DFP and water, as well as homogeneous ACN/water mixtures. Reactions were also carried out under an argon atmosphere in the presence and absence of anti-oxidants. The results of the experiments showed that L-cysteine facilitated oligomer synthesis in both the three phase system and the ACN/water mixture. The overall oligomer yields were found to be better than 75% in the presence of L-Cysteine. Oligopeptide yields obtained through reactions carried out under the argon atmosphere were less than 20%.

Rapid vapor concentrator and detection system for nitroaromatics

An automated, rapid-cycling vapor concentrator and sensor was designed and evaluated for detection of nitroaromatic compounds. The concentrator consists of an inert deactivated fused silica capillary loop. The temperature of the loop was manipulated through contact with a cold plate or a hot plate. Plates were maintained at pre-selected temperatures with a thermoelectric cooler and a cartridge heater. The low thermal mass of the loop permitted rapid trapping and desorption cycles. The chemical inertness of the fused silica tubing not only led to efficient transfer of nitroaromatics from the air stream to the detection system but also minimized cross contamination between samples. The detection system consisted of a tandem arrangement of electron attachment detectors and an electron attachment reactor. These devices were operated with compact custom electronics. The use of the electron attachment reactor and thermoelectric cooler permitted enhanced selectivity. The device was evaluate for rapid determination of nitroaromatic from air streams at trace concentrations. Detection limits down to sub parts per billion were obtained.

Mass spectrometric characterization of electron attachment reaction products

Neutral electron attachment reaction products of selected analytes were characterized with a dual column gas chromatography mass spectrometer system. The characterization confirmed that electron attachment reaction of polychlorinated aromatics lead to the formation of hydrodechlorination products. Nitroaromatics, by contrast, do not yield any discernable neutral products. Nitroaromatic molecules therefore may be amenable to solute modulation through electron attachment reactions.

Enhanced detection of nitroaromatic vapors with a cryotrap and solute modulation through electron attachment reactions

An integrated approach for enhanced detection of nitroaromatic compounds in the vapor phase is being investigated. The approach involves the use of a very low volume cryoconcentrator with rapid desorbing capabilities. The concentrator desorber is coupled to solute modulated detection systems. Modulation of nitroaromatics via electron attachment reactions holds potential for nitroaromatics because of high electron affinity of these compounds. Under suitable conditions, i.e., low solute concentration and high electron population, these reactions occur at coulometric limits. The results show that the concentrator system permits rapid, quantitative enrichment of semivolatile nitroaromatics. Results of electron attachment reaction show that these reactions lead to disintegration of nitroaromatic radicals while the potentially interfering compounds such as polyhalogenated aromatics undergo hydrochlorination and yield distinctive products. These differences can be used for modulation of nitroaromatic compounds at low concentrations.