Graft polymerization of wood sawdust and peat with ethylene carbonate. A novel method for the preparation of supports with enhanced mechanical properties to be used in biofiltration of organic vapors.

The graft polymerization reaction between ethylene carbonate (EC) and scots pine sawdust (SPS) or peat moss (PM) offers a solvent-free approach to the simple and inexpensive aliphatic derivatization of these lignocellulosic fibers. This reaction was studied with liquid or vapor EC phases in three different reactor configurations: batch stirred (BSR), semi-continuous stirred (SSR) and continuous tubular in the gas phase (CVTR). The use of a vapor phase allowed a satisfactory grafting yield and minimal production of non-grafted polyol by-products. The crosslinking agent 4,4'-methylenebis(phenylisocyanate) (MDI) achieved superior characteristics to form shaped tablets resistant to water disaggregation, a high water retention capacity and high compression strength, characteristics that conventional organic supports like PM or PM-polyurethane foam mixtures used in biofiltration of waste gases do not completely possess.

Enzyme-mediated solvent extraction of carotenoids from marigold flower (Tagetes erecta).

Marigold flowers are the most important source of carotenoids for application in the food industry. However, the extraction gives almost 50% losses of the carotenoids depending on conditions for silaging, drying, and solvent extraction. In the past decades, macerating enzymes have been successfully applied to improve the extraction yield of valued compounds from natural products. In this work, an alternative extraction process for carotenoids is proposed, consisting of a simultaneous enzymatic treatment and solvent extraction. The proposed process employs milled fresh flowers directly as raw material, eliminating the inefficient silage and drying operations as well as the generation of hard to deal with aqueous effluents present in traditional processes. The process developed was tested at the 80 L scale, where under optimal conditions a carotenoid recovery yield of 97% was obtained.

Effect of beta-galactosidase hydration on alcoholysis reaction in organic one-phase liquid systems.

Alcoholysis reactions were performed in organic one-phase liquid systems with E. coli beta-galactosidase to produce heptyl-beta-galactoside from lactose and 1-heptanol. The reaction rate was highly dependent on the amount of water solubilized in the alcohol. A larger amount of water led to a system of two liquid phases in which the alcoholysis rate was 73% faster than in the one-phase system. No hydrolysis reaction of either lactose or product was observed in one-phase liquid systems up to 20 h, independent of the water content. Solubility of lactose in the organic phase increased with the water content in the system and the reaction followed the Michaelis-Menten model. Water activity was calculated for heptanol containing different amounts of water and the obtained values were used to estimate the hydration of beta-galactosidase from known models. Enzyme activity correlated with sorbed water, similar to the behavior reported for lysozyme in low water environments. It is concluded that water contribution to enzyme hydration dominates the rate of reaction compared to its effect on lactose solubilization.

Solubility of purified lutein diesters obtained from Tagetes erecta in supercritical CO(2) and the effect of solvent modifiers.

Purified lutein diesters deposited on commercial nonporous glass beads were solubilized in supercritical CO(2) in a computerized batch extractor, and their solubilities were compared to their solubilities in hexane. Densities of 0.7, 0.8, and 0.9 g/mL were evaluated without modifiers. Both pressure and temperature increased solubility, although temperatures >50 degrees C promoted carotenoid loss as determined by mass balance. Solubility was enhanced by the use of modifiers and was related to their log P. Chloroform (log P = 2) increased 2.8 times the amount of solubilized lutein diesters compared to pure CO(2) at the same extraction conditions (0.9 g/mL and 40 degrees C) to yield 65% of the amount extracted with hexane. Supercritical CO(2) extraction of lutein diesters could represent a cleaner technology as compared to the current industrial use of hexane with important ecological and health-related implications.

Selective enzyme-mediated extraction of capsaicinoids and caratenoids from chili guajillo puya (Capsicum annum L.) using ethanol as solvent.

The selective extraction of capsaicinoids and carotenoids from chili guajillo "puya" flour was studied. When ethanol was used as solvent, 80% of capsaicinoids and 73% of carotenoids were extracted, representing an interesting alternative for the substitution of hexane in industrial processes. Additionally, when the flour was pretreated with enzymes that break the cell wall and then dried, extraction in ethanol increased to 11 and 7% for carotenoid and capsaicinoid, respectively. A selective two-stage extraction process after the treatment with enzymes is proposed. The first step uses 30% (v/v) ethanol and releases up to 60% of the initial capsaicinoids, and the second extraction step with industrial ethanol permits the recovery of 83% of carotenoids present in the flour.

Alcoholysis and reverse hydrolysis reactions in organic one-phase system with a hyperthermophilic beta-glycosidase.

Alcoholysis and reverse hydrolysis reactions were performed enzymatically in one-phase water-saturated 1-heptanol systems. Lactose or glucose was used as substrate to produce heptyl-beta-galactoside and/or heptyl-beta-glucoside, respectively. When alcoholysis of lactose was performed at 37 degrees C with beta-galactosidase from Escherichia coli, the initial rate was 14 nmol/mL min, and the limiting factors were the poor solubility of the substrate in 1-heptanol and low thermal stability of the enzyme. When a hyperthermophilic beta-glycosidase was used at 90 degrees C, the rate was 3.14-fold higher; in this case a higher concentration of soluble lactose in the water-saturated heptanol was available to the enzyme due to the higher temperature. The hyperthermophilic beta-glycosidase was also able to use glucose and galactose as substrates to achieve the reverse hydrolysis reaction. As a consequence, when lactose was used as substrate, heptyl-beta-galactoside was formed by alcoholysis, while the released glucose moiety was used in a secondary reverse hydrolysis reaction to produce heptyl-beta-glucoside. Both reactions followed Michaelis-Menten kinetics behavior. Neither lactose nor heptyl glycosides were hydrolyzed by this enzyme in water-saturated heptanol. However, the conversion was limited by a strong product inhibition and the formation of oligosaccharides, especially at high substrate concentrations, reducing the final glycoside yield.

Selectivity of methyl-fructoside synthesis with beta-fructofuranosidase.

Enzyme synthesis of methyl fructoside was studied using beta-fructofuranosidase from Sacharomyces cerevisiae and sucrose and methanol as substrates. Taking into account the inhibition and deactivation effects of methanol on the enzyme, a system with 4.9M (20%, v/v) methanol was selected. At this alcohol level, 35% of sucrose is converted to fructoside at low or high substrate concentrations. The effect of enzyme concentration, pH, and temperature on both the synthesis and the hydrolysis of the fructoside was investigated. It was found that if the reaction proceeds at pH 6.0, 4 degree C and/or 0.014 mg/mL (3 U/mL) of beta-fructofuranosidase at varying sucrose concentrations, methyl fructoside may be obtained with a minimum loss of the fructoside at the end of the reaction.

Sources of microorganisms in pozol, a traditional Mexican fermented maize dough.

Freshly prepared pozol, a traditional Mexican fermented maize dough, contained (c.f.u./g wet wt): lactic acid bacteria, 10(4) to 10(6); aerobic mesophiles, 10(4) to 10(5); Enterobacteriaceae, 10(2) to 10(3); yeasts, 10(2) to 10(4); and mould propagules, <10(3). After 30 h at 28°C the numbers were, respectively: 10(9), 7×10(6), 5×10(5), 10(6) and 10(4). Soaking alkali-treated grains overnight allowed lactic acid bacteria, aerobic mesophiles and Enterobacteriaceae to grow and these then constituted the primary microbial flora of the pozol dough. Grinding in a commercial mill inoculated the dough with lactic acid bacteria, aerobic mesophiles, Enterobacteriaceae and yeasts. Other processing stages, including the nature of the surface upon which the balls were made, handling of the dough, and air, contributed only minor numbers of microbes compared with the two major sources, soaking and grinding. The pH of pozol fell from an initial value of 7.3 to 4.6 after 30 h incubation at 28°C. The numbers of Enterobacteriaceae and other aerobic mesophilic bacteria remained constant between 11 and 30 h incubation and there was no evidence of the acidic conditions having any lethal effects on these organisms.

Enzymatic oxidation of ethanol in the gaseous phase.

The enzymatic conversion of gaseous substrates represents a novel concept in bioprocessing. A critical parameter in such systems is the water activity, A(w) The present article reports the effect of A(w) on the catalytic performance of alcohol oxidase acting on ethanol vapors. Enzyme activity in the gas-phase reaction increases several orders of magnitude, whereas the thermostability decreases drastically when A(w) is increased from 0.11 to 0.97. The enzyme is active on gaseous substrates even at hydration levels below the monolayer coverage. Enhanced thermostability at lower hydrations results in an increase in the optimum temperature of the gas-phase reaction catalyzed by alcohol oxidase. The apparent activation energy decreases as A(w) increases, approaching the value obtained for the enzyme in aqueous solution. The formation of a pread-sorbed ethanol phase on the surface of the support is not a prerequisite for the reaction, suggesting that the reaction occurs by direct interaction of the gaseous substrate with the enzyme. The gas-phase reaction follows Michaelis-Menten kinetics, with a K(m) value almost 100 times lower than that in aqueous solution. Based on vapor-liquid equilibrium data and observed K(m) values, it is postulated that during the gas-phase reaction the ethanol on the enzyme establishes an equilibrium with the ethanol vapor similar to that between ethanol in water and ethanol in the gas phase.

A colorimetric method for the enzymatic analysis of gases: the determination of ethanol and formaldehyde vapors using solid alcohol oxidase.

A novel enzymatic approach to the direct determination of ethanol vapors in the gas phase is described. The system is composed of alcohol oxidase, peroxidase, and the color indicator 2,6-dichloroindophenol dispersed on microcrystalline cellulose (avicel). Simple devices are developed for the semiquantitative determination of ethanol in the breath. The devices are optimized to produce a sharp color change at a set time of 1 min for ethanol concentrations above the legal limit for driving (kinetic method) or a stable final color after 5 min (equilibrium method). Such color changes are detectable by simple visual observation. Using TLC plastic sheets and a transmittance densitometer, the system can also be used as a quantitative method for the determination of ethanol or formaldehyde vapors. Dehydrated enzymes may be useful for the analysis of hazardous gases.

Enzyme-catalyzed, gas-phase reactions.

Dehydrated preparations of alcohol oxidase adsorbed on DEAE-cellulose vigorously catalyze a gas-phase oxidation of ethanol vapors with molecular oxygen. The gas-phase reaction is strongly dependent on the water activity of the system. The enzymatic activity is severely inhibited by the product hydrogen peroxide. This inhibition can be alleviated, however, by an addition of catalase or peroxidase to the dry preparation. Such dehydrated, bienzymic catalysts afford a complete and selective conversion of the substrate to acetaldehyde. Dry alcohol oxidase is much more thermostable than in aqueous solution. The results of this work suggest that dehydrated enzymes have potential applications in the analysis of gaseous compounds and in the development of novel gas-solid bioreactors.

Lipid content and fatty acid composition of green algae Scenedesmus obliquus grown in a constant cell density apparatus.

The lipids of alga Scenedesmus obliquus grown under controlled conditions were separated and fractionated by column and thin-layer chromatography, and fatty acid composition of each lipid component was studied by gas-liquid chromatography (GLC). Total lipids were 11.17%, and neutral lipid, glycolipid and phospholipid fractions were 7.24%, 2.45% and 1.48% on a dry weight basis, respectively. The major neutral lipids were diglycerides, triglycerides, free sterols, hydrocarbons and sterol esters. The glycolipids were: monogalactosyl diglyceride, digalactosyl diglyceride, esterified sterol glycoside, and sterol glycoside. The phospholipids included: phosphatidyl choline, phosphatidyl glycerol and phosphatidyl ethanolamine. Fourteen fatty acids were identified in the four lipid fractions by GLC. The main fatty acids were C18:2, C16:0, C18:3(alpha), C18:1, C16:3, C16:1, and C16:4. Total unsaturated fatty acid and essential fatty acid compositions of the total algal lipids were 80% and 38%, respectively.