Potassium sorbate reduces production of ethanol and 2 esters in corn silage.

The objective of this work was to evaluate the effects of biological and chemical silage additives on the production of volatile organic compounds (VOC; methanol, ethanol, 1-propanol, methyl acetate, and ethyl acetate) within corn silage. Recent work has shown that silage VOC can contribute to poor air quality and reduce feed intake. Silage additives may reduce VOC production in silage by inhibiting the activity of bacteria or yeasts that produce them. We produced corn silage in 18.9-L bucket silos using the following treatments: (1) control (distilled water); (2) Lactobacillus buchneri 40788, with 400,000 cfu/g of wet forage; (3) Lactobacillus plantarum MTD1, with 100,000 cfu/g; (4) a commercial buffered propionic acid-based preservative (68% propionic acid, containing ammonium and sodium propionate and acetic, benzoic, and sorbic acids) at a concentration of 1 g/kg of wet forage (0.1%); (5) a low dose of potassium sorbate at a concentration of 91 mg/kg of wet forage (0.0091%); (6) a high dose of potassium sorbate at a concentration of 1g/kg of wet forage (0.1%); and (7) a mixture of L. plantarum MTD1 (100,000 cfu/g) and a low dose of potassium sorbate (91 mg/kg). Volatile organic compound concentrations within silage were measured after ensiling and sample storage using a headspace gas chromatography method. The high dose of potassium sorbate was the only treatment that inhibited the production of multiple VOC. Compared with the control response, it reduced ethanol by 58%, ethyl acetate by 46%, and methyl acetate by 24%, but did not clearly affect production of methanol or 1-propanol. The effect of this additive on ethanol production was consistent with results from a small number of earlier studies. A low dose of this additive does not appear to be effective. Although it did reduce methanol production by 24%, it increased ethanol production by more than 2-fold and did not reduce the ethyl acetate concentration. All other treatments increased ethanol production at least 2-fold relative to the control, and L. buchneri addition also increased the 1-propanol concentration to approximately 1% of dry matter. No effects of any treatments on fiber fractions or protein were observed. However, L. buchneri addition resulted in slightly more ammonia compared with the control. If these results hold under different conditions, a high dose of potassium sorbate will be an effective treatment for reducing VOC production in and emission from silage. Regulations aimed at reducing VOC emission could be ineffective or even increase emission if they promote silage additives without recognition of different types of additives.

Metabolic responses of Saccharomyces cerevisiae to valine and ammonium pulses during four-stage continuous wine fermentations.

Nitrogen supplementation, which is widely used in winemaking to improve fermentation kinetics, also affects the products of fermentation, including volatile compounds. However, the mechanisms underlying the metabolic response of yeast to nitrogen additions remain unclear. We studied the consequences for Saccharomyces cerevisiae metabolism of valine and ammonium pulses during the stationary phase of four-stage continuous fermentation (FSCF). This culture technique provides cells at steady state similar to that of the stationary phase of batch wine fermentation. Thus, the FSCF device is an appropriate and reliable tool for individual analysis of the metabolic rerouting associated with nutrient additions, in isolation from the continuous evolution of the environment in batch processes. Nitrogen additions, irrespective of the nitrogen-containing compound added, substantially modified the formation of fermentation metabolites, including glycerol, succinate, isoamyl alcohol, propanol, and ethyl esters. This flux redistribution, fulfilling the requirements for precursors of amino acids, was consistent with increased protein synthesis resulting from increased nitrogen availability. Valine pulses, less efficient than ammonium addition in increasing the fermentation rate, were followed by a massive conversion of this amino acid in isobutanol and isobutyl acetate through the Ehrlich pathway. However, additional routes were involved in valine assimilation when added in stationary phase. Overall, we found that particular metabolic changes may be triggered according to the nature of the amino acid supplied, in addition to the common response. Both these shared and specific modifications should be considered when designing strategies to modulate the production of volatile compounds, a current challenge for winemakers.

An economical biorefinery process for propionic acid production from glycerol and potato juice using high cell density fermentation.

An economically sustainable process was developed for propionic acid production by fermentation of glycerol using Propionibacterium acidipropionici and potato juice, a by-product of starch processing, as a nitrogen/vitamin source. The fermentation was done as high-cell-density sequential batches with cell recycle. Propionic acid production and glycerol consumption rates were dependent on initial biomass concentration, and reached a maximum of 1.42 and 2.30 g L(-1) h(-1), respectively, from 50 g L(-1) glycerol at initial cell density of 23.7 gCDW L(-1). Halving the concentration of nitrogen/vitamin source resulted in reduction of acetic and succinic acids yields by ~39% each. At glycerol concentrations of 85 and 120 g L(-1), respectively, 43.8 and 50.8 g L(-1) propionic acid were obtained at a rate of 0.88 and 0.29 g L(-1) h(-1) and yield of 84 and 78 mol%. Succinic acid was 13 g% of propionic acid and could represent a potential co-product covering the cost of nitrogen/vitamin source.

Metabolic effects of feeding ethanol or propanol to postpartum transition Holstein cows.

Eight lactating Holstein cows implanted with a ruminal cannula and permanent indwelling catheters in major splanchnic blood vessels were used to investigate metabolism of propanol and ethanol in the postpartum transition period. Cows were randomly allocated to 1 of 4 treatments in a randomized design with a 2 by 2 factorial arrangement of treatments. Factor 1 was 2.6g of calcium carbonate/kg of dry matter (DM) versus 1.5 g of 2-hydroxy-4-(methylthio)-butanoic acid isopropyl ester/kg of DM. Factor 2 was supplementation with 14 g of propanol/kg of DM (propanol treatment; PT) versus 14 g of ethanol/kg of DM (ethanol treatment; ET). Only factor 2 data are presented in the present paper. Treatments were administered in silage-based total mixed rations and cows were fed the experimental total mixed ration from the day of parturition. Daily rations were fed in 3 equally sized portions at 8-h intervals. Eight hourly sets of ruminal fluid, arterial, and hepatic portal and hepatic vein samples were collected at day -15 ± 5, 4, 15, and 29 relative to parturition. Dry matter intake and milk yield increased with days in milk (DIM), but were not affected by treatment. From prepartum to 4 DIM ruminal concentrations of propanol and ethanol increased with PT and ET, respectively. Postpartum, alcohol intake increased 49% in PT and 34% in ET from 4 to 29 d in milk, respectively. Ruminal concentrations of the alcohols remained unaffected by DIM. Treatments did not affect total ruminal volatile fatty acid concentrations, but the molar proportion of acetate increased in ET and the molar proportion of propionate increased in PT compared with the contrasting treatment. Propanol treatment decreased milk fat content at 15 to 29 DIM compared with ET. The net portal release of propanol and ethanol increased with increasing ruminal concentration of the respective alcohol. The portal release of alcohol accounted for 43 to 85% of ingested propanol and 36 to 57% of ingested ethanol. Hepatic uptake of propanol and ethanol equaled the net portal flux and no effect of treatment was detected for net splanchnic release of propanol and ethanol. In conclusion, ruminal metabolism is a major component of alcohol metabolism in dairy cows. The postpartum transition dairy cow has sufficient metabolic capacity to cope with high dietary concentrations of primary alcohols even when alcohol intake is abruptly increased at the day of calving. Alcohol intake affects milk fat content and alcohol composition of silage might be important to improve predictions of milk composition.

Production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) by Cupriavidus necator from waste rapeseed oil using propanol as a precursor of 3-hydroxyvalerate.

Waste rapeseed oil is a useful substrate for polyhydroxyalkanoates (PHA) production employing Cupriavidus necator H16. In fed-batch mode, we obtained biomass and PHA yields of 138 and 105 g l(-1), respectively. Yield coefficient and volumetric productivity were 0.83 g PHA per g oil and 1.46 g l(-1) h(-1), respectively. Propanol at 1% (v/v) enhanced both PHA and biomass formation significantly and, furthermore, resulted in incorporation of 3-hydroxyvalerate units into PHA structure. Thus, propanol can be used as an effective precursor of 3-hydroxyvalarete for production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) copolymer. During the fed-batch cultivation, propanol concentration was maintained at 1% which resulted in 8% content of 3-hydroxyvalerate in copolymer.

Fecal excretion of alcohols and organic anions in neonatal dairy calves.

To clarify colonic fermentation during the perinatal period, 22 dairy calves less than 6 weeks old were used. They were given a milk replacer following colostrum feeding. A total 100 samples of normal feces including meconium were collected from the rectum of the calves. Fecal pH, alcohols, lactate and volatile fatty acids (VFAs) were analyzed. Higher ethanol and n-propanol concentrations were found in many fecal samples particularly in the first 2 weeks after birth, but these metabolites showed consistently lower concentrations thereafter. By contrast, higher concentrations of methanol were observed in some samples for all ages examined. Fecal VFA increased abruptly within a few days of birth, and mainly consisted of acetate and n-butyrate. During the first 2 weeks, the proportion of n-butyrate in VFAs decreased and that of propionate increased gradually. Proportions of VFAs were almost stable at 3-6 weeks of age (acetate, propionate and n-butyrate in increasing order). Higher concentrations of lactate and lower pHs were observed in the fecal samples during the first 2 weeks, and concentrations decreased thereafter. Accelerated colonic production of ethanol and n-propanol was confirmed during the early 2 weeks, in addition to organic acid fermentation as reported previously.

Esterification reactions catalyzed by lipases immobilized in organogels: effect of temperature and substrate diffusion.

Rhizomucor miehei lipase was immobilized in hydroxy(propylmethyl) cellulose or agar gels containing lecithin or AOT microemulsions. The effect of the diffusion of substrates and products to this catalyst was studied, as well as the effect of temperature on the initial rate of ester synthesis. The composition of the gel affects the reaction rate due to mass transport phenomena. The apparent activation energies were higher for the systems based on agar, independently of the microemulsion used, and lower for the systems based on AOT microemulsions, independently of the polymer used.

Comparison of partial least-square method and canonical correlation analysis in a quantitative structure-retention relationship study.

The retention of 7 monotetrazolium and 9 ditetrazolium salts was determined on alumina and reversed-phase (RP) alumina layers using n-hexane-1-propanol and water-1-propanol mixtures as eluents. The retention capacity and the specific surface area of solutes in contact with the stationary phases were calculated. The relationship between retention characteristics and physicochemical parameters of solutes was elucidated by canonical correlation analysis and partial least-square regression analysis. Both methods found significant relationships between the chromatographic and physicochemical parameters, however, the results were different according to the method applied. Calculations suggested that the retention on both alumina and RP alumina layers is of mixed character, hydrophobic, electronic and steric parameters are equally involved in the retention.

Enzymatic reduction of xenobiotic alpha,beta-unsaturated ketones: formation of allyl alcohol metabolites from shogaol and dehydroparadol.

A novel reductive metabolism of shogaol [1-(4'-hydroxy-3'-methoxyphenyl)-deca-4-ene-3-one], a major pungent and pharmacologically active principle of ginger, was investigated in rat liver in vitro. The ethyl acetate extractable metabolites formed by incubation of this alpha,beta-unsaturated ketone with rat liver 12,000 x g supernatant fortified with NADPH-generating system were analyzed by high performance chromatography and gas chromatography/mass spectrometry. In addition to the saturated ketone and reduced alcohol metabolites, an allyl alcohol, 1-(4'-hydroxy-3'-methoxyphenyl)-deca-4-ene-3-ol, was identified as a new metabolite of shogaol. Likewise, dehydroparadol [1-(4'-hydroxy-3'-methoxyphenyl)-deca-1-ene-3-one], a non-pungent analog of shogaol, was also reduced to the corresponding allyl alcohol by the postmitochondrial fraction of rat kidney in the presence of NADPH-generating system.

Free radical metabolism of alcohols by rat liver microsomes.

By using e.s.r. spectroscopy coupled with the spin trapping technique we have detected the formation of free radical intermediates by rat liver microsomes incubated with either ethanol, 2-propanol or 2-butanol in the presence of a NADPH regenerating system and 4-pyridyl-l-oxide-t-butyl nitrone (4-POBN) as spin trap. The e.s.r. spectra have been identified as due to the hydroxyalkyl free radical adducts of 4-POBN. The free radical formation depends upon the activity of the microsomal monoxygenase system and is blocked by omitting NADP+ from the incubation mixture, by anaerobic incubation or by enzyme denaturation. The involvement of hydroxyl radicals (OH.) produced through a Fenton-type reaction from endogenously formed hydrogen peroxide is suggested by the opposite effects exerted on the e.s.r. signal intensity by azide and catalase. Consistently, iron chelation by desferrioxamine inhibits the free radical formation, while the supplementation of EDTA-iron increases it by several fold. Inhibitors of cytochrome P450-dependent monoxygenase system reduce to various extents the production of free radical intermediates suggesting that reactive oxygen species might be formed at the active site of cytochrome P450 where they react with alkyl alcohol molecules. The data presented support the hypothesis that free radical species are generated during the microsomal metabolism of alcohols and suggest the possibility that ethanol-derived radicals might play a role in the pathogenesis of the liver lesions consequent upon alcoholic abuse.

The alcohols: ethanol, methanol, isopropanol, ethylene glycol.

More than 6 per cent of poisonings involve alcohols and glycols, reflecting their availability in a wide range of household products, including aftershave, brake fluid, gas line antifreeze, model airplane fuel, mouthwash, rubbing alcohol, and windshield washing solution. Diagnosis involves recognition of an osmolal gap and variable degrees and delays in development of an anion gap metabolic acidosis. Therapeutic modalities are similar for methanol and ethylene glycol, both cases requiring ethanol-blocking of alcohol dehydrogenase and hemodialysis. More often, treatment of ethanol and isopropanol poisoning is limited to supportive care.

[Action of isopropanol on rat lipid metabolism: complementary studies on mechanisms implicated in hepatic accumulation of triacylglycerides]. / Action de l'isopropanol sur le métabolisme lipidique chez le rat: études complémentaires sur les mécanismes impliqués dans l'accumulation hépatique des triacylglycérols

Isopropanol administration (3 g/kg, p.o.) determines in the rat liver an inhibition of fatty acid oxidation, an enhancement of fatty acid esterification into triacylglycerols as well as an inhibition of lipoprotein secretion which appears to be related to alterations in hepatic phospholipids and which differentiates isopropanol from ethanol induced fatty liver. Disturbances in peripheral lipolysis following isopropanol administration are found only in mature rats and are not necessary to the fatty liver induction.