Addition Of Propionic Acid Research Articles

Ensiling conditions and changes of cannabinoid concentration in industrial hemp

ABSTRACT Hemp (Cannabis sativa L.) is an important source of fibre and seed oil and protein. By-products of industrial hemp fibre production, like hemp seeds and cakes, can be used as feed for all animal species as fat and protein source and the whole hemp plant (including stalk and leaves) might be a suitable fibre source for ruminants. However, a previous feeding experiment with leaf-flower-seed hemp silage, made from an industrial hemp variety, demonstrated detrimental effects on cow health parameters and a significant transfer of several cannabinoids, including the psychoactive tetrahydrocannabinol (∆9-THC), into cow’s milk, posing a potential risk to the safety of consumers. Based on those observations, the present study tested the hypothesis that anaerobic fermentation, as during ensiling, increases the content of ∆9-THC in hemp. Therefore, silages of whole plants from the industrial hemp Cannabis sativa L. var. Ivory were prepared in a multifactorial design, with the four treatments 1) untreated control (CON), 2) addition of 10 mL per kg fresh weight homofermentative lactobacilli at 105 cfu/mL (LBAC), 3) addition of 10 mL per kg fresh weight homofermentative lactobacilli at 105 cfu/mL plus 30 g molasses (LBACmol) and 4) addition of propionic acid (10 mL/kg fresh weight) (PRO). Ultra high performance liquid chromatography coupled with tandem mass spectrometry with electrospray ionisation (UHPLC-MS/MS) was performed for analysis of cannabinoids in fresh hemp material and after 10 and 90 days of ensiling. The study revealed that ensiling decreased all acid forms of analysed cannabinoids in hemp at about 40–65% of the initial values after 90 days of storage, with the exception of cannabinolic acid (CBNA), and CBGA, the acidic form of cannabigerol (CBG). This decrease in most acidic forms was accompanied by an increase of the corresponding non-acidic forms of all cannabinoids, including the psychoactive ∆9-THC. Thus, although ensiling decreases the total cannabinoid content, psychoactive compounds like ∆9-THC can increase, enhancing the risk for animal health and a transfer of these substances into animal derived products.

Exploring 2,4,6-Trichlorophenol Degradation Characteristics and Functional Metabolic Gene Abundance Using Sludge Fermentation Broth as the Carbon Source

The use of sludge fermentation broth (FB) as a co-metabolic carbon source for treating 2,4,6-trichlorophenol (2,4,6-TCP) wastewater is a novel strategy. The key to the feasibility of this strategy is whether the FB can promote the growth of functional microorganisms that are capable of degrading 2,4,6-TCP. This study focused on long-term acclimatized sludge and investigated the impact of key operating parameters such as the sludge FB concentration and the influent concentration of 2,4,6-TCP on the removal efficiency of chlorophenol. The research findings revealed that when the influent concentration of sludge FB exceeded 300 mg COD/L, it significantly inhibited the degradation of 2,4,6-TCP. Simulation experiments using individual VFA components as influent carbon sources showed that excessive propionic acid addition can inhibit the degradation of 2,4,6-TCP, indicating the need to control the concentration of propionic acid in the fermentation conditions. Metagenomic analysis further showed that sludge FB can promote the enrichment of microbial chlorophenol degradation genes, including PcpA, pcaF, pcaI, Mal-r, chqB, and fadA. The abundances of these six chlorophenol degradation genes were as follows: 1152 hits (PcpA), 112 hits (pcaF), 10,144 hits (pcaI), 12,552 hits (Mal-r), 8022 hits (chqB), and 20,122 hits (fadA). Compared with other types of carbon sources, sludge FB demonstrates distinct advantages in terms of leading to the highest chlorophenol degradation concentration and the abundance of functional microbial communities. This study has successfully demonstrated the feasibility of using sludge FB as a co-metabolic carbon source for the degradation of 2,4,6-TCP.

Use of propionic acid additions to enhance zinc removal from mine drainage in short residence time, flow-through sulfate-reducing bioreactors

The effectiveness of liquid carbon additions to enhance zinc removal in laboratory-scale short hydraulic residence time (19 h) compost bioreactors receiving synthetic mine water with a high influent zinc concentration (45 mg/L) was investigated. Effective removal of such elevated zinc concentrations could not be sustained by sulfate reduction and/or other attenuation processes without carbon supplementation. Propionic acid addition resulted in improved and sustained performance by promoting the activities of sulfate reducing bacteria, leading to efficient zinc removal (mean 99%) via bacterial sulfate reduction. In contrast, cessation of propionic acid addition led to carbon limitation and the growth of sulfur oxidising bacteria, compromising zinc removal by bacterial sulfate reduction. These research findings demonstrate the potential for modest liquid carbon additions to compost-based passive treatment systems to engineer microbial responses which enhance rates of zinc attenuation in a short hydraulic residence time, enabling remediation of highly polluting mine drainage at sites with limited land availability.

Oriented bio-feeding control of the anaerobic biodegradation of ethinyl estradiol

Up to 95% of hormones are excreted into domestic wastewater with urine or feces, but their macromolecules are difficult to biodegrade. This project studies the treatment of Ethinyl Estradiol (EE2) in swine wastewater in an Upstream Solids Reactor (USR), and explores a new method for oriented bio-feeding to regulate the anaerobic biodegradation process. It was found that the metabolism of lactic acid and propionic acid was accompanied by changes in EE2 content, but lactic acid molecules were not readily bioavailable, so adding propionic acid was more suitable. However, controlling the pH to lower (4.73) and higher (8.73) values inhibited further fermentation of acetic acid and propionic acid, which was not favorable for the removal of EE2. This is simply due to the fact that propionic acid as a carbon source changes the preference of the microbes for consuming EE2. The order of the effect of addition of propionic acid on the removal of EE2 was as follows: P400>P800>P0>P200 (addition of propionic acid). The P400 removal efficiency increased from 60% to 85%. In the metabolism of EE2, after oxidation, hydrolysis, ketosis, hydroxylation and enzymatic action, dienoic acid and oleic acid were generated, and there was no secondary pollution from EE2 metabolites. In conclusion, feeding microorganisms with propionic acid can enhance the anaerobic biodegradation of EE2, providing a new strategy for the anaerobic biodegradation and bioremediation of refractory pollutants.

ADDITION OF PROPIONIC ACID ON NUTRIENT DIGESTIBILITY AND ITS EFFECT ON PRODUCTION AND CARCASS QUALITY OF BROILER

This study was aimed to determine protein and crude fiber digestibility by adding propionic acid in rations and its effect on production and carcass quality broiler chicken. This research was carried out using 180-day old chicks (DOC) broiler chicken with Cobb strain. This research method used a completely randomized design (CRD) consisting of three treatments and six replications for every treatment. The treatment in this study consisted of: T0 = ration without propionic acid; T1 = addition of 0.5% propionic acid in the ration; T2 = 0.75% addition of propionic acid in the ration. Parameters observed included crude protein, crude fiber digestibility, feed consumption, body weight gain, feed conversion, live weight, carcass percentage, and percentage of abdominal fat in broiler chickens. The results showed that the addition of 0.5% propionic acid had a significant effect (P<0.05) on crude protein and crude fiber's digestibility in broiler chickens. Significantly increased feed consumption up to 2.29%; body weight gain up to 7.49 %, decreased feed conversion by 4.86%; increased body weight by 12.69%; carcass percentage by 4.12% and decreased 33% of abdominal fat broiler chicken. This research concludes that the addition of propionic acid in the ration at a dose of 0.5% could be increase the digestibility of crude protein and crude fiber rations, can improve the production performance and carcass quality of broiler chickens.

The effect of propionic acid accumulation on methane production in dry mesophilic anaerobic fermentation

The dry anaerobic digestion performances were investigated at the temperature of 35±1°Cwith addition of propionic acid at different concentrations in five lab-scale reactors (R1-R5) to investigate the effect of propionic acid accumulation on methane production in dry mesophilic anaerobic digestion. And the volatile fatty acids, biogas and microbial community were detected. The active of microbial community and the methane generation would be inhibited when the propionic acid exceeded 30 gL1, which affected not only syntrophic propionate-oxidizing bacteria but also acetate-utilizing methanogens. Eubacteria decreased sharply accompany with the higher concentration of propionic in R4 and R5. The relative abundance of acetoclastic methanogens was directly correlated with volatile solids removals and methane generation in dry anaerobic reactors. Otherwise, the quantity of syntrophic propionate-oxidizing bacteria was positively linear correlated with propionic acid when the concentration was below 30 gL1. The methanogenic bacteria activity in R3 was the best with the methane yield of 27.01 mLCH4 g-1 VS d-1. The results suggested that appropriate propionate could enhance methane production in the dry anaerobic fermentation.

Propiyonik Asit Katkısının Toplam Karışım Rasyonu Yemin Aerobik Stabilite Özellikleri Üzerine Etkileri

Bu araştırmada, farklı düzeylerde propiyonik asit ilavesinin toplam karışım rasyonu yemin aerobik stabilite özellikleri üzerine etkileri araştırılmıştır. Çalışmada, propiyonik asit temeline dayalı katkı maddesinin dört farklı oranda ilavesinin (%0, 1,5, 3,0 ve 4,5), 26°C ve 30°C depolama koşullarında etkisi araştırılmıştır. Yem örnekleri her muamele grubunda 3‘er tekerrür olmak üzere 7 gün süre ile depolanmıştır. Aerobik stabilite süresince yem örneklerinde kimyasal ve mikrobiyolojik parametrelere ilişkin analizler yürütülmüştür. Her muamele grubunda sıcaklık değerleri ve ortam sıcaklığı 7 gün süreyle sıcaklık sensörleri ile ölçülüp kaydedilmiştir. Araştırmada katkı maddesi ilavesi toplam karışım rasyonu yemin pH, kuru madde, nötral çözücülerde çözünmeyen lif ve maya içeriklerini düşürmüş, ham protein, ham yağ, suda çözünebilir, laktik asit ve laktik asit bakteri içeriklerini yükseltmiş, küf gelişimini ise önlemiştir. Araştırma sonucunda %4,5 oranında propiyonik asit ilavesi toplam karışım rasyonunun 26°C 7 gün, 30°C ise 5 gün süre ile stabil kalmasını sağlamıştır.

THE EFFECT OF PROPIONIC ACID ADDITION IN POULTRY DIETS ON THE INTERNAL ORGANS OF BROILER CHICKENS

This study aims to determine the effects of adding propionic acid in the poultry diets on the internal organs of broiler chickens. The livestock used were 180 broilers with Cobb strain. This study used a completely randomized design (CRD) consisting of 3 treatments and 6 replications.The treatments in this study consisted of: P0= commercial feed without propionic acid addition; P1= commercial feed with addition of 0.5%propionic acid; and P2= commercial feed with 0.75% propionic acid. The parameters observed included live weight, spleen percentage, gizzardpercentage, liver percentage, and small intestine length. The results showed that the addition of propionic acid in the broiler feed had a significant effect (P0.05) on the live weight and had no significant effect (P0.05) on the percentage of spleen, percentage of gizzard, percentage of liver, and small intestine length. The conclusion of this study was that the addition of propionic acid in poultry feed at a dose of 0.75% did not negatively affect the internal organs and the length of the small intestine of broiler chickens.

Improving the quality of rice straw silage with Moringa oleifera leaves and propionic acid: Fermentation, nutrition, aerobic stability and microbial communities

Mixed ensiling is believed an effective way to improve nutrient preservation and utilization. The effect of mixing Moringa oleifera leaves (MOL) on silage quality, aerobic stability and microbial communities of rice straw ensiled with/without propionic acid were investigated after 140 days fermentation. The results showed that mixing MOL decreased the pH (4.69 vs 3.85), butyric acid (17.4 g/kg DM vs not detected), ammonia-N (3.36 vs 2.17 g/kg DM) and fiber contents (626 vs 462 g/kg DM) but increased protein content (88.4 vs 125 g/kg DM) of rice straw silages. It also increased the relative abundance of Lactobacillus (12.96% vs 50.82%) at unsealing and Issatchenkia (2.02% vs 36.03%) after exposure to air, and might improve aerobic stability of silages. The addition of propionic acid could inhibit deaminization activity during ensiling and exposure to air. It is suggested mixing MOL could improve the fermentation quality and nutrition of rice straw silage.

Formulation of spore toxin complex of Bacillus thuringiensis and Lysinibacillus sphaericus grown under solid state fermentation

Formulation of whole solid-state fermentation (SSF) products of Bacillus thuringiensis israelensis (Bti) and Lysinibacillus sphaericus (Ls14N1) and their extracts was studied. Results of formulation of final SSF products showed that drying at 40 °C was one of the most efficient methods for formulation of both tested cultures with preserving complete mosquitocidal activities for at least 8 months. Ls14N1 final whole SSF product was efficiently formulated by addition of propionic acid at 0.3% or acetic acid at 0.3% and was completely active against Culex pipiens larvae after 8 months storage at room temperature. Also, addition of ascorbic acid 0.05%, sodium benzoate 0.3%, citric acid 0.2% or sodium chloride 10% were promising preservatives for Ls14N1 SSF product. However, Bti SSF product was formulated by addition of 25–70% sugar and completely preserved active for 4 months. On the other hand, formulation of liquid extracts of SSF product was studied to have liquid and powder preparations. The best preservatives for spore toxin complex (STC) liquid extract of Ls14N1were calcium chloride 20–40%, sodium benzoate 3–6%, sodium chloride 10–100%, potassium sorbate 2% or acetic acid 1%. Also, STC liquid extract of Ls14N1 was efficiently formulated in solid form by addition of Chipsy starch, wheat flour or wheat germ meal as carriers. Those formulations were nearly mosquitocidal active after 10 months storage. For formulation of Bti liquid extract, sodium benzoate 3–6% or sodium chloride 10–20% were the best preservatives. On the other hand, Chipsy starch and wheat flour were the most promising carriers for preparation of solid formulation. All these Bti formulations were completely active for 8 months. This study may contain simple, cost effective and efficient methods for preparation of mosquitocidal formulations of Ls and Bti mosquitocidal toxins produced under SSF technology.

Acclimation Strategy Using Complex Volatile Fatty Acid Mixtures Increases the Microbial Fuel Cell (MFC) Potential

AbstractThe start‐up of microbial fuel cells (MFCs) requires biofilm development onto electrodes and acclimation of the microbial community to specific substrates. This process is time‐consuming and shows low effectivity when complex substrates are utilized. The varying proportions and complex mixtures of volatile fatty acids (VFAs) in bioprocess effluents makes it difficult to predict the power output of VFA‐based MFCs when this technology is coupled to a previous bioprocess. In this work, the effect of the degree of reduction of single VFAs on MFC potential was investigated, and a novel acclimation procedure involving the feeding of gradually more complex VFA mixtures is proposed. The power output obtained with butyric acid (6.1 ± 2 mW m−2) was higher than that obtained with propionic acid (5.0 ± 1 mW m−2), as expected based on their degree of reduction. The MFC potential generated by an acetic acid‐fed MFC reached 60 mV, but an acetic‐butyric acid mixture reduced the cell potential by one order of magnitude. The subsequent addition of propionic acid to the acetic‐butyric mixture increased the MFC potential from 1.9 ± 0.1 mV to 35 ± 10 mV in sequential feeding cycles. Consequently, the feeding sequence of acetic, acetic‐butyric, and acetic‐butyric‐propionic acids is proposed as an efficient strategy for the acclimation of MFCs to complex substrates.

Fate of Escherichia coli O157:H7 and bacterial diversity in corn silage contaminated with the pathogen and treated with chemical or microbial additives

Inhibiting the growth of Escherichia coli O157:H7 (EC) in feeds may prevent the transmission or cycling of the pathogen on farms. The first objective of this study was to examine if addition of propionic acid or microbial inoculants would inhibit the growth of EC during ensiling, at silo opening, or after aerobic exposure. The second objective was to examine how additives affected the bacterial community composition in corn silage. Corn forage was harvested at approximately 35% dry matter, chopped to a theoretical length of cut of 10 mm, and ensiled after treatment with one of the following: (1) distilled water (control); (2) 1 × 105 cfu/g of EC (ECCH); (3) EC and 1 × 106 cfu/g of Lactobacillus plantarum (ECLP); (4) EC and 1 × 106 cfu/g of Lactobacillus buchneri (ECLB); and (5) EC and 2.2 g/kg (fresh weight basis) of propionic acid, containing 99.5% of the acid (ECA). Each treatment was ensiled in quadruplicate in laboratory silos for 0, 3, 7, and 120 d and analyzed for EC, pH, and organic acids. Samples from d 0 and 120 were also analyzed for chemical composition. Furthermore, samples from d 120 were analyzed for ammonia N, yeasts and molds, lactic acid bacteria, bacterial community composition, and aerobic stability. The pH of silages from all treatments decreased below 4 within 3 d of ensiling. Escherichia coli O157:H7 counts were below the detection limit in all silages after 7 d of ensiling. Treatment with L. buchneri and propionic acid resulted in fewer yeasts and greater aerobic stability compared with control, ECCH, and ECLP silages. Compared with the control, the diversity analysis revealed a less diverse bacterial community in the ECLP silage and greater abundance of Lactobacillus in the ECLP and ECA silages. The ECLB silage also contained greater abundance of Acinetobacter and Weissella than other silages. Subsamples of silages were reinoculated with 5 × 105 cfu/g of EC either immediately after silo opening or after 168 h of aerobic exposure, and EC were enumerated after 6 or 24 h, respectively. All silages reinoculated with EC immediately after silo opening (120 h) had similar low pH values (<4.0) and EC counts were below the detection limit. The ECCH and ECLP silages reinoculated with EC after 168 h of aerobic exposure had relatively high pH values (>5.0) and EC counts (5.39 and 5.30 log cfu/g, respectively) 24 h later. However, those treated with L. buchneri or propionic acid had lower pH values (4.24 or 3.96, respectively) and lower EC counts (1.32 log cfu/g or none, respectively). During ensiling, EC was eliminated from all silages at pH below 4.0. During aerobic exposure, the growth of EC was reduced or prevented in silages that had been treated with L. buchneri or propionic acid at ensiling, respectively.

Method of propionic acid–based preservative addition and its effects on nutritive value and fermentation characteristics of wet brewers grains ensiled in the summertime

ABSTRACT This research evaluated nutritional value and DM loss of wet brewers grains (WBG) mixed or top-dressed with a propionic acid–based preservative. On d 0, treatments were randomly assigned to 19-L plastic buckets (6 buckets per treatment) and consisted of WBG without preservative (control), or WBG mixed or top-dressed with a commercial propionic acid–based preservative (Myco Curb; Kemin Industries) at a rate of 1 g/kg of WBG (wet weight). Buckets were individually sealed and stored at ambient temperature with exposure to sunlight and precipitation for 14 or 28 d (3 buckets per treatment for each storage day). On d 14, total DM loss was least for control, greatest for top-dressed, and intermediate for WBG mixed with propionic acid (P ≤ 0.02). On d 28, total DM loss was similar between methods of propionic acid addition (P = 0.64), but both methods were less than the control (P

Elucidation of first step of the allylmalonyl-CoA biosynthetic pathway by expression of heterologous KSIII gene and enhancement of 36-methyl-FK506 production by genetic and chemical engineering

We identified another tcsABCD genes encoding biosynthesis of the allylmalonyl-CoA in new FK506 producing strain, Streptomyces sp. KCCM 11116P. The functionality of tcsABCD is confirmed by gene deletion. To validate the functionality of these genes, tcsABCD genes were heterologously expressed in Streptomyces hygroscopicus ATCC 14891 using pSE34. The resulting strain produced the FK506 which showed a molecular ion [M+NH4]+ at m/z 821 as verified by LC/ESI–MS. To address the function of TcsB in the allylmalonyl-CoA pathway, we pursued the construction of two different combinations: the heterologous FabH-like β-ketoacyl-acyl carrier protein synthase III gene expression and chemical complementation. Plasmid-based expression of the fabH homolog dpsC in ΔTcsB using pSE34 and pSET152(ermE*) led to restoration of approximately 32.2 and 28.7 % of the levels of FK506 relative to Streptomyces sp. KCCM 11116P, respectively. Furthermore, the addition of propionic acid to the culture of ΔTcsB restored FK506 production up to 35.6 % of overall FK506 levels in Streptomyces sp. KCCM 11116P. We have engineered production of 36-methyl-FK506 in ΔTcsB. The heterologous expression of Syteptomyces glaucescens FabH in ΔTcsB gave rise to 5.9-fold increase in the 36-methyl-FK506 level as compared with mutasynthetic production by 4-methylpentanoic acid. Supplementing the culture broth of ΔTcsB expressing S. glaucescens FabH with valine resulted in an additional 2.5-fold increase in the 36-methyl-FK506 titer. Overall, this study shows that TcsB was found to maintain a very high-specific activity for propionyl-CoA in allylmalonyl-CoA biosynthetic work and S. glaucescens FabH which use isobutyryl-CoA as substrate can initiate methyl side chain biosynthesis in 36-methyl-FK506 in ΔTcsB.

Biosynthesis of poly(4-hydroxybutyrate) in recombinant Escherichia coli grown on glycerol is stimulated by propionic acid

One of the most promising polyhydroxyalkanoates (PHAs) for medical applications is poly(4-hydroxybutyrate) (P4HB) due to its biodegradability, biocompatibility and mechanical properties. Currently, the major hurdle for expanding P4HB applications is the production and recovery cost. In this study, we investigated the stimulating factors for P4HB biosynthesis with the ultimate goal of reducing production cost. We found that addition of propionic acid to the culture medium stimulates the P4HB accumulation in recombinant Escherichia coli JM109 grown on glycerol. This stimulating effect was significantly weakened by addition of exogenous methionine, whereas it was not influenced by addition of cysteine. These results suggest that propionic acid enhances P4HB synthesis by reducing the intracellular methionine pool. Utilizing these findings for P4HB production in batch cultures on glycerol, the volumetric yield of P4HB could be improved 4 fold from 0.9g/L to 3.7g/L by adding 2g/L propionic acid into the medium.

Enhancement in mechanical properties of bulk nanocrystalline Fe–Ni alloys electrodeposited using propionic acid

A method for enhancement of the mechanical properties of electrodeposited bulk nanocrystalline Fe–Ni alloys was explored. Bulk nanocrystalline Fe–Ni alloys were prepared using electrolytes that primarily consisted of iron sulfate and nickel sulfamate with propionic acid. Varying the concentration of propionic acid in the deposition bath produced no significant change in the C, S, or Ni content or grain sizes of the electrodeposited alloys. In contrast, the hardness of bulk nanocrystalline Fe–Ni alloys increased from 4.0 to 5.0GPa with the increase of propionic acid concentration from 0 to 3.0g/L. In addition, the tensile strength also increased from 1.6 to 1.7GPa while maintaining a good tensile ductility of ~10%. These increases for electrodeposited alloys can be explained by grain boundary relaxation strengthening. After annealing at relatively mild temperatures, the alloys electrodeposited without propionic acid exhibited higher strength than at the as-deposited state, while the strength of the alloys electrodeposited using 3.0g/L propionic acid remained unchanged. The results of this study indicate that the addition of propionic acid to the deposition bath could remove the excess grain boundary defects of Fe–Ni alloys in as-deposited states, requiring no additional thermal treatments and enhancing the mechanical strength to high levels.

Mixed culture syngas fermentation and conversion of carboxylic acids into alcohols

Higher alcohols such as n-butanol and n-hexanol have higher energy density than ethanol, are more compatible with current fuel infrastructure, and can be upgraded to jet and diesel fuels. Several organisms are known to convert syngas to ethanol, but very few can produce higher alcohols alone. As a potential solution, mixed culture fermentation between the syngas fermenting Alkalibaculum bacchi strain CP15 and propionic acid producer Clostridium propionicum was studied. The monoculture of CP15 produced only ethanol from syngas without initial addition of organic acids to the fermentation medium. However, the mixed culture produced ethanol, n-propanol and n-butanol from syngas. The addition of propionic acid, butyric acid and hexanoic acid to the mixed culture resulted in a 50% higher conversion efficiency of these acids to their respective alcohols compared to CP15 monoculture. These findings illustrate the great potential of mixed culture syngas fermentation in production of higher alcohols.

Effects of propionic acid and Lactobacillus buchneri (UFLA SIL 72) addition on fermentative and microbiological characteristics of sugar cane silage treated with and without calcium oxide

AbstractThe objective of this work was to evaluate the effects of a new strain of Lactobacillus buchneri (UFLA SIL 72) isolated from sugar cane (Saccharum spp.) silage and the addition of propionic acid [1% based on fresh matter (FM)] to silages treated with and without calcium oxide (1% of FM) at 60 and 170 d of ensiling. A randomized block design with a 2 × 2 × 2 × 2 factorial arrangement of treatments was used to analyse the results. The use of calcium oxide reduced the ethanol content and neutral detergent fibre in all silages, increased pH values and favoured the growth of clostridia and yeasts. The addition of propionic acid reduced the yeast population, but it was not able to reduce ethanol content of silage. The addition of L. buchneri resulted in silages with higher concentration of propionate, reduced the levels of ethanol and reduced the population of clostridia in all silages. The use of calcium oxide is not recommended for silage of sugar cane.

Kinetics and mechanism for the acid-catalyzed addition of propionic acid to tetradecenes and hexadecenes

We developed a kinetic model for the reversible direct addition of propionic acid to linear tetradecences and linear hexadecenes on Amberlyst 15 at 93°C. The model addresses concurrent double bond isomerization of the olefins and assumes carbenium ion formations to be rate limiting for all conversions; it is detailed enough to include terms for multiple isomers of esters and olefins. The reaction was first order in olefin and in ester but was one-half order in propionic acid. Gas chromatography was the analytical method employed to follow the reactions, and this study represents a novel use of this analytical method to elucidate carbenium ion behavior. The model includes five rate-determining steps and five fast steps. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 354–371, 2010

Lignite humic acids aggregates studied by high resolution ultrasonic spectroscopy

The thermodynamic stability of lignite humic acids (sodium salt) aggregates was studied by high resolution ultrasonic spectroscopy within the temperature interval from 5 to 90°C. The changes in differential ultrasonic velocity (U12) showed strong differences among humic solutions within the concentration range from 0.005 to 10 g L−1. Measurement revealed several transitions which were attributed to the weakening of humic secondary structure. Concentration around 1 g L−1 seemed to be a limit under which the change of the prevalence and importance of hydration occurred. Above this concentration the difference in U12 decreased following the temperature increase which was explained as a dominance of hydrophilic hydration. In contrast, below this concentration, the temperature dependence of U12 resulted in increasing tendency which was attributed to the prevalence of hydrophobic hydration, i.e. uncovering of apolar groups towards surrounding water. Additional experiments in which the humic sample was modified by hydrochloric acid resulted in a slight structural stabilization which lead to the conclusion that humic micelle-like subaggregates form an open-layer assemblies easily accessible for interaction with an extraneous molecule. That was partly verified by addition of propionic acid which brought about even larger reconformation of humic aggregates and exhibition of polar groups towards hydration water.