Volatile Acid Production Research Articles

Similarity between biotransformation rates and turnover rates of organic matter biodegradation in anaerobic environments

Methods have been developed to assess the rate of substrate transformation in anoxic environments based upon the rate of product formation. Transformation rate constants based on the production of gases, 14CH 4 and 14CO 2, ( k g) averaged 96.7% (SD = 14%) of the turnover rate constant ( k) based upon loss of [U- 14C]glucose, [I- 14C]lactate, [I- 14C]-or [2- 14C]acetate when examined in sewage sludge or lake sediments. Lower k g values, ≈ 1 2 of k , were obtained from [3- 14C]lactate in all habitats because [3-C]lactate produced [2-C]acetate which was later consumed by methanogens. Inclusion of volatile organic acid production in the transformation rate constant determinations ( k gv = 14 CH 4 , [ 14C]volatile organic acids) resulted in a k gv = 0.89 of the value for k for [3-C]lactate as expected, transformation rate constants decreased as the food chain was ascended with acetate > lactate > glucose. Cellulose, a polymer whose turnover rate constant could not be determined, was transformed considerably slower than glucose and k g = k gv. Transformation rate constants are a rapid and accurate technique for assessing turnover of specific metabolites in anoxic habitats and may be suited for examining the decomposition of polymers and compounds whose loss from ecosystems are difficult to quantify.

Production of biomass, carbon dioxide, volatile acids, and their interrelationship with decrease in chemical oxygen demand, during distillery waste treatment by bacterial strains

The products of the biodegradation of distillery waste with certain bacteria have been found to be biomass, carbon dioxide, and volatile acids. Volatile acid production levelled off after 48 to 72 h and correlated with the reduction in COD values. Carbon dioxide production did not exhibit such a correlation. The relationship of biomass to carbon dioxide production showed a biphasic pattern, indicating the preferential utilization of some substrates over others. Carbon dioxide production in the later phase may be due to the metabolism of secondary metabolites which do not differ much in their COD values.

Development of alcoholic fermentation in non-sterile musts from ‘Pedro Ximenez’ grapes inoculated with pure cultures of selected yeasts

Non-sterile musts from grapes of the ‘Pedro Xime´nez’ variety collected in three degrees of ripeness were subjected to fermentation by using pure cultures of five yeast races selected from the Montilla-Moriles region. Four were physiological races of Saccharomyces cerevisiae (cerevisiae A, cerevisiae B, chevalieri and capensis), and the fifth was from the species Torulaspora delbrueckii. Despite the occurrence of indigenous flora, the five inoculated yeasts succeeded in replicating and taking over the fermentations, which they conducted according to their own features to yield wines similar to those obtained from sterile musts fermented by them. The most outstanding results, consistent with those obtained on sterile musts, were the high rate of fermentation of the cerevisiae races in the three types of must, and the low volatile acidity production of T. delbrueckii, particularly in the ripest must.

Viabilidade do tratamento do soro de queijo com digestão anaeróbia

O principal objetivo deste trabalho con sistiu em avaliar a digestão anaeróbia de soro de queijo (68.000mg DQO/l), sem correção de pH, em digestores tipo mistura completa, semi-contínuos em escala laboratorial, mantidos à temperatura de 35° ± 1°C. Foi utilizado como inóculo estéreo bovino, com teor de sólidos totais igual a 8%. O experimento foi desenvolvido num período de 100 dias, onde os primeiros 20 dias foram caracterizados pela aclimatação do inóculo e quatro tempos de retenção (¸) de 20 dias. Foi adicionado em cada reator uma carga de 3,0g DQO/l de reator/dia. No primeiro ¸ a carga foi dividida em 3 partes e adicionada aos digestores em intervalos de 8 horas. No segundo ¸ a carga foi dividida em 2 partes e adicionada aos digestores em intervalos de 12 horas; no terceiro ¸ foi utilizado intervalo de 6 horas para a alimentação com a carga de DQO dividida em 4 porções; o quarto ¸ foi caracterizado pela alimentação da carga total de uma única vez. O acompanhamento do experimento foi feito por análises de acidez, alcalinidade e pH, juntamente com produção de biogás; foi avaliado também a DQO no efluente. Foi constatado que os sistemas de alimentação empregados no presente trabalho, influenciaram no desenvolvimento do processo, sendo que a produção de ácidos graxos voláteis foi acentuada durante os TRH estudados levando a um desequilíbrio populacional e, consequentemente, a uma baixa eficiência de tratamento. Nestas condições, a produção de biogás expressa em 1.biogás/g DQO destruído foi de 0,35 l/g.

Ozonated cotton stalks as a silage additive: Fermentation data on lucerne with particular reference to protein degradation

AbstractFermentation patterns of lucerne silages were studied in laboratory silos. The treatments consisted of: (a) fresh (200 g kg>−l DM) lucerne, ensiled without any treatment (L); (b) lucerne wilted to 525 g kg−1 DM prior to ensilage (WL); (c) fresh lucerne + cotton stalks at a ratio of 60:40 on a dry matter (DM) basis (L + CS); and (d) fresh lucerne + ozone‐treated cotton stalks at the same ratio as above (L+O3). Silos were opened after 90 days and the silages analysed. The highest DM loss was found in the L silage (14·7%), whereas in the L+O3 silage DM loss was practically nil. Both wilting and the addition of untreated cotton stalks proved to be effective in reducing DM losses during fermentation. The production of lactic acid and volatile organic acids in the L+ O3 and WL silages was lower than in the L and L+CS silages. The poorest ability to preserve forage protein was found in the L silage, in which only 28 % of the protein was recovered after 90 days. The greatest ability to preserve protein was found in the L+O3 silage, in which 78 % of the protein was maintained. Ammonia production followed generally similar patterns. Amino acids underwent extensive degradation in the L silage. Recovery of amino acids in the WL silage was in the range 69–93 %, and in the L + O3 silage it was almost complete. Ozonated CS proved to be a good silage additive with respect to energy and protein preservation. Its future use in the field would allow direct ensilage of fresh leguminous material immediately after harvest, producing a high quality silage.

Formation of short chain volatile organic acids in the automated AOM method

AbstractThe end point in the automated AOM stability test for fats is related to the rapid production of volatile acids at the end of the induction period and usually measured by conductivity of an aqueous solution of the exit gases. It has been postulated that the reaction involves the transitory presence of a diperoxide which decomposes into two aldehydes and formic acid. The volatile acids produced by several oils were composed mainly of formic acid and significant amounts of acetic acid. In addition, acids with three or more carbon atoms, including propionic, butyric and caproic, were detected. It was found that the temperature of the water in the receiving jars was important in relation to retention of the formic acid. At temperatures above 20 C significant losses may occur. The relationships between peroxide value of the oils, the conductivity of the exit gas solutions and the organic acid content was investigated for the following fats and oils: sunflower, canola, olive, corn, peanut and soybean oil, triolein, lard and butterfat.

Effects of dimetridazole on methanization of swine manure: The importance of propionic acid concentration

This study describes the influence of an animal food additive (dimetridazole) on the methanization of swine manure. The results from batch digesters show that, depending on dimetridazole concentration, activation or inhibition of the anaerobic digestion process occurs. The presence of dimetridazole favours Volatile Acid production. Up to a concentration of 710 μmol litre −1, in the case of a steady-state digester, there was an increase in methane production. At higher concentrations, an accumulation of propionic acid, rather than acetic acid, was observed and this resulted in inhibition of the process.

The effect of downtime on the operational performance and steady state biomass distribution of anaerobic fluidised beds

The operational capabilities of four anaerobic fluidised bed reactors restarted after periods of downtime of 39 and 89 days were determined, together with a profile of biomass activity at steady state through the bed length of two reactors. Full operational performance was retained after the shorter downtime period, but restart required manipulation after the 89-day shutdown due to poor COD removal and high volatile acid production. Biomass activity was greatest in the upper third of the reactors, with attached biomass being more active than suspended.

Acclimation of anaerobic fluidised beds to two pharmaceutical wastes

Abstract The acclimation of anaerobic fluidised beds to two pharmaceutical wastes gradually introduced with the influent feed was examined. Feed was applied at a COD concentration of 2500 mgl‐1, at an organic loading rate of 4.5 kg COD m‐3d‐1 and with an HRT of 0.53d, and operation continued until the feed comprised 100% industrial waste. Final COD removals reached 54% and 45% for the propanol ‐ (A) and the dimethylformamide ‐ (B) containing wastes respectively. Analytical results suggested that waste A was nutrient limited and caused inhibition of methanogenesis, whereas waste B appeared to contain a non‐biodegradable or toxic fraction which did not inhibit methanogenesis but caused a reduction in COD removal and erratic volatile acids production.

Performance of bacterial strains used for distillery waste treatment on different substrates

Six bacterial strains were isolated and acclimatized on distillery waste. The performance of these bacterial strains in respect to growth, reduction in chemical oxygen demand (COD) values, carbon dioxide production and volatile acid production were studied on five different substrates. Glucose and xylose exhibited growth patterns similar to that on spentwash. Glucose, xylose, casein hydrolysate and amino acids led to very good reduction in COD values compared with glycerol. Rate of substrate consumption was maximum in the case of glucose followed by amino acids, casein hydrolysate, xylose and glycerol. Production of volatile acids and carbon dioxide from glucose amounted to ≈ 50% of the theoretical yield based on glycolysis and the tricarboxylic acid cycle. Production of carbon dioxide followed the usual microbiological growth pattern while volatile acids did not show any such pattern. Carbon dioxide and volatile acids appear to be the major degradation products in distillery waste treatment by these bacteria.

Detailed study of anaerobic digestion of Spirulina maxima algal biomass

Biomass of the blue-green alga Spirulina maxima was converted to methane using continuous stirred tank digesters with an energy conversion efficiency of 59%. Digesters were operated using once-a-day feeding with a retention time (theta) between 5 and 40 days, volatile solid concentrations (S(to)) between 20 and 100 kg VS/m(3), and temperatures between 15 and 52 degrees C. The results indicated a maximum methane yield of 0.35 m(3) (STP)/kg VS added at theta 30 days and S(to) 20 kg VS/m(3). Under such conditions, the energy conversion of the algal biomass to methane was 59%. The maximum methane production rate of 0.80 m(3) (STP)/m(3) day was obtained with theta= 20 days and S = 100 kg VS/m(3). The mesophilic condition at 35 degrees C produced the maximum methane yield and production rate. The process was stable and characterized by a high production of volatile acids (up to 23, 200 mg/L), alkalinity (up to 20, 000 mg/L), and ammonia (up to 7000 mg/L), and the high protein content of the biomass produced a well buffered environment which reduced inhibitory effects. At higher loading rates, the inhibition of methanogenic bacteria was observed, but there was no clear-cut evidence that such a phenomenon was due to nonionized volatile acids or gaseous ammonia. The kinetic analysis using the model proposed by Chen and Hashimoto indicated that the minimum retention time was seven days. The optimum retention time increased gradually from 11 to 16 days with an increase in the initial volatile solid concentration. The kinetic constant K decreased with the improvement in the digester performance and increased in parallel with the ammonia concentration in the culture media.

Formation of volatile acids in the various stages of fish sauce fermentation.

The rate of production of volatile acids present in the intermediate products at 3, 4, 10 and 15 months of fermentation of commercial Patis obtained in the Philippines and fish sauce of small scale preparation made in the laboratry was investigated. Also, an attempt to clarify the origin of these acids was conducted. Results of these experiments showed that concentrations of low molcular volatile acids were found to be higher in gut than in the whole and in flesh of fish in the both 24hours and 1 week incubations. It was also found that acids increased quantitatively and qualitatively with the progress of fermentation. It seems that almost all the acids identified in the sauce were formed within 3 months of fermentation. In this study, when fish was incubated without the addition of salt, most of the acids found reached very high levels compared with that in the fish incubated with the addition of salt. This might suggest involvement of bacterial action in the production of volatile acids.

Mathematical Modelling of the Anaerobic Digestion Process: Regulatory Mechanisms for the Formation of Short-Chain Volatile Acids from Glucose

A model of the anaerobic digestion process is presented which attempts to explain the complex patterns of volatile acid production in the anaerobic digestion process. The hydrogen-utilising methane bacteria are identified as the controlling organisms for the redox potential of the process. Mathematical expressions for the regulation of metabolism by hydrogen are derived from the known redox potential of the NAD/NADH couple.

Studies on the Nutrition of Macropodine Marsupials. 5.microbial Fermentation in the Forestomach of Thylogale Thetis and Macropus Eugenii.

Rates of volatile fatty acid (VFA) and ammonia production at different sites along the forestomach of Thylogale thetis, the red-necked pademelon, and Macropus eugenii, the tammar wallaby, were estimated in vitro and in vivo. Estimates of the flow of microbial nitrogen from the stomach were also obtained in vivo. In both species VFA production was faster in vitro and in vivo in the sacciform forestomach than in the tubiform forestomach. The ratio of total VFA production to digestible organic matter (OM) intake was similar in the 2 species, and similar to published estimates for ruminants. Net production of ammonia in vivo was faster in the sacciform forestomach than in the tubiform forestomach of T. thetis but not of M. eugenii. The ratio of total net ammonia production to nitrogen intake was similar in the 2 species, and net synthesis of microbial protein per kilogram OM apparently fermented in the stomach of T. thetis and M. eugenii was similar to that in ruminants. The decrease in fermentation rate along the forestomach of both species was consistent with the previously reported pattern of apparent digestion of OM in the macropodine stomach. Although this pattern of microbial activity differs from that in ruminants, the overall fermentation is extensive. Thus the lower fibre digestibility often found in macropodines compared with sheep may be related to a faster rate of passage of particulate digesta through the macropodine forestomach, but it is not due to a less efficient microbial fermentation.

Some factors influencing the effect of alkali treatment on crop residues

SUMMARYFive agricultural by-products, maize stover and cobs, wheat straw, grape marc and sunflower husks, were treated with alkaline reagents under various conditions.Maize stover and wheat straw reacted quickly with both sodium hydroxide applied at a level of 4 g NaOH/100 g dry residue and a mixture of calcium and sodium hydroxides (1:1), which led to changes in chemical composition and increases in digestibility. However, ensilage of the treated product at about 37% dry matter (D.M.) was not successful.When dried grape marc was treated with sodium hydroxide (4·3 g NaOH/100 g dry residue) apparent lignin content increased, although other changes in composition and digestibility were similar to the above. Nevertheless, digestibility remained low. Moreover, when previously ground marc was treated in the same way lignin and cellulose fractions increased markedly while digestibility decreased.Treatment of maize cobs with increasing amounts of sodium hydroxide (2·1–4·2 g/100 g dry residue) at 80% D.M. gave progressively more favourable results, although no improvement in digestibility was noted when half the sodium hydroxide was replaced by calcium hydroxide. Similar positive results were obtained under industrial conditions at application rates of 3·2 and 4·5 g sodium hydroxide per 100 g dry residue. Pelleting the product led to a further increase in digestibility.Sunflower husks also showed a decrease in hemicellulose content and increases in digestibility and volatile acid content after treatment with 4·4 g NaOH/100 g dry residvie under industrial conditions. Lignin content was unchanged. The pelleted products (about 80% D.M.) were stable for more than 6 months when stored in paper sacks.Except with grape marc loss of hemicellulose provided a general indication of the success of alkali treatment, although correlation with increased digestibility did not reach statistical significance (r = 0·34). Volatile acid production and alterations in lignin content were not suitable as general indicators.In general, alkali treatment of the examined materials improved digestibility, although the products with a high water content were subject to undesirable fermentative changes during storage and therefore should be used within a few days.

Interactions of Lactobacillus and Propionibacterium in Mixed Culture

Four species of Lactobacillus (L. acidophilus, L. casei, L. delbrueckii and L. bulgaricus) were paired with four species of Propionibacterium (P. pentosaceum, P. shermanii, P. acidipropionici and P. freudenreichii) and were grown in pure and mixed culture to assess associative interactions. Experiments were performed using a defined synthetic medium with glucose as an energy source and casamino acids as a nitrogen source. A differential respirometer (32°C) and Warburg flasks were used; growth, carbon dioxide, and acid production were measured. Fifteen of the 16 paired cultures had less growth, acid, and carbon dioxide produced than pure culture controls. In some pairs, both cultures were inhibited by mixed cultivation while in others only the Propionibacterium was inhibited. In several mixtures, the Lactobacillus culture was apparently unaffected by mixed culturing. In P. shermanii and L. acidophilus mixed culture, a beneficial synergistic effect on growth, carbon dioxide, and volatile and nonvolatile acid production was observed. Little lactate accumulated in the mixed culture medium and was apparently used as an energy source and resulted in increased carbon dioxide and acid production by the P. shermanii.

Acid production and proteolytic activity in milk by selectedLactobacillus γ-radiation induced mutants

Selected γ radiation-induced mutants and parent cultures ofLactobacillus andL. casei were estimated for titratable and volatile acid production of biacetyl and acetoin and for proteolytic activity as compared to the parents.

Anaerobic digestion: microbial and biochemical aspects of volatile acid production

The production of organic acids has been tested with bacterial flora selected from a municipal sludge digestor. In order to elucidate the basic mechanisms by which glucose is converted to volatile fatty acids, the examination of non-methanogenic bacteria was attempted. Both lactate-producers and lactate-utilizers were found among these bacteria. When mixed isolates were used as the inoculum, the accumulation of lactic acid and its further conversion to propionic and butyric acids was demonstrated at a carbon conversion rate of about 0.75. It is therefore suggested that this metabolic sequence may occur as a normal process in acidogenic fermentation, which is the first step in anaerobic digestion.

Development of Microbial Populations in Fermented Wastes from Frozen Vegetable Processing

Changes in microbial populations were evaluated in fermented silage-like products prepared from wastes generated during frozen vegetable processing. Lactobacillus plantarum (107/g) was used to inoculate wastes from black-eyed peas, corn, potatoes, turnip greens and green beans. Populations of facultative anaerobic flora (lactobacilli, lactic acid cocci), anaerobes (clostridia) and lactate-hydrolyzing microflora differed in silages of different composition. Development of microflora correlated with pH decline and production of volatile and nonvolatile acids. Lactic and acetic acids were produced early while secondary metabolic end products (propionic, butyric acids) accumulated later in silages as populations of clostridia and propionibacteria increased. Minimum pH levels were attained after 2 and 4 days of fermentation. Black-eyed pea and potato silages had relatively high pH levels (>4.50). This was correlated with low soluble carbohydrate content. No generalized role could be determined for population changes of fungi or coliforms. The most desirable waste silages can be produced from temperature-stressed materials adjusted to proper composition to ensure optimum fermentation patterns.

The production of volatile acids from glucose by soy yeast (Saccharomyces rouxii) NRRLY—1096

SummaryThe glucose metabolism of Saccharomyces rouxii NRRLY—1096, the soy yeast, under aerobic and anaerobic conditions, was investigated. The study was carried out at pH 4.5 and 7.0 with cells previously grown at either pH. The pH at which the cells had been grown as well as the pH at which glucose was fermented were found to affect the pattern of fermentation. A typical yeast type fermentation was obtained with cells grown at pH 4.5 and fermenting glucose at the same acid pH. An ability to fix CO2 for formic acid synthesis was demonstrated by cells grown at neutral pH. Acetic acid was produced by cells fermenting glucose at neutral pH irrespective of the pH at which they had been grown. Various schemes of glucose fermentation were therefore proposed. From results of the present study, optimal conditions for the formation of the desired fermentation products, resulting in the flavour and bouquet of good quality soy sauce, are suggested.