Aerobic metabolism of Streptococcus agalactiae.

Comparing the effects of the two acids treatments, lactic acid was found to be more effective in both concentrations used. Lactic acid sprayed samples, particularly with 2%, showed the greater acceptability than did those sprayed with acetic acid throughout the storage days. From microbial and visual quality standpoints, meat sample sprayed with 2% seemed to be more acceptable regarding meat color and bacterial numbers with proper hygiene and handling procedures could provide safer meat with good qualityandto ensure safe public health.

Succinic, acetic, and lactic acids are the major anaerobic fermentation acids excreted in vitro by Hymenolepis diminuta. In parasites recovered from immature (6-day) infections in white rats that were fed ad lib. in the dark for 12 hr, approximately equal amounts of succinic and lactic acids, and less acetic acid, were excreted. In the succeeding 12-hr period of fasting in the light, production of succinic and acetic acids from endogenous glycogen reserves was unaffected, whereas that of lactic acid decreased markedly. The pattern was different in parasites recovered from 10and 14-day infections, in that quantitative differences in acid excretion during feeding and fasting periods were not observed, lactic acid production was relatively small, and succinic acid constituted about half of the total excreted acids. An active pyruvate decarboxylase enzyme complex presumably accounted for the formation of acetate from pyruvate. The existence of lactate dehydrogenase, and a phosphoenolpyruvate carboxykinase leading to succinate production were already known. A calculation of the carbon content of excreted acids in terms of ,moles phosphoenolpyruvate carbon/mg protein showed that the rates of excretion of fermentation acids in 6and 14-day infections did not differ. Succinic, acetic, and lactic acids comprise most of the total fermentation acids excreted in vitro by Hymenolepis diminuta recovered from patent (15 day) infections in rats (Fairbairn et al., 1961). It is known that phosphoenolpyruvate is a key intermediate in the formation of these acids since it reacts with carbon dioxide in the presence of phosphoenolpyruvate carboxykinase and GDP or IDP to form oxaloacetate and thence succinic acid, and is also converted to pyruvate by pyruvate kinase (Bueding and Saz, 1968) and hence to L(+) lactate by lactate dehydrogenase (Walkey and Fairbairn, 1973). Acetic acid is presumably formed by oxidative decarboxylation of pyruvate, although the existence of this enzyme complex has not been studied. Different isoenzymes of L(+) -lactate dehydrogenase occur in the anterior regions of the mature tapeworm strobila or in immature (6 day) parasites, and in infective eggs obtained from mature proglottids (Walkey and Fairbairn, 1973). Similar observations have been made on pyruvate kinase (Carter and Fairbairn, unpublished). There is reason to believe, therefore, that quantitative differences in the forReceived for publication 11 February 1974. * This work was supported by Grants AI-08491 and 5 TOI AI-226 from the NIH, Bethesda, Maryland 20014. t Present address: The Wellcome Research Laboratories, Beckenham, Kent BR3 3BS, England. mation and excretion of succinic, acetic, and lactic acids may exist in different regions of the strobila, or in parasites at different stages of development in the definitve host. This is not surprising, as the strobila of H. diminuta contains hundreds of proglottids representing all stages of continuous growth and differentiation. In the present investigation we have compared the in vitro anaerobic excretion of succinic, acetic, and lactic acids by H. diminuta recovered from infected rats after 6 and 14 days, respectively, and have demonstrated the decarboxylation of pyruvate by a pyruvate decarboxylase enzyme complex. MATERIALS AND METHODS In order to make possible a comparison of the present experiments with other recently completed experiments (Carter and Fairbairn, unpublished), white, male Sprague-Dawley rats (Holtzman strain) weighing about 150 g each were infected with 30 cysticercoids of H. diminuta injected into the stomach through a catheter. After ensuring that all cysticercoids had been delivered from the catheter, the rats were caged in pairs and maintained on a 12 hr light-12 hr dark daily photoperiod. Food (commercial pellets) was provided only during the dark half of the cycle, from 8:00 PM to 8:00 AM. Rats harboring parasites to be recovered on the 10th or 14th day after infection were maintained in this manner. When parasites were to be recovered after infection for 6 days the procedure was the same except that greater numbers of rats were infected, each with 300 to 500 cysticercoids, in order that sufficient weight of tissue would be available for

Sensitivity of Acid-Adapted and Acid-Shocked Shigella flexneri to Reduced pH Achieved with Acetic, Lactic, and Propionic Acids

Cellular respiration is one of the main ways organisms make energy. It works by linking the oxidation of an electron donor (like sugar) to the reduction of an electron acceptor (like oxygen). Electrons pass between the two molecules along what is known as an ‘electron transport chain’. This process generates a force that powers the production of adenosine triphosphate (ATP), a molecule that cells use to store energy. Respiration is a common way for cells to replenish their energy stores, but it is not the only way. A simpler process that does not require a separate electron acceptor or an electron transport chain is called fermentation. Many bacteria have the capacity to perform both respiration and fermentation and do so in a context-dependent manner. Research has shown that respiration can contribute to bacterial diseases, like tuberculosis and listeriosis (a disease caused by the foodborne pathogen Listeria monocytogenes). Indeed, some antibiotics even target bacterial respiration. Despite being often discussed in the context of generating ATP, respiration is also important for many other cellular processes, including maintaining the balance of reduced and oxidized nicotinamide adenine dinucleotide (NAD) cofactors. Because of these multiple functions, the exact role respiration plays in disease is unknown. To find out more, Rivera-Lugo, Deng et al. developed strains of the bacterial pathogen Listeria monocytogenes that lacked some of the genes used in respiration. The resulting bacteria were still able to produce energy, but they became much worse at infecting mammalian cells. The use of a genetic tool that restored the balance of reduced and oxidized NAD cofactors revived the ability of respiration-deficient L. monocytogenes to infect mammalian cells, indicating that this balance is what the bacterium requires to infect. Research into respiration tends to focus on its role in generating ATP. But these results show that for some bacteria, this might not be the most important part of the process. Understanding the other roles of respiration could change the way that researchers develop antibacterial drugs in the future. This in turn could help with the growing problem of antibiotic resistance.

SUMMARY: Evidence is presented that under the conditions described 11 strains of Actinomyces spp., representing strains described as A. israelii, A. israelii-like or A. naeslundii, require carbon dioxide for anaerobic growth. Some of these strains, under these conditions, are obligate anaerobes to microaerophils, while others appear to be facultative anaerobes. Cultures which are capable of aerobic growth may or may not require carbon dioxide for such growth. Of three strains of Lactobacillus bifidus tested, all required carbon dioxide for anaerobic growth. One avian strain required carbon dioxide to give limited aerobic growth; the remaining strains did not grow significantly under aerobic conditions. Comparisons of several strains of Actinomyces spp. with L. bifidus indicated that of eleven sugars tested, the sugar of choice for growth of Actinomyces spp. was glucose or maltose, whereas lactose or maltose was preferred by strains of L. bifidus. All strains of each group of organisms were found to be catalase-negative; none liquefied gelatin; all eleven strains of Actinomyces spp. reduced nitrate to nitrite, but none of the bifid strains possessed this ability; production of acetylmethylcarbinol was variable in both groups. All strains of Actinomyces spp. tested formed L (+) lactic acid, although the results suggested that small amounts of D (-) lactic acid were also formed. Fermentation analyses indicated that strains of L. bifidus and Actinomyces spp. form the same products from glucose and carbon dioxide (lactic, acetic, formic and succinic acids). However, strains of Actinomyces spp. form predominantly lactic acid with small amounts of acetic, formic and succinic acids; whereas the strains of L. bifidus form approximately equal amounts of lactic and acetic acids (based on glucose fermented) with trace amounts of succinic and formic acids. Actinomyces strains fermented but 34-59% of the glucose supplied as compared to the strains of L. bifidus which used from 59 to 89% of the glucose (1% glucose medium).

Growth limits of psychrotrophic Bacillus cereus as a function of temperature, pH, water activity, and lactic or acetic acid

Behavior of Acid-Adapted and Unadapted Escherichia coli O157:H7 When Exposed to Reduced pH Achieved with Various Organic Acids

Inhibitory activity of lactic and acetic acid on Aspergillus flavus growth for food preservation

Effect of organic acids on biofilm formation and quorum signaling of pathogens from fresh fruits and vegetables

Behavior of Listeria monocytogenes at 7, 13, 21, and 35°C in Tryptose Broth Acidified with Acetic, Citric, or Lactic Acid

The combined effects of lactic acid and acetic acid on ethanol production by S. cerevisiae in corn mash, as influenced by temperature, were examined. Duplicate full factorial experiments (three lactic acid concentrations x three acetic acid concentrations) were performed to evaluate the interaction between lactic and acetic acids on the ethanol production of yeast at each of the three temperatures, 30, 34, and 37 degrees C. Corn mash at 30% dry solids adjusted to pH 4 after lactic and acetic acid addition was used as the substrate. Ethanol production rates and final ethanol concentrations decreased (P<0.001) progressively as the concentration of combined lactic and acetic acids in the corn mash increased and the temperature was raised from 30 to 37 degrees C. At 30 degrees C, essentially no ethanol was produced after 96 h when 0.5% w/v acetic acid was present in the mash (with 0.5, 2, and 4% w/v lactic acid). At 34 and 37 degrees C, the final concentrations of ethanol produced by the yeast were noticeably reduced by the presence of 0.3% w/v acetic acid and >or=2% w/v lactic acid. It can be concluded that, as in previous studies with defined media, lactic acid and acetic acid act synergistically to reduce ethanol production by yeast in corn mash. In addition, the inhibitory effects of combined lactic and acetic acid in corn mash were more apparent at elevated temperatures.

BACKGROUNDDuring anaerobic digestion of wastes, volatile fatty acid (VFA) production has been studied, but little attention has been paid to alcohols and lactic acid. Thermodynamically, lactic acid and alcohols are better substrates to produce methane than other VFA. This research identified the metabolites produced during the fermentation of the organic fraction of municipal solid waste and studied their methanization in a second stage. Analysis of the methane production curves is provided and explained according to Gibbʼs free energy of acetogenesis and methanogenesis. Based on the Michaelis–Menten model, a kinetic analysis is presented.RESULTSThe specific methane production of the identified acids and alcohols are acetic acid, 343 NL/kgCOD; ethanol, 296; methanol, 181; butyric acid, 108; lactic acid, 64. Lactic and butyric acids present a long adaptation phase followed by a fast and short methane production. Acetic acid and ethanol finished the reaction in less than 16 h. The highest methane production rates (Vmax) were for butyric acid, methanol, and ethanol with 2136, 1934, and 1928 NmL L–1, respectively. The best affinity (lowest Km) values were for acetic and lactic acids and ethanol with 1.2, 1.9, and 2.0 gCOD L–1.CONCLUSIONTogether, acetic acid and ethanol represent 92% of all fermentation products. No endogenous methane production was observed during the methanization from acetic acid and ethanol. The highest specific methane production belongs to acetic acid (98% of the theoretical) and the lowest corresponds to lactic acid. Except for propionic acid, the methanization of the selected substrates follows the Michaelis and Menten model. © 2021 Society of Chemical Industry (SCI).

Purpose. To substantiate new criteria for evaluation of corn silage quality with bio-preservatives. Methods. Zootechnical method to determine feed digestibility in animal experiments. It is incorporated in amphorae of 1.8 tons of corn silage mass of the beginning of wax ripeness. The first amphora was without preservative, the second was with bio preservative No. 1 and the third one was with bio preservative No. 2. The silo of 3 amphorae according to the standard was evaluated. In all 3 amphorae, the silo was of good quality, but the digestibility of dry matter in the balance experiments on the rams was different. Results. The most commonly accepted criteria for evaluating silo quality are its pH value and the solids content. The high quality silo has a pH of water extract in the range of 3.6—3.9. Such pH values are created by the high content of lactic acid and low ammonia content. Under these conditions, the nutrient retention in the silage feed is the highest compared to other acidity parameters. Thus, under pH higher than 4.4 and dry matter content of 30 %, the fermentation in the silo process takes place by the proteolytic type and, as a result, butyric acid, amines and ammonia, not lactic acid, are formed. Due to the fact that butyric acid is much weaker than lactic acid and thus has a low preservative capacity, the silo is of poor quality. Therefore, high levels of ammonia, amines and butyric acid cause poor quality of the silo. High quality silo contains up to 20 % free acids (2/3 – lactic acid and 1/3 acetic acid). Our research has shown that silage packed with bio-preservatives based on lactic and propionic acid bacteria has a higher digestibility of nutrients than the same starting mass (raw material), which is ensiled without a bio-preservative. Lactic acid bacteria synthesize B vitamins (B1, B2, B5 and B7) and essential amino acids, and propionic bacteria further synthesize vitamin B12, forming mucus and giving the silage a specific, pleasant taste, providing better feed for animals, e.g. cows, substances, which is a consequence of the higher productive action of the feed. Digestibility of dry matter of silage, which was incorporated without a biological preservative, was at the rate of 53.9 %, and it was 8.8 % higher with bio-preservative No. 1. Studies conducted with an air-dry matter of 3 silos to obtain a suspension have provided the basis for evaluating bacterial preservatives for their ability to stimulate the growth of microbial protein in the silage. Conclusions. On the basis of the conducted researches new criteria for evaluation of corn silage quality were experimentally substantiated. Indicators of high-quality silage, namely, pH, total acidity, lactic, content of acetic and butyric acids and ammonia, include the digestibility of dry matter in animals, and the determination of bacterial protein as an important factor in the influence of lactic and propionic acid bacteria of bio-preservatives on the biological value of feed protein, which is a criterion for evaluating biological preservatives for the ability to stimulate bacterial protein gain in silage.

Characterization of spoilage yeasts isolated from fermented vegetables and Inhibition by lactic, acetic and propionic acids

The anaerobic oxidation of glucose by methylene blue in an alkaline solution containing phosphate or bicarbonate was studied by THUNBERG methylene blue method. To determine the oxidation, products of glucose, the paper chromatography, the color reaction and the isolation of produced matter were studied. By paper chromatogram of oxidation products, seven acid spots appeared in a paper sprayed with bromphenol blue reagent. The seven acid spots were congruent with gluconic acid, 5-ketogluconic acid, 2-ketogluconic acid, glycolic acid, succinic acid, lactic acid, and glyceric anid. The oxidation products indicated the color reactions of gluconic acid, 5-ketogluco nic acid, 2-ketogluconic acid, glycolic acid, succinic acid, lactic acid and glyceric acid. Fromthe oxidation products we obtained gluconic acid as Ca-salt. In the oxidation products of glucose we recognized that there was gluconic acid, and moreover we assumed that there were 5-ketogluconic, acid, 2-ketogluconic acid, glycolic acid, succinic acid, lactic acid, and glycric acid.