Showing papers on "Fermentation published in 1980"

Culture Method to Study Fungal Growth in Solid Fermentation

Abstract: A new culture method is described to study the growth of Aspergillus niger on cassava meal in the solid state. This method uses preparations of the cooked starchy substrate as a homogeneous granulated product containing spores, salts and water. An incubation device aerates the mass with humidified air at a controlled temperature. Homogeneous development of mycelia, without sporulation, occurred in the substrate mass. From physiological studies, optimal conditions for A. niger growth on cassava in the solid state were 50–55% moisture, 35°C, a nitrogen source comprising 60% ammonium and 40% urea (on a nitrogen basis) and 2×107 spores/g of substrate. Growth kinetics were established and changes in pH, protein, carbohydrate and water content were determined during the incubation. Growth rate and yield were quite similar to those described in the literature for A. niger cultivated in liquid media under optimal conditions.

Ethanol Production by Thermophilic Bacteria: Relationship Between Fermentation Product Yields of and Catabolic Enzyme Activities in Clostridium thermocellum and Thermoanaerobium brockii

Abstract: Significant quantitative differences in end-product yields by two strains of Clostridium thermocellum and one strain of Thermoanaerobium brockii were observed during cellobiose fermentation. Most notably, the ethanol/H2 and lactate/acetate ratios were drastically higher for T. brockii as compared with C. thermocellum strains LQRI and AS39. Exogenous H2 addition (0.4 to 1.0 atm) during culture growth increased the ethanol/acetate ratio of both T. brockii and AS39 but had no effect on LQRI. All strains had an operative Embden-Meyerhof glycolytic pathway and displayed catabolic activities of fructose-1,6-diphosphate–activated lactate dehydrogenase, coenzyme A acetylating pyruvate and acetaldehyde dehydrogenase, hydrogenase, ethanol dehydrogenase, and acetate kinase. Enzyme kinetic properties (apparent Km, Vmax, and Q10 values) and the specificity of electron donors/acceptors for different oxidoreductases involved in pyruvate conversion to fermentation products were compared in the three strains. Both species contained ferredoxin-linked pyruvate dehydrogenase and pyridine nucleotide oxidoreductases. Ferredoxin-nicotinamide adenine dinucleotide (NAD) reductase activity was significantly higher in T. brockii than in AS39 and was not detectable in LQRI. H2 production and hydrogenase activity were inversely related to ferredoxin-NAD reductase activity in the three strains. Ferredoxin-NAD phosphate reductase activity was present in cell extracts of both species. Alcohol dehydrogenase activity in C. thermocellum was NAD dependent, unidirectional, and inhibited by low concentrations of NAD and ethanol. Ethanol dehydrogenase activity of T. brockii was both NAD and NADP linked, reversible, and not inhibited by low levels of reaction products. The high lactate yield of T. brockii correlated with increased fructose-1,6-diphosphate. The relation of catabolic enzyme activity and quantitative differences in intracellular electron flow and fermentation product yields of these thermophilic bacteria is discussed.

Microbiology of Methanogenesis in Thermal, Volcanic Environments

Abstract: Microbial methanogenesis was examined in thermal waters, muds, and decomposing algal-bacterial mats associated with volcanic activity in Yellowstone National Park. Radioactive tracer studies with [(14)C]glucose, acetate, or carbonate and enrichment culture techniques demonstrated that methanogenesis occurred at temperatures near 70 degrees C but below 80 degrees C and correlated with hydrogen production from either geothermal processes or microbial fermentation. Three Methanobacterium thermoautotrophicum strains (YT1, YTA, and YTC) isolated from diverse volcanic habitats differed from the neotype sewage strain DeltaH in deoxyribonucleic acid guanosine-plus-cytosine content and immunological properties. Microbial methanogenesis was characterized in more detail at a 65 degrees C site in the Octopus Spring algal-bacterial mat ecosystem. Here methanogenesis was active, was associated with anaerobic microbial decomposition of biomass, occurred concomitantly with detectable microbial hydrogen formation, and displayed a temperature activity optimum near 65 degrees C. Enumeration studies estimated more than 10(9) chemoorganotrophic hydrolytic bacteria and 10(6) chemolithotrophic methanogenic bacteria per g (dry weight) of algal-bacterial mat. Enumeration, enrichment, and isolation studies revealed that the microbial population was predominantly rod shaped and asporogenous. A prevalent chemoorganotrophic organism in the mat that was isolated from an end dilution tube was a taxonomically undescribed gram-negative obligate anaerobe (strain HTB2), whereas a prevalent chemolithotrophic methanogen isolated from an end dilution tube was identified as M. thermoautotrophicum (strain YTB). Taxonomically recognizable obligate anaerobes that were isolated from glucose and xylose enrichment cultures included Thermoanaerobium brockii strain HTB and Clostridium thermohydrosulfuricum strain 39E. The nutritional properties, growth temperature optima, growth rates, and fermentation products of thermophilic bacterial strains 39E, HTB2, and YTB were determined.

Ammonia production by intestinal bacteria: the effects of lactose, lactulose and glucose.

Abstract: Ammonia production by eight groups of intestinal bacteria was measured, and the effect on ammonia production of lowered pH and ambient ammonia concentration was determined. Endogenous ammonia production from bacterial protoplasm was also examined. To examine the mechanisms by which fermentable substrates reduce ammonia formation in a faecal incubation system, the effect of lactose, lactulose or glucose on ammonia release by pure cultures of intestinal bacteria was studied. The largest amounts of ammonia were generated by gram-negative anaerobes, clostridia, enterobacteria, and Bacillus spp. Gram-positive non-sporing anaerobes, streptococci and micrococci formed modest amounts, and lactobacilli and yeasts formed very little ammonia. All groups of bacteria formed less ammonia at pH 5.0 than at pH 7.0 and production of ammonia was not inhibited when 30 mmol ammonia/litre was included in the medium. Small amounts of ammonia were formed due to endogenous metabolism of bacterial cells. Washed cell suspensions of four isolates of Bacteroides, one clostridial isolate and two streptococcal isolates formed less ammonia from alanine, methionine or histidine after growth in the presence of either lactose or lactulose. In contrast, the Bacteroides isolates formed more ammonia from aspartate than from either lactose or lactulose. Also, cultures of gram-negative anaerobes and enterobacteria, and to a lesser extent clostridia and streptococci, formed significantly less ammonia in nutrient broth when lactose, lactulose or glucose was included in the medium. This decrease in ammonia formation was not due to a fall in pH of the medium. Ammonia production by gram-positive non-sporing anaerobes was not affected by carbohydrate fermentation. These results suggest that gram-negative anaerobic bacteria make a major contribution to ammonia generated from peptides and amino acids in vivo, and that ammonia may be formed from bacterial cells in the colon. Fermentation of lactose and lactulose may repress the formation and inhibit the activity of enzymes responsible for ammonia release. In the human colon these substrate effects may decrease the amount of ammonia available to exert a toxic effect on the host, and thus contribute to the beneficial effects of lactulose when it is used in the treatment of portosystemic encephalopathy.

INHIBITION OF Saccharomyces cerevisiae BY NATURALLY OCCURRING HYDROXYCINNAMATES

Abstract: The antifungal activities of caffeic, p-coumaric, ferulic, and chloro-genie acids against Saccharomyces cerevisiae were investigated. Caffeic acid was found to exhibit little inhibition of growth, although the lag period was extended in the presence of 1000 ppm. Chloro-genie acid had no effect on the organism. In contrast, p-coumaric acid at 100 ppm increased the lag phase of S. cerevisiae, and above 250 ppm, inhibition after 72 hr growth was proportional to the concentration present. Ferulic acid caused an increase in lag phase at 50 ppm, while as little as 250 ppm resulted in complete inhibition. These results suggest that naturally occurring hydroxycinnamates may interfere with the fermentation of fruits by this yeast.

Glucose Fermentation Pathway of Thermoanaerobium brockii

Abstract: Thermoanaerobium brockii was shown to catabolize glucose via the Embden-Meyerhof-Parnas pathway into ethanol, acetic acid, H2-CO2, and lactic acid. Radioactive tracer studies, employing specifically labeled [14C]glucose, demonstrated significant fermentation of 14CO2 from C-3 and C-4 of the substrate exclusively. All extracts contained sufficient levels of activity (expressed in micromoles per minute per milligram of protein at 40°C) to assign a catabolic role for the following enzymes: glucokinase, 0.40; fructose-1,6-diphosphate aldolase, 0.23; glyceraldehyde-3-phosphate dehydrogenase, 1.73; pyruvate kinase, 0.36; lactate dehydrogenase (fructose-1,6-diphosphate activated), 0.55; pyruvate dehydrogenase (coenzyme A acetylating), 0.53; hydrogenase, 3.3; phosphotransacetylase, 0.55; acetaldehyde dehydrogenase (coenzyme A acetylating), 0.15; ethanol dehydrogenase, 1.57; and acetate kinase, 1.50. All pyridine nucleotide-linked oxidoreductases examined were specific for nicotinamide adenine dinucleotide, except ethanol dehydrogenase which displayed both nicotinamide adenine dinucleotide- and nicotinamide adenine dinucleotide phosphate-linked activities. Fermentation product balances and cell growth yields supported the glucose catabolic pathway described. Representative balanced end product yields (in moles per mole of glucose fermented) were: ethanol, 0.94; l-lactate, 0.84; acetate, 0.20; CO2, 1.31; and H2, 0.50. Growth yields of 16.4 g of cells per mole of glucose were demonstrated. Both growth and end product yields varied significantly in accordance with the specific medium composition and incubation time.

Regulation of citric acid production by oxygen: Effect of dissolved oxygen tension on adenylate levels and respiration in Aspergillus niger

Abstract: The mechanism of the control of citric acid accumulation by oxygen was investigated by means of pilot plant fermentation using Aspergillus niger. The critical dissolved oxygen tension (DOT) for oxygen uptake of this fungus was about 18–21 and 23–26 mbar for trophophase and idiophase, respectively. Minimal DOT for citric acid production was about 25 mbar. Citric acid production increased steadily between 40–150 mbar. Short time changes in the DOT produced immediate, irreversible changes in the rate of product formation. Adenine nucleotides paralleled growth but showed no evidence for control function in the oxygen effect on citric acid fermentation. A branched respiratory system was identified by experiments using specific inhibitors (antimycin, cyanide, azide, rotenone, amytal and salicylhydroxamic acid). Growth was sensitive towards inhibitors of the standard respiratory chain, but only slightly sensitive towards salicylhydroxamic acid (SHAM). Citric acid synthesis was highly sensitive towards SHAM during trophophase, but sensitive towards antimycine during idiophase. Interruptions in aeration cause an impairment of the SHAM sensitive oxidase during trophophase, and of the antimycin sensitive oxidase during idiophase.

Ethanol production with an immobilized cell reactor

Abstract: Ethanol is produced from cellulosic material such as corn stover by treating the cellulosic material in a first hydrolysis stage with a dilute acid solution to hydrolyze pentosans to xylose, separating solids from the resultant hydrolysate, treating the solids in a second hydrolysis stage with a concentrated acid solution to hydrolyze hexosans to glucose, and fermenting the glucose to ethanol by passing a solution of the glucose over a fixed film of yeast prepared by attaching yeast with a polyfunctional agent to a proteinaceous material coated on a solid support. The use of a first hydrolysis stage avoids the production of furfural which is toxic and inhibits yeast fermentation. Xylose produced from the first stage may also be fermented to ethanol with the fixed film of yeast.

Method for producing L-lysine by fermentation

Abstract: An L-lysine producing microorganism which is obtained by incorporation into a host strain of the genus Escherichia of a hybrid plasmid having inserted therein a DNA fragment with genetic information controlling L-lysine production which is derived from a donor strain which is resistant to an L-lysine analogue, is useful for the production of high levels of L-lysine by fermentation

Effect of Anaerobiosis on Rice Seedlings: Growth, Metabolic Rate, and Fate of Fermentation Products

Abstract: When 3 d old aerobic rice seedlings are subjected to 48 h of anaerobiosis a strong alcoholic fermentation system is induced which operates at a constant rate during the treatment. Ethanol accumulates in seedling tissues during the first hours of anaerobiosis to reach a limit value which is maintained thereafter. Of the total ethanol production during the anaerobic treatment, only 2% is accounted for by ethanol stored in tissues, the remaining 98% is found in the growth medium. Concomitant effects of anaerobiosis on seedling growth, consumption of endosperm reserves, and variations in the level of activity of alcohol dehydrogenase (ADH) and soluble proteins are reported.

Alcohol manufacturing process

Abstract: A continuous process for the production of alcohol, preferably ethanol, from cellulosic materials. The cellulosic materials are delignified such that the hemicellulose and the cellulose can be subsequently acid hydrolyzed into simple sugars. These sugars are fermented in the presence of yeast to yield ethanol and carbon dioxide. The alcohol vapor is removed from the fermentation solution under a reduced pressure and subsequently distilled. Carbon dioxide gas may be sparged throughout the fermenting solution in order to aid in the removal of the alcohol from the fermenting solution. The gaseous carbon dioxide is captured and utilized in the manufacture of additional quantities of ethanol or other basic chemicals.

Current biological research in conversion of cellulosic carbohydrates into liquid fuels: how far have we come

Abstract: Current developments in the conversion of cellulosic carbohydrates into liquid fuels are reviewed. Four processes using mixed microbial cultures are described that directly convert cellulose and hemicellulose to ethanol. The production of sugars, which are converted to liquid fuels by fermentation, by dilute acid hydrolysis are described together with yeast fermentation of starch-derived glucose to ethanol. It is predicted that the most significant advances towards biological production of liquid fuels from cellulosic carbohydrates will occur through the discovery of new microorganisms with expanded genetic versatilities and altered membrane compositions. 125 references.

Production of n-butanol from whey filtrate using clostridium acetobutylicum N.C.I.B. 2951

Abstract: Sulphuric acid whey filtrate has been shown to be a useful substrate for the production of n-butanol by fermentation. Using whey filtrate supplemented with 0.5% yeast extract, yields of 1.5%(w/v) n-butanol have been obtained. The ratio of butanol:acetone:ethanol products approximates 10:1:1.

Process for making fermentable sugars and high-protein products

Abstract: Disclosed is a dry or wet milling process for making fermentable sugars and high-protein products from starch bearing material, characterized by saccharification of the starch followed by recovery of fiber and other non-protein materials and of destarched protein as separate products, leaving a sugar solution that is essentially free of insoluble materials. The sugars are fermented to ethanol and carbon dioxide by the action of added yeast. After fermentation, the yeast is recovered for use in fermenting additional quantities of sugars supplied either for batch or continuous processing. The alcohol is then removed leaving a dilute solution of unfermentable soluble materials, and this liquid, in whole or in part, is recycled to preceding steps in the process.

Effect of environmental pH on fermentation balance of Lactobacillus bulgaricus.

Abstract: When Lactobacillus bulgaricus NLS-4 was grown anaerobically in continuous culture with limiting glucose, a shift in the pH of the medium from the acidic to the alkaline range caused this normally homofermentative bacterium to catabolize glucose in a heterofermentative fashion. The change in the nature of the fermentation was accompanied by a decrease in lactate dehydrogenase biosynthesis in alkaline conditions. The lactate dehydrogenase from this organism did not require fructose 1,6-diphosphate or manganese ions (Mn2+) for catalytic activity. Involvement of the phosphoroclastic split in the pyruvate conversion in an alkaline environment was also confirmed. The high lactate dehydrogenase synthesis in acidic medium together with the participation of the phosphoroclastic split under alkaline conditions may explain the shift from homolactic to heterolactic fermentation of L. bulgaricus NLS-4 with the change of environmental pH.

The Reversible Dehydration of (R)‐2‐Hydroxyglutarate to (E)‐Glutaconate

Abstract: 1. During fermentation with whole cells of Acidaminococcus fermentans or Clostridium microsporum the pro-3S hydrogen of (R)-2-hydroxyglutarate or of its precursor (S)-glutamate is eliminated stereospecifically. Since (E)-glutaconate but not its Z isomer is fermented by whole cells or cell-free extracts of A. fermentans, the overall dehydration of (R)-2-hydroxyglutarate to (E)-glutaconate can be described as syn. 2. The fermentation of (E)-glutaconate required acetyl phophate, CoA and NAD, that of (S)-glutamate or (R)-2-hydroxyglutarate additionally MgCl2, FeSO4 and dithioerythritol. The fermentations of all three substrates were inhibited by avidin and stimulated by biotin. 3. The hydration of (E)-glutaconate was measured enzymically by the formation of (R)-2-hydroxyglutarate. The dehydration of the hydroxy acid was assayed by the release of 3HOH from (2R)-2-hydroxy[3-3H]glutarate. Optimum conditions were found by activation of the cell-free extract with MgCl2, FeSO4, dithioerythritol, acetyl phosphate anmd NADH followed by the reaction which only required acetyl phosphate and CoA as cofactors. Activation and reaction had to be performed anaerobically. 4. The dehydration was inhibited by 2 mM azide, 1 mM arsenate, 1 mM hydroxylamine, 20 micro M dinitrophenol or 10 micro M carbonylcyanide p-trifluoromethoxyphenylhydrazone. 5. It is concluded that the actual substrates of the dehydration are the corresponding thiol esters. The data indicate a catalytical phosphorylation during the reaction.

Effects of controlled gas environments in solid-substrate fermentations of rice

Abstract: The gas environment is solid-substrate fermentations of rice significantly affected levels of biomass and enzyme formation by a fungal species screened for high amylase production. Constant oxygen and carbon dioxide partial pressures were maintained at various levels in fermentations by Aspergillus oryzae. Control of the gas phase was maintained by a “static” aeration system admitting oxygen on demand and stripping excess carbon dioxide during fermentation. Constant water vapor pressures were also maintained by means of saturated salt solutions. High Oxygen pressures stimulated amylase productivity significantly. On the other hand, amylase production was severely inhibited at high carbon dioxide pressures. While relatively insensitive to oxygen pressure, maximum biomass productivities were obtained at an intermediate carbon dioxide pressure. High oxygen transfer rates were obtained at elevated oxygen pressures, suggesting, in view of the stimulatory effect of oxygen on amylase production, a stringent oxygen requirement for enzyme synthesis. Solid-substrate fermentations were highly advantageous as compared with submerged cultures in similar gas environments. Not only were amylase productivities significantly higher, but the enzyme was highly concentration in the aqueous phase of the semisolid substrate particles and could be extracted in a small volume of liquid. Results of this work suggest that biomass and product formation in microbial processes may be amenable to control by the gas environment. This is believed to offer an interesting potential for optimizing selected industrial fermentation processes with respect to productivity and energy consumption.

Extracellular microbial polysaccharides: Kinetics of Pseudomonas sp., Azotobacter vinelandii, and Aureobasidium pullulans batch fermentations

Abstract: The generality of a fermentation kinetic model (developed earlier for xanthan gum production by Xanthamonas campestris) is tested by application to several other polysaccharide-producing fermentations. With literature batch data for exopolysac-charides from Azotobacter vinelandii, Pseudomonas sp., and Aureobasidium pullulans, the model is shown to provide a reasonable description for biomass (X), product (polysaccharide, P), and substrate (S) evolution in time. Thus a general kinetic model for microbial fermentations that produce exopolysaccharides is established.

Effects of nitrogen fertilization of grapevines on amino acid metabolism and higher-alcohol formation during grape juice fermentation.

Abstract: The nitrogen nutritional status of the grapevine can have a determining effect on higher-alcohol (n-propanol, isobutanol, isoamyl alcohol, and active amyl alcohol) concentrations in wine fermented from the juice. Concentrations of key amino acids (valine, leucine, and isoleucine) and others were measured in grape juice and wine made from Thompson Seedless grapes grown under several levels of nitrogen fertilization. Lower levels increased isobutyl, active, and isoamyl alcohol production, and lowered n-propanol production. Above nitrogen fertilization at about 112 kg/ha, higher-alcohol concentrations in the wine changed negligibly.

Iron absorption from maize ( Zea mays ) and sorghum ( Sorghum vulgare ) beer

Abstract: 1. Iron absorption from maize (Zea mays) and sorghum (Sorghum vulgare) beer was more than twelve-fold greater than from a gruel made from the constituents used to prepare the beer. 2. The effect of changes occurring during brewing were investigated. These changes include a decrease in the solid content, and the formation of 30 ml ethanol/1 and 5 ml lactic acid/1. 3. The presence of solid material was found to inhibit Fe absorption markedly, especially when the solid content was 100 g/l or more. 4. The presence of ethanol potentiated Fe absorption but the effect was only modest in gruels with a high solid content. 5. Fe absorption from a 2 ml lactic acid/l solution was four-fold greater than from a hydrochloric acid solution of the same pH. When lactic acid was added to a gruel containing 200 g solids/l the mean absorbtion rose from 0.4 to 1.2 %. 6. In a direct comparison, Fe absorption from beer was significantly better than from a gruel of similar pH containing lactic acid. 7. The results suggest that at least three factors are responsible for the enhanced Fe absorption from maize and sorghum beer. These include the removal of solids during fermentation and the presence of ethanol and of lactic acid in the final brew. 8. In order to reproduce the way in which beer is brewed domestically in Fe containers, a study was done in which beer was prepared in the presence of Fe wire. Under such circumstances Fe was rapidly dissolved and the final Fe concentration of the brew was 89 mg/l. However, the nature of the Fe-containing compound or compounds was not elucidated.

The Prediction of Fermentation Behavior by a Kinetic Model

Abstract: A general kinetic model for the prediction of the fermentation behavior of grape juices is presented. The rates of sugar utilizaton, alcohol production, yeast population growth, and temperature change are predicted for wine fermentations with the Montrachet strain (#522 UCD) of Saccharomyces cerevisiae . Unknown quantities are estimated by fitting the solution of the model to the experimental data of Castor and Archer (5). Predictions are then presented which show the influence of initial conditions such as the sugar content, must temperature and yeast inoculum strength on the fermentation behavior.

Fermentation of D-xylose by yeasts using glucose isomerase in the medium to convert D-xylose to D-xylulose

Abstract: A method to obtain the fermentative conversion by yeasts of D-xylose to ethanol is described. The method depends on a combination of two factors; (1) the ability of glucose isomerase to isomerise D-xylose to D-xylulose and (2) the ability of a number of yeasts to ferment D-xylulose.

The effect of fermentation temperature on the quality parameters and price evaluation of Central African black teas

Abstract: Tea was fermented at 15, 25 and 35°C and otherwise manufactured according to commercial practice on several occasions in early May and mid-November 1977. Fermentation at 15°C resulted in teas containing greater amounts of the desirable theaflavin class of pigments. Teas produced at the higher temperatures contained more of the thearubigin pigments, including the polymeric fraction known as the non-dialysable material. Colour development was also more rapid at 25 and 35°C. Teas produced at the low temperature were accorded higher evaluation and a linear relationship between evaluation and theaflavin content was established which explained > 70% of the variation in value data. It is suggested that, since the price premium for quality is high and the market stable, the installation of temperature control equipment to regulate the production of oxidation products would improve the quality of the product and benefit Central African tea industry.