Rapid Fermentation Research Articles

Studies on immobilized Saccharomyces cerevisiae. I. Analysis of continuous rapid ethanol fermentation in immobilized cell reactor

Rapid fermentation of cane molasses into ethanol has been studied in batch, continuous (free-cell and cell-immobilized systems) by a strain of Saccharomyces cerevisiae at temperature 30 degrees C and pH 5.0. The maximum productivity of ethanol obtained in immobilized system was 28.6 g L(-1) h(-1). The cells were immobilized by natural mode on a carrier of natural origin and retention of 0.132 g cells/g carrier was achieved. The immobilized-cell column was operated continuously at steady state over a period of 35 days. Based on the parameter data monitored from the system, mathematical analysis has been made and rate equations proposed, and the values of specific productivity of ethanol and specific growth rate for immobilized cells computed. It has been established that immobilized cells exhibit higher specific rate of ethanol formation compared to free cells but the specific growth rate appears to be comparatively low. The yield of ethanol in the immobilized-cell system is also higher than in the free-cell system.

Studies on immobilized Saccharomyces cerevisiae. III. Physiology of growth and metabolism on various supports

In earlier communications general analyses of rapid ethanol fermentation by Saccharomyces cerevisiae immobilized on inert supports were described. In this article physiology of growth and metabolism (parameters like rates of CO(2) evolution and O(2) uptake, respiratory quotient, and generation time) of Saccharomyces cerevisiae immobilized on different supports are reported. Values of the ratio of specific oxygen uptake rate for immobilized cells to free cells have been found to be 0.732, 0.781 and 0.785 for carrier A, carrier B, and covalently crosslinked controlled pore glass (CPG, specific surface area of 439 m(2) g(-1)), respectively. Rates of specific CO(2) evolution for immobilized cells to free cells for these supports are 0.784, 0.822, and 0.783, respectively. Marked reduction in generation time of Saccharomyces cerevisiae on all the supports has been observed. No change in size (4.8-5 microm) and specific growth rate (micro(m) = 0.275 h(-1)) of cells leaving the reactor has been observed.

9.6 Grass Silages Ensiled with Either Formic Acid or a Lactobacillus Preparation and their Digestion by Jersey Cattle

The use of silage additives containing lactic acid bacteria and enzymes to promote a rapid homolactic type fermentation has met with some success in the United States but the little evidence available (see Burghardi, Goodrich and Meiske, 1980) suggests that, for grass silages, the value of this type of additive is limited. However, in laboratory silos, inoculation with lactic acid bacteria has been shown to be effective in reducing proteolysis (Carpintero, Henderson and McDonald, 1979).The recent availability in the UK of a commercial product containing a lactic acid bacteria inoculum and the non-toxicity and ease of application of this product prompted this investigation, which describes the assessment of a silage prepared with this type of additive in comparison with a well characterized additive, formic acid.

Fate of Salmonella newport and Salmonella typhimurium Inoculated into Summer Sausage

Various fermentation schedules and finishing temperatures used in the summer sausage industry were investigated for their ability to eliminate Salmonella newport or Salmonella typhimurium inoculated into raw ingredients during the formulation phase of production. Summer sausage was produced with and without the aid of a starter culture. Use of the starter culture, a Lactobacillus plantarum strain, provided for a more rapid fermentation and subsequent decrease in pH. Elimination of Salmonella was dependent upon the initial contamination level, serotype involved, rate of fermentation and processing temperature.

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Use of the rapid fermentation test in determining carbohydrate reactions of fastidious bacteria in clinical laboratories.

The rapid fermentation test was used to determine the carbohydrate reactions of some of the fastidious bacteria encountered in clinical laboratories, such as: Haemophilus species, including Haemophilus vaginalis; Actinobacillus actinomycetemcomitans; Cardiobacterium hominis; Kingella species; Corynebacterium species; Propionibacterium species; and Erysipelothrix rhusiopathiae. Results were usually obtained within 4 h by using inocula from 24- or 48-h blood or chocolate agar media.

Rapid ethanol fermentation in immobilized yeast cell reactor

Rapid ethanol fermentation in immobilized yeast cell reactor

Comparison ofLeuconostoc OenosStrains ML-34 and PSU-1 to Induce Malo-Lactic Fermentation in Pennsylvania Red Table Wines

<i>Leuconostoc oenos</i> strains ML-34 and PSU-1 were compared for their ability to induce a rapid malo-lactic fermentation following pure culture inoculation into Pennsylvania red table wines. PSU-1 consistently induced malo-lactic fermentation faster than ML-34 in wines made using the traditional method of color extraction from both French-American hybrid and <i>Vitis vinifera</i> varieties grown under eastern conditions. PSU-1 also induced malo-lactic fermentation more rapidly than ML-34 in wines made using several variations in the hot-press method of color extraction. The fastest rates of malo-lactic fermentation were observed in wines made without the addition of pectic enzyme or sulfur dioxide. The differences in time required for complete malo-lactic fermentation between wines inoculated with the two bacterial strains were rather consistent and were greater in those wines made without treatment with pectic enzyme.

Rapid ethanol fermentation of cellulose hydrolysate. I. Batch versus continuous systems

AbstractRapid fermentation of bagasse hydrolysate to ethanol under anaerobic conditions by a strain of Saccharomyces cerevisiae has been studied in batch and continuous cultures at pH 4.0 and 30°C temperature with cell recycle. By using a 23.6 g/liter cell concentration, a concentation of 9.7% (w/v)ethanol was developed in a period of 6 hr. The rate of fermentation was found to increase with supplementation of yeast vitamins in the hydrolysate. In continuous culture employing cell recycle and a 0.127 v/v/m air flow rate, a cell mass concentration of 48.5 g/liter has been achieved. The maximum fermentor productivity of ethanol obtained under these conditions was 32.0 g/liter/hr, which is nearly 7.5 times higher than the normal continuous process without cell recycle and air sparging. The ethanol productivity was found to decrease linearly with ethanol concentration. Conversion of glucose in the hydrolysate to ethanol was achieved with a yield of 95 to 97% of theoretical.

Rapid ethanol fermentation of cellulose hydrolysate. II. Product and substrate inhibition and optimization of fermentor design

AbstractHigh concentrations of both ethanol and sugar in the fermentation broth inhibit the growth of yeast cells and the rate of product formation. Inhibitory effects of ethanol on the yeast strain Saccharomyces cerevisiae NRRL‐Y‐132 were studied in batch and continuous chemostat cultures. Growth was limited by either glucose or ethanol. Feed medium was supplemented with different ethanol concentrations. Ethanol was found to inhibit growth and the activity of yeast to produce ethanol in a noncompetitive manner. A linear kinetic pattern for growth and product formation was observed according to μ = μm (1 – P/Pm) and v = vm (1 – P/Pm′), where μm is the maximum specific growth rate at P = 0 (hr−1); Pm is the maximum specific product formation rate at P = 0 (hr−1); Pm is the maximum ethanol concentration above which cells do not grow (g/liter); Pm′ is the maximum ethanol concentration above which cells do not produce ethanol (g/liter). Substrate inhibition studies were carried out using short‐time experimental techniques under aerobic and anaerobic condition. The degree of substrate inhibition was found to be higher than that has been reported for ethanol fermentation of pure sugar. The kinetic relationships thus obtained were used to compute growth, substrate utilization, and alcohol production patterns and have been discussed with reference to batch and continuous fermentation of enzymatically produced bagasse hydrolysate.

Effects on Must and Wine Composition, Rates of Fermentation, and Wine Quality of Nitrogen Fertilization ofVitis ViniferaVar. Thompson Seedless Grapevines

Thompson Seedless vines were treated for three years with various levels of nitrogen fertilizer. The vineyard had not been fertilized for over seven years preceding. The clarified grape juice was analyzed for various components. The rates of fermentation, concentration of esters, and wine quality were dependent on the level of nitrogen fertilization. Fertilization with 112 kg N/ha (100 lb-N/acre) was sufficient for the juice to have a rapid fermentation and the wine to be of good quality. Juice from vines not fertilized fermented more slowly, resulted in wines of poorer quality, and was deficient in a number of chemical components.

Regulation of rumen lactate metabolism and the role of lactic acid in nutritional disorders of ruminants

This paper present recent results concerning both the role of lactate as an intermediate in rumen fermentation, and the rapid accumulation of lactic acid in ruminant “lactic acidosis” and related syndromes. Special attention is given to the factors which regulate microbial lactate formation and fermentation in the rumen. When readily fermentable carbohydrates are presented to the rumen microflora there is at first a rapid fermentation to normal end-products which include the volatile fatty acids. These cause a decrease in the pH which may fall below the critical value of 5.5. As a result changes occur in the microbial population: protozoa are killed, methanogenic bacteria and lactate fermenters are inhibited, streptococci and finally lactobacilli are selectively increased. In many anaerobic and facultative aerobic bacteria lactic acid formation is selectively increased within the cell during rapid fermentation of carbohydrate. When the rate of glycolysis is high, increased intracellular levels of fructose-1, glycolysis is high, increased intracellular levels of fructose-1, 6-diphosphate may activate the enzyme lactate dehydrogenase. The importance of the buffer capacity of rumen contents and saliva and the rate of salivation in preventing the acidic conditions within the rumen are stressed. Bicarbonate is the most important buffer component in preventing the decrease in pH. The lactate fermentation capacity of rumen contents is determined by the substrate concentration and by the diet which is fed to the animals. During adaptation to a concentrate diet or to a diet which contains lactic acid there is an increase in the number of lactilytic bacteria. Feeding lactates or lactate containing silages, although it raises the capacity of the rumen contents to ferment lactic acid, has not proved to be a satisfactory way to adapt ruminants to high-energy rations. In the case of lactate feeding this may be because a group of CO2-requiring organisms is selectively encouraged instead ofMegasphaera elsdenii, the only important lactate fermenter which is able to grow at low pH values. This hypothesis and suggestions for further work on this problem are discussed.

Oil production by fermentation of lactose and the effect of temperature on the fatty acid composition1

AbstractStrains of the yeastsCandida curvata andTrichosporon cutaneum were isolated that were able to ferment the lactose of cheese whey and ultrafiltered whey permeate to produce oil. Rapid fermentation rates and lactose utilization were achieved by the Gcurvata strains. The fermentation was more efficient on permeate than whey, because the organisms used whey protein very poorly. Methods of extracting the oil were compared, and the best results were obtained by sequential extraction with methanol and benzene or by ethanol and hexane. The fatty acid composition of the yeasts varied with the growth temperature, fermentation time, and medium. The oil was rich in 18:1, 16:0, and 18:0. The process is a technically feasible means of using whey permeate.

Use of a rapid fermentation test for identification of anaerobic bacteria

Rapid fermentation tests of carbohydrates were performed on 84 strains of anaerobic bacteria, and the result is compared with a commercially available micromultitest, API. An overall correlation of 87% was achieved between the two systems. The rapid fermentation test is easy to perform, since it is done aerobically, and easy to read. This study shows that RFT is useful in routine diagnosis of anaerobic bacteria, if it is used in combination with other relevant biochemical tests, morphologic examination, and gas chromatography.

Urine Glucose Tests for Diabetic Patients with Impaired Vision

A colorimetric test procedure called Mega-Diastix is described for detection and measurement of glucose in urine. The test is designed for use by diabetic patients with imparied vision. Data establishing the performance capabilities of this rapid, convenient test are presented. As an internal standard, the recommended procedure utilizes effervescent control tablets for preparation of simulated urine. Also described is a touch fermentation test for detection of urinary glucose by totally blind patients. Data are given that demonstrate the accuracy and ease of performance of this test, which entails a rapid yeast fermentation. An internal standard is also incorporated into the procedure for this test.

Rapid ethanol fermentations using vacuum and cell recycle

AbstractCell recycle and vacuum fermentation systems were developed for continuous ethanol production. Cell recycle was employed in both atmospheric pressure and vacuum fermentations to achieve high cell densities and rapid ethanol fermentation rates. Studies were conducted with Saccharomyces cerevisiae (ATCC No. 4126) at a fermentation temperature of 35°C. Employing a 10% glucose feed, a cell density of 50 g dry wt/liter was obtained in atmospheric‐cell recycle fermentations which produced a fermentor ethanol productivity of 29.0 g/liter‐hr. The vacuum fermentor eliminated ethanol inhibition by boiling away ethanol from the fermenting beer as it was formed. This permitted the rapid and complete fermentation of concentrated sugar solutions. At a total pressure of 50 mmHg and using a 33.4% glucose feed, ethanol productivities of 82 and 40 g/liter‐hr were achieved with the vacuum system with and without cell recycle, respectively. Fermentor ethanol productivities were thus increased as much as twelvefold over conventional continuous fermentations. In order to maintain a viable yeast culture in the vacuum fermentor, a bleed of fermented broth had to be continuously withdrawn to remove nonvolatile compounds. It was also necessary to sparge the vacuum fermentor with pure oxygen to satisfy the trace oxygen requirement of the fermenting yeast.

Regulation of Lactose Fermentation in Group N Streptococci

Group N streptococci, which have the lactose phosphoenolpyruvate (PEP)-dependent phosphotransferase system (PTS) and phospho-beta-d-galactosidase (beta-Pgal), grew rapidly on lactose and converted more than 90% of the sugar to l-lactate. In contrast, Streptococcus lactis 7962, which does not have a beta-Pgal, grew slowly on lactose and converted only 15% of the sugar to l-lactate. With glucose and galactose, this strain had growth rates and fermentation patterns similar to those of other S. lactis strains, suggesting that the rapid and homolactic fermentation of lactose that is characteristic of group N streptococci is dependent upon a functional PEP-dependent PTS and the presence of beta-Pgal. Seventeen strains of group N streptococci were examined for the activator specificities of pyruvate kinase and lactate dehydrogenase. The properties of each enzyme from all the strains, including S. lactis 7962, were similar. Pyruvate kinase had a broad activator specificity, whereas activation of lactate dehydrogenase was specific for ketohexose diphosphate. All intermediates of lactose metabolism from the hexose phosphates to the triose phosphates activated pyruvate kinase. No activation was obtained with adenosine 5'-monophosphate. K and Mg were required for pyruvate kinase activity but could be replaced by NH(4) and Mn, respectively. Lactate dehydrogenase was activated equally by fructose-1,6-diphosphate and tagatose-1,6-diphosphate, the activation characteristics being pH dependent. The roles of pyruvate kinase and lactate dehydrogenase in the regulation of lactose fermentation by group N streptococci are discussed.

Instability and linkage of silver resistance, lactose fermentation, and colony structure in Enterobacter cloacae from burn wounds.

A strain of Enterobacter cloacae from a burn wound has displayed unstable resistance to silver nitrate and a linkage of this characteristic to that for rapid lactose fermentation and mucoidcolony structure. Attempts to demonstrate transferability of these unstable determinants gave negative results.

Influence of the rate of ethanol production and accumulation on the viability of Saccharomyces cerevisiae in "rapid fermentation".

Whereas "rapid fermentation" of diluted clover honey (25 degrees Brix) fortified with yeast nutrients using 8 X 10(8) brewers' yeast cells per ml resulted in an ethanol content of 9.5% (wt/vol; 12% vol/vol) in 3 h at 30 C, death rate of the yeast cells during this period was essentially logarithmic. Whereas 6 h was required to reach the same ethanol content at 15 C, the yeast cells retained their viability. Using a lower cell population (6 X 10(7) cells/ml), a level at which the fermentation was no longer "rapid," the yeast cells also retained their viability at 30 C. Ethanol added to the medium was much less lethal than the same or less quantities of ethanol produced by the cell in "rapid fermentation." It was considered possible that ethanol was produced so rapidly at 30 C that it could not diffuse out of the cell as rapidly as it was formed. The hypothesis was postulated that ethanol accumulating in the cell was contributing to the high death rate at 30 C. It was found that the intracellular ethanol concentration reached a level of approximately 2 X 10(11) ethanol molecules/cell in the first 30 min of fermentation at 30 C. At 15 C, with the same cell count, intracellular ethanol concentration reached a level of approximately 4 X 10(10) ethanol molecules/cell and viability remained high. Also, at 30 C with a lower cell population (6 X 10(7) cells/ml), under which conditions fermentation was no longer "rapid," intracellular ethanol concentration reached a similar level (4 X 10(10) molecules ethanol/cell) and the cells retained their viability. Alcohol dehydrogenase (ADH) lost its activity in brewers' yeast under conditions of "rapid fermentation" at 30 C but retained its activity in cells under similar conditions at 15 C. ADH activity was also retained in fermentations at 30 C with cell populations of 6 X 10(7)/ml. It would appear that an intracellular level of about 5 X 10(10) ethanol molecules/cell is normal and that this level does not damage either cell viability or ADH activity. Higher intracellular ethanol concentrations, such as 2 X 10(11) molecules ethanol/cell (a fourfold increase in intracellular ethanol concentration), are accompanied by inactivation of ADH and loss of cell viability.

Carbohydrate fermentation plate medium for confirmation of Neisseria species.

A carbohydrate fermentation plate medium is described for rapid and reliable confirmation of Neisseria gonorrhoeae, N. meningitidis, and other Neisseria species. The medium is based on a modification of NYC (U.S. Patent 3,846,241) medium, originally designed for the isolation of pathogenic Neisseria (3). A total of 715 clinical isolates were tested for their carbohydrate fermentation reactions on the medium, in parallel with cystin-Trypticase agar medium. In 82% of the strains tested, results were in agreement on both media and 18% gave conflicting results. The NYC modification provides rapid and accurate fermentation patterns for use in routine confirmation procedures for Neisseria species.