Showing papers on "Fermentation published in 1995"

Technological and economic potential of poly(lactic acid) and lactic acid derivatives

Abstract: Lactic acid has been an intermediate-volume specialty chemical (world production ∼ 40,000 tons/yr) used in a wide range of food processing and industrial applications. Lactic acid has the potential of becoming a very large volume, commodity-chemical intermediate produced from renewable carbohydrates for use as feedstocks for biodegradable polymers, oxygenated chemicals, plant growth regulators, environmentally friendly ‘green’ solvents, and specialty chemical intermediates. The recent announcements of new development-scale plants for producing lactic acid and polymer intermediates by major U.S. companies, such as Cargill, Ecochem (DuPont/ConAgra), and Archer Daniels Midland, attest to this potential. In the past, efficient and economical technologies for the recovery and purification of lactic acid from crude fermentation broths and the conversion of lactic acid to the chemical or polymer intermediates had been the key technology impediments and main process cost centers. The development and deployment of novel separations technologies, such as electrodialysis (ED) with bipolar membranes, extractive distillations integrated with fermentation, and chemical conversion, can enable low-cost production with continuous processes in large-scale operations. The use of bipolar ED can virtually eliminate the salt or gypsum waste produced in the current lactic acid processes. Thus, the emerging technologies can use environmentally sound processes to produce environmentally useful products from lactic acid. The process economics of some of these processes and products can also be quite attractive. In this paper, the recent technical advances in lactic and polyactic acid processes are discussed. The economic potential and manufacturing cost estimates of several products and process options are presented. The technical accomplishments at Argonne National Laboratory (ANL) and the future directions of this program at ANL are discussed.

Acid adaptation of Escherichia coli O157:H7 increases survival in acidic foods.

Abstract: Escherichia coli O157:H7 was adapted to acid by culturing for one to two doublings at pH 5.0. Acid-adapted cells had an increased resistance to lactic acid, survived better than nonadapted cells during a sausage fermentation, and showed enhanced survival in shredded dry salami (pH 5.0) and apple cider (pH 3.4). Acid adaptation is important for the survival of E. coli O157:H7 in acidic foods and should be considered a prerequisite for inocula used in food challenge studies.

The influence of Brettanomyces/dekkera sp. yeasts and lactic acid bacteria on the ethylphenol content of red wines

Abstract: The ability of various lactic acid bacteria isolated from wine to synthesize volatile phenols from trans p -coumaric and ferulic acid was studied in a model medium and compared with that of Saccharomyces cerevisiae and Dekkera intermedia . Quantitative analysis of the produced vinylphenols and ethylphenols showed that some strains of Lactobacillus brevis and Pediococcus pentosaceus were capable of decarboxylating p -coumaric acid to form 4-vinylphenol as actively as S. cerevisiae , whereas the same bacteria had a much less marked effect on ferulic acid. The other bacteria, Leuconostoc oenos in particular, only synthesize very small quantities of vinylphenols. Apart from Lactobacillus plantarum , none of the other lactic acid bacteria studied released any significant quantities of ethylphenols during culture. However, the quantities of ethylphenols produced by L. plantarum were still very small compared to those formed by D. intermedia and have no negative impact whatsoever on the wine9s aroma. The influence of lactic acid bacteria on the volatile phenol content of wine is, therefore, very restricted. These findings confirm that Brettanomyces/Dekkera are responsible for the development of a phenolic character in red wines. These yeasts multiply by fermenting the small quantities of residual sugars (glucose, fructose, galactose, and trehalose) in the wine. The fermentation of barely 275 mg/ L of sugars, much less than the normal residual sugar level of new red wine at the end of the usual fermentation process, is sufficient to synthesize an excessive quantity of ethylphenols with alteration of the aromatic quality of the wine.

Sourdough Fermentation or Addition of Organic Acids or Corresponding Salts to Bread Improves Nutritional Properties of Starch in Healthy Humans

Abstract: Postprandial blood glucose and insulin responses to barley bread containing organic acids or corresponding salts were evaluated in healthy human subjects. The satiety score and the rate and extent of in vitro starch digestion were also studied. Lactic acid was generated by use of a homofermentative starter culture or added to the dough. In addition, products were baked with Ca-lactate, or with Na-propionate at two different concentrations. Consumption of the product baked with a high concentration of Na-propionate significantly lowered the postprandial blood glucose and insulin responses, and significantly prolonged the duration of satiety compared with all other breads. When subjects consumed the breads baked with sourdough, lactic acid and Na-propionate, their glucose and insulin responses were reduced compared with the wholemeal bread alone. The rate of in vitro amylolysis was reduced only by ingestion of the breads containing lactic acid, suggesting that the beneficial impact of Na-propionate on metabolic responses and satiety was related to effects other than a reduced rate of starch hydrolysis. All bread products had a similar concentration of in vitro resistant starch of 1.3-2.1 g/100 g (starch basis). It is concluded that sourdough baking and other fermentation processes may improve the nutritional features of starch. The results also demonstrate that certain salts of organic acids may have metabolic effects.

Amino Acid and Ammonium Utilization by Saccharomyces cerevisiae Wine Yeasts From a Chemically Defined Medium

Abstract: The utilization of amino acids and ammonium by nine wine strains of Saccharomyces cerevisiae was systematically studied in a chemically defined medium resembling the composition of grape juice. Both quantitative and qualitative differences in the utilization of assimilable nitrogen were observed. The mean concentration of total nitrogen utilized during the catabolism of 1.11 M (200 g/L) glucose when all amino acids were in excess was 400 mg N/L with a range of 140 mg N/L. Nitrogen utilization was influenced by the presence of air in the fermentation headspace, ammonium supplementation and initial glucose concentration. The kinetics of utilization of individual amino acids varied between strains. However, arginine, serine, glutamate, threonine, aspartate and lysine typically comprised the bulk of the nitrogen consumed. Addition of ammonium delayed and reduced the extent of accumulation of most amino acids but increased the total nitrogen consumed.

Lignin Peroxidases, Manganese Peroxidases, and Other Ligninolytic Enzymes Produced by Phlebia radiata during Solid-State Fermentation of Wheat Straw

Abstract: The white rot fungus Phlebia radiata 79 (ATCC 64658) produces lignin peroxidase (LiP), manganese peroxidase (MnP), glyoxal oxidase (GLOX), and laccase in the commonly used glucose low-nitrogen liquid medium. However, the enzymes which this fungus utilizes for selective removal of lignin during degradation of different lignocellulosic substrates have not been studied before. Multiple forms of LiP, MnP, GLOX, and laccase were purified from P. radiata culture extracts obtained after solid-state fermentation of wheat straw. However, the patterns of extracellular lignin-modifying enzymes studied were different from those of the enzymes usually found in liquid cultures of P. radiata. Three LiP isoforms were purified. The major LiP isoform from solid-state cultivation was LiP2. LiP3, which has usually been described as the major isoenzyme in liquid cultures, was not expressed during straw fermentation. New MnP isoforms have been detected in addition to the previously reported MnPs. GLOX was secreted in rather high amounts simultaneously with LiP during the first 2 weeks of growth. GLOX purified from P. radiata showed multiple forms, with pIs ranging from 4.0 to 4.6 and with a molecular mass of ca. 68 kDa.

The formation of biogenic amines by fermentation organisms

Abstract: A total of 523 strains representing 35 species related to food fermentation organisms of practical importance were investigated for their potential for formation of biogenic amines (BA). The investigation was performed with resting cells in phosphate buffer (pH 5.5) and the formation of the following BAs was followed: putrescine, cadaverine, histamine, tyramine and 2-phenylethylamine. No potential was observed in species of lactococcus, Leuconostoc, Pediococcus, Streptococcus and several Lactobacillus spp., such as L. Pentosus and L. sake. A remarkable potential to form BA was observed in strains of carnobacteria, Lactobacillus buchneri, L. curvatus, L. reuteri, Staphylococcus carnosus and, to a lesser extent, in L. alimentarius, L. brevis, L. bavaricus, L. delbrueckii ssp. lactis, Micrococcus spp. and S. piscifermentans. In well known species with a practical function in the fermentation of dairy products, wine or cabbage a potential was observed for few strains only. In view of their role as starters in food fermentation, or their potential use in protective cultures and as probiotics, BA formation by the organisms has to be taken into consideration by selecting appropriate strains.

Production and properties of three pectinolytic activities produced by Aspergillus niger in submerged and solid-state fermentation

Abstract: Three extracellular pectinases were produced byAspergillus niger CH4 by submerged and solid-state fermentation, and their physicochemical and kinetic properties were studied. The highest productivities of endo- and exo-pectinase and pectin lyase were obtained with solid-state fermentation. The kinetic and physicochemical properties of these enzymes were influenced by the type of culture method used. All activities were very different in terms of pH and temperature optima, stability at different pH and temperature values and affinity for the substrate (K m values). In solid-state fermentation, all pectinase activities were more stable at extreme pH and temperature values but theK m values of endo-pectinase and pectin lyase were higher with respect to those activities obtained by the submerged-culture technique. The pectin lyase activity obtained by the submerged-culture technique showed substrate inhibition but the enzyme obtained by solid-state fermentation did not. Electrophoresis, using sodium dodecyl sulphate/polyacrylamide gel with enzymatic extracts obtained for both culture methods, showed the same number on protein bands but some differences were found in their electrophoretic position. The results obtained in this work suggest that the culture method (submerged or solid-state) may be responsible for inducing changes in some of the pectinolytic enzymes produced byA. niger.

The genus Lactococcus

Abstract: Lactococci are coccoid Gram-positive, anaerobic bacteria which produce l(+)-lactic acid from lactose in spontaneously fermented raw milk which is left at ambient temperatures around 20–30°C for 10–20 h. They are commonly called ‘mesophilic lactic streptococci’. It is tempting to suggest that the first isolation, identification and description of the chemical entity lactic acid by Carl Wilhelm Scheele from sour milk in Sweden in the year 1780, was actually l (+)-lactic acid produced by lactococci. The microbial nature of lactic fermentation was recognized in 1857 by Louis Pasteur. The first bacterial pure culture on earth, obtained and scientifically described by Joseph Lister (1873) was Lactococcus lactis, at that time called: ‘Bacterium lactis’. Admitting then that we had here to deal with only one bacterium, it presents such peculiarities both morphologically and physiologically as to justify us, I think, in regarding it a definite and recognizable species for which I venture to suggest the name Bacterium lactis. This I do with diffidence, believing that up to this time no bacterium has been defined by reliable characters. Whether this is the only bacterium that can occasion the lactic acid fermentation, I am not prepared to say.

Differential importance of trehalose in stress resistance in fermenting and nonfermenting Saccharomyces cerevisiae cells.

Abstract: The trehalose content in laboratory and industrial baker's yeast is widely believed to be a major determinant of stress resistance. Fresh and dried baker's yeast is cultured to obtain a trehalose content of more than 10% of the dry weight. Initiation of fermentation, e.g., during dough preparation, is associated with a rapid loss of stress resistance and a rapid mobilization of trehalose. Using specific Saccharomyces cerevisiae mutants affected in trehalose metabolism, we confirm the correlation between trehalose content and stress resistance but only in the absence of fermentation. We demonstrate that both phenomena can be dissociated clearly once the cells initiate fermentation. This was accomplished both for cells with moderate trehalose levels grown under laboratory conditions and for cells with trehalose contents higher than 10% obtained under pilot-scale conditions. Retention of a high trehalose level during fermentation also does not prevent the loss of fermentation capacity during preparation of frozen doughs. Although higher trehalose levels are always correlated with higher stress resistance before the addition of fermentable sugar, our results show that the initiation of fermentation causes the disappearance of any other factor(s) required for the maintenance of stress resistance, even in the presence of a high trehalose content.

Method for making succinic acid, bacterial variants for use in the process, and methods for obtaining variants

Abstract: A method for producing succinic acid in high concentration by fermentation employs a variant of strain 130Z which is resistant to concentrations of about 1 g/l to about 8 g/l of sodium monofluoroacetate The variant produces succinic acid in concentrations of about 80 g/l to about 110 g/l and the fermentation product contains less formic and acetic acids than the product obtained using the parent strain under identical conditions The novel variants and a method of obtaining such variants also are described

Preventing in vitro lactate accumulation in ruminal fermentations by inoculation with Megasphaera elsdenii

Abstract: In vitro fermentations containing a mixed culture of ruminal bacteria (ruminal fluid from a hay-fed steer), buffer, and primarily rapidly degradable substrates (starch, glucose, cellulose, cellobiose, and trypticase) were inoculated with an overnight culture of Megasphaera elsdenii B159. Triplicate flasks were either uninoculated or inoculated to obtain a final concentration of 8.7 x 10(5) and 8.7 x 10(6) colony forming units of M. elsdenii per milliliter of culture fluid. Inoculation with M. elsdenii prevented an accumulation of lactic acid and excessive drop in pH. Lactate peaked at more than 40 mM in untreated cultures. In cultures inoculated with a low dose of M. elsdenii, lactate concentration peaked at approximately 25 mM at 5 h of fermentation but decreased rapidly to less than 5 mM by 7 h of fermentation. With the addition of the high dose of M. elsdenii, lactate was never greater than 2 mM (P < .05) throughout fermentation. Cultures treated with M. elsdenii had greater amounts (P < .05) of isobutyrate, butyrate, isovalerate, and valerate than untreated cultures. After 24 h of fermentation, one-half of the culture fluid was transferred to an equal volume of fresh buffer with substrate but was not inoculated with further quantities of M. elsdenii. Six hours after transfer, cultures that had been originally treated with M. elsdenii had lower (P < .05) amounts of lactate than untreated cultures. Inoculation with M. elsdenii has potential to prevent lactate accumulation in diets containing readily fermentable carbohydrates.

Production of poly(D‐3‐hydroxybutyrate) from CO2, H2, and O2 by high cell density autotrophic cultivation of Alcaligenes eutrophus

Abstract: Hydrogen-oxidizing bacterium, Alcaligenes eutrophus autotrophically produces biodegradable plastic material, poly(D-3-hydroxybutyrate), P(3HB), from carbon dioxide, hydrogen, and oxygen. In autotrophic cultivation of the microorganism, it is essential to eliminate possible occurrence of gas explosions from the fermentation process. We developed a bench-plant scale, recycled-gas, closed-circuit culture system equipped with several safety features to perform autotrophic cultivation of A. eutrophus by maintaining the oxygen concentration in the substrate gas phase below the lower limit for a gas explosion (6.9%). The culture vessel utilized a baskettype agitator, resulting in a K(L) a value of 2970 h(-1). Oxygen gas was also directly fed to the fermentor separately from the other gases. As a result, 91.3 g . dm(-3) of the cells and 61.9 g . dm(-3) of P(3HB) were obtained after 40 h of cultivation under this oxygen-limited condition. The results compared favorably with those reported for mass production of P(3HB) by heterotrophic fermentation. (c) 1995 John Wiley & Sons, Inc.

The growth kinetics and fermentation behaviour of some non-Saccharomyces yeasts associated with wine-making

Abstract: The growth kinetics and fermentation behaviour of five non-Saccharomyces yeast species associated with wine-making were evaluated.The results showed that the Candida stellata and Torulspora delbrueckii species are interesting for biotechnological applications in wine-making, whereas small-size apiculate yeasts could be profitably used in the production of wine for vinegar manufacture.

Fermentation of raw glycerol to 1,3-propanediol by new strains of Clostridium butyricum

Abstract: Industrial glycerol obtained through the transesterification process using rapeseed oil did not support growth of several strains ofClostridium butyricum obtained from bacterial culture collections. Ten new strains ofC. butyricum were obtained from mud samples from a river, a stagnant pond, and a dry canal. These new isolates fermented the commercial glycerol and produced 1,3-propanediol as a major fermentation product with concomitant production of acetic and butyric acids. Four of the ten isolates were able to grow on industrial glycerol obtained from rapeseed oil. One strain,C. butyricum E5, was very resistant to high levels of glycerol and 1,3-propanediol. Using fed-batch fermentation, 109 g L−1 of industrial glycerol were converted into 58 g of 1,3-propanediol, 2.2 g of acetate and 6.1 g of butyrate per liter.

Aerobic and anaerobic starvation metabolism in methanotrophic bacteria.

Abstract: The capacity for anaerobic metabolism of endogenous and selected exogenous substrates in carbon- and energy-starved methanotrophic bacteria was examined. The methanotrophic isolate strain WP 12 survived extended starvation under anoxic conditions while metabolizing 10-fold less endogenous substrate than did parallel cultures starved under oxic conditions. During aerobic starvation, the cell biomass decreased by 25% and protein and lipids were the preferred endogenous substrates. Aerobic protein degradation (24% of total protein) took place almost exclusively during the initial 24 h of starvation. Metabolized carbon was recovered mainly as CO(inf2) during aerobic starvation. In contrast, cell biomass decreased by only 2.4% during anaerobic starvation, and metabolized carbon was recovered mainly as organic solutes in the starvation medium. During anaerobic starvation, only the concentration of intracellular low-molecular-weight compounds decreased, whereas no significant changes were measured for cellular protein, lipids, polysaccharides, and nucleic acids. Strain WP 12 was also capable of a limited anaerobic glucose metabolism in the absence of added electron acceptors. Small amounts of CO(inf2) and organic acids, including acetate, were produced from exogenous glucose under anoxic conditions. Addition of potential anaerobic electron acceptors (fumarate, nitrate, nitrite, or sulfate) to starved cultures of the methanotrophs Methylobacter albus BG8, Methylosinus trichosporium OB3b, and strain WP 12 did not stimulate anaerobic survival. However, anaerobic starvation of these bacteria generally resulted in better survival than did aerobic starvation. The results suggest that methanotrophic bacteria can enter a state of anaerobic dormancy accompanied by a severe attenuation of endogenous metabolism. In this state, maintenance requirements are presumably provided for by fermentation of certain endogenous substrates. In addition, low-level catabolism of exogenous substrates may support long-term anaerobic survival of some methanotrophic bacteria.

Hydrogen production from continuous fermentation of xylose during growth of Clostridium sp. strain No.2

Abstract: Experimental conditions are presented for continuous fermentation of xylose and glucose to hydrogen (H2), using Clostridium sp. strain No. 2 growing in 300 mL of culture containing 0.3% substrate, either without pH control or with the pH controlled at 6.0. The H2 production rate increased in proportion to increasing dilution rate within the range of about 0.4 to 1.0 h−1. The maximal H2 production rates of 21.03 and 20.40 mmol∙h−1∙L−1 were obtained from xylose and glucose with dilution rates of 0.96 and 1.16 h−1, respectively, at pH 6.0. About 2.06 mol H2 with a dilution rate of 0.21 h−1 at pH 6.0 and 2.36 mol H2 with a dilution rate of 0.18 h−1 were formed per mole of xylose and glucose consumed, respectively, at uncontrolled pH.Key words: hydrogen production, continuous fermentation, xylose, Clostridium sp. strain no. 2.

Effect of acetic acid on xylose fermentation to xylitol by Candida guilliermondii.

Abstract: The effect of acetic acid concentration on xylose fermentation to xylitol by Candida guilliermondii FTI 20037 was evaluated in semisynthetic medium containing different concentrations of the acid. Increasing acetic acid concentration up to 1.0 g/1 favored xylitol yield and productivity, with maximum values of 0.82 g/g and 0.57 g/.h1, respectively. The presence of acetic acid reduced cell production at all concentration. Furthermore, acetic acid was assimilated by the yeast together with the sugars and was depleted from the medium at concentrations of less than 3.0 g/1. The ability of this yeast to assimilate acetic acid suggests that these cells act as agents of medium detoxification. This behavior may lead to a viable microbiological process of xylitol production by C. guilliermondii FTI 20037 using xylose-rich lignocel-lulosic hydrolysates in which acetic acid is commonly present, causing inhibition of fermentative activity.