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PubMed1979

Application of balancing methods in modeling the penicillin fermentation.

This paper shows the application of elementary balancing methods in combination with simple kinetic equations in the formulation of an unstructured model for the fed-batch process for the production of penicillin. The rate of substrate uptake is modeled with a Monod-type relationship. The specific penicillin production rate is assumed to be a function of growth rate. Hydrolysis of penicillin to penicilloic acid is assumed to be first order in penicillin. In simulations with the present model it is shown that the model, although assuming a strict relationship between specific growth rate and penicillin productivity, allows for the commonly observed lag phase in the penicillin concentration curve and the apparent separation between growth and production phase (idiophase-trophophase concept). Furthermore it is shown that the feed rate profile during fermentation is of vital importance in the realization of a high production rate throughout the duration of the fermentation. It is emphasized that the method of modeling presented may also prove rewarding for an analysis of fermentation processes other than the penicillin fermentation.

Chemical Phenomena↗
PubMed1989

The fate of aflatoxins during the production of "Ogiri", a West African fermented melon seed condiment from artificially contaminated seeds.

Twenty-six market samples and four laboratory-prepared samples of "ogiri" were screened for aflatoxin contamination. Aflatoxins were not detected in any of the samples. The fermented product (ogiri) was prepared with Aspergillus flavus-contaminated melon seeds. Losses of 64.7% aflatoxin B1 and 82.9% aflatoxin G1 were observed at the end of the third day of fermentation of the ground melon seeds. The samples were completely detoxified at the fourth day of fermentation. Increase in pH of the mash from 6.2 to 7.2 was observed during fermentation.

Aflatoxins↗
PubMed1994

Ethanolic fermentation in transgenic tobacco expressing Zymomonas mobilis pyruvate decarboxylase.

During oxygen limitation in higher plants, energy metabolism switches from respiration to fermentation. As part of this anaerobic response the expression of genes encoding pyruvate decarboxylase (PDC) and alcohol dehydrogenase (ADH) is strongly induced. In addition there is ample evidence for post-translational regulation. In order to understand this multi-level regulation of the anaerobic response, we provided tobacco with the constitutive capacity of ethanolic fermentation by expressing a PDC gene derived from the obligate anaerobe Zymomonas mobilis. The protein accumulated to high levels and was active in an in vitro assay. During the first 2-4 h of anoxia, acetaldehyde accumulated to 10- to 35-fold and ethanol to 8- to 20-fold higher levels than in wild-type. Under normoxic conditions no accumulation of acetaldehyde and ethanol could be measured. Instead, the two products may be immediately re-metabolized in tobacco leaf tissue. We show that aerobic fermentation takes place when the respiratory system is inhibited. Although these conditions enhance ethanolic fermentation under normoxia, they fail to increase ADH transcript levels. These results indicate that anaerobic transcription is triggered not by the metabolic consequences of oxygen limitation, but directly through an oxygen-sensing system.

Acetaldehyde↗
PubMed1993

Aeration and mixing in vortex fermenters.

The overall apparent volumetric gas-liquid mass transfer coefficient (kLa) and the mixing time (t95) were determined in a 240 dm3 vortex aerated fermenter over stirrer speed and air flow ranges of 300-800 rpm and 10-45 normal dm3 min-1, respectively. The mass transfer data obtained in an aqueous salt solution (2.5 kg m-3 NaCl in water) compared well with the measurements in a fermentation medium used in culture of certain microaerophilic bacteria. Over the ranges examined, the gas-liquid mass transfer coefficient depended only on air flow rate; the dependence was linear with flow. Mixing time declined with increasing agitation according to a power-law relationship. The mixing and mass transfer characteristics of the vortex aerated system were compared with that of a 'standard' stirred tank fermenter (27 dm3). The mixing time variations with respect to agitation rate were remarkably similar for the two types of fermenters examined.

Aerobiosis↗
PubMed1989

Hindgut fermentations in nonavian species.

A brief comparative discussion of the hindgut of insects, mammals, fishes, and reptiles includes morphology of the hindgut, general appearance, content, materials fermented, fermentation products, microorganisms involved, and value of the hindgut to the host animal. The problems faced by small animals in securing adequate energy from a hindgut fermentation to be of value to the animal are presented. It is suggested that our present analytical methods are not adequate and that new approaches to analyzing the hindgut fermentation value should be investigated, such as using fecal bacterial mass as an index. It is also suggested that experimental and commercial feeding should be designed so that herbivores are not converted to omnivores.

Animals↗
PubMed1996

Process optimization for continuous ethanol fermentation by alginate-immobilized cells of Saccharomyces cerevisiae HAU-1.

Continuous ethanol production by immobilized cells of Saccharomyces cerevisiae HAU-1 has been studied using synthetic and molasses based medium in column reactors. Immobilization of 30% yeast cells biomass (wet) in 1.5% calcium alginate gel resulted in the production of 20.8 g. l-1.h-1 alcohol at a dilution rate of 0.36 h-1 with approximately 1/3rd volume of the column reactor packed with gel beads. Optimum diameter of the beads was found to be 3.5 mm for efficient fermentation. The size of the column reactor (length to diameter ratio) also affected the productivity and fermentation efficiency due to gas hold-up and mass transfer effects. Molasses could also be fermented by this system but at a lower fermentation efficiency which could be improved, to some extent, by supplementation with nutrients.

Alginates↗
PubMed2004

Fermentative production of chemicals that can be used for polymer synthesis.

The fermentative production of chemicals that can be used as monomers for the synthesis of polymers has become an important topic in biotechnology research because of the limited nature of petroleum and environmental issues. In particular, the fermentative production of metabolites such as dicarboxylic acids, amino acids, and diols, which are suitable as building blocks for subsequent polymerization, has attracted much attention. Various wild-type and metabolically engineered microorganisms have been developed for the efficient production of these chemicals from renewable resources. In addition, the development of fermentation strategies to achieve the highest possible productivities has been another focus of research, considering that these monomers should be produced at costs low enough to compete with petroleum-derived ones. In this paper, the metabolic pathways leading to the synthesis of such important monomers including succinic acid, lactic acid, fumaric acid, propan-1,2-diol, and propan-1,3-diol are reviewed. In addition, the metabolic engineering and fermentation strategies for their production are reviewed.

Biotechnology↗
PubMed2004

Production of D-lactic acid by bacterial fermentation of rice starch.

D-Lactic acid was synthesized by the fermentation of rice starch using microorganisms. Two species: Lactobacillus delbrueckii and Sporolactobacillus inulinus were found to be active in producing D-lactic acid of high optical purity after an intensive screening test for D-lactic acid bacteria using glucose as substrate. Rice powder used as the starch source was hydrolyzed with a combination of enzymes: alpha-amylase, beta-amylase, and pullulanase to obtain rice saccharificate consisting of maltose as the main component. Its average gross yield was 82.5%. Of the discovered D-lactic acid bacteria, only Lactobacillus delbrueckii could ferment both maltose and the rice saccharificate. After optimizing the fermentation of the rice saccharificate using this bacterium, pilot scale fermentation was conducted to convert the rice saccharificate into D-lactic acid with a D-content higher than 97.5% in a yield of 70%. With this yield, the total yield of D-lactic acid from brown rice was estimated to be 47%, which is almost equal to the L-lactic acid yield from corn. The efficient synthesis of D-lactic acid can open a way to the large scale application of high-melting poly(lactic acid) that is a stereocomplex of poly(L-lactide) and poly(D-lactide). Schematic representation of the production of D-lactic acid starting from brown rice as described here.

Fermentation↗
PubMed2003

Proteome analysis of aerobic and fermentative metabolism in Rhizobium etli CE3.

Rhizobium etli undergoes a transition from an aerobic to a fermentative metabolism during successive subcultures in minimal medium. This metabolic transition does not occur in cells subcultured in rich medium, or in minimal medium containing either biotin or thiamine. In this report, we characterize the aerobic and fermentative metabolism of R. etli using proteome analysis. According to their synthesis patterns in response to aerobic (rich medium, minimal medium with biotin or minimal medium with thiamine) or fermentative (minimal medium without supplements) growth conditions, proteins were assigned to five different classes: (i) proteins produced only in aerobic conditions (e.g., catalase-peroxidase KatG and the E2 component of pyruvate dehydrogenase); (ii) protein produced under both conditions but strongly induced in aerobic metabolism (e.g., malate dehydrogenase and the succinyl-CoA synthetase beta subunit); (iii) proteins that were induced equally under all conditions tested (e.g., AniA, DnaK, and GroEL); (iv) proteins downregulated during aerobic metabolism, and (v) proteins specific to only one of the conditions analyzed. Northern blotting studies of katG expression confirmed the proteome data for this protein. The negative regulation of carbon metabolism proteins observed in fermentative metabolism is consistent with the drastic physiological changes which occur during this process.

Aerobiosis↗
PubMed2004

Butanol fermentation research: upstream and downstream manipulations.

An overview of advances in acetone-butanol fermentation research is presented with specific reference to the history of acetone-butanol fermentation, genetic manipulation of the butanol-producing Clostridium beijerinckii NCIMB 8052, as well as upstream and downstream processing. Specific reference is made to the development of the hyperamylolytic, hyper-"butanolagenic" C. beijerinckii BA101 strain. Amylolytic enzyme production by C. beijerinckii BA101 was 1.8- and 2.5-fold greater than that of the C. beijerinckii NCIMB 8052 strain grown in starch and glucose, respectively. We confirmed the presence of a phosphoenolpyruvate (PEP)-dependent phosphotransferase system (PTS) associated with cell extracts of C. beijerinckii BA101 by glucose phosphorylation by PEP and ATP-dependent glucose phosphorylation. It was found that C. beijerinckii BA101 was defective in PTS activity and that it compensates for this defect with enhanced glucokinase activity, resulting in an ability to transport and utilize glucose during the solventogenic stage. The principal problem associated with acetone-butanol fermentation by C. beijerinckii or C. acetobutylicum is butanol toxicity/inhibition to the culture. To solve this problem, we have attempted various alternative in situ/online techniques of butanol removal including membrane-based systems such as pervaporation, liquid-liquid extraction, and gas stripping. We found that gas stripping and pervaporation appear to be the most promising of the in situ acetone-butanol fermentation and recovery techniques but, in terms of cost-effective industrial applications, gas stripping appears to be the most promising.

Acetone↗
PubMed2003

Genome-wide monitoring of wine yeast gene expression during alcoholic fermentation.

The transcriptome of a wine yeast was monitored throughout an alcoholic fermentation under conditions mimicking an enological environment. Major changes in gene expression occurred during fermentation, affecting more than 2000 genes, as the yeast adapted to changing nutritional, environmental and physiological conditions. The genes of many pathways are regulated in a highly coordinated manner, and genes involved in the key metabolic pathways of fermentation are strongly expressed. We showed that, during fermentation of a synthetic medium mimicking a natural must in which growth arrest was caused by nitrogen exhaustion, entry into the stationary phase triggered major transcriptional reprogramming. Many TOR target genes involved in nitrogen utilization or other functions are induced at this stage, suggesting that this signalling pathway plays a critical role in changes in gene expression in response to nitrogen depletion. Entry into stationary phase is a key physiological event and is followed by a general stress response. The superimposition of multiple stresses, including starvation and ethanol stress, gives rise to a unique stress response, involving hundreds of genes encoding proteins involved in various cellular processes, many of unknown function.

Ethanol↗
PubMed2004

Yeast involved in fermentation of Coffea arabica in East Africa determined by genotyping and by direct denaturating gradient gel electrophoresis.

Samples of Coffea arabica were collected during the different stages of the fermentation from two production sites in Tanzania. The yeasts community was identified by genotyping using ITS-PCR and sequence analysis of the D1/D2 domain of the 26S rRNA gene. For confirmation, denaturating gradient gel electrophoresis (DGGE) of PCR-amplified 26S rRNA gene was performed to detect yeast directly from coffee samples without cultivation. Yeast counts were in the range 4.0 x 10(4) - 5.0 x 10(7) CFU/g with an increase during fermentation. Three yeasts species were dominant. The predominant yeast found during fermentation and drying was Pichia kluyveri. Pichia anomala was found in high numbers during drying of coffee beans. Hanseniaspora uvarum was the predominant yeast during fermentation but decreased during drying. Kluyveromyces marxianus, Candida pseudointermedia, Issatchenkia orientalis, Pichia ohmeri and Torulaspora delbrueckii occurred in concentrations of 10(3) CFU/g or below in coffee samples. Saccharomyces cerevisiae and Candida xestobii were not isolated by cultivation, but by the DGGE technique. A good agreement was found between the sequence analysis of the D1/D2 domain of the 26S rRNA gene and sequencing of the DGGE bands.

Base Sequence↗
PubMed2000

Determination of carbohydrates, sugar alcohols, and glycols in cell cultures and fermentation broths using high-performance anion-exchange chromatography with pulsed amperometric detection.

Cell cultures and fermentation broths are complex mixtures of organic and inorganic compounds. Many of these compounds are synthesized or metabolized by microorganisms, and their concentrations can impact the yields of desired products. Carbohydrates serve as carbon sources for many microorganisms, while sugar alcohols (alditols), glycols (glycerol), and alcohols (methanol and ethanol) are metabolic products. We used high-performance anion-exchange chromatography with pulsed amperometric detection (HPAE-PAD) to simultaneously analyze for carbohydrates, alditols, and glycerol in growing yeast (Saccharomyces cerevisiae) cultures and their final fermentation broths. Both cultures were grown on complex undefined media, aliquots centrifuged to remove particulates, and the supernatants diluted and directly injected for analysis. Pulsed amperometry allowed a direct detection of the carbohydrates, alditols, and glycols present in the cultures and fermentation broths with very little interference from other matrix components. The broad linear range of three to four orders of magnitude allowed samples to be analyzed without multiple dilutions. Peak area RSDs were 2-7% for 2, 3-butanediol, ethanol, glycerol, erythritol, rhamnose, arabitol, sorbitol, galactitol, mannitol, arabinose, glucose, galactose, lactose, ribose, raffinose, and maltose spiked into a heat-inactivated yeast culture broth supernatant that was analyzed repetitively for 48 h. This method is useful for directly monitoring culture changes during fermentation. The carbohydrates in yeast cultures were monitored over 1 day. A yeast culture with medium consisting primarily of glucose and trace levels of trehalose and arabinose showed a drop in sugar concentration over time and an increase in glycerol. Yeast growing on a modified culture medium consisting of multiple carbohydrates and alditols showed preference for specific carbon sources and showed the ability to regulate pathways leading to catalysis of alternative carbon sources.

Carbohydrates↗
PubMed2002

Three-phase oxygen absorption and its effect on fermentation.

The absorption rate of oxygen in the presence of a second, dispersed, organic phase can be significantly increased due to the higher solubility and diffusivity of oxygen in the organic phase. The oxygen supply of micro-organisms, which is very often a limiting factor during fermentation, can be improved, and the critical level of oxygen in the fermentation broth can be avoided by using dispersed organic phase. This paper reviews the models of the enhanced absorption rates and their integration into mass balance equations of fermentation. Several calculations were carried out to illustrate the effect of the dispersed organic phase and kinetic parameters on the absorption rates and on fermentation with double-substrate-limitation kinetics applying batch and continuous operation modes. Using software taking from the literature, the effect of the organic phase on the baker's yeast production is also presented in fed-batch mode.

Absorption↗
PubMed1991

Anaerobic degradation of sorbic acid by sulfate-reducing and fermenting bacteria: pentanone-2 and isopentanone-2 as byproducts.

Strictly anaerobic bacteria were enriched and isolated from freshwater sediment sources in the presence and absence of sulfate with sorbic acid as sole source of carbon and energy. Strain WoSo1, a Gram-negative vibrioid sulfate-reducing bacterium which was assigned to the species Desulfoarculus (formerly Desulfovibrio) baarsii oxidized sorbic acid completely to CO2 with concomitant stoichiometric reduction of sulfate to sulfide. This strain also oxidized a wide variety of fatty acids and other organic compounds. A Gram-negative rod-shaped fermenting bacterium, strain AmSo1, fermented sorbic acid stoichiometrically to about equal amounts of acetate and butyrate. At concentrations higher than 10 mM, sorbic acid fermentation led to the production of pentanone-2 and isopentanone-2 (3-methyl-2-butanone) as byproducts. Strain AmSo1 fermented also crotonate and 3-hydroxybutyrate to acetate and butyrate, and hexoses to acetate, ethanol, hydrogen, and formate. The guanine-plus-cytosine content of the DNA was 41.8 +/- 1.0 mol%. Sorbic acid at concentrations higher than 5 mM inhibited growth of this strain while strain WoSo1 tolerated sorbic acid up to 10 mM concentration.

Bacteria, Anaerobic↗
PubMed1993

Scale-up of purine nucleoside fermentation from a shaking flask to a stirred-tank fermentor.

Scaling-up purine nucleoside fermentation by a mutant strain of Bacillus subtilis from a shaking flask to a stirred-tank fermentor was attempted. The dimensions and the operating conditions of the stirred tank were determined in order to satisfy the optimum conditions of O2 transfer and power consumption per unit volume for the shaking flask. When the purine nucleoside fermentation was carried out in the stirred-tank fermentor under these conditions, in which the temperature simulated that in the shaking flask, the total amount of purine nucleosides produced was almost the same as that in the shaking flask, but the accumulation ratio of guanosine to total nucleosides was different from that in the flask. Since urea could not be utilized so efficiently in the stirred-tank fermentor, the NH4+ concentration and the pH of the culture broth were lower than those in the shaking-flask culture during fermentation. The activity of inosine monophosphate dehydrogenase and the accumulation ratio were significantly affected by the NH+4 concentration. When the pH of the stirred-tank culture was maintained at 6.9 by ammonia water to keep the NH+4 level higher, the ratio was improved to the same level as that observed in the shaking-flask culture. The fermentation heat calculated from the shaking-flask data and its pattern of change were similar to those in the stirred-tank fermentor.

Ammonia↗
PubMed1993

Relationship between thermal behaviour, fermentation performance and fatty acid composition in two strains of Saccharomyces cerevisiae.

Two Saccharomyces cerevisiae strains, one specifically of S. cerevisiae and another belonging to the physiological race S. uvarum, exhibited associative and dissociate thermal profiles, respectively. The S. cerevisiae subsp. uvarum strain, which displayed the dissociative profile, was characterized by a higher aptitude for fermenting glucose in a superoptimal temperature range as well as by a lower fatty acid unsaturation degree. On the other hand, both strains exhibited a similar fatty acid composition modulation pattern with regard to temperature: the unsaturation level presented two relative maxima at 15 and 40 degrees C. However, on the basis of Central Composite Design results, supplementation with an oleic acid source under semi-anaerobic conditions did not improve the fermentative performances in either strain. The modelling of fermentation rate in relation to certain variables indicated that the fermentative performance at superoptimal temperatures, and particularly the optimal temperature (Topt) and maximal temperature (Tmax) of the strain displaying a dissociative profile, could be increased by acting on medium composition.

Biotechnology↗
PubMed1991

Optimization of serum-free fermentation processes for antibody production.

Serum free fermentation procedures of cell cultures have got a wide application in production of biochemicals. But, cells cultured in serum free media in general are more sensitive to changes in culture condition, especially to nutrient limitation. There are no substances from serum which can support the cells when conditions are changing. In this study special attention is directed to amino acid utilization of mouse hybridoma in batch, chemostat and perfusion fermentations. Detailed data are presented which show the considerable difference of amino acid consumption rates in different fermentation modes. Already, in batch mode there are differences of the two investigated mouse hybridoma cell lines, although they are derived from the same myeloma line. In chemostat running at a dilution rate representing maximal growth rate most of the consumption rates are significant higher than in batch. On the other hand, in perfusion mode the rates are lower than in batch. This indicates clearly the different conditions of the fermentation modes. Therefore, it is necessary to develop serum free processes under the desired production conditions. An accurate analysis of the process is strongly recommended.

Amino Acids↗