Diagnosing lactic acid fermentation based on specific rates of growth,substrate consumption and product formation

The on-line calculated specific rates of growth, substrate consumption and product formation were used to diagnose microbial activities during a lactic acid fermentation. The specific rates were calculated from on-line measured cell mass, and substrate and product concentrations. The specific rates were more sensitive indicators of slight changes in fermentation conditions than such monitored data as cell mass or product concentrations.List of Symbols 1/h specific rate of cell growth - 1/h specific rate of substrate consumption - 1/h specific rate of product formation - ^* dimensionless specific rate of cell growth - ^* dimensionless specific rate of substrate consumption - ^* dimensionless specific rate of product formation - _max 1/h maximum specific rate of cell growth - _max 1/h maximum specific rate of substrate consumption - _max 1/h maximum specific rate of product formation - X g/l cell mass concentration - S g/l substrate concentration - S ^* dimensionless substrate concentration - S ₀ g/l initial substrate concentration - P g/l product concentration     

Simulation of cell growth,substrate consumption and product formation with recombinant Escherichia coli

Summary The growth of recombinant Escherichia coli, consumption of different amino acids and glucose as well as fusion protein formation are simulated by a structured mathematical model and compared with measurements carried out in a stirred tank reactor under well-controlled conditions. The model parameters were identified based on the variation in cell concentration, particular amino acids, and glucose as well as intracellular products during cultivation. The dependence of the model parameters on cultivation time and culture conditions (temperature, medium composition, dissolved oxygen concentration) are discussed.Offprint requests to: K. Schügerl     

Modeling of microbial substrate conversion,growth and product formation in a recycling fermentor

Paracoccus denitrificans and Bacillus licheniformis were grown in a carbon- and energy source-limited recycling fermentor with 100% biomass feedback. Experimental data for biomass accumulation and product formation as well as rates of carbon dioxide evolution and oxygen consumption were used in a parameter optimization procedure. This procedure was applied on a model which describes biomass growth as a linear function of the substrate consumption rate and the rate of product formation as a linear function of the biomass growth rate. The fitting procedure yielded two growth domains for P. denitrificans. In the first domain the values for the maximal growth yield and the maintenance coefficient were identical to those found in a series of chemostat experiments. The second domain could be described best with linear biomass increase, which is equal to a constant growth yield. Experimental data of a protease producing B. licheniformis also yielded two growth domains via the fitting procedure. Again, in the first domain, maximal growth yield and maintenance requirements were not significantly different from those derived from a series of chemostat experiments. Domain 2 behaviour was different from that observed with P. denitrificans. Product formation halts and more glucose becomes available for biomass formation, and consequently the specific growth rate increases in the shift from domain 1 to 2. It is concluded that for many industrial production processes, it is important to select organisms on the basis of a low maintenance coefficient and a high basic production of the desired product. It seems less important that the maximal production becomes optimized, which is the basis of most selection procedures.     

Inter-species differences in maximum specific growth rates and cell yields of bifidobacteria cultured on oligosaccharides and other simple carbohydrate sources

The abilities of seven bifidobacterial isolates ( Bifidobacterium adolescentis , B. bifidum (two strains), B. catenulatum , B. infantis , B. longum , B. pseudolongum ) to utilize 15 different carbohydrate sources (eight oligosaccharide products, and a variety of monosaccharides and disaccharides) were studied, with regard to maximum specific growth rates and production of bacterial cell mass. Results showed that substrate utilization was highly variable and that considerable interspecies and interstrain differences existed. Galactooligosaccharides and oligofructose, with a low degree of polymerization, supported best growth of the test micro-organisms. In contrast, xylooligosaccharides and pyrodextrins were almost invariably poor bifidobacterial substrates. In many species, maximum specific growth rates and bacterial cell yields were higher on oligosaccharides compared to their monosaccharide constituents, particularly with respect to fructooligosaccharides. Bifidobacterium pseudolongum , B. longum and B. catenulatum were the most nutritionally versatile isolates studied in relation to the range of oligosaccharide products utilized, and the extent to which bacteria could grow on these substrates.     

Interrelationship between oxygen consumption,superoxide anion and hydrogen peroxide formation in phagocytosing guinea pig polymorphonuclear leucocytes

The paper presents an experimental procedure for a simultaneous assay of oxygen consumption, O2- release and H2O2 accumulation at a very early stage of the respiratory burst that is induced by phagocytosis in guinea pig polymorphonuclear leucocytes. The main findings are as follows: (a) The oxygen consumption that is measurable does not correspond to all oxygen that is reduced. The relationship between the actual oxygen consumed and the amount that is reduced depends on the fate of the intermediate products O2- and H2O2. (b) O2- is measurable extracellularly by the reduction of cytochrome c. When cytochrome c oxidizes the extracellular O2-, molecular oxygen is formed. This fact is shown by a decrease of oxygen consumption. The molar ratio between the O2- detected and the oxygen given back is 1. (c) The amount of O2- released from the cells accounts for only a small part of oxygen actually reduced. (d) H2O2 is detectable only in the presence of NaN3. In this condition almost all oxygen consumed is recovered in the form of H2O2. The molar ratio O2/H2O2 is near unity. The amount of H2O2 derived from dismutation of O2- released is only an aliquot of the total H2O2 accumulated. Thus, most of H2O2 is derived from intracellular sources. (e) In the absence of inhibitors of H2O2 degrading reactions, no detectable accumulation of peroxide occurs. Under these conditions, the main part of H2O2 formed is degraded in almost equal amount by catalase and myeloperoxidase, while only a small aliquot is degraded by NaN3 insensitive reactions.     

Immobilized cell microchannel bioreactor for evaluating fermentation characteristics of mixed substrate consumption and product formation

An immobilized cell microchannel bioreactor was designed to test continuous fermentation. The fermentation set-up included a bottom hydrophilic quartz channel to immobilize cells using 0.4 wt% polyethyleneimine and a top channel designed to continuously remove metabolically generated carbon dioxide using hydrophobic polypropylene. To evaluate fermentation characteristics of immobilized cells, ethanol fermentation was carried out using Saccharomyces cerevisiae and Pichia stipitis. The immobilized cell microchannel bioreactor was used to identify long-term activity of immobilized S. cerevisiae cells. The continuous flow microchannel bioreactor was operated stably over a period of 1 month. The immobilized cell microchannel bioreactor was used to examine the characteristics cells that consumed mixed substrates. The concentration ratio of glucose to xylose for simultaneous utilization of hemicellulosic sugars was evaluated using the microchannel bioreactor and the results were compared with those obtained by using conventional batch fermentation with P. stipitis.     

Mobility, growth patterns and substrate in some fossil and Recent corals

The article analyses the relationships between mobile corals, the associated benthic fauna and the physical character of their substrates. Different types of coral mobility are here classified under three headings: (1) Passive rotation by water movement or by intervention of infaunal, benthic or nektic organisms. (2) Lifelong towing by a symbiotic sipunculid worm. (3) Auto-mobility, defined as self-induced movement which allows unburial, righting and lateral migration. In each case the morphology of the skeleton reflects the type of mobility, which can therefore be traced in the fossil record. Two examples of auto-mobile corals, Cycloseris (Recent) and Chomatoseris (= Anabacia) (Jurassic) are reviewed in detail; their main common architectural features are concentric growth and lack of epitheca. Both genera prefer loose, muddy sands. Mobility in corals allows them to flourish under circumstances unfavourable for sedentary forms. They are good indicators of loose, soft, sand substrates ranging from lagoonal through peri-reefal to deeper water environments. Though relatively few in species at any given time, mobile corals are geographically widespread and may be locally extremely abundant (>1500 per m²). World distribution maps are given for the Recent Cycloseris cyclolites, Diaseris distorta, Heteropsammia, Heterocyathus and Manicina areolata and for the Jurassic Chomatoseris. Cet article analyse Ies relations entre les coraux mobiles, la faune benthique associée et les propriétés physiques de leur substrat. On peut classer les différents types de mobilité chez les coraux selon trois catégories: (1) Rotation passive due aux mouvements de l'eau, à l'intervention de l'endofaune, d'organismes benthoniques ou nectoniques. (2) Remorquage par un ver Sipunculide symbiotique. (3) Auto-mobilité, définie comme mouvements propres, permettant au polypier de s'extraire du sédiment, de se retourner et de se déplacer latéralement. Dans tous les cas la morphologie du squelette est liée au type de mobilité qui peut done être reconnu chez les fossiles. Deux exemples de coraux auto-mobiles sont ici revus en détail: Cycloseris (actuel) et Chomatoseris (=Anabacia) (Jurassique); les traits communs entre ces deux formes sont la croissance concentrique et l'absence d'épithèque. Les deux genres préfèrent les sables boueux meubles. La mobilité chez les coraux permet leur épanouissement dans des circonstances défavorables aux formes sédentaires. Ce sont de bons indicateurs de fond meuble (sable ou sable vaseux). On les trouve dans les lagons, les zones péri-récifales et jusque dans des eaux plus profondes. Les genres mobiles, dont le nombre connu est encore faible, ont cependant une large distribution géographique et peuvent localement être représentés par de nombreux individus (>1500 par m²). Des cartes de répartition mondiale sont établies pour les coraux actuels Cycloseris cyclolites, Diaseris distorta, Heteropsammia, Heterocyathus, Manicina areolata et pour le genre jurassique Chomatoseris.     

The role of malic acid in the metabolism of Schizosaccharomyces pombe: substrate consumption and cell growth

Summary The effect of initial concentrations of malate varying from 0 to 28.6 g/l was studied. The acid was found to be inhibitory for growth of Schizosaccharomyces pombe but not for its deacidification activity. Malate was never integrated into biomass but partly transformed into ethanol if the aeration rate was weak (oxygen limitation). In the absence of glucose, resting cells of S. pombe were able to degrade malic acid if their concentration was sufficient, but their viability gradually decreased. However, for 0.15 g/l of growing cells (inoculum) 6 g/l of glucose was necessary to consume 8 g/l of malate. When the medium did not contain sugar no growth was observed despite the partial consumption of malate, showing that the acid was neither a carbon source nor an energy source. Offprint requests to: P. Strehaiano     

Effect of specific growth rates on productivity in continuous open and partial cell retention animal cell bioreactors.

A clonal derivative of a transfectant of the SP2/0 myeloma cell line producing a chimeric monoclonal antibody was cultivated in both continuous open and continuous partially-closed bioreactors. Using an open system for the determination of kinetic parameters, we showed that the production of this chimeric mAb was growth associated. As such, the volumetric productivity increased linearly with increasing dilution rate up to the maximum dilution rate. Three continuous cultivations employing partial cell retention were conducted. In agreement with mathematical predictions, the product titer and volumetric productivity were independent of the degree of cell retention when the total dilution was held constant. When cells were maintained at a low specific growth rate, the product titer was independent of dilution rate and the volumetric productivity increased with increasing dilution rate, again in agreement with mathematical predictions. Since the partially-closed bioreactor could be operated at dilution rates in excess of the maximum specific cellular growth rate, volumetric productivities were greater than those achievable in the open bioreactor. However, when cells were maintained at a high specific growth rate, cell accumulation was limited and product titers decreased at high dilution rates. Therefore, the volumetric productivity in this latter case did not increase at higher dilution rates.     

Kinetics of substrate consumption and product formation in closed acetic fermentation systems

This paper proposes a kinetic model for substrate consumption and product formation, in low alcohol media, of Acetobacter aceti in submerged culture. The model considers ethanol consumption for growth of biomass and formation of secondary products by a chemical route. Experimental data were obtained in the laboratory using a variety of discontinuous fermentation apparatus with automatic control, and either open or closed gas recirculation systems. Operating conditions applied were those typical of acetic fermentation process in the food industry. The fit of equations to the experimental data gives high theoretical-experimental determination coefficients.     

On weight dependence of net growth efficiency and specific respiration rates among field populations of invertebrates

Summary Annual net growth efficiency (NGE) is approximated here by 100 P _a/(P _a+R _a), P _a and R _a being the annual production and respiration rates of populations per unit area. Published NGE values for 15 temperate invertebrate populations range from 13 to 55%. Contrary to the literature on NGE among speices, the dependence of NGE on species size (as body weight at the onset of sexual maturity, W _s) is not yet determined although the ranges of P _a and R _a, divided by the mean biomass , approach two orders of magnitude. The rates of 13 of these populations decline with a -0.35 power of W _s rather than the -0.25 power of comparative physiology. A possible reason may be a trend towards larger specimens (relative to W _s or full size) in populations of larger species. Among species, a significant dependence of NGE on W _s (or full size) is not demonstrable for laboratory populations of unicellular organisms and field populations of mammals so that the cost per unit of production might generally be independent of the rate of production by the population.     

Use of iron from transferrin and microbial chelates as substrate for heme synthetase in transformed and primary erythroid cell cultures

The enzymatic heme production in cell-free extracts of virus-transformed Friend erythroleukemia cells and primary bone marrow cells from rabbits has been measured by determining the activity of heme synthetase after addition of iron sulfate, transferrin or microbial iron chelates. In transformed cells the amounts of heme formed did not show significant differences independent of which substrate was offered. In cell-free extracts of primary bone marrow cells no increase of heme production could be observed.     

Specific rates of substrate oxidation and product formation in autotrophically growingChromatium vinosum cultures

Eighty-six species of fungi belonging to sixty-four genera were examined for their ability to metabolize naphthalene. Analysis by thin-layer and high pressure liquid chromatography revealed that naphthalene metabolism occurred in forty-seven species belonging to thirty-four genera from the major fungal taxa. All organisms tested from the order Mucorales oxidized naphthalene with species of Cunninghamella, Syncephalastrum and Mucor showing the greatest activity. Significant metabolism was also observed with Neurospora crassa, Claviceps paspali and four species of Psilocybe. The predominant metabolite formed by most organisms was 1-naphthol. Other products identified were, 4-hydroxy-1-tetralone, trans-1,2-dihydroxy-1,2-dihydronaphthalene, 2-naphthol, 1,2-and 1,4-naphthoquinone.     

Use of the abiotic proton balance for determining linear relations among net conversion rates of primary metabolites in fermentation processes

Linear relations among net conversion rates of primary metabolites in fermentation processes can be determined by using the macroscopic or pathway balancing methods. It is shown that the process observability can be improved by incorporating both the abiotic proton balance and the pH control reagent addition rate measurement into the balancing methods. (c) 1996 John Wiley & Sons, Inc.     

Use of iron from transferrin and microbial chelates as substrate for heme synthetase in transformed and primary erythroid cell cultures.

The enzymatic heme production in cell-free extracts of virus-transformed Friend erythroleukemia cells and primary bone marrow cells from rabbits has been measured by determining the activity of heme synthetase after addition of iron sulfate, transferrin or microbial iron chelates. In transformed cells the amounts of heme formed did not show significant difeerences independent of which substrate was offered. In cell-free extracts of primary bone marrow cells no increase of heme production could be observed.     

Acetylcholinesterase in cell adhesion, neurite growth and network formation

The expression of acetylcholinesterase is not restricted to cholinergically innervated tissues and relates to both neurotransmission and multiple biological aspects, including neural development, stress response and neurodegenerative diseases. Therefore, the classical function of acetylcholinesterase has to be distinguished from its non-classical, e.g. enzymatic from non-enzymatic, functions. Here, the roles of acetylcholinesterase in cell adhesion, promoting neurite outgrowth and neural network formation are reviewed briefly, together with potential mechanisms to support these functions. Part of these functions may depend on the structural properties of acetylcholinesterase, for example, protein-protein interactions. Recent findings have revealed that laminin-1 is an interaction partner for acetylcholinesterase. The binding of acetylcholinesterase to this extracellular matrix component may allow cell-to-cell recognition, and also cell signalling via membrane receptors. Studies using monolayer and 3D spheroid retinal cultures, as well as the acetylcholinesterase-knockout mouse, have been instrumental in elaborating the non-classical functions of acetylcholinesterase.     

Effects of microwave treatment on growth,photosynthetic pigments and some metabolites of wheat

Wheat (Triticum aestivum L. Sakha 61) grains were exposed to microwave radiation of a wavelength 2.85 cm and frequency 10.525 GHz for 15, 45, or 75 min. The exposed grains were germinated and then harvested after 7 and 14 d. While 15-and 45-min exposure of the grains stimulated seedling shoot length and fresh and dry masses, the exposure for 75 min had no pronounced effects. 15 and 75-min irradiation increased succulence and pigment contents in 7-and 14-d-old seedlings. While the ratios chlorophyll (Chl) a/b, carotenoids (Car)/Chl were higher in 7-d-old seedlings than in the control ones for all doses, they decreased in 14-d-old seedlings. The microwave radiation increased protein and amino acid contents, but decreased the contents of saccharides, nucleic acids, and phenolic compounds. Low dose (15 min) stimulated proline synthesis, whereas the other doses showed negative effect on its production.