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PubMed2003

Pulsed addition of limiting-carbon during Aspergillus oryzae fermentation leads to improved productivity of a recombinant enzyme.

Fungal morphology in many filamentous fungal fermentations leads to high broth viscosity which limits oxygen mass transfer, and often results in reduced productivity. The objective in this study was to determine if a simple, fed-batch, process strategy-pulsed addition of limiting-carbon source-could be used to reduce fungal broth viscosity, and increase productivity of an industrially relevant recombinant enzyme (glucoamylase). As a control, three Aspergillus oryzae fed-batch fermentations were carried out with continuous addition of limiting-carbon. To determine the effect of pulse-feeding, three additional fermentations were carried out with limiting-carbon added in 90-second pulses, during repeated five-minute cycles. In both cases, overall carbon feed-rate was used to control dissolved oxygen concentration, such that increased oxygen availability led to increased addition of limiting-carbon. Pulse-fed fermentations were found to have smaller fungal mycelia, lower broth viscosity, and improved oxygen mass transfer. As a result, more carbon was added to pulse-fed fermentations that led to increased enzyme productivity by as much as 75%. This finding has significant implications for the bioprocessing industry, as a simple process modification which is likely to cost very little to implement in most production facilities, has the potential to substantially increase productivity.

Aspergillus oryzae↗

PubMed2004

Solid-state fermentation: a continuous process for fungal tannase production.

Truly continuous solid-state fermentations with operating times of 2-3 weeks were conducted in a prototype bioreactor for the production of fungal (Penicillium glabrum) tannase from a tannin-containing model substrate. Substantial quantities of the enzyme were synthesized throughout the operating periods and (imperfect) steady-state conditions seemed to be achieved soon after start-up of the fermentations. This demonstrated for the first time the possibility of conducting solid-state fermentations in the continuous mode and with a constant noninoculated feed. The operating variables and fermentation conditions in the bioreactor were sufficiently well predicted for the basic reinoculation concept to succeed. However, an incomplete understanding of the microbial mechanisms, the experimental system, and their interaction indicated the need for more research in this novel area of solid-state fermentation.

Bioreactors↗

PubMed2006

Modeling product formation in anaerobic mixed culture fermentations.

The anaerobic conversion of organic matter to fermentation products is an important biotechnological process. The prediction of the fermentation products is until now a complicated issue for mixed cultures. A modeling approach is presented here as an effort to develop a methodology for modeling fermentative mixed culture systems. To illustrate this methodology, a steady-state metabolic model was developed for prediction of product formation in mixed culture fermentations as a function of the environmental conditions. The model predicts product formation from glucose as a function of the hydrogen partial pressure (P(H2)), reactor pH, and substrate concentration. The model treats the mixed culture as a single virtual microorganism catalyzing the most common fermentative pathways, producing ethanol, acetate, propionate, butyrate, lactate, hydrogen, carbon dioxide, and biomass. The product spectrum is obtained by maximizing the biomass growth yield which is limited by catabolic energy production. The optimization is constrained by mass balances and thermodynamics of the bioreactions involved. Energetic implications of concentration gradients across the cytoplasmic membrane are considered and transport processes are associated with metabolic energy exchange to model the pH effect. Preliminary results confirmed qualitatively the anticipated behavior of the system at variable pH and P(H2) values. A shift from acetate to butyrate as main product when either P(H2) increases and/or pH decreases is predicted as well as ethanol formation at lower pH values. Future work aims at extension of the model and structural validation with experimental data.

Adenosine Triphosphate↗

PubMed2006

Structured kinetic model to represent the utilization of multiple substrates in complex media during rifamycin B fermentation.

Industrial fermentations typically use media that are balanced with multiple substitutable substrates including complex carbon and nitrogen source. Yet, much of the modeling effort to date has mainly focused on defined media. Here, we present a structured model that accounts for growth and product formation kinetics of rifamycin B fermentation in a multi-substrate complex medium. The phenomenological model considers the organism to be an optimal strategist with an in-built mechanism that regulates the sequential and simultaneous uptake of the substrate combinations. This regulatory process is modeled by assuming that the uptake of a substrate depends on the level of a key enzyme or a set of enzymes, which may be inducible. Further, the fraction of flux through a given metabolic branch is estimated using a simple multi-variable constrained optimization. The model has the typical form of Monod equation with terms incorporating multiple limiting substrates and substrate inhibition. Several batch runs were set up with varying initial substrate concentrations to estimate the kinetic parameters for the rifamycin overproducer strain Amycolatopsis mediterranei S699. Glucose and ammonium sulfate (AMS) demonstrated significant substrate inhibition toward growth as well as product formation. The model correctly predicts the experimentally observed regulated simultaneous uptake of the substitutable substrate combinations under different fermentation conditions. The modeling results may have applications in the optimization and control of rifamycin B fermentation while the modeling strategy presented here would be applicable to other industrially important fermentations.

Actinomycetales↗

PubMed2006

Retrospective optimization of time-dependent fermentation control strategies using time-independent historical data.

We have previously shown the usefulness of historical data for fermentation process optimization. The methodology developed includes identification of important process inputs, training of an artificial neural network (ANN) process model, and ultimately use of the ANN model with a genetic algorithm to find the optimal values of each critical process input. However, this approach ignores the time-dependent nature of the system, and therefore, does not fully utilize the available information within a database. In this work, we propose a method for incorporating time-dependent optimization into our previously developed three-step optimization routine. This is achieved by an additional step that uses a fermentation model (consisting of coupled ordinary differential equations (ODE)) to interpret important time-course features of the collected data through adjustments in model parameters. Important process variables not explicitly included in the model were then identified for each model parameter using automatic relevance determination (ARD) with Gaussian process (GP) models. The developed GP models were then combined with the fermentation model to form a hybrid neural network model that predicted the time-course activity of the cell and protein concentrations of novel fermentation conditions. A hybrid-genetic algorithm was then used in conjunction with the hybrid model to suggest optimal time-dependent control strategies. The presented method was implemented upon an E. coli fermentation database generated in our laboratory. Optimization of two different criteria (final protein yield and a simplified economic criteria) was attempted. While the overall protein yield was not increased using this methodology, we were successful in increasing a simplified economic criterion by 15% compared to what had been previously observed. These process conditions included using 35% less arabinose (the inducer) and 33% less typtone in the media and reducing the time required to reach the maximum protein concentration by 10% while producing approximately the same level of protein as the previous optimum.

Bioreactors↗

PubMed2004

Effect of fermentation on the starch digestibility, resistant starch and some physicochemical properties of sorghum flour.

The effect of natural fermentation of Tabat sorghum cultivar (Sorghum bicolor L. Moench) at 37 degrees C for up to 36 h on pH, titratable acidity, starch digestibility, resistant starch and total starch was studied. The pH of the fermenting dough decreased sharply with a concomitant increase in the titratable acidity. In vitro starch digestibility markedly increased as a result of fermentation, while resistant starch and total starch decreased. Results showed that iodine absorption capacity increased during fermentation. Fermented sorghum had more soluble starch and swelling power at 100 degrees C than at 85 degrees C.

Chemical Phenomena↗

PubMed2004

Biosynthesis of proteases by Rhizopus oligosporus IHS13 in low-cost medium by solid-state fermentation.

The present study describes the biosynthesis of proteases by a locally isolated mould culture of Rhizopus oligosporus IHS13 in a low-cost medium by solid-state fermentation technique. The fermentation was carried out in a low-cost medium such as sunflower meal, wheat bran and rice bran. Sunflower meal and wheat bran in a ratio of 1:1 and moistened with distilled water was found to be the best substrate for protease synthesis. All the three substrates are very cheap agricultural by-products found in Pakistan. The production of proteases in sunflower meal and rice bran was also investigated but the results were unsatisfactory. Different cultural conditions such as rate of fermentation, effect of incubation temperature, effect of pH and depth of the fermentation medium were also optimized. The maximum enzyme synthesis was found after 72 h of fermentation at a temperature of 30 degrees C. The optimum pH and depth of the medium for protease synthesis were found to be 5.0 and 20 mm respectively. The maximum enzyme biosynthesis found during the course of present studies was 7.0 U ml(-1).

Culture Media↗

PubMed2006

Molecular weight of guar gum affects short-chain fatty acid profile in model intestinal fermentation.

Dietary fiber exerts many beneficial physiological effects; however, not all types of dietary fiber display the same effects. Partially hydrolyzed guar gum (PHGG), a lower molecular weight form of guar gum, is more easily incorporated into food, but may have less pronounced physiological effects than the native form. The aim of this study was to identify differences in intestinal fermentability based on the molecular weight of guar gum. Guar gum of four molecular masses (15, 20, 400, and 1,100 kDa) was fermented using a batch in vitro fermentation system. Human fecal inoculum was the source of microbes. The 400-kDa fraction produced the greatest concentrations of total short-chain fatty acid (SCFA) at 8 h and the highest amounts of butyrate at 24 h. At 24 h, the 400-kDa fraction produced more total SCFA and propionate than the 15 kDa, but was not different than 20 kDa or 1,100 kDa fractions. The molecular weight of guar gum was positively correlated with acetate production and negatively correlated with propionate production. This study concludes that 400-kDa guar gum may be optimal for intestinal fermentability. In conclusion, the molecular weight of guar gum affects in vitro fermentability and should be considered when adding to a food or beverage.

Acetic Acid↗

PubMed2003

Comparison of the Escherichia coli proteomes for recombinant human growth hormone producing and nonproducing fermentations.

Two-dimensional electrophoretic analyses of Escherichia coli cells producing recombinant human growth hormone (Nutropin) in fermentations were conducted. The resulting two-dimensional protein profiles were compared with those of nonproducing (blank) cells. A qualitative comparison was performed to address regulatory issues in the biopharmaceutical industry, and a semiquantitative comparison was performed to reveal information about the physiological state of the cells. The protein spots unique to production fermentation profiles were all related to recombinant human growth hormone (hGH); these included intact hGH, charge variants of hGH, and a proteolytically cleaved form of hGH, as expected. There were no E. coli host cell proteins unique to either the production or blank fermentation profiles. Rather, all detectable differences in E. coli proteins were quantitative in nature. Specifically, the levels of IbpA (inclusion body binding protein A), Ivy (inhibitor of vertebrate lysozyme), and a cleaved form of GroEL (Hsp60 homolog) were higher in hGH production profiles, whereas the levels of GlmU protein and PspA (phage shock protein A) were higher in blank profiles. In general, the high degree of similarity between proteomes for hGH-producing and nonproducing cells suggests that E. coli proteins from a nonproducing (blank) fermentation are appropriate for eliciting antibodies that are then used in immunoassays to measure host cell proteins in samples from production fermentations.

Algorithms↗

PubMed1996

Fed-batch fermentation with and without on-line extraction for propionic and acetic acid production by Propionibacterium acidipropionici.

Fed-batch propionic and acetic acid fermentations were performed in semi-defined laboratory medium and in corn steep liquor with Propionibacterium acidipropionici strain P9. On average, over four experiments, 34.5 milligrams propionic acid and 12.8 milligrams acetic acid were obtained in about 146 h in laboratory medium with 79 milligrams glucose added over five feeding periods. The highest concentration of propionic acid, 45 milligrams, was obtained when the glucose concentration was not allowed to drop to zero. In corn steep liquor 35 milligrams propionic acid and 11 milligrams acetic acid were produced in 108 h from 59.4 milligrams total lactic acid provided as seven feedings of corn steep liquor. Extractive fed-batch fermentations were conducted in semi-defined medium using either flat-sheet-supported liquid membranes or hollow-fiber membrane extraction to remove organic acids from the culture medium. As operated during the course of the fermentation, these systems extracted 25% and 22% of the acetic acid and 36.5% and 44.5% of the propionic acid, respectively, produced in the fermentation. Total amounts of acids produced were about the same as in comparable nonextractive fermentations: 30-37 milligrams propionic acid and 13 milligrams acetic acid were produced in 150 h. Limitations on acid production can be attributed to limited substrate feed, not to failure of the extraction system.

Acetic Acid↗

PubMed1993

Zymobacter palmae gen. nov., sp. nov., a new ethanol-fermenting peritrichous bacterium isolated from palm sap.

Zymobacter palmae gen. nov., sp. nov. was proposed for a new ethanol-fermenting bacterium that was isolated from palm sap in Okinawa Prefecture, Japan. The bacterium is gram-negative, facultatively anaerobic, catalase-positive, oxidase-negative, nonsporeforming and peritrichously flagellated. It requires nicotinic acid for growth. It ferments hexoses, alpha-linked di- and tri-saccharides, and sugar alcohols (fructose, galactose, glucose, mannose, maltose, melibiose, saccharose, raffinose, mannitol and sorbitol). Fifteen percent of maltose in broth medium is effectively fermented, whereas glucose with a concentration higher than 10% delayed growth initiation and decreased growth rates. Maltose is fermented to produce ethanol and CO2 with a trace amount of acids. Approximately 2 mol of ethanol are produced from 1 mol moiety of hexose of maltose. The organism possesses ubiquinone-9. The G + C content of the DNA is 55.8 +/- 0.4 mol%. Major cellular fatty acids were palmitic and oleic acids and cyclopropanic acid of C19:0. Characteristic hydroxylated acid was 3-hydroxy dodecanoic acid. The bacterium is distinct from other ethanol-fermenting bacteria belonging to the genera Zymomonas Kluyver and van Niel 1936 and Saccharobacter Yaping et al. 1990 with respect to chemotaxonomic and other phenotypic characters to warrant to compose a new genus and a new species. The type strain is strain T109 (= IAM 14233).

Base Sequence↗

PubMed1992

Hindgut fermentation in the wombats: two marsupial grazers.

The wombats Vombatus ursinus and Lasiorhinus latifrons have a capacious proximal colon with only a vestigial caecum. The pattern of microbial fermentation in the hindgut of both species was studied in captive animals fed a pelleted straw diet and in wild wombats feeding on their natural winter diets. Digesta pH was low in the stomach but near neutrality along the hindgut, indicating effective absorption and/or buffering of the colonic contents. Initial proportions and production rates of short chain fatty acids in vitro reflected the fermentation of plant cell walls. Proportions of isobutyrate, isovalerate and n-valerate increased towards the distal colon indicating proteolysis and subsequent fermentation of amino acids. The low ammonia content of digesta fluid suggested that ammonia released from these amino acids was absorbed and utilized by the wombats and their gut microbes. Wild wombats had higher concentrations and production rates of short chain fatty acids than captive animals, which was consistent with the higher apparent digestibility of their natural diet. The energy from short chain fatty acids in captive animals was 30-33% of digestible intake. Energy intakes were low and similar to resting metabolic rates estimated for marsupials. Actual resting metabolic rates of the wombats are probably lower than these estimates, and the proportion of energy derived from fermentation substantially higher than the 53-61% estimated in wild wombats. The energy from fermentation clearly enables wombats to utilize diets high in fibre.

Animals↗

PubMed1994

Effect of roasting and fermentation on viscosity of cereal-legume based food formulas.

With the view of preparing semi-liquid weaning foods of high energy content, the influence of roasting (stationary hot air treatment) and fermentation (with natural and pure culture inocula) on the viscosity of maize-sorghum-soya porridges was investigated. Roasting resulted in porridges of significantly higher viscosity (cooked porridge cooled to 40 degrees C). Porridges made from the individual ingredients (maize, sorghum, soya) did not show this behaviour. Natural fermentation of mixed ingredients resulted in lower porridge viscosities (cooked porridge cooled to 40 degrees C, as well as hot-paste peak viscosity) when pH was 5.0-5.5. At lower pH the viscosity of the final porridges increased. Fermentation experiments of individual ingredients inoculated with pure cultures of Lactobacillus plantarum and Candida famata lead to the conclusion that various factors contribute to the effect of fermentation on porridge viscosity. Porridges of minimum viscosity are obtained at pH 5.0-5.5 corresponding with a moderate extent of fermentation. From a consumer safety point of view, it would be preferable to acidify to lower pH values (pH < 4.5). If necessary, viscosity adjustments could be made using malted cereals.

Candida↗

PubMed1994

Nutritional improvement of lentils, chick pea, rice and wheat by natural fermentation.

Effect of natural fermentation process (4 days) on the non-protein nitrogen, crude and true protein, amino acids content and in vitro digestibility of two kinds of legumes (lentils and chick pea) and two kinds of cereals (rice and wheat) was investigated. Non-protein nitrogen increased significantly (p < 0.001) in the fermented products. Little increase has occurred in the crude protein while no significant change was observed in the fermented true protein samples. It was observed that methionine and cystine which are considered the limiting amino acids in legume seeds were close to those of FAO/WHO patterns. Also, lysine content (the first limiting amino acid in cereals was higher in fermented rice than that of FAO/WHO pattern. Moreover, fermentation process improved significantly, the in vitro digestibility of both legume and cereal products.

Amino Acids↗

PubMed1996

Usage patterns and contribution of fermented foods to the nutrient intakes of low income households in Emene, Nigeria.

This study investigated the usage consumption pattern and chemical composition of fermented foods consumed in 191 rural households (1030 individuals) in Emene. The result showed that fermented foods were widely used and consumed by most age groups (under 2 years to adults) because of poor socioeconomic status. Fermentation period varied with type of food and was mostly carried out as a means of detoxifying certain foods. Generally, fermented foods contributed substantially to the daily caloric (46.3 to 79.9% for males and 57.5 to 78% for females); calcium (33.8 to 63.5% for males and 48.3 to 55.4% for females); iron (34.4 to 58.6% for males and 47.4 to 74.6% for females); and thiamin (23 to 58.5% for males and 37.5 to 60% for females) intakes. The contributions of fermented foods to protein (10 to 40.7%) and ascorbic acid (1.9 to 18.7%) intakes were however, low. When compared with the FAO recommendations, the daily intakes of protein, calcium, riboflavin, niacin and ascorbic acid by the subjects were low due to large consumption of starchy root crops. Poor financial status was the most limiting factor to adequate nutrient intake. Such results point out the need for nutrition education related to improved methods of preparation and food selection.

Adolescent↗

PubMed1996

Effect of natural fermentation on the content of inositol phosphates in lentils.

The effects of natural fermentation upon phytic acid and less phosphorylated inositol phosphates of Lens culinaris var vulgaris cultivar Magda-20 were investigated. Seven fermentation runs were made following a 2(2) complete factorial design with three replicated centre points to study the effect of different conditions of temperature (28, 35 and 42 degrees C) and broth concentration (79, 150 and 221 g/l). Samples were taken for each of them at daily intervals (0, 24, 48, 72 and 96 h). The pH value declined sharply in the first 24 h of fermentation, becoming stabilized from this time. The relation between lactic acid and titratable acidity presented important differences between the different fermentations, ranging from 30-80%. Phytic acid (IP6), inositol pentakis (IP5), tetrakis (IP4) and tris-(IP3) phosphates were quantitatively determined. The content of total inositol phosphates showed a maximum reduction of 63% at 72 h under the fermentation conditions of 42 degrees C and 79 g/l.

Chromatography, High Pressure Liquid↗

PubMed1992

The effect of fermentation on the nutrient status and on some toxic components of Icacinia manni.

The effect of fermentation on the nutrient status and on some toxic components of Icacinia manni was investigated. Chemical analysis of both unfermented and fermented products revealed an increase in protein, ash and fibre content while the lipid and carbohydrate content showed a decrease. The results indicated that fermentation resulted in protein enrichment of the fermented Icacinia manni mash. Fermentation was also observed to cause a marked decrease in the level of some toxic components (oxalic acid, phytic acid and hydrocyanic acid) of the product. The possibility of incorporating Icacinia manni among the edible starchy plant tubers is discussed.

Fermentation↗

PubMed1992

Suitability of using sieved or unsieved maize mash for production of "OGI"--a fermented cereal food.

Proximate analysis of sieved and unsieved maize mash revealed that there was a decrease in the protein and lipid content of the sieved maize mash as compared to that of the unsieved maize mash. Crude fibre and ash was completely absent in the sieved maize mash, while they were present in the unsieved mash. Chemical analysis of the fermented unsieved maize mash revealed an increase in the protein content from 9.9% (unfermented) to 13.4% after 3 days of fermentation, whereas the protein content of the sieved maize mash increased from 7.1% (unfermented) to 8.4% after the same period of fermentation. Furthermore, the results revealed that the protein content of the fermented unsieved maize mash was 32.1% higher than that of the fermented sieved maize mash indicating that the unsieved maize mash was of a better nutrient quality and should be preferred to sieved maize mash for use in "Ogi" production.

Carbohydrates↗