Design and simulation of a fuzzy controller for fed-batch yeast fermentation

In baker's yeast fermentation, the process is non-linear and the response of the system to changes in glucose feeding has a very long delay time. Therefore, a conventional system can not give satisfactory results. In this paper, a fuzzy controller designed to control a fed-batch fermenter is presented. The fuzzy controller uses Respiratory Quotient (RQ) as a controller input and produces glucose feeding rate as control variable. The controller has been tested on a simulated fed-batch fermenter. The results show that the maximum yeast production is possible by keeping the specific growth rate (μ) and the glucose concentration (C _s) at preset values (μ _Cand C _s,c) and minimizing the ethanol production.     

Evaluation of bacterial contamination in a fed-batch alcoholic fermentation process

Alcoholic fermentation by a commercial baker's yeast in a fed-batch process with cell recycling and high-test molasses as substrate was strongly inhibited by Lactobacillus fermentum CCT 1407 after a few recycles. When total acidity (mainly lactic acid) exceeded 4.8 g/l broth it seriously interfered with yeast bud formation and viability and above 6.0 g/l it decreased alcoholic efficiency.     

Improving Spirulina platensis biomass yield using a fed-batch process

Increasing interest is being shown in the cyanobacterium Spirulina platensis because of its nutritional properties when used as food supplement and possible therapeutic effects. One of the most important areas being studied is the development of alternative nutrient sources which can be used to decrease the production costs of commercially produced S. platensis and obtain high productivity. Water from Mangueira Lagoon (Rio Grande do Sul State, Brazil) has high levels of carbonates and a high pH and has the potential to be used as a culture medium for S. platensis, although some nutrient supplementation may be required. We tested the effect of unsupplemented Mangueira Lagoon water (MLW) or MLW supplemented with 1.125 or 2.250 mg/l of urea and/or 21 or 42 mg/l of sodium bicarbonate on the growth of S. platensis in fed-batch culture using a 3(2) factorial design and found that there the addition of 1.125 mg/l of urea resulted in a 2.67 fold increase times in the final biomass concentration of S. platensis.     

Spruce sugars and poultry hydrolysate as growth medium in repeated fed-batch fermentation processes for production of yeast biomass

Bioprocess and Biosystems Engineering - The production of microbial protein in the form of yeast grown on lignocellulosic sugars and nitrogen-rich industrial residues is an attractive approach for...     

补料发酵工艺的应用及其研究进展

综述了补料工艺在发酵工业中应用和研究。介绍了补料发酵工艺及其优点,着重讨论了补料发酵动力学和控制理论研究,以期为补料发酵的应用提供充分的参考依据。     

Experimental optimization of a real time fed-batch fermentation process using Markov decision process

This article describes a methodology that implements a Markov decision process (MDP) optimization technique in a real time fed-batch experiment. Biological systems can be better modeled under the stochastic framework and MDP is shown to be a suitable technique for their optimization. A nonlinear input/output model is used to calculate the probability transitions. All elements of the MDP are identified according to physical parameters. Finally, this study compares the results obtained when optimizing ethanol production using the infinite horizon problem, with total expected discount policy, to previous experimental results aimed at optimizing ethanol production using a recombinant Escherichia coli fed-batch cultivation. (c) 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55: 317-327, 1997.     

2,3-Butanediol production using Klebsiella oxytoca ATCC 8724: Evaluation of biomass derived sugars and fed-batch fermentation process

For this study, 2,3-butanediol (BD) fermentation from pure and biomass-derived sugar were optimized in shake-flask and 5-L bioreactor levels using Klebsiella oxytoca ATCC 8724. The results showed that 70 g/L of single sugar (glucose or xylose) and 90 g/L of mixed-sugar (glucose:xylose = 2:1) were optimum concentrations for efficient 2,3-BD fermentation. At optimum sugar concentrations, 2,3-BD productivities were 1.03, 0.64 and 0.50 gL⁻¹ h⁻¹, and yields were 0.43, 0.36 and 0.35 g/g in glucose, xylose and mixed-sugar medium, respectively. The lack of simultaneous utilization of glucose and xylose led to the lowest productivity in the mixed-sugar medium. Detoxification of biomass hydrolyzates was necessary for efficient 2,3-BD fermentation when sugar concentrations in the medium was 90 g/L or higher, but not with sugar concentrations of 30 g/L or less. A fed-batch fermentation using glucose medium led to an increase 2,3-BD titer to 79.4 g/L and yields 0.47 g/g, while productivity decreased to 0.79 gL⁻¹ h⁻¹. However, the fed-batch process was inefficient using mixed-sugar and biomass hydrolyzates because of poor xylose utilization. These results indicated that appropriate biomass processing technologies must be developed to generate separate glucose and xylose streams to produce high 2,3-BD titer from biomass-derived sugar using a fed-batch process.     

Fuzzy supervisory control of fed-batch baker's yeast process

Summary A fuzzy supervisory system for bioprocess control was developed, and applied to baker's yeast fermentation. The system was based on hierarchical bioprocess control with fuzzy phase recognition and separate fuzzy control of each process phase. A two-level knowledge base included rules both for the phase recognition and control. The system was tested by using experimental data of fed-batch baker's yeast cultivations and by process simulations.     

Simultaneous saccharification and fermentation of sweet sorghum carbohydrates to ethanol in a fed-batch process

Summary The simultaneous saccharification and fermentation (SSF) of sweet sorghum carbohydrates to ethanol by Fusarium oxysporum F3 alone or in mixed culture with Saccharomyces cerevisiae 2541 or Zymomonas mobilis CP4 in a fed-batch fermentation process was studied. While SSF was adequately carried out by the first microorganism the process achieved its maximum value by the mixed culture of the fungus and yeast. Under optimum conditions, ethanol yields and concentrations as high as 29.7 g of ethanol per 100 g of dry sorghum stalk and 7.5 % (w/v) respectively were obtained. These values together with the high yield of sorghum crop in Greece make this process promising and worthy of further investigation for the production of fuel bioethanol.     

Phenotypes and fed-batch fermentation of ubiquinone-overproducing fission yeast using ppt1 gene

Ubiquinone (UQ), a component of the electron transfer system in many organisms, has been widely used for pharmaceuticals and cosmetics. In this study, we cloned and overexpressed the full-length ppt1 (MTppt1) gene, which encodes p-hydroxybenzoate:polyprenyltransferase and ERppt1 gene, which was modified to be localized on endoplasmic reticulum in fission yeast. The yeast MTppt1 and ERppt1 transgenic lines showed about 3.7 and 5.1 times increment in UQ content and the recombinant yeasts with a higher UQ level are more resistant to H(2)O(2), Cu(2+) and NaCl, and interestingly their growth was also faster than the wild type at lower temperature. For large-scale cultivation, the direct feedback control of glucose using an on-line ethanol concentration monitor for ubiquinone production of yeast ERppt1 by high-cell-density fermentation was investigated and the fermentation parameters (e.g., dissolved oxygen, pH, ethanol concentration, oxygen uptake rate, carbon dioxide evolution rate and respiration quotient) were also discussed. After 90 h cultures, the yeast dry cell weight reached 57 gl(-1) and the ubiquinone yield reached 23 mgl(-1). In addition, plasmid stability was maintained at high level throughout the fermentation.     

A cellular automata model for simulating fed-batch penicillin fermentation process

A cellular automata model to simulate penicillin fed-batch fermentation process (CAPFM) was established in this study, based on a morphologically structured dynamic penicillin production model, that is in turn based on the growth mechanism of penicillin producing microorganisms and the characteristics of penicillin fed-batch fermentation. CAPFM uses the three-dimensional cellular automata as a growth space, and a Moore-type neighborhood as the cellular neighborhood. The transition rules of CAPFM are designed based on mechanical and structural kinetic models of penicillin batch-fed fermentation processes. Every cell of CAPFM represents a single or specific number of penicillin producing microorganisms, and has various state. The simulation experimental results show that CAPFM replicates the evolutionary behavior of penicillin batch-fed fermentation processes described by the structured penicillin production kinetic model accordingly. __________ Translated from ACTA BIOPHYSICA, 2005, 21(2) [译自: 生物物理学报, 2005,21(2)]     

Production of pullulan by a fed-batch fermentation

Summary In pullulan production from sucrose byAureobasidium pullulans, a sugar concentration higher than 5% (w/v) inhibited cell growth and the production of exopolysaccharide. By a fed-batch fermentation, the inhibitory effects of the high sugar concentration were overcome and 58.0 g/1 of exopolysaccharide were obtained from 10% sucrose.Abbreviations m, n relationship parameters for the growth and non-growth associated product formation - X, Xmax biomass and maximum biomass concentration (g cell/1) - P product concentration (g exopolysaccharide/1) - specific growth rate of cell (hr^–1)     

A cellular automata model for simulating fed-batch penicillin fermentation process

A cellular automata model to simulate penicillin fed-batch fermentation process(CAPFM)was established in this study,based on a morphologically structured dynamic penicillin production model,that is in turn based on the growth mechanism of penicillin producing microorganisms and the characteristics of penicillin fed-batch fermentation.CAPFM uses the three-dimensional cellular automata as a growth space,and a Moore-type neighborhood as the cellular neighborhood.The transition roles of CAPFM are designed based on mechanical and structural kinetic models of penicillin batch-fed fermentation processes.Every cell of CAPFM represents a single or specific number of penicillin producing microorganisms,and has various state.The simulation experimental results show that CAPFM replicates the evolutionary behavior of penicillin batch-fed fermentation processes described by the structured penicillin production kinetic model accordingly.     

A fuzzy logic controller to control nutrient dosage in a fed-batch baker's yeast process

A fuzzy logic controller designed to control glucose feeding in a fed-batch baker's yeast process is presented. Feeding is carried out in portions and the controller determines the time at which glucose should be added and computes the size of the portion to provide the maximum glucose uptake rate. Moreover, the controller detects and prevents the occurrence of overdosage. The experimental results indicate that yield and specific growth rate obtained with the controller approached 55% and 0.13 h^–1, respectively.     

Combining yield coefficients and exit-gas analysis for monitoring of the baker's yeast fed-batch fermentation

Baker's yeast is one of the micro-organisms that is studied most in literature. Therefore, a lot of knowledge on the biochemical pathways and corresponding yield coefficients is available. This knowledge is combined with measurements of oxygen and carbon dioxide in the exit-gas to determine the coefficients appearing in the stoichiometric equations. In this manner, two measurements are sufficient to yield on-line estimates for biomass, glucose, ethanol and the specific growth rate, and information about the (ill-defined) nitrogen source NH_q. This is not possible if the yield coefficients are not included in the estimation procedure. A sensitivity analysis illustrates that this estimation scheme is rather insensitive to uncertainties on the yield coefficients.     

Ethanol tolerance of immobilized brewers' yeast cells

A method based on the survival of yeast cells subjected to an ethanol or heat shock was utilized to compare the stress resistance of free and carrageenan-immobilized yeast cells. Results demonstrated a significant increase of yeast survival against ethanol for immobilized cells as compared to free cells, while no marked difference in heat resistance was observed. When entrapped cells were released by mechanical disruption of the gel beads and submitted to the same ethanol stress, they exhibited a lower survival rate than entrapped cells, but a similar or slightly higher survival rate than free cells. The incidence of ethanol- or heat-induced respiratory-deficient mutants of entrapped cells was equivalent to that of control or non-stressed cells (1.3 ± 0.5%) whereas ethanol- and heat-shocked free and released cells exhibited between 4.4% and 10.9% average incidence of respiration-deficient mutants. It was concluded that the carrageenan gel matrix provided a protection against ethanol, and that entrapped cells returned to normal physiological behaviour as soon as they were released. The cell growth rate was a significant factor in the resistance of yeast to high ethanol concentrations. The optimum conditions to obtain reliable and reproducible results involved the use of slow-growing cells after exhaustion of the sugar substrate.     

Control of yeast fed-batch process through regulation of extracellular ethanol concentration

At high growth rates, the biomass yield of bakers yeast (Saccharomyces cerevisiae) decreases due to the production of ethanol. For this reason, it is standard industrial practice to use a fed-batch process whereby the specific growth rate, , is fixed at a level below the point of ethanol production, i.e., _crit. Optimally, growth should be maintained at _crit, but in practice, this is difficult because _crit is dependent upon strain and culture conditions. In this work, growth was maintained at a point just above _crit by regulating ethanol concentration in the bioreactor. The models used for control design are shown, as are the experimental results obtained when this strategy was implemented. This technique should be applicable to all microorganisms that exhibit an overflow type metabolism.     

柠檬酸清液发酵的补料工艺研究进展

柠檬酸是一种重要的食品添加剂。微生物批次发酵是当前国内外柠檬酸企业的主流生产方式,而更高生产强度的补料发酵工艺开发逐渐成为行业领域的关注热点。本文分别对不同菌种发酵的补料工艺进行比较,从补料培养基、补料起始点、补料控制方式等角度介绍各自的补料工艺控制,为柠檬酸工业发酵的补料工艺提出可行性建议。