Luedeking-Piret Model Research Articles

Reliable determination of the growth and hydrogen production parameters of the photosynthetic bacterium Rhodobacter capsulatus in fed batch culture using a combination of the Gompertz function and the Luedeking-Piret model

In this study, experimental results of hydrogen producing process based on anaerobic photosynthesis using the purple non-sulfur bacterium Rhodobacter capsulatus are scrutinized. The bacterial culture was carried out in a photo-bioreactor operated in a quasi-continuous mode, using lactate as a carbon source. The method is based on the continuous stirred tank reactors (CSTR) technique to access kinetic parameters. The dynamic evolution of hydrogen production as a function of time was accurately simulated using Luedeking-Piret model and the growth of R. capsulatus was computed using Gompertz model. The combination of both models was successfully applied to determine the relevant parameters (λ, μmax, α and β) for two R. capsulatus strains studied: the wild-type strain B10 and the H2 over-producing mutant IR3. The mathematical description indicates that the photofermentation is more promising than dark fermentation for the conversion of organic substrates into biogas.

Kinetic analysis and modeling of L-valine production in fermentation batch from E. coli using glucose, lactose and whey as carbon sources

In this study the effect of the carbon source on L-valine production kinetics using genetically modified E. coli was researched. Glucose, lactose, Whey (W) and deproteinized whey (DW) were tested as carbon sources, keeping the carbon/nitrogen (C/N) ratio constant. Biomass generation and substrate consumption were modeled with Contois and Mass Conservation models, respectively, whereas Mass Conservation Balance and Luedeking-Piret models were used for product obtaining. Results showed that L-valine production is partially associated to growth, with values of 0.485 g L-valine/(g dry cell weight.h), and a product loss effect at a specific rate (β) of 0.019 g L-valine/(g dry cell weight.h) with W. The yield of this product increased 36 % using W concerning glucose or lactose as carbon sources. On the other hand, Mass Balance and Luedeking-Piret models adjust properly to experimental data (R2 >0.90). In conclusion whey is a promising substrate for obtaining L-valine using genetically-modified E. coli.

Statistical optimization of exopolysaccharide production by Leuconostoc pseudomesenteroides JF17 from native Atlantic Forest juçara fruit

Leuconostoc pseudomesenteroides belongs to a group of lactic acid bacteria normally isolated from fruits, which has the capacity to produce exopolysaccharides (EPS). The present study aimed to optimize the EPS production of L. pseudomesenteroides JF17, isolated from juçara fruits (palm trees threatened with extinction in the Atlantic Forest), using the response surface methodology (RSM), besides evaluating the fermentation kinetics. The maximum production of EPS 53.77 mg/mL was obtained under ideal conditions of MRS broth supplemented with sucrose at 18%, w/v, fermentation temperature of 20 °C and initial pH of 7.30. The Luedeking-Piret model suggested that the production of EPS by the JF17 strain appeared to be associated with the cell growth of the microorganism, in addition to having high efficiency in the production of the polysaccharide from the substrate (Y p/s = 17.85 ± 0.74 mg EPS/log CFU ). Thus, the ideal optimization conditions and kinetic parameters can be useful for increasing the scale up of the fermentation process in the industrial production of EPS by L. pseudomesenteroides JF17.

Optimizing the growth-associated β-galactosidase production by probiotic <i>Lactobacillus reuteri</i> B-14171: experimental design, culture medium volume increase, and cell growth modeling

This study reports an optimized culture medium in submerged cultivation to produce β-galactosidase by Lactobacillus reuteri. Four culture medium parameters were optimized (pH, lactose, casein, and inactive beer yeast), and the effect of different volumes of the optimized culture medium on the bioprocess was evaluated regarding β-galactosidase production. Different kinetic models were applied to predict enzymatic production as a function of biomass and substrate. It is the first time that both the effect of increasing the culture medium volume and mathematical modeling on the β-galactosidase production by L. reuteri have been studied. Besides, different bioprocess parameters were calculated based on the experimental data to verify the feasibility of enzymatic production. The achieved enzymatic activity for the optimized culture medium (12.75 g L-1 lactose; 1.88 g L-1 casein; 1.65 g L-1 inactive beer yeast and pH 5.61) resulted in an increase of 4.74-fold compared to the initial activity. Three culture medium volumes (200, 800, and 3,200 mL) were evaluated, and no significant difference was observed on maximum and total productivities (Pm and Pp), as well as on the product formation yield on biomass (YP/X). The Logistic model resulted in a good fit to the experimental data for all tested volumes, and the modified Luedeking-Piret model provided a satisfactory prediction of the enzymatic activity. The optimized culture medium reported in this work is an outstanding alternative to produce β-galactosidase by L. reuteri, which is microbial growth-associated, and the production was not affected by increasing the culture medium volume.

Kinetic modeling of biosurfactant production by Bacillus subtilis N3-1P using brewery waste

Abstract Costs associated with production of favorable biologically produced surfactants continue to be a significant obstacle to large scale application. Using industrial wastes and by-products as substrate and optimization of cultural conditions are two strategies of producing biosurfactants with a reasonable price. Also, modeling the biosurfactant production bioprocess improves the commercial design and monitoring of biomass growth, biosurfactant production, and substrate utilization. In this study, the indigenous Bacillus subtilis N3-1P strain and a local brewery waste as the carbon source were used to produce a biosurfactant. The batch cultivation was performed under the optimum conditions. Models describing the biomass growth, biosurfactant production, and substrate utilization were developed by fitting the experimental data to the logistic, Contois and Luedeking-Piret models using MATLAB software and regression analysis. The kinetic parameters including the maximum specific growth rates (µ max), the Contois constant (K), parameters of the Luedeking-Piret modelswere calculated. Yields including Y X/S , and Y P/X were found to be 0.143 gX/gS, and 0.188 gP/gX, respectively. The experimental and predicted model showed good agreement. The developed models are a key step in designing reactors for scale up of biosurfactant production.

Mathematical Modeling of Lactobacillus paracasei CBA L74 Growth during Rice Flour Fermentation Performed with and without pH Control

The mathematical modeling of fermentation processes allows for the formulation of predictions about the kinetics of biomass growth and metabolite production as well as setting or verifying the best operative conditions in view of the economical convenience of the process. For this purpose, we performed a kinetic study of a rice flour fermentation process using Lactobacillus paracasei CBA L74 with and without pH control; the pH value was set to 5.8 under pH control. Monod, Logistic, and Contois models were proposed to describe the bacterial growth rate in both conditions. The best mathematical model, which was able to describe the experimental data obtained without pH control, was the Contois model, as the specific growth rate was influenced by both the glucose reduction (from 14.31 g/L to 10.22 g/L) and the biomass production (2 log growth) that occurred during fermentation. Conversely, when pH control was implemented, both Monod and Contois models satisfactorily described the specific growth rate trend. The estimated kinetic parameters confirmed that biomass production (2 log growth) and glucose consumption (from 14.31 g/L to 6.06 g/L) did not affect the microorganism’s growth capacity when the fermenting medium was maintained at an optimal pH. The lactic acid production rate described by the Luedeking–Piret model did not appear to be linked to growth in the absence of pH control while, on the other hand, this model was unsuitable for describing the experimental lactic acid concentration when pH control was applied. The kinetic modeling of lactic acid production and the percentage of added glucose in the protocol with controlled pH will be optimized in the future.

Process optimization and mathematical modelling of photo-fermentative hydrogen production from dark fermentative cheese whey effluent by Rhodobacter sphaeroides O.U.001 in 2-L cylindrical bioreactor

In this study, organic acids present in dark fermentative cheese whey effluent (DFCWE) were utilized to produce biological hydrogen via photo fermentation by R. sphaeroides O.U.001 cells in 2-L double-walled cylindrical PBR with a working volume of 1.5 L. Plackett-Burman design-based analysis revealed organic acid concentration (OA), temperature, and light intensity as the most significant variables. Experiments were performed at different conditions of (OA, 8–16 g L−1), temperature (25–37 °C), and light intensity (8–12 klx). Optimum values were obtained by Box-Behnken design matrix (BBD) based on the impact on hydrogen production rate (HPR) and under optimum values (OA concentration, 12 g L−1; temperature, 31 °C; and light intensity, 10 klx); HPR of 41.94 mL L−1 h−1 was obtained, which lies in close proximity with the predicted production rate of 41.65 mL L−1 h−1 with the correlation coefficient (R2) and coefficient of variance as 0.9801 and 0.0521, respectively. PBR performance for treating DFCWE was checked by performing mathematical modelling using four models. Kinetic study of DFCWE consumption and growth profile of the bacterial cell were investigated by fitting experimental values into Monod and logistic equations, respectively. Parameters of the modified Gompertz equation and Luedeking-Piret models gave proper simulated fitting with experimental H2 production obtained under optimized bioprocess variables. Metabolite analysis revealed that acetic and lactic acids were utilized to produce biohydrogen under uncontrolled pH. Findings of the current investigation could be a promising strategy for obtaining better hydrogen productivity in photo fermentation.

Prospective evaluation of xylitol production using Dabaryomyces hansenii var hansenii, Pachysolen tannophilus, and Candida guillermondii with sustainable agricultural residues

In this study, agro-wastes, including corncob, rice straw, and wheat straw, were used as substrate for xylitol production using Dabaryomyces hansenii var hansenii, Pachysolen tannophilus, and Candida guillermondii. The experiments were performed using batch fermentation using hemicellulose hydrolyzate as substrate under optimum levels of the screened significant nutrients and process variables. Screening and optimization were carried out for all the systems using statistical methods based on experimental designs. Kinetics and modeling for xylitol production were developed using the logistic model for microbial growth, substrate utilization kinetics for the substrate utilization, and Luedeking-Piret model for the product formation. The model parameters were compared for all xylitol production carried out using pretreated hemicellulose hydrolyzates from corncob, rice straw, and wheat straw. Experimental analysis and modeling results revealed a maximum xylitol yield when corncob was hydrolyzed with Pachysolen tannophilus.

Modelling the kinetics of biomass and lactic acid production during Rohu fish pickle fermentation

Fish pickle was prepared from Rohu (Labeo rohita) by fermentation for 15 days and the changes in biomass growth, lactic acid production, and pH were evaluated. The data obtained were fitted in two most widely accepted microbial growth models: Modified Gompertz, and Logistic model and three well known lactic acid production models: Luedeking-Piret, Monteagudo et al., and Balannec et al. model for lactic acid fermentation. Model constants and coefficients were determined by a nonlinear regression method. All the models were validated using statistical parameters namely, coefficient of determination (R2), root mean square error (RMSE), reduced chi-square (χ2) and the reduced sum of squares (RSS). The results revealed that the viable cell counts increased from 0.91×107 cfu/ml to 9×109 cfu/ml after nine days of fermentation. The lactic acid increased by about 11.6 times in 12 days and remained constant for the rest of the fermentation period. The pH decreased from 6.5 to 4.2 on the 15th day of fermentation and then increased slightly till the final day of fermentation. The Logistic model and Luedeking-Piret model were best fitted to describe the biomass growth and lactic acid production by LAB during the fermentation period of pickle. The growth-associated and non-growth associated coefficients were determined to be 0.813 and 0.005, respectively. Based on these estimated parameters, it is concluded that lactic acid production in the fish pickle was a mixed type.

Utilization of A. niger strains isolated from pistachio husk and grape skin in the bioleaching of valuable elements from red mud

Due to the high heavy and rare element contents, bauxite residue rejects (red mud) are simultaneously an ecological hazard and economic virtue. The abilities of two strains of Aspergillus niger isolated from pistachio husk and grape skin were investigated in the bioleaching of metals from the red mud produced in the Iran Alumina Company. Citric acid secretion (~15 g/l) by both strains was ten times more than oxalic acid (~1.5 g/l) and kinetically obeyed the Luedeking-Piret model. Also, both Gompertz and logistic equations correlated with cell growth and substrate consumption. Considering the best results of the bioleaching experiments, the grape-skin strain extracted about 92% Al, 88% V, 67% Ti, 66% Sr, and 29% Sc from the activated residue; while, the metal recoveries by pistachio-husk strain were 53% Al, 31% V, 67% Ti, 44% Sr, and 38% Sc. Finally, according to the kinetic studies, the shrinking core model could perfectly simulate the process, and the product layer diffusion was determined as the rate-determining step.

Effect of thermal pretreated organic wastes on the dark fermentative hydrogen production using mixed microbial consortia

The present study investigates the effect of thermal pretreated organic waste as a feedstock for the dark fermentative hydrogen (H2) production. Acidogenic mixed consortia was used for H2 production from starchy wastewater supplemented with groundnut de-oiled cake (GDOC). Physicochemical changes in GDOC after pretreatment were analyzed by using SEM, XRD and FTIR spectra. Maximum cumulative H2 production and H2 yield of 3.24 L L−1 and 12.05 mol H2 kg−1 CODremoved, respectively were achieved using the pretreated feedstock, which is 20% higher than that of the untreated one. Several kinetic models such as Logistic model, first order reaction kinetics, Pirt model, modified Gompertz model and Luedeking–Piret model were used to find out the effect of pretreatment on the kinetic parameters. Material analysis indicated that the fermentation was dominated by butyric acid pathway. Gaseous energy recovery was improved by two folds after the pretreatment. This is the first attempt to analyze the effect of thermal pretreatment of feedstock on different kinetic parameters associated with dark fermentation.

Biotransformation of paper mill sludge by Serratia marcescens NITDPER1 for prodigiosin and cellulose nanocrystals: A strategic valorization approach

Paper mill sludge (PMS), a lignocellulosic waste from paper industry, is an ecological burden of environmental concern. Present study explored PMS as substrate for prodigiosin production in solid state fermentation (SSF) and concurrent source of cellulose for Cellulose nanocrystals (CNCs) preparation, using Serratia marcescens NITDPER1. Batch studies revealed maximum pigment production 47 ± 3.2 mg/L after 60 h and ligninolytic potentials via kraft lignin degradation (59 % after 72 h), lignin-mimicking dye decolourization and lignin monomer utilization. In SSF, highest yield was 30.05 ± 1.7 mg/g (24 h) with growth-associated (α = 20.84) and non-growth associated (β = 0.63) parameters determined through Luedeking-Piret model. Lambda max (535 nm), Thin-Layer Chromatography (TLC) (Rf = 0.9), High-Performance Liquid Chromatography (HPLC) (RT = 2.865), Fourier-transform infrared spectra (FT-IR) and Nuclear magnetic resonance (NMR) confirmed it as prodigiosin that exhibited antioxidant potential (IC50 = 47 ± 3.5 μg/mL). After SSF, the delignified (54 %) residual PMS was utilized for preparing CNCs, that displayed particle size 130.8 nm, zeta potential -13.4 mv, polydispersity index 0.404, stability upto 490 °C and revealed desirable properties in Field-emission scanning electron microscopy (FESEM), FT-IR and X-ray diffraction (XRD). Phytotoxicity studies confirmed both prodigiosin and CNCs as non-toxic. This study unveiled biorefinery perspectives for paper industries through production of two commercially important commodities from waste using eco-friendly approach.

Statistical and kinetic modeling of Aspergillus niger inulinase fermentation from carob extract and its partial concentration

This study aimed to optimize inulinase production conditions from carob extract by using the Box-Behnken Design of Response Surface Methodology, to purify partially with ultrafiltration, and to model kinetically the inulinase fermentation. Based on the results, the optimal conditions were 250 rpm agitation speed, 2.3% inoculum size (v/v), and 135 mL medium volume, which yielded 1560.17 U/mL inulinase activity, 1198.36 U/mL invertase-type activity, 1.30 I/S ratio, 163.06 U/mL/d maximum inulinase fabrication rate, and 193.37 U/mL/d maximum invertase-type fabrication rate. With the ultrafiltration process, the inulinase and invertase-type activities were increased to 6278.69 and 7622.39 U/mL with 1.19 and 1.50 purification coefficients, respectively. Regarding modeling with the Luedeking-Piret model, enzyme and protein productions were not related to the substrate depletion due to negative a values. Consequently, carob extract can be evaluated for the fabrication conditions of A. niger inulinase and the purified enzyme can be used for the fabrication of fructooligosaccharides.

Dynamic modelling of growth and flavonoid production from Ocimum tenuiflorum suspension culture.

A structured-segregated dynamic model for biomass growth, sucrose utilization and flavonoid production in Ocimum tenuiflorum suspension culture is proposed, considering a dynamic heterogeneous population of viable active, viable nonactive and dead cell. The sucrose hydrolysis (into glucose and fructose), substrate uptake by biomass and intracellular flavonoid production are modelled using Contois kinetics, a competitive double-substrate Monod, and Luedeking-Piret model, respectively. The conversion of active to viable-nonactive biomass has been formulated as a function of the total substrate and biomass concentrations. Parameters for the dynamic model are evaluated while minimizing the sum of square errors between modelled and measured biomass, cell viability, glucose, fructose and intracellular flavonoid contents. Bootstrap confidence intervals and dynamic relative sensitivity analysis of these model parameters are presented. The knowledge gained from the population-based model in plant suspension culture can provide the basic framework for prediction and optimization of the bioprocess system for phytochemical production.

Utilization of sugarcane straw for production of β-glucan biopolymer by Lasiodiplodia theobromae CCT 3966 in batch fermentation process

β-Glucans as emerging biopolymer are widely produced by microorganisms in fermentation processes using commercial sugars which make process non-economic. Lignocellulosic substances are inexpensive carbon sources, which could be exploited for sustainable production of β-glucans. In this study, a lignocellulosic material, namely sugarcane straw (SCS) was utilized for the production of extracellular β-glucan by Lasiodiplodia theobromae CCT3966. SCS was subjected to acid and subsequent alkaline pretreatment, followed by enzymatic saccharification using cellulase enzyme. Quantity of 48.65 g/L glucose was released after enzymatic hydrolysis. β-Glucan production was performed by cultivation of fungal strain in SCS hydrolysate at 28 °C and initial culture pH 7. Highest β-glucan yield and productivity of 0.047 gg−1 and 0.014 gL-1h−1, respectively was obtained at 72 h fermentation time. Kinetic study of β-glucan production revealed experimental biosynthesis of β-glucan from SCS hydrolysate followed the trend generated by Logistic and Luedeking-Piret models. Chemical structure of biopolymer produced showed β-glucan constitution.

Long-term Operation of Continuous Culture of the Hyperthermophilic archaeon, Thermococcus onnurineus for Carbon Monoxide-dependent Hydrogen Production

In this study, we performed a kinetic analysis of CO-dependent H2 production by metabolically engineered Thermococcus onnurineus NA1, MC01 in terms of the cell activity as well as mass transfer rate. We conducted continuous cultures with varying dilution rate, CO flow rate, or agitation speed. Despite oscillations in cell density, the cultures reached steady states at all operating conditions. As the dilution rate increased from 0.1 to 0.3 h−1, specific activity of H2 production (SAHP) and volumetric cell production rate were linearly increased. Also, the SAHP remained almost constant at the fixed dilution rate of 0.3 h−1 even though the CO transfer rate was changed by adjusting the CO flow rate or the agitation speed. This relationship could be expressed as a typical Luedeking-Piret model, implying that high cell density culture with a sufficient growth rate is essential to obtain higher H2 productivity. On the other hand, more elevated CO transfer at the same dilution rate improved H2 production rate (HPR) by the increase of the cell density, not in the rise of SAHP. Through the continuous culture, 108 mmol/g-cell/h and 121 mmol/L/h of SAHP and HPR, respectively, could be achieved at a dilution rate of 0.3 h−1 with CO supply rate of 0.07 vvm and agitation speed of 700 rpm. Considering high H2 production activity and long-term stability of the strain over 1,000 h, MC01 is confirmed to have an outstanding potential for CO-dependent H2 production.

Enhanced production of Aspergillus niger inulinase from sugar beet molasses and its kinetic modeling.

The fermentation medium contains many complex components (vitamins, minerals, etc.) for better growth of the microorganisms. The increasing purity and number of these components used in the medium seriously affect the cost of the microbial process. This study aimed to further optimize the concentration of the components used in the medium (yeast extract and peptone) for inulinase fabrication by Aspergillus niger from sugar-beet molasses in shake flask fermentation by using Central Composite Design (CCD) and to kinetically identify the fermentation. The results indicated that the optimal medium composition consisted of only 4.2% (w/v) yeast extract. By using the fermentation environment, the inulinase generation, inulinase/sucrase ratio, maximum inulinase generation rate, maximum sugar depletion rate, and substrate utilization yield were determined as 1294.5 U/mL, 1.2, 159.6 U/mL/day, 7.4g/L/day, and 98.1%, respectively. The kinetic analysis of the fungal development (logistic model) indicated that a specific development rate and initial biomass concentration were 0.89/day and 1.79g/L, respectively. Inulinase and sucrase productions are mixed-development associated since the α value ≠ 0 (8.46 and 4.31 U/mgX) and the β value ≠ 0 (5.15 and 4.83 U/mgX day), respectively (Luedeking-Piret model). Besides, the maintenance value (Z) (0.009 gS/gX day) was lower than γ value (1.044 gS/gX), showing that A. niger commonly uses the substrates for enzyme fabrication and fungal development (modified Luedeking-Piret model). The enzyme activity was increased by optimizing the concentration of the components used. It was demonstrated that the proposed kinetic models can victoriously define fungal development, enzyme fabrication, and sugar depletion.

Production kinetics of β-carotene from Planococcus sp. TRC1 with concomitant bioconversion of industrial solid waste into crystalline cellulose rich biomass

Cost effective bioprocessing of nutraceuticals in present global scenario is a matter of concern. This study explored Paper mill sludge (PMS) and sugarcane bagasse (SCB) as inexpensive substrate for Planococcus sp. TRC1 mediated valuable β-carotene production and residual treated biomass as value added crystalline cellulose source simultaneously. Both biomass supported significant bacterial growth reaching highest yield 38.54 ± 1.4 mg/g on PMS (36 h) and 47.13 ± 1.9 mg/g (48 h) on SCB in solid state fermentation. Luedeking-Piret model revealed growth associated production with α and much lower β values of 5.18 and 0.24 for PMS and 4.5 and 0.165 for SCB. Cost analysis exhibited decrementation of pigment cost/mg by 84 % compared to synthetic media. Optimum production conditions were 30 °C temperature, pH 7, 10 % inoculum and initial moisture content 80 % (PMS) and 85 % (SCB). TLC (Rf = 0.9), HPLC (RT = 7.646) and lambda max (465 nm) confirmed pigment’s β-carotene nature with significant antioxidant and antimicrobial activity. It showed stability at varied temperature, pH and light conditions along with negligible phytotoxicity on Vigna radiata. Planococcus sp. TRC1 delignified PMS (41 %) and SCB (38 %) and FT-IR, FESEM and XRD suggested crystalline nature of residual cellulose rich fraction shedding light on a biorefinery approach for valorization of industrial solid wastes.

Mathematical modeling of ethanol production from glycerol by Enterobacter aerogenes concerning the influence of impurities, substrate, and product concentration

The application of biodiesel derived crude glycerol for ethanol production using Enterobacter aerogenes TISTR 1468 involved multiple interactions among substrate (glycerol), impurities (methanol) and product (ethanol and acetic acid). A mathematical model based on Monod and Luedeking-Piret models were established to simulate the cell performance in the presence of inhibitors. The Monod model was modified by adding the inhibition factors in terms of critical concentration (C*Ac< C*EtOH< C*MeOH< C*Gly) and its inhibition degree (ni) (nGly>nMeOH>nAc>nEtOH with the values of 119.06, 13.33, 1 and 0.0383, respectively). The Luedeking-Piret model confirmed that ethanol and acetic acid were predominantly growth-associated products. Glycerol up to 24.31 g/L and 31.32 g/L were optimum for cell growth and ethanol productivity, respectively. The cell performance was affected by methanol even at its lowest concentration tested (7.92 g/L). The applicability of the new two-phase growth model during the growth phase and stationary phase in the crude glycerol medium was validated and proved accurate (r2> 0.98).

Identification of Functional Bioprocess Model for Recombinant E. Coli Cultivation Process

The purpose of this study is to introduce an improved Luedeking–Piret model that represents a structurally simple biomass concentration approach. The developed routine provides acceptable accuracy when fitting experimental data that incorporate the target protein concentration of Escherichia coli culture BL21 (DE3) pET28a in fed-batch processes. This paper presents system identification, biomass, and product parameter fitting routines, starting from their roots of origin to the entropy-related development, characterized by robustness and simplicity. A single tuning coefficient allows for the selection of an optimization criterion that serves equally well for higher and lower biomass concentrations. The idea of the paper is to demonstrate that the use of fundamental knowledge can make the general model more common for technological use compared to a sophisticated artificial neural network. Experimental validation of the proposed model involved data analysis of six cultivation experiments compared to 19 experiments used for model fitting and parameter estimation.