Predictive model development and simulation of photobioreactors for algal biomass growth estimation

In the current scenario of energy requirement and the commercialization aspect of algal biofuel and biomass, it is important that means of predicting the production be available. In this paper, the mathematical models are developed for the tubular, bubble column and airlift photobioreactors to predict the productivity of the algal biomass. A modified Monod kinetic equation, incorporating the effect of nutrient and CO2 concentrations, light availability and oxygen built-up, is used to the estimate specific growth rate of the biomass. The light availability inside the reactor is defined in terms of the modified Beer–Lambert’s law as a function of distance from the surface where light is incident and the cell mass concentration. This allows a more accurate measurement of the shading effect. The equations are solved for different reactor types and their estimated productivities are successfully validated against values available in published literature. The model predicts comparatively better productivity for the tubular reactor (1.5 g/L day) than the bubble column and airlift reactor (1.42 and 1.35 g/L day respectively) because tubular reactor has shorter light/dark cycles and better light availability. The analysis is also done to identify the effect of nutrient, carbon dioxide, light and hydrodynamics on the overall productivity.

Performance and Kinetics of Bioaugmentation, Biostimulation, and Natural Attenuation Processes for Bioremediation of Crude Oil-Contaminated Soils

Bioremediation of contaminated sites is usually limited due to the inadequate availability of nutrients and microorganisms. This study was conducted to assess the impact of bioaugmentation (BA) and biostimulation (BS) on petroleum hydrocarbon degradation efficiency. In addition, treatment performance and kinetics of different remediation processes were investigated. For this purpose, four tanks containing oil-contaminated soils were tested. Tank 1 was operated as the natural attenuation process. Then, a microbial inoculum and nutrients were added to tank 2 to promote BA and BS. In tank 3, only the BA process was adopted, whereas in tank 4, only the BS process was adopted. After 63 days of operation, the total petroleum hydrocarbon (TPH) in tank 2 was reduced from 1674 to 430 mg/kg, with 74% reduction. Tank 1, tank 3, and tank 4 indicated TPH reductions of 35%, 41%, and 66%, respectively. Microbiological analysis of the inoculum indicated that Alcanivorax was the dominant bacterium. The population of TPH degrader bacteria in tank 2 soil was two orders of magnitude higher than in the control tank. Reaction rate data were fitted with a first-order reaction rate model. The Monod kinetic constants, maximum specific growth rate (µmax), and substrate concentration at half-velocity constant (Ks) were also estimated. This study showed that the TPH removal efficiency in the combined BA and BS process was higher than in other processes tested. The populations of TPH degrading microorganisms in soil tanks were positively related to TPH removal efficiency during bioremediation of petroleum-contaminated soils.

Analyzing transient respirometric data by analytical algorithm for Monod kinetic parameters

This study aims to develop an analytical algorithm with oxygen update (Ou) data obtained from transient respirometric measurement. Based on Monod kinetics, this study formulates a novel two-phase analytical model for an oxygen uptake rate plot (OUR vs. Ou) obtained by respirometric techniques. The first phase is a hyperbolic equation relating to exogenous and endogenous respiration, while the second phase is a linear equation for endogenous respiration only. An algorithm was therefore developed to analyze four Monod parameters by locating the best phase-separating point at which the absolute average relative error (ARE) of OUR is minimized. An analysis using test data on acetate verified that the algorithm is capable of transient kinetic parameter estimation with an ARE below 5–10%. A sensitivity analysis on domestic wastewater coupled with a Monte Carlo simulation concluded that the kinetic test must be conducted at a relatively high initial substrate level (So/Xo ≧ 1 and So/Ks ≧ 10) for reliable parameter estimation. Moreover, it is crucial to conduct the kinetic test with sufficient and acclimated seed culture for the degradation of substrate. The results of this study can be used to develop an automatic transient kinetic analyzer with modern programmable respirometers.

Model kinetika inhibisi substrat pada pertumbuhan Kluyveromyces lactis

Substrat inhibition kinetic model of Kluyveromyces lactis growthFood industry waste such as whey may be utilized as substrates in fermentation processes. Kluyveromyces lactis is yeast that can metabolize the lactose content of whey. In fermentation process design, the kinetics data and growth model of the microorganism are essential. This research was done to identify the growth kinetic model of Kluyveromyces lactis FNCC 3024 in lactose, glucose, and galactose substrates. Substrate concentration was varied as 5, 10, 20, 50, 100, and 150 g/L. Yeast growth profile in glucose and lactose substrates indicated substrate inhibition effect, while the growth profile in galactose substrate did not. Non-competitive substrate inhibition kinetic model was more suitable for glucose and lactose models, with a relatively small sum of squares of errors, namely 9.956 x 10-3 for glucose and 3.777 x 10-3 for lactose. Monod kinetic model for galactose substrate produced the lowest sum of squares of errors, namely 1.358 x 10-3. The maximum specific growth rate obtained from the modeling for glucose, lactose, and galactose substrates were 0.295, 0.265, and 0.147 hour-1.Keywords: kinetics, growth, inhibition, substrate, Kluyveromyces lactis Abstrak Limbah industri makanan seperti whey dapat dimanfaatkan sebagai substrat dalam proses fermentasi. Kluyveromyces lactis adalah salah satu ragi yang dapat memetabolisme kandungan laktosa dari whey. Pada perancangan proses fermentasi sangat diperlukan data kinetika dan model pertumbuhan dari mikroorganisme. Penelitian ini dilakukan untuk mengetahui model kinetika pertumbuhan batch Kluyveromyces lactis FNCC 3024 pada substrat laktosa, glukosa dan galaktosa. Konsentrasi substrat divariasi sebesar 5, 10, 20, 50, 100 dan 150 g/L. Profil pertumbuhan ragi pada substrat glukosa dan laktosa menunjukkan adanya inhibisi substrat sedangkan profil pertumbuhan pada substrat galaktosa inhibisi substrat tidak tampak. Model kinetika inhibisi subtrat non-kompetitif lebih tepat digunakan untuk substrat glukosa dan laktosa dengan kuadrat beda yang cukup kecil yaitu 9,956 x 10-3 untuk glukosa dan 3,777 x 10-3 untuk laktosa. Model kinetika Monod untuk substrat galaktosa memberikan jumlah kuadrat residual terkecil yaitu 1,358 x 10-3. Laju pertumbuhan spesifik maksimum yang dihasilkan dan pemodelan untuk substrat glukosa, laktosa dan galaktosa berturut-turut adalah 0,295, 0,265 dan 0,147 jam-1.Kata kunci : kinetika, pertumbuhan, inhibisi, substrat, Kuyveromyces lactis

Determining anaerobic degradation kinetics from batch tests

Data obtained from a biomethane potential (BMP) test were used in order to obtain the parameters of a kinetic model of solid wastes anaerobic degradation. The proposed model considers a hydrolysis step with a first order kinetic, a Monod kinetic for the soluble organic substrate degradation and a first order decay of microorganisms. The instantaneous release of methane was assumed. The parameters of the model are determined following a direct search optimization procedure. A ‘multiple-shooting’ technique was used as a first step of the optimization process. The confidence interval of the parameters was determined by using Monte Carlo simulations. Also, the distribution functions of the parameters were determined. Only the hydrolysis first order constant shows a normal distribution.

Simultaneous Heterotrophic Nitrification and Aerobic Denitrification byChryseobacteriumsp. R31 Isolated from Abattoir Wastewater

A heterotrophic carbon utilizing microbe (R31) capable of simultaneous nitrification and denitrification (SND) was isolated from wastewater of an Indian slaughterhouse. From an initial COD value of 583.0 mg/L, 95.54% was removed whilst, from a startingNH4+-N concentration of 55.7 mg/L, 95.87% was removed after 48 h contact. The concentrations of the intermediates hydroxylamine, nitrite, and nitrate were low, thus ensuring nitrogen removal. Aerobic denitrification occurring during ammonium removal by R31 was confirmed by utilization of both nitrate and nitrite as nitrogen substrates. Glucose and succinate were superior while acetate and citrate were poor substrates for nitrogen removal. Molecular phylogenetic identification, supported by chemotaxonomic and physiological properties, assigned R31 as a close relative ofChryseobacterium haifense. TheNH4+-N utilization rate and growth of strain R31 were found to be higher at C/N = 10 in comparison to those achieved with C/N ratios of 5 and 20. Monod kinetic coefficients, half saturation concentration(Ks), maximum rate of substrate utilization(k), yield coefficient,(Y)and endogenous decay coefficient(Kd)indicated potential application of R31 in large-scale SND process. This is the first report on concomitant carbon oxidation, nitrification, and denitrification in the genusChryseobacteriumand the associated kinetic coefficients.

Biodegradation of n-eicosane and VOCs: Cometabolism in a marine consortium

Several batch scale assays were performed in order to establish a correlation between the microbial removals of neicosane, in presence of different concentrations of volatile organic compounds (VOCs) which showed a partial removing.The selected VOCs were toluene and benzene. Results with benzene showed that the removal of this aromatic compoundwas decreased in presence of n-eicosane and the lowest removal was obtained when VOC concentration was higher. Theremoval of hydrocarbon was increased when VOC concentration was increased. In the assays with toluene, n-eicosanereached a higher removal when VOC concentration was increased, but the aromatic compound showed a decrease in itselimination dynamics. Control assays performed with VOCs at 28 mg/L without hydrocarbon showed higher removaldynamics for benzene than toluene. Also control assays of n-eicosane at two different concentrations but without anyVOC showed that its removal dynamic decreased in the absence of the aromatic compounds for both assays. The kineticadjustrnent obtained for toluene (Hill kinetic model) showed that the removal rate of this compound increased while itsconcentration at water-phase was higher. Although, when it was used a concentration of 50 mg/L or higher, the removalrate became almost constant. For benzene, the higher removal rate was reached with 38 mg/L. With higher concentration,the kinetic model showed inhibition, so the adjustrnent analyses fitted for a Monod kinetic model. n-Eicosane showed abetter adjustrnent with the Haldane kinetic model with an initial concentration of 188 mg/L for the highest removal rate.

Preferences, Utility Function, and Control Design of Complex Cultivation Process

In the control design are overcome restrictions connected with the observability of the Monod kinetics and with the singularities of the optimal control of Monod kinetic models.