Abstract Spatial control over features within multifunctional catalysts can unlock efficient one-pot cascade reactions, which are themselves a pathway to aviation biofuels via hydrodeoxygenation. A ...synthesis strategy that encompasses spatial orthogonality, i.e., one in which different catalytic species are deposited exclusively within discrete locations of a support architecture, is one solution that permits control over potential interactions between different sites and the cascade process. Here, we report a Pd doped hierarchical zeolite, in which Pd nanoparticles are selectively deposited within the mesopores, while acidity is retained solely within the micropores of ZSM-5. This spatial segregation facilitates hydrodeoxygenation while suppressing undesirable decarboxylation and decarbonation, yielding significant enhancements in activity (30.6 vs 3.6 mol dodecane mol Pd −1 h −1 ) and selectivity (C 12 :C 11 5.2 vs 1.9) relative to a conventionally prepared counterpart (via wet impregnation). Herein, multifunctional material design can realise efficient fatty acid hydrodeoxygenation, thus advancing the field and inspiring future developments in rationalised catalyst design.
In this study, we propose a set of nonlinear differential equations to model the dynamic growth of avascular stage tumors, considering nutrient supply from underlying tissue, innate immune response, ...contact inhibition of cell migration, and interactions with a chemotherapeutic agent. The model has been validated against available experimental data from the literature for tumor growth. We assume that the size of the modeled tumor is already detectable, and it represents all clinically observed existent cell populations; initial conditions are selected accordingly. Numerical results indicate that the tumor size and regression significantly depend on the strength of the host immune system. The effect of chemotherapy is investigated, not only within the malignancy, but also in terms of the responding immune cells and healthy tissue in the vicinity of a tumor.
•We develop a novel multiscale model for microalgal photoautotrophic growth.•The model is segregated-structured type based on Population Balance Equations.•We combine the model with cultivation ...experiments of Haematococcus pluvialis.•We successfully predict cell number, average volume and density distribution dynamics.•Model can accurately describe the nutrient depletion phase including cell lysis.
Haematococcus pluvialis can produce significant amounts of industrially important compounds belonging to lipids and starch classes, including various specific pigments such as β-carotene, lutein and astaxanthin, as well as lipids, carbohydrates and proteins. Their production can vary depending on environmental stress conditions like nutrient starvation. However, stress conditions lead also to undesired phenomena such as cell lysis, which is likely to be related to products loss. The microorganism develops towards smaller single cell volumes during the growth process, and eventually, more likely towards lysis when fission (i.e. cell division) slows down. The lysis process takes place simultaneously with nutrient depletion, so both growth and lysis are linked to the change of environmental conditions. In this work, we develop a novel multiscale segregated-structured model based on Population Balance Equations (PBEs) to describe the photoautotrophic growth of H.pluvialis, in particular cell growth, and lysis, making possible the description of the relationship between cell volume/transition, cell loss, and metabolic product availability. Cell volume is the internal coordinate of the population balance model, and its link with intrinsic concentrations is also presented. The model parameters are fitted against experimental data, extensive sensitivity analysis is performed and the model predictive capabilities are tested in terms of cell density distributions, as well as 0th and 1st order moments.
Design and optimization of microalgae processes have traditionally relied on the application of unsegregated mathematical models, thus neglecting the impact of cell-to-cell heterogeneity. However, ...there is experimental evidence that the latter one, including but not limited to variation in mass/size, internal composition and cell cycle phase, can play a crucial role in both cultivation and downstream processes. Population balance equations (PBEs) represent a powerful approach to develop mathematical models describing the effect of cell-to-cell heterogeneity. In this work, the potential of PBEs for the analysis and design of microalgae processes are discussed. A detailed review of PBE applications to microalgae cultivation, harvesting and disruption is reported. The review is largely focused on the application of the univariate size/mass structured PBE, where the size/mass is the only internal variable used to identify the cell state. Nonetheless, the need, addressed by few studies, for additional or alternative internal variables to identify the cell cycle phase and/or provide information about the internal composition is discussed. Through the review, the limitations of previous studies are described, and areas are identified where the development of more reliable PBE models, driven by the increasing availability of single-cell experimental data, could support the understanding and purposeful exploitation of the mechanisms determining cell-to-cell heterogeneity.
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In this work, a bioprocess for the fermentation of A. succinogenes for the production of succinic acid from glycerol was developed, employing a continuous bioreactor with recycle. Moreover, a new ...bioprocess model was constructed, based on an existing double substrate limitation model, which was validated with experimental results for a range of operating parameters. The model was used to successfully predict the dynamics of the continuous fermentation process and was subsequently employed in optimisation studies to compute the optimal conditions, dilution rate, reflux rate and feed glycerol concentration, that maximise the productivity of bio-succinic acid. In addition, a Pareto front for optimal volumetric productivity and glycerol conversion combinations was computed. Maximum volumetric productivity of 0.518 g/L/h, was achieved at the optimal computed conditions, which were experimentally validated. This is the highest bio-succinic acid productivity reported so far, for such a continuous bioprocess.
Evolutionary, pattern forming partial differential equations (PDEs) are often derived as limiting descriptions of microscopic, kinetic theory-based models of molecular processes (e.g., reaction and ...diffusion). The PDE dynamic behavior can be probed through direct simulation (time integration) or, more systematically, through stability/bifurcation calculations; time-stepper-based approaches, like the Recursive Projection Method Shroff, G. M. & Keller, H. B. (1993) SIAM J. Numer. Anal. 30, 1099-1120 provide an attractive framework for the latter. We demonstrate an adaptation of this approach that allows for a direct, effective ("coarse") bifurcation analysis of microscopic, kinetic-based models; this is illustrated through a comparative study of the FitzHugh-Nagumo PDE and of a corresponding Lattice-Boltzmann model.
•We develop a new procedure combining model parameter estimation with identifiability.•Identifiability is determined based on the flatness of likelihood profiles.•Parameter correlations are obtained ...using LASSO-based fittings of flat profile data.•The main novelty lies on using model reduction to generate parameter correlations.
Parameter estimation for model equations of biological systems can be complicated when some of the parameters are not identifiable. For example this can occur if parameters are very insensitive or if there are correlations between the parameters such that ranges of different parameter values give the same model output. To solve these issues, a logical procedure is suggested which incorporates sensitivity analysis and existing methods for testing for identifiability together with a LASSO based model reduction method for obtaining potential correlations between parameters. This procedure aims to separate the full set of parameters into a subset of identifiable parameters, a subset of insensitive parameters and provide correlations for determining values of non-identifiable parameters. The combined methodology is illustrated through two case studies: A simple two-compartment pharmacokinetic model and a complex kinetic model for the bioproduction of succinic acid from glycerol.
We propose an input–output stability analysis for closed-loop systems of piece-wise affine models under unstructured uncertainty and controlled by multi-model linear MPC with input constraints. ...Integral quadratic constraints (IQCs) are employed to assess the robustness of MPC under uncertainty. We efficiently create a model pool, by performing linearization on selected transient points. All the possible uncertainties and nonlinearities (including the controller) can be introduced in the framework, assuming that they admit the appropriate IQCs, whilst the dissipation inequality can provide sufficient conditions for stability through the incorporation of IQCs. We demonstrate the existence of static multipliers, which can reduce the conservatism of the stability analysis significantly. The proposed methodology is demonstrated through two illustrative case studies.
•A novel microbial limonene production process at industrial plant scale is designed.•Limonene is recovered by a new combined gas-stripping/solvent-scrubbing method.•Multi-parameter techno-economic ...analysis is conducted to assess economic viability.•Minimum selling price is $19.9/kg as limonene productivity reaches 0.7 kg/(m3·h).•Uncertainties of parameters used in TEA were addressed by sensitivity analysis.
To satisfy the growing demand for limonene, novel pathways for microbial production of limonene have been sought. A techno-economic analysis is carried out for one such process producing limonene from sugar at an industrial plant scale to assess potential economic viability. A conceptual design of the process is developed, in which a gas stripping-solvent scrubbing method is chosen for recovering limonene from bioreactors based on consideration of payback time and process operability. Minimum limonene selling prices are estimated over a range of fermentation productivity based on the calculation of net present value using discounted cash flow method. Under 45% of the maximum theoretical yield, the selling price reaches $19.9/kg, which could be competitive with established production processes when fermentation productivity is above 0.7 kg/(m3·h). Reduction of cost could be realised through improvement of microbial strains, utilisation of cheaper feedstocks, reduction in capital investment and strategic business planning.
•Economically feasible production routes simulation for ethanol and furfural.•Non heat integrated biochemical routes annual profitability is $3.28 million.•Non heat integrated thermochemical routes ...annual profitability is $1.10 million.•Heat integration increases profitability and lowers ethanol production cost.•Heat integrated biochemical route produces per gallon ethanol at $2.0.
In a quest of alternative energy source of fossil fuels, lignocellulosic biomass is intensively studying to produce different liquid fuels and chemicals. Both fuel (bioethanol) and chemical (furfural) were produced simultaneously in this study through two different production routes, biochemical and thermochemical route. Actually, this study firstly defined production pathway in details for each production route from extensive literature survey. Later details production pathway simulation was carried out in Aspen Plus simulation software for each production route individually. As well as heat integration was carried out within each production route to make overall production process as energy efficient and more profitable. Finally, an economic analysis of each production route ensured economic feasibility as well as annual profitability for bioethanol and furfural coproduction in individual route. Moreover, a comparative study between production routes in terms of annual profitability showed that heat integrated biochemical route is more profitable for bioethanol and furfural coproduction. Based on processing of 658201.14 ton dry lignocellulosic biomass (corn stover) per year, heat integrated biochemical production route can produce per gallon bioethanol by $2.0 and can make $49.95 million annual profit, whereas, the values were $3.07 and $20.07 respectively for heat integrated thermochemical route.
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