Hybrid extended Luenberger-asymptotic observer for bioprocess state estimation

State observers generate estimates of non-measured variables based on a mathematical model of the process and some available hardware sensor signals. On the one hand, exponential observers, such as Luenberger observers or Kalman filters, have an adjustable rate of convergence, but strongly rely on the accuracy of the process model. On the other hand, asymptotic observers use a state transformation in order to avoid using the (usually uncertain) kinetic model, but have a rate of convergence imposed by the process dilution rate. In an attempt to combine the advantages of both techniques, a hybrid observer is developed, which evaluates a level of confidence in the process model and, accordingly, evolves between the two above-mentioned limit cases (exponential or asymptotic observer). In particular, attention is focused on a hybrid “Luenberger-asymptotic” observer, for which a rigorous stability/convergence analysis is provided. The efficiency and usefulness of the proposed observer is demonstrated with a bioprocess application example.     

Diseases and pests in energy crop plantations

The Pest and Disease Management Activity was established in response to an awareness of the potential importance of pests and diseases in woody biomass production systems. Annual surveys in Canada, Eire, England, N. Ireland, Scotland and Sweden from 1987–1991 confirmed that rust disease (Melampsora spp.) is currently the most serious problem in willow biomass production in Europe. Other pests and diseases cause problems only on a local scale, though they could become more generally severe. Increasing clonal susceptibility to rust and an an increasing association of premature defoliation with lower rust severity levels have occurred over the period. A high degree of intrinsic variability in pathogen populations is expressed as four formae speciales (f.spp.) and at least eight pathotypes of the most common rust species, M. epitea. The same f.spp. appear to occur among pathotypes in Sweden, New Zealand and the UK. A network of field experiments has been established, in collaboration with the Joint Trials Activity, to enable the rust pathotype composition to be compared between five countries. It also aims to identify an international set of standard willow clones to be utilized for characterizing rust pathotypes globally.     

A practical robust control scheme for yeast fed-batch cultures – An experimental validation

Model-based control of bioprocess is a difficult task due to the challenges associated with bioprocess modeling and the lack of on-line measurements. In this study, a robust controller using minimal process knowledge and minimal measurement information is developed and applied to the ethanol regulation in cultures of Saccharomyces cerevisiae. A Youla parametrization is selected in order to reject the disturbance associated to the substrate demand for cell growth and to robustify the control scheme to unstructured uncertainties and measurement noise. The performance of this control scheme is illustrated in simulation and with real on-line experimental data.     

Production of Biodiesel Using Liquid Lipase Formulations

Looking back at the literature for enzymatic biodiesel, it is evident that the research has been focused on using immobilized lipase to enable re‐use of the enzyme due to price constraints on lipases used for catalyzing the transesterification process. The use of liquid formulations of lipase for biodiesel has recently been implemented in the industry. Technology for using liquid formulated lipases for enzymatic biodiesel production is new and, since enzyme prices have been reduced, it is now possible to simplify the process considerably and apply it for very low‐quality oils. In this paper, the use of liquid lipase formulations for enzymatic biodiesel will be described along with a general proposal for an industrial‐scale enzymatic biodiesel process with >95 % yield.     

Reflections on interdisciplinarity and teaching chemical engineering on an interdisciplinary degree programme in biotechnology

Some reflections on interdisciplinarity are presented based on the author's experience of more than twenty years teaching chemical and bioprocess engineering as a minor subject of an interdisciplinary programme in biotechnology. Key literature on interdisciplinary education is reviewed and some generic challenges faced in the delivery of interdisciplinary programmes are outlined. Finally, specific challenges faced by chemical engineers teaching chemical engineering as a minor component of an interdisciplinary programme are discussed. For an interdisciplinary programme to be successful, it needs to be designed and planned with great care, but also requires constant management and review to avoid the slide into unintended multidisciplinarity.     

Technological invention to product innovation: A project management approach

The optimal allocation of resources at the firm level to transform emergent technological invention into commercially successful products depends on the effective assessment and selection of projects. This study develops a multidisciplinary model for differentiating, prioritizing, and selecting investment in technological projects within an organization’s portfolio. Approaches from project portfolio and strategic technology management are integrated to explore how a particular product within a diverse project portfolio may be prioritized and developed. Our results suggest that the application of the suggested model to a portfolio of biotechnology projects may enhance the assessment of internal capabilities and external competitiveness, thereby providing a basis for firms to prioritize and preferentially allocate scarce resources within a portfolio of heterogeneous technologies.     

Biotransformation of glycerol into 1,3‐propanediol

Today, glycerol is mainly a by‐product of fat splitting and biodiesel production. Further growth of the biodiesel market would result in a fall in the price of glycerol. Particularly glycerol‐water from rapeseed oil methyl ester production, for example, would be an interesting raw material if it could be utilised in fermentation without further pretreatment. Under anaerobic conditions, bacteria can transform glycerol into 1,3‐propanediol (PDO), which can be used as a monomer in the chemical industry. PDO can be produced biotechnologically from glycerol with the aid of bacteria. Another way would be the utilization of glucose instead of glycerol, which would provide independence from the fluctuating glycerol market. However, under certain conditions, the classic technique based on glycerol can be quite interesting with regard to technical and economic aspects: A concerted, extensive search for new microorganisms (screening) and improved process design (fed‐batch with pH‐controlled substrate dosage) allowed the product concentrations, which were relatively low at a maximum of 70–80 g/L as a result of product inhibition, to be raised to more than 100 g/L. An additional advantage of the new technique and the newly isolated strains is the utilisation of low‐priced crude glycerol or glycerol‐water. This is a factor which should not be underestimated and has a direct effect on the product costs. Further on, the use of immobilised cells compared to freely suspended cells enables an increase of productivity from about 2 up to 30 g /Lh.     

Hydrodynamics of power-law fluids in trickle-flow reactors: Mechanistic model, experimental verification and simulations

A fully predictive one-dimensional mechanistic model was developed for describing the hydrodynamics of power-law fluids in trickle-bed reactors. The model is a generalization of the slit approach to the case of non-Newtonian fluids obeying Ostwald-deWaele rheological behavior. Without recourse to adjustable parameters, the proposed model enabled prediction of the experimental values of (i) total two-phase total pressure drop and total liquid holdup in the trickle flow regime, (ii) frictional pressure drop in single-phase flows through packed beds, and (iii) total liquid holdup in gravity driven liquid downflow and stagnant gas through packed beds. Parametric simulations guided by knowledge of the behavior of highly viscous Newtonian liquids in trickle beds highlighted the capability of the model in the simulation and design of trickle flow operation using power-law fluids.