Ioannis K. Kookos

Valorization of industrial waste and by-product streams via fermentation for the production of chemicals and biopolymers

The transition from a fossil fuel-based economy to a bio-based economy necessitates the exploitation of synergies, scientific innovations and breakthroughs, and step changes in the infrastructure of chemical industry. Sustainable production of chemicals and biopolymers should be dependent entirely on renewable carbon. White biotechnology could provide the necessary tools for the evolution of microbial bioconversion into a key unit operation in future biorefineries. Waste and by-product streams from existing industrial sectors (e.g., food industry, pulp and paper industry, biodiesel and bioethanol production) could be used as renewable resources for both biorefinery development and production of nutrient-complete fermentation feedstocks. This review focuses on the potential of utilizing waste and by-product streams from current industrial activities for the production of chemicals and biopolymers via microbial bioconversion. The first part of this review presents the current status and prospects on fermentative production of important platform chemicals (i.e., selected C2-C6 metabolic products and single cell oil) and biopolymers (i.e., polyhydroxyalkanoates and bacterial cellulose). In the second part, the qualitative and quantitative characteristics of waste and by-product streams from existing industrial sectors are presented. In the third part, the techno-economic aspects of bioconversion processes are critically reviewed. Four case studies showing the potential of case-specific waste and by-product streams for the production of succinic acid and polyhydroxyalkanoates are presented. It is evident that fermentative production of chemicals and biopolymers via refining of waste and by-product streams is a highly important research area with significant prospects for industrial applications.

An algorithmic method for the selection of multivariable process control structures

Abstract In process systems, the selection of suitable sets of manipulated and controlled variables and the design of their interconnection, known as the control structure selection problem, is an important structural optimisation problem. The operating performance of a plant depends on the control structure selected as well as the characteristics of the disturbances acting on the plant. The economic penalty associated with the variability of main process variables close to active constraints is used in this work in order to develop a quantitative measure for the ranking of alternative control structures. Based on this measure, a general methodology is presented for the generation of promising control structures where general centralised, linear time invariant, output feedback controllers are used to form the closed loop system. The special case of optimal static output feedback controllers is further investigated in this paper. Furthermore, the problem of selecting proper weights in forming quadratic integral performance indices in designing optimal multivariable controllers is addressed. The validity and usefulness of the method is demonstrated through a number of case studies.

Formulation of fermentation media from flour-rich waste streams for microbial lipid production by Lipomyces starkeyi

Flour-rich waste (FRW) and by-product streams generated by bakery, confectionery and wheat milling plants could be employed as the sole raw materials for generic fermentation media production, suitable for microbial oil synthesis. Wheat milling by-products were used in solid state fermentations (SSF) of Aspergillus awamori for the production of crude enzymes, mainly glucoamylase and protease. Enzyme-rich SSF solids were subsequently employed for hydrolysis of FRW streams into nutrient-rich fermentation media. Batch hydrolytic experiments using FRW concentrations up to 205 g/L resulted in higher than 90% (w/w) starch to glucose conversion yields and 40% (w/w) total Kjeldahl nitrogen to free amino nitrogen conversion yields. Starch to glucose conversion yields of 98.2, 86.1 and 73.4% (w/w) were achieved when initial FRW concentrations of 235, 300 and 350 g/L were employed in fed-batch hydrolytic experiments, respectively. Crude hydrolysates were used as fermentation media in shake flask cultures with the oleaginous yeast Lipomyces starkeyi DSM 70296 reaching a total dry weight of 30.5 g/L with a microbial oil content of 40.4% (w/w), higher than that achieved in synthetic media. Fed-batch bioreactor cultures led to a total dry weight of 109.8 g/L with a microbial oil content of 57.8% (w/w) and productivity of 0.4 g/L/h.

Process design and optimization of novel wheat-based continuous bioethanol production system

A novel design of a wheat‐based biorefinery for bioethanol production, including wheat milling, gluten extraction as byproduct, fungal submerged fermentation for enzyme production, starch hydrolysis, fungal biomass autolysis for nutrient regeneration, yeast fermentation with recycling integrated with a pervaporation membrane for ethanol concentration, and fuel‐grade ethanol purification by pressure swing distillation (PSD), was optimized in continuous mode using the equation‐based software General Algebraic Modelling System (GAMS). The novel wheat biorefining strategy could result in a production cost within the range of

Sunflower-based biorefinery: Poly(3-hydroxybutyrate) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) production from crude glycerol, sunflower meal and levulinic acid

0.96–0.50 gal−1 ethanol (

Conversion of biodiesel‐derived glycerol into biotechnological products of industrial significance by yeast and fungal strains

0.25–0.13 L−1 ethanol) when the production capacity of the plant is within the range of 10–33.5 million gal y−1 (37.85–126.8 million L y−1). The production of value‐added byproducts (e.g., bran‐rich pearlings, gluten, pure yeast cells) was identified as a crucial factor for improving the economics of fuel ethanol production from wheat. Integration of yeast fermentation with pervaporation membrane could result in the concentration of ethanol in the fermentation outlet stream (up to 40 mol %). The application of a PSD system that consisted of a low‐pressure and a high‐pressure column and employing heat integration between the high‐ and low‐pressure columns resulted in reduced operating cost (up to 44%) for fuel‐grade ethanol production.

A targeting approach to the synthesis of membrane networks for gas separations

Polyhydroxybutyrate (PHB) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [P(3HB-co-3HV)] production was developed in bioreactor cultures using the strain Cupriavidus necator DSM 7237 cultivated on crude glycerol, sunflower meal (SFM) hydrolysates and levulinic acid as the sole fermentation feedstocks. Bacterial growth and PHB production was influenced significantly by the free amino nitrogen and inorganic phosphorus content of the SFM hydrolysate. Fed-batch bioreactor fermentations led to the production of 27gL(-1) PHB with an intracellular content of 72.9% (w/w). Continuous feeding of levulinic acid led to the production of up to 23.4gL(-1) P(3HB-co-3HV) with an intracellular content of 66.4% (w/w) and a 3HV content of 22.5mol%. A maximum 3HV content of 31mol% was achieved at earlier fermentation time (53h). Thus, levulinic acid could be combined with biodiesel industry by-products for the production of high P(3HB-co-3HV) concentration, intracellular content and industrially useful 3HV content.

On-line PI controller tuning for integrator/dead time processes

Oleochemical activities (e.g. biodiesel production, fat saponification) generate annually very high amounts of concentrated glycerol‐containing waters (called crude glycerol) as the principal residues of these processes. Crude glycerol is an industrial residue the valorization of which attracts remarkable and constantly increasing interest. In the current investigation, biodiesel‐derived glycerol was employed as substrate for yeast and fungal strains cultivated under nitrogen‐limited conditions in shake flasks. Glucose was employed as reference substrate. Several yeasts (Candida diddensiae, Candida tropicalis, Pichia ciferrii, Williopsis saturnus, Candida boidinii, and Candida oleophila) rapidly assimilated glucose and converted it into ethanol, despite aerobic conditions imposed, and were Crabtree‐positive. None of these yeasts produced ethanol during growth on glycerol or accumulated significant quantities of lipid during growth on glucose or glycerol. Only Rhodosporidium toruloides produced notable lipid quantities from glucose and to lesser extent from glycerol. Yarrowia lipolytica LFMB 20 produced citrate ≈58 g/L growing on high‐glucose media, while on high‐glycerol media ≈42 g/L citrate and ≈18 g/L mannitol. During growth on glucose/glycerol blends, glycerol was assimilated first and thereafter glucose was consumed. Fungi produced higher lipid quantities compared with yeasts. High lipid quantities were produced by Mortierella ramanniana, Mucor sp., and mainly Mortierella isabellina, with glycerol being more adequate for M. ramanniana and glucose for Mucor sp. and M. isabellina. M. isabellina ATHUM 2935 produced lipids of 8.5 g/L, 83.3% w/w in dry cell weight (DCW) and conversion yield per unit of glucose consumed ≈0.25 g/g. The respective values on glycerol were 5.4 g/L, 66.6% w/w in DCW and ≈0.22 g/g. Lipids of all microorganisms were analyzed with regards to their fatty acid composition, and M. isabellina presented the closest similitude with rapeseed oil. Crude lipids produced by this fungus and extracted with chloroform/methanol blend, were composed mostly of triacylglycerols, thus indicating that these solvents are adequate for triacylglycerol extraction.

Optimization of batch and fed-batch bioreactors using simulated annealing.

Abstract In this paper, the problem of optimizing the performance of membrane-based gas separations is investigated. A large number of papers has been presented in the past that deal with this subject with emphasis on the production of nitrogen or oxygen enriched air and the separation of the CO 2 /CH 4 gas mixture. This paper introduces a new approach where the membrane material is optimized together with the structure and the parameters of the membrane network. A superstructure representation of the membrane-based gas separation networks is also proposed. Two case studies are presented to demonstrate the usefulness of the new methodology as a rigorous tool for the optimization of membrane permeation processes.

Techno-economic evaluation of a complete bioprocess for 2,3-butanediol production from renewable resources

This paper presents two new methods for tuning PI controllers for integrator plus dead time models (IPDT). The simple IPDT model was found to be a useful approximation of more complex models such as first-order plus dead time models with large time constants. The use of IPDT models can, in these cases, simplify and also accelerate the auto-tuning step especially in MIMO processes. The advantages of the proposed methods over the known tuning methods are demonstrated through simulation examples.