Towards the integration of fermentation and crystallisation - A study on the production of L-phenylalanine

Industrial biotechnology can be defined as the utilization of living organisms or their enzymes for the industrial production of food, beverages, commodity chemicals and pharmaceuticals, among others. A biotechnological production process, so-called bioprocess, mostly comprises product formation (e.g. by fermentation) and product recovery and purification. In order to be commercially interesting, industrial fermentation processes should result in high product concentrations. High product concentrations during fermentation translate into high productivity and are also linked to simpler and more efficient recovery and purification processes. Although high product concentrations can be achieved by several tools provided by modern biotechnology, factors such as product toxicity to the micro-organism, product degradation or control mechanisms like feedback repression continue to be limiting. In these cases, it may be beneficial to remove the product from the vicinity of the micro-organism as soon as it is being formed. This approach, known as in situ product removal or in situ product recovery (ISPR), has been described in literature with techniques such as adsorption, extraction and membrane technology. Recently, product recovery by crystallisation has received att ention for products that are commercialised in crystal form. In such cases, product recovery by crystallisation might not only lead to higher fermentation productivities (by reducing product toxicity and/or degradation) but also to simpler downstream operations (by recovering the product already in crystal form), without requiring the use of auxiliary materials. The feasibility of such a concept should be evaluated at early stages of process development. At early stages, however, the available information and experimental data are usually limited. Generic methods or rules of thumb, derived from the study of model systems, should contribute in this evaluation. In this thesis, the production of the amino acid L-phenylalanine (Phe) by Escherichia coli is used as a model system. This thesis shows that the concept of product recovery by crystallisation during fermentation to improve the production of Phe is viable. The approach used in this thesis allowed exploring the possibilities and limitations of the process by means of simple experiments with aqueous model solutions and black-box models. Although this approach can be used for evaluating the potential of product recovery by crystallisation during fermentation in other processes, it fails in taking into account the particularities of the system. These particularities can strongly impact the feasibility of the integrated process.BiotechnologyApplied Science

Process for the recovery of lipids or hydrocarbons

The invention is directed to a method for recovering a lipid or hydrocarbon from a fermentation mixture, comprising the steps of - providing a fermentation mixture wherein the lipid or hydrocarbon is produced by microbial fermentation in a fermentation vessel, which mixture comprises an aqueous phase and a liquid product phase, wherein the liquid product phase comprises the lipid or hydrocarbon; and - feeding at least part of the aqueous phase and part of the liquid product phase to a second vessel, thereby forming a second mixture; and - promoting phase-separation of the aqueous and product phase by injecting a gas into the second mixture, thereby separating the product phase from the aqueous phase; and - collecting the product phase comprising the lipid or hydrocarbon.BT/BiotechnologyApplied Science

Photo-Optical In-Situ Measurement of Drop Size Distributions: Applications in Research and Industry

The exact knowledge of Drop Size Distributions (DSD) plays a major role in various fields of applications to control and optimize processes, as well as reduce waste. In the microbial production of advanced biofuels, oil droplets are produced under turbulent conditions in an aqueous medium containing many surface active components, making DSD knowledge essential for process optimization. The capability of a photo-optical measurement method for DSD measurement in fermentation broth and in plate separators is illustrated aiming at cost reduction in the microbial production of advanced biofuels. Measurements were carried out with model mixtures in a bioreactor, and at the inlet and outlet of a plate separator. In the bioreactor, the method was effective in detecting a broad range of droplet sizes and in differentiating other disperse components, e.g., microbial cells and gas bubbles. In the plate separator, photo-optical measurement effectively determined the influence of the varied parameters on the separation efficiency.BT/Bioprocess Engineerin

Techno-economic assessment of the use of solvents in the scale-up of microbial sesquiterpene production for fuels and fine chemicals

Sesquiterpenes are a group of versatile, 15-carbon molecules with applications ranging from fuels to fine chemicals and pharmaceuticals. When produced by microbial fermentation at laboratory scale, solvents are often employed for reducing product evaporation and enhancing recovery. However, it is not clear whether this approach constitutes a favorable techno-economic alternative at production scale. In this study empirical correlations, mass transfer and process flow sheeting models were used to perform a techno-economic assessment of solvent-based processes at scales typical for flavors and fragrances (25 MT year−1) and the fuel market (25 000 MT year−1). Different solvent-based process options were compared to the current state of the art, which employs surfactants for product recovery. The use of solvents did reduce the sesquiterpene evaporation rate during fermentation and improved product recovery but it resulted in costs that were higher than, or similar to, the base case due to the additional equipment cost for solvent-product separation. However, when selecting solvents compatible with the final product formulation (e.g. in a kerosene enrichment process), unit costs as low as $0.7 kg−1 can be achieved while decreasing environmental impact.BT/Bioprocess EngineeringBT/Biotechnology and Societ

Impact of flocculant addition in oil recovery from multiphasic fermentations

Emulsion formation is a major concern when dealing with multiphasic fermentations. Flocculants can be used together with other demulsification techniques to improve oil recovery in multiphasic fermentations. In this paper, the impact of adding flocculants during a multiphasic fermentation with 10 wt% dodecane, to destabilize the broth emulsion, improve creaming formation and enhance oil recovery is studied. Flocculants, CaCl2 and (NH4)2SO4 were shown to be the most promising flocculants. Flocculant addition, their time of addition, and its impact on multiphasic fermentations has been evaluated by comparing fermentation performance against reference fermentations and three oil recovery methods: gravity settling, gas enhanced oil recovery and centrifugation. When adding 75 mM of (NH4)2SO4 during fermentation, the creaming rate during gravity settling increased 3-fold and the oil recovery by gas enhanced oil recovery was 35%, without altering fermentation performance. Addition of CaCl2 during fermentation resulted in 88% and 67% oil recovery for early and late addition, which is a 4 and 3-fold increase in comparison with the reference. Yet, CaCl2 deviated from standard fermentation performance when added immediately after second phase addition. In conclusion, flocculant addition during multiphasic fermentation can be used to destabilize microbial emulsions and potentially improve in situ oil recovery.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.BT/Bioprocess EngineeringExecutive boardChemE/Transport Phenomen