Research Iris Cornet

Abstract

Microbial oil is a necessary alternative to fossil or vegetable oil in the future. However, large-scale production is not yet economically viable. Diluted lignocellulosic waste streams are a cheap and therefore interesting source of carbon for microbial oil production. The use of reversible immobilisation of an oleaginous yeast in a continuous reactor with collection of the cells in which the oil has accumulated still has many shortcomings. High cell concentration, high oil accumulation and efficient remobilisation are extremely important. This requires a complex interaction between the carrier material, the microorganism and the medium composition. Several highly innovative solutions are being investigated in this project. It will be evaluated whether the lignocellulose-derived inhibitors (furan aldehydes, organic acids and phenolics) in the substrate enhance the natural immobilisation of the yeast cells. To further increase the immobilisation efficiency, the application of co-immobilisation of yeast with mould as well as the use of zwitterionic polymers for simple reversible immobilisation will be investigated. Strain improvement, taking into account all the required characteristics of the microorganisms, will be carried out using adaptive laboratory evolution. These innovations should lead to an efficient system where the inhibitors from diluted lignocellulosic waste streams are valorised in the form of microbial oil.

Researcher(s)

• Promoter: Cornet Iris
• Co-promoter: Vlaeminck Siegfried

Research team(s)

• Biochemical Wastewater Valorization & Engineering (BioWaVE)

Project type(s)

• Research Project

Abstract

Single-cell protein (SCP) production on food and beverage effluents is a resource-efficient water treatment approach, upgrading organics and nitrogen into protein for animal feed. These effluents are economically suitable for high-rate production of aerobic heterotrophic microorganisms (AHM) in open systems. However, fluctuations intrinsic to this approach lead to variability in nutritional quality of the SCP, and production costs of biomass downstream processing, still challenge the applicability of SCP technology. While an array of environmental biotech solutions showed the potential of biostimulation (co-substrate dosing) or bioaugmentation (target organism seeding), these tools have not yet been explored for SCP production on wastewater. SMArT aims to create a more stable and predictable microbial community leading to better nutritional quality using smart biostimulation and -augmentation strategies, based on renewable co-substrates, high-chance-to-thrive bacteria and yeast in a novel nursery concept. Biostimulant choice and dose will be tested with target AHM from enrichment cultures and literature. A sidestream nursery reactor is envisaged with optimal growth conditions to be coupled to the mainstream SCP reactor. Based on biomass yield and quality, the most prosperous configuration will be tested with real effluent. The advanced community engineering technology of SMArT aims a better SCP product that is attractive as a reliable and sustainable feed ingredient.

Researcher(s)

• Promoter: Vlaeminck Siegfried
• Co-promoter: Cornet Iris
• Fellow: González Cámara Sergio

Research team(s)

• Biobased sustainability engineering (SUSTAIN)

Project type(s)

• Research Project

Abstract

The aim of "FLAXIT" is to develop highly selective biocatalytic reactions for creating completely renewable molecules using flaxseed as the resource. For each ton of long flax fiber, 0.7 ton of flaxseed is produced in Belgium, which is considered a side stream, out of which 30-40% is oil and utilized mainly for low end technical applications. The other 60-70% is used as feed. With the intention of doubling the flax production to meet the growing fiber demand, flax growers in Belgium will produce higher volumes of flaxseed as by-product. In this project we will utilize the diverse biomolecules namely oil (consisting of polyunsaturated fatty acids), carbohydrates and proteins present in flaxseed to their best potential. With the help of extraction and biocatalytic transformations, we will create new value chains which open novel opportunities for farmers, industry, and society in Belgium. This project brings together a multidisciplinary team to use enzymatic- and microbial transformations to produce (i) methyl-, ethyl- and polyglycerol esters from flaxseed oil for personal care and cosmetic applications, (ii) long chain dicarboxylic acids from the flaxseed oil and carbohydrates for e.g. new polymers and cosmetic applications, and (iii) protein/peptides & water soluble dietary fibers from the defatted flaxseed cake for techno-functional applications in foods. In this way, we aim to obtain a zero-waste biorefinery for the valorization of flaxseed.

Researcher(s)

• Promoter: Cornet Iris

Research team(s)

• Biochemical Wastewater Valorization & Engineering (BioWaVE)

Project type(s)

• Research Project

Abstract

The overall scientific goal of WODCA is to create new, sustainable, affordable long-chain dicarboxylic acids (LCDA) from waste oil that are relevant for industrial applications such as high-performance polymers, lubricants, coatings, corrosion inhibitors, etc. For this purpose, new non-pathogenic micro-organisms are developed as biocatalysts in an optimised fermentation process based on used frying oil, followed by an innovative membrane-based purification to obtain high purity LCDAs suitable for various Flemish chemical companies.

Researcher(s)

• Promoter: Cornet Iris

Research team(s)

• Biochemical Wastewater Valorization & Engineering (BioWaVE)

Project type(s)

• Research Project

Abstract

This project aims to develop innovative ways of producing advanced (bio)fuels from microalgae and lignocellulosic matrices for road or air transport and applicable on national territory. It focuses on the development of innovative and competitive technological production schemes in order to position Belgium as a differentiated strategic partner and player for the eco-efficient production of advanced alternative (bio)fuels of second and third generation. The project is a cooperation between ULiège, UGent, UCLouvain and UAntwerpen. Within this project, BioWAVE, UAntwerpen coordinates research on the biochemical conversion and fermentation of optimized and modified lignocellulosic matrices with the innovative goal to combine a unique pre-treatment approach with a unique detoxification process for the one-step production of second-generation bioethanol. Bioethanol will be produced from lignocellulose, such as poplar wood and maize straw, wild type and genetically modified with a lower lignin content as provided by UGent. This process is a multi-step approach involving unitary operations of pretreatment, hydrolysis (often enzymatic), fermentation and rectification/distillation to produce bioethanol that would be suitable for integration into transportation fuels. An option favoured in this ADV_BIO project is steam explosion. Although attractive at first glance because it uses only water and no chemical agents, steam explosion generates "toxic" compounds that inhibit the subsequent saccharification process and may also inhibit bioethanol fermentation, thus reducing production yields. The main inhibitors are furan compounds (2-furfural or 5-hydroxymethylfurfural), weak organic acids, but also phenolic compounds that come from the degradation of lignin. The latter are considered to be the most problematic and must be eliminated from the reaction media. A research action is aiming at preventing lignin from hindering the conversion of lignocellulosic biomass by, first of all, the application of plants, with a lower lignin content. In the steam explosion, the lignin bonds are broken and phenolic degradation products are released into the liquid. It has been proven that repolymerisation into lignin can occur after a very severe pre-treatment, with newly formed bonds that are more difficult to break down. The addition of renewable additives during the steam explosion process will be investigated to prevent this unwanted repolymerisation. Removal of the remaining phenolic compounds, and possibly other inhibiting compounds, can be achieved by using biological detoxification as an integrated or additional step. Laccase detoxification of lignocellulosic matrices treated by steam explosion has been shown to increase the sugar yield during enzymatic hydrolysis. During this detoxification process, furan compounds and organic acids are also eliminated. In this research part improved lignocellulose biomass (UGent) will be applied in a relevant industrial process for bioethanol production, using steam explosion and simultaneous saccharification and fermentation. In addition, innovative technologies, i.e. supplementation during steam explosion to improve depolymerisation, and laccase as well as microbial detoxification, are applied to increase overall conversion.

Researcher(s)

• Promoter: Cornet Iris

Research team(s)

• Biochemical Wastewater Valorization & Engineering (BioWaVE)

Project type(s)

• Research Project

Abstract

In LIPTYDA we will create sustainable long-chain dicarboxylic acids (LCDAs) that are of great interest to several Flemish companies as they target different applications like high-grade polymers, plasticizers and lubricants. Current dicarboxylic acid production largely relies on fossil-based inputs and chemical processes, and is moreover limited to medium-chain products. In LIPTYDA we will focus on the novel long-chain dicarboxylic acids starting from grease trap waste (GTW); abundantly available in the food processing industry where it is collected during water treatment. GTW re-use is marginal as it is contaminated with food solids, and it is consequently mainly incinerated or deposited at landfills. Nevertheless, we see huge potential for GTW in biological fermentation processes: various LCDA producing yeast species thrive on lipids. First, we will thoroughly characterize the GTW and based on the outcome develop a suitable pretreatment. Next, we will apply advanced screening and synthetic biology approaches to obtain a yeast strain able to grow at high temperatures. Indeed, this is required to have GTW in the liquid state and guaranty good conversion to LCDAs. Finally, as we work with unusual temperatures and novel strains and feedstock, we will develop a new fermentation process using advanced reactor and cultivation technology.

Researcher(s)

• Promoter: Cornet Iris

Research team(s)

• Biochemical Wastewater Valorization & Engineering (BioWaVE)

Project type(s)

• Research Project

Abstract

Diluted phenol-rich streams occur regularly in lignocellulose-based biorefineries. Today, phenols are often regarded as waste. Some microorganisms can convert phenols into valuable intracellular components by fermentation. This makes the troublesome waste stream a raw material and an economic opportunity. To efficiently concentrate these dilute phenolic streams by conversion to intracellular components, it is necessary to speed up the process. In practice this often happens by increasing the amount of microorganisms, the biocatalyst, and consequently creating high cell concentrations. There is no efficient economic process for integrated fermentation and recovery of intracellular products. Our hypothesis is that the design of a new reactor type, namely a reversible immobilized cell reactor (RIR), offers a possible solution. In this reactor successively adhesion of the cells on a suitable support, fermentation, and finally desorption, to recover the intracellular components occurs. As a case study, the production of microbial oil is investigated starting from the phenolic hydrolysate obtained during the thermochemical treatment of lignocellulose. The aim of this project is to design an economically feasible process for valorising this phenolic flow. The new process will contribute to obtaining a biomass based circular economy.

Researcher(s)

• Promoter: Cornet Iris
• Co-promoter: Dries Jan
• Co-promoter: Vlaeminck Siegfried
• Fellow: Broos Waut

Research team(s)

• Biochemical Wastewater Valorization & Engineering (BioWaVE)

Project type(s)

• Research Project

Abstract

Natural deep eutectic solvents (NADES) show great promise as media for enzymatic reactions in sectors where (bio)compatibility with natural or medical products is a must. Whereas in theory they can be tailored to the envisioned reaction, ensuring optimized yields, to date the knowledge is predominantly empirical, with some mechanistic reports giving a fragmented view at best. Therefore, even merely explaining experimental observations is not straightforward, let alone making predictions. This doctoral study aims at building a structured, holistic understanding of the effect of NADES media on enzymatic reactions, whereby effects on solubility, solvation, viscosity, inhibition and denaturation will be distinguished. The solubility, solvation energy and viscosity will be predicted by first principles and molecular dynamics calculations, serving as input for a group contribution model using machine learning. Experiments will train and validate the model, and learnings from observed reaction kinetics will be further benchmarked against molecular dynamics calculations of enzyme structures and interactions in NADES. Structural changes of the enzyme will be demonstrated using Raman optical activity spectroscopy. The combination of these methods ensures fundamental knowledge acquisition, while the group contribution model is part of a structured methodology. The findings of this project are transferable to other uses of NADES.

Researcher(s)

• Promoter: Billen Pieter
• Co-promoter: Cornet Iris
• Co-promoter: Neyts Erik
• Fellow: Kovács Attila

Research team(s)

• Intelligence in PRocesses, Advanced Catalysts and Solvents (iPRACS)

Project type(s)

• Research Project

Abstract

During the thermochemical pretreatment biotechnological production of chemicals from the polysaccharides in lignocellulose, a solid fraction is obtained, consisting mainly of cellulose, and a lignin waste stream, the so-called, xylose rich fraction (XRF). XRF contains some residual sugar, toxic lignin-derived phenolic and sugar-derived furans. The goal of the research project is to investigate a technique to obtain almost complete removal of the lignin waste stream by using lipid producing bacteria, i.e., Rhodococcus sp. Rhodococcus is known to be able to metabolise phenol compounds. However to succeed, some hurdles have to be taken. (i) The furans and some phenolics can be toxic to the microorganism, (ii) repolymerisation of the lignin can occur (iii) the lignin is probably not completely converted, (iv) oligomers of lignin and lignin cellulose complexes can still be present, (v) it is not known if the Rhodococcus can degrade these oligomers. By analysis of the sugars, furans, phenolics, and the nature of the oligomers or particles, insight can be gained. Based on this knowledge, a toolbox of techniques to solve this will be applied, i.e. adaptation of the microorganism, commercial cellulases and laccases, alfa-naphtol to prevent repolymerisation of the lignin, using other bacteria, ….

Researcher(s)

• Promoter: Cornet Iris
• Co-promoter: Tavernier Serge

Research team(s)

• Biochemical Wastewater Valorization & Engineering (BioWaVE)

Project type(s)

• Research Project

Abstract

During the thermochemical pretreatment biotechnological production of chemicals from the polysaccharides in lignocellulose, a solid fraction is obtained, consisting mainly of cellulose, and a lignin waste stream, the so-called, xylose rich fraction (XRF). XRF contains some residual sugar, toxic lignin-derived phenolic and sugar-derived furans. The goal of the research project is to investigate a technique to obtain almost complete removal of the lignin waste stream by using lipid producing bacteria, i.e., Rhodococcus sp. Rhodococcus is known to be able to metabolise phenol compounds. However to succeed, some hurdles have to be taken. (i) The furans and some phenolics can be toxic to the microorganism, (ii) repolymerisation of the lignin can occur (iii) the lignin is probably not completely converted, (iv) oligomers of lignin and lignin cellulose complexes can still be present, (v) it is not known if the Rhodococcus can degrade these oligomers. By analysis of the sugars, furans, phenolics, and the nature of the oligomers or particles, insight can be gained. Based on this knowledge, a toolbox of techniques to solve this will be applied, i.e. adaptation of the microorganism, commercial cellulases and laccases, alpha-naphtol to prevent repolymerisation of the lignin, using other bacteria, …. The present project focuses on the first part of this research, namely characterizing the xylose-containing waste stream and investigating the toxicity of the individual components for Rhodococcus.

Researcher(s)

• Promoter: Cornet Iris

Research team(s)

• Biochemical Wastewater Valorization & Engineering (BioWaVE)

Project website

Project type(s)

• Research Project

Abstract

Pretreatment is a critical step in the conversion of lignocellulose into biofuels and biochemicals. During pretreatment, the recalcitrance of lignocellulose is reduced, making the carbohydrates more accessible for enzymatic saccharification. Fungal delignification by white rot fungi is an environmentally friendly alternative to chemical and physicochemical methods and is carried out in solid-state fermentation with mild reaction conditions and without the formation of microbial inhibitors. However, disadvantages of this technology include long pretreatment time, non-selective and low delignification, low enzymatic hydrolysis and required sterilisation of the raw material. This study investigates the possibility of improving and characterising the solid-state fungal pretreatment of poplar wood by Phanerochaete chrysosporium. The effects of MnSO4 and CuSO4 supplements on the delignification of sterilised wood are investigated using response surface methodology. Solid-state fermentations are carried out for 4 weeks in sterile ventilated bottles. The mechanism of the coordinated action of metal ions on lignin degradation is elucidated by relating fungal growth and ligninolytic enzyme activity to lignocellulose degradation as a function of pretreatment time. The optimised system with metal supplements is then applied to the pre-treatment of non-sterilised wood using different inoculation, nutrient and culture techniques. The fermentations are then analysed with infrared spectroscopy, in particular NIR and ATR-FTIR spectroscopy, to develop rapid quantification methods for lignin. Finally, the feasibility of producing fermentable sugars from sterilised and non-sterilised poplar wood using fungal pretreatment is evaluated through techno-economic analysis. Pretreatment of the wood with 2.01 µmol CuSO4 and 0.77 µmol MnSO4 g-1 wood resulted in a 1.9-fold higher lignin degradation, a 2.3-fold higher selectivity value for delignification and a 2.9-fold higher glucose yield. This can be explained by the joint action of Mn2+ and Cu2+ ions, with Mn2+ ions stimulating manganese peroxidase production and Cu2+ prolonging it. Fungal pretreatment under non-sterile conditions using dishes without sterile aeration. resulted in a similarly high glucose yield (28.51 ± 0.28%) as the traditional method using sterilised wood, sterile aeration and spores as inoculum, while reducing the amount of wood to be sterilised by 71.2%. Infrared spectroscopy-based methods with high coefficients of determination (R_CV^2 ≥ 0.87) were developed for rapid and reliable prediction of lignin in mouldy pre-treated wood. The techno-economic study showed that using non-sterilised wood as substrate and pre-colonised wood as inoculum resulted in a 14.5% (€2.15/kg) reduction in sugar production costs compared to using sterilised wood. This cost reduction can be attributed to the lower running costs due to the reduced need for sterilisation. Although promising cost reductions were demonstrated, mould pretreatment remained more expensive than conventional chemical and physicochemical methods due to high capital costs caused by factors such as long pretreatment time and low sugar yields. To overcome these challenges, it is crucial to prioritise further research focusing on screening and developing fungal strains with fast growth rates, high optimal growth temperature and selective lignin degradation capacities, as well as process optimisation and scale-up.

Researcher(s)

• Promoter: Vlaeminck Siegfried
• Co-promoter: Cornet Iris
• Co-promoter: Tavernier Serge
• Fellow: Wittner Nikolett

Research team(s)

Project website

Project type(s)

• Research Project

Abstract

This proposal aims at demonstrating the suitability and elucidating the effect of new green solvent media, natural deep eutectic solvents (NADES), on enzymatic reactions. NADES are eutectic mixtures of two or more biological primary metabolites (saccharides, amino and other organic acids, polyols, urea, choline) that are liquid at or slightly above room temperature, due to networking hydrogen bond interactions. Although they have been investigated earlier as green extraction media, reports on their use for enzymatic reactions are limited. For the first time, we will investigate their influence on enzymatic reactions by disaggregating the following effects: solvation energy, mass transfer in bulk and enzyme-substrate-intermediates stability. A well-known enzymatic conversion, i.e. deacetylation of a crude mannosylerythritol lipid (MEL) mixture aided by Novozym 435 (a commercial lipase), will be performed in selected NADES as a case example. Although no multi-parametric regression modeling will be done, qualitative (and semi-quantitative) insights will be gathered through coupling parametric solubility modeling (Hansen model, with experimental validation and input) with physicochemical characterization (viscosity, surface tension) of NADES systems, and concentration (substrate, enzyme) and temperature dependent kinetic experiments and modeling. The anticipated outcome of the project is a clear indication of enzymatic performance in fit for purpose NADES, and a breakdown of marginal efficiency change into solvation, activity and mass transfer differences with respect to traditional organic solvent systems.

Researcher(s)

• Promoter: Billen Pieter
• Co-promoter: Cornet Iris

Research team(s)

• Intelligence in PRocesses, Advanced Catalysts and Solvents (iPRACS)
• Biochemical Wastewater Valorization & Engineering (BioWaVE)

Project type(s)

• Research Project

Abstract

Very-long-chain fatty acids (VLCFAs) are fatty acids with a chain length of more than 20 carbons. They represent a valuable class of chemicals which can be used in several industries. Nowadays, these are produced from vegetable oils and petrochemical feedstock. In order to make the VLCFA production more sustainable, microbial VLCFA synthesis by Rhodococcus species seems to be a perfect tool. Unfortunately, current knowledge on VLCFA production with Rhodococcus is limited. Therefore, this project proposes to fill this gap. For investigation of the triggering effects to achieve high VLCFA production different agro-industrial substrates will be used as raw material. The triggering effect of the compounds on gene expression of the VLCFA pathway will be evaluated by RT-qPCR. The desired triggers should increase the VLCFA titer. Different Rhodococcus strains will be examined and evaluated for VLCFA synthesis. VLCFA production will be further optimized by screening of several medium compositions, optimization of environmental factors and, finally, the feeding pattern. Establishment of high VLCFA productivities can lead to a new production process of valuable building blocks for chemical industry.

Researcher(s)

• Promoter: Tavernier Serge
• Co-promoter: Cornet Iris
• Co-promoter: Wijnants Marc
• Fellow: Van Herck Jolien

Research team(s)

• Biochemical Wastewater Valorization & Engineering (BioWaVE)

Project type(s)

• Research Project

Abstract

Pretreatment of lignocellulose biomass is necessary to degrade the lignin, decrease the cellulose crystallinity and increase the surface area for the subsequent required enzymatic hydrolysis. Fungal pretreatment is based on solid state cultivation where the fungal mycelia penetrate and attack the solid substrate through direct contact by releasing ligninolytic enzymes. In this project the mechanisms and optimal conditions of this complex process are investigated to enable a decrease in pretreatment time by using a stable consortium of collaborating microorganisms. Separate fungal strains are growing on polar wood chips in a computer controlled solid state fermenter. The process is followed up by measuring the deligninolytic enzyme activities, cellulase activities, carbohydrate concentrations in order to evaluate the capabilities of each strain. Also the growth rate will be determined by measuring the oxygen uptake rate of the solid state culture. All acquired information will be important to select the right strains that will enable a microbial consortium where a synergetic cooperation with high lignin removal will be obtained. This final pretreatment efficiency will be evaluated on ethanol productivity in a simultaneous saccharification and fermentation process of the pretreated poplar wood.

Researcher(s)

• Promoter: Cornet Iris

Research team(s)

• Biochemical Wastewater Valorization & Engineering (BioWaVE)

Project website

Project type(s)

• Research Project

Abstract

Although good performance of solid state fermentation (SSF) on the lab scale, the industrial scale process has drawbacks, such as, poor heat transfer and difficult pH control. Bottleneck is the lack of information about the kinetics in SSF systems caused by the heterogeneous nature and complexity of the process. This project aims to model the kinetics of Monascus growth on rice based on experiments in a computer controlled solid state fermenter.

Researcher(s)

• Promoter: Cornet Iris
• Co-promoter: Apers Sandra
• Co-promoter: Cos Paul

Research team(s)

• Biochemical Wastewater Valorization & Engineering (BioWaVE)

Project type(s)

• Research Project