| 1. |
- Adeboye, Peter, 1982, et al.
(författare)
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Conversion of lignin-derived phenolic compounds by Saccharomyces cerevisiae
- 2014
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Ingår i: 36th Symposium on Biotechnology for Fuels and Chemicals, April 2-May 1st, Clearwater Beach, Florids, USA.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Lignin breakdown during biomass pretreatment releases a wide array of phenolic compounds in lignocellulose hydrolysates. Phenolic compounds, together with organic acids and furaldehydes are known to be inhibitors of microbial fermentation, thus limiting the efficient bioconversion of lignocellulose biomass. The goal of our study is to improve S. cerevisiae tolerance to phenolic compounds from lignocellulose hydrolysates and investigate its conversion capacities. In particular, we aimed i) to establish a correlation between the phenolic compounds structure and the effect on yeast growth, and ii) to investigate the conversion/detoxification products of selected representative compounds in order to provide strain engineering strategies for enhanced phenolics conversion.First, the effect on S. cerevisiae growth of 13 different phenolic compounds commonly found in lignocellulose hydrolysates was characterized. The compounds could be grouped in three clusters, according to their effect on lag phase duration, specific growth rate and cell density. Next, coniferyl aldehyde, p-coumaric acid and ferulic acid were chosen as representative compounds and their conversion product by S. cerevisiae in aerobic culture in bioreactor were identified and followed throughout the fermentation time. Understanding the effect of different phenolics on yeast and their conversion/ detoxification pathways is the first step not only in strain engineering for enhanced robustness, but also for designing new biorefinery concepts, where the bioconversion of lignin-derived aromatics could potentially be the source of new bio-based chemicals.
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| 2. |
- Adeboye, Peter, 1982, et al.
(författare)
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DETOXIFICATION AS A STRATEGY FOR DEVELOPING TOLERANCE IN Saccharomyces cerevisiae TO PHENOLIC COMPOUNDS
- 2014
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Ingår i: ISSY31: 31ST INTERNATIONAL SPECIALISED SYMPOSIUM ON YEAST.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Several phenolic compounds are formed as products of lignin breakdown during pretreatment of lignocellulosic biomass. These phenolic compounds are inhibitory to cell growth and function as biocatalysts in the production of second generation biofuels from degraded lignocellulosic biomass. Our research is focused on developing a Saccharomyces cerevisiae strain with improved resistance to phenolic compounds.As part of our study, we have focused on understanding the ability of S. cerevisiae to tolerate and convert phenolic compounds. We aim to understand the conversion mechanisms of phenolic compounds and adapt the knowledge to the engineering and use of S. cerevisiae on a biotechnological platform for bioethanol production and prospective, novel bio-based chemicals.We have investigated toxicity of various phenolic compounds against S. cerevisiae. Our results showed that phenolic compounds have varied toxicity against S. cerevisiae and the toxicity may be dependent on the structure of the compound involved. Under aerobic batch cultivation conditions, we have also studied the conversion of phenolic compounds by S. cerevisiae using coniferyl aldehyde, ferulic acid and p-coumaric acid as representative phenolic compounds. We compiled a list of conversion products of the three starting compounds under investigation and we proposed a possible conversion pathway, currently being investigated.In this talk, we present the proposed conversion pathway through which S. cerevisiae converts and detoxifies coniferyl aldehyde, ferulic acid and p-coumaric acid under aerobic cultivation condition.
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| 3. |
- Adeboye, Peter, 1982, et al.
(författare)
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Detoxification in Saccharomyces cerevisiae under phenolics stress
- 2013
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Ingår i: Conference on Physiology of Yeast and Filamentous Fungi.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Phenolic compounds, commonly found in woods hydrolysates and biorefinery side streams are products of lignin breakdown during wood pretreatment. They are formed alongside other products such as organic acids and furaldehydes. Phenolic compounds are widely varied and are known to be inhibitory to cell performance, thus making the efficient bioconversion of lignocellulose biomass to products such as bioethanol, a difficult task. As part of our aim at developing robust Saccharomyces cerevisiae for lignocellulosic fermentation, we have studied the interaction of S. cerevisiae cells with a selected subset of phenolic compounds. Three phenolic compounds; 3-methoxy-4-hydroxycinnamaldehyde, 3-methoxy-4-hydroxycinnamic acid and 4-hydroxycinnamic acid, were selected as representative phenolic compounds and model substrates. These substances represent phenolic aldehydes and acids thus providing an opportunity to closely compare different phenolic compound groups on the same –cinnamic- structural background, at the same time they offer a chance to probe the influence of side groups such as the methoxy group on the phenolic compound toxicity. Our studies show that when S. cerevisiae is exposed to the selected phenolic compounds, the cells carry out a process of detoxification that involves several conversion steps in transforming the toxic phenolic compounds to other phenolic compounds with much higher toxicity limits that confirm them to be less toxic. The toxicity limit here has been defined as the concentration at which S. cerevisiae performance in the presence of phenolic compounds is decreased to about 20% in comparison to the control in Yeast minimal Mineral medium without phenolic compounds. Furthermore, products and observed patterns of the conversion indicate that S. cerevisiae likely employs a common conversion route for the different phenolic compounds.
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| 4. |
- Adeboye, Peter, 1982, et al.
(författare)
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Fermentation of Biorefinery Streams
- 2011
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Ingår i: Yeast Retreat, Tjärnö, Sweden. August 15-17, 2011..
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Fermentation of biorefinery streams with S. cerevisiaePeter Adeboye, Eva Albers, Maurizio Bettiga and Lisbeth OlssonOur project aims at developing robust bioprocessing steps for the production of materials and energy from biomass, such as second‐generation ethanol by fermentation with Saccharomyces cerevisiae. We will concentrate on the fermentation of different biorefinery streams, generated by innovative biomass treatments. Fermentability of the substrates generated by the other project partner (Innventia AB) will be investigated, as well as maximum ethanol productivity and yield. Since lignocellulosic material can be a nutrient‐(especially nitrogen‐) poor and challenging substrate for the fermenting microorganism, the impact of different substrates on yeast metabolism will be investigated. Therefore, part of the research efforts of the project will be dedicated to fundamental studies on the effect of exposure to lignocellulose hydrolysate on energy metabolism, redox power homeostasis, cell integrity and viability. In addition, the effects of nutrient limitations will also be considered.
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| 5. |
- Adeboye, Peter, 1982, et al.
(författare)
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FERMENTATION OF BIOREFINERY STREAMS
- 2011
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Ingår i: PHD COURSE ON INDUSTRIAL BIOTECHNOLOGY FOR LIGNOCELLULOSE BASED PROCESSED.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Side streams generated from pulping processes have been of interest in the generation of alternative fuels due to the various wood compositional residues such as fermentable sugars leached out with it during the pulping process. These streams, due to their composition of fermentable sugars and other wood carbohydrate residues and the potential to ferment such carbohydrate residues in them for bioethanol production are in that case Biorefinery streams. Although these streams contain several growth inhibitory compounds such as furfural, numerous phenolic derivatives of lignin, several organic acids and are also known to be nutrient- (especially nitrogen-) poor thus constituting a challenging type of substrates for the fermenting microorganism, these traits however make for interesting grey areas for research on cell response to stress . Using biorefinery streams generated by innovative biomass treatments, our project aims at developing robust bioprocessing steps for the production of materials and energy, such as second-generation ethanol by fermentation with Saccharomyces cerevisiae. Fermentability of the substrates generated by the other project partner (Innventia AB) will be investigated, as well as maximum ethanol productivity and yield. The impact of different substrates on yeast metabolism will be investigated. Therefore, part of the research efforts of the project will be dedicated to fundamental studies on the effect of exposure to lignocellulose hydrolysate on energy metabolism, redox power homeostasis, cell integrity and viability. In addition, the effects of nutrient limitations will also be considered.
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| 6. |
- Adeboye, Peter, 1982, et al.
(författare)
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In situ conversion of phenolic compounds as a tool to phenolic tolerance development by S. cerevisiae
- 2015
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Phenolic compounds in hydrolysates are degradation products from the lignin component of wood. They are diverse in nature and they account for some of the inhibitory activities observed during lignocellulosic fermentation. S. cerevisiae possesses the ability to convert some phenolic compounds. We are currently studying the interaction between S. cerevisiae and selected phenolic compounds namely; coniferyl aldehyde, ferulic acid and p-coumaric acid to understand the ability of S. cerevisiae to convert the selected compounds. Preliminary results show that the three phenolic compounds are being converted into several other less inhibitory phenolic compounds common to the three compounds. We hypothesised a conversion route and engineered S. cerevisiae strains to test the hypothesis, the preliminary result shows faster conversion in an engineered strain.
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| 7. |
- Albers, Eva, 1966, et al.
(författare)
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Comparison of industrial xylose fermentation with yeast performed at different process scale
- 2012
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Ingår i: 13th International Congress on Yeasts, ICY 2012, August 26-30, Madison, USA.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Second generation of bioethanol production with yeast from lignocellulosic material may contribute to a sustainable production of energy. However, the commercialization of cellulose-to-ethanol remains challenging due to various limitations in process technology and microbial physiology. Despite that the technical progress lately has come far, lignocellulose bioethanol production is still not well established in full production scale. Production scale demands large financial investments and to minimize the risk knowledge about cellular performance of the yeast as response to conditions of large scale is needed. Large scale may impose specific conditions that normally are not present in smaller scale. Such conditions are then needed to be identified and mimicked in smaller scale to obtain crucial scaling-up data. In this project, we wanted to establish scalable cultivation processes and compare the performance at different scales. Experiments were performed at three process scales: lab (1.5 l), process development unit (15 l) and demonstration (10 m3) scales, with an industrial recombinant xylose fermenting Saccharomyces cerevisiae strain and corn cob, bagasse, and spruce lignocellulosic material. It was found that separate fermentation and SSF experiments could be reproducible at all scales. An ethanol level could be obtained above 4 % which is the threshold for feasible down-stream processing. Demonstration scale experiments on xylose-rich liquid of pre-treated corn cobs resulted in a 90% conversion of xylose to ethanol and on the slurry in SSF cultivation an ethanol yield of 0.44 g/g xylose was obtained.
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| 8. |
- Albers, Eva, 1966, et al.
(författare)
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Development and large scale performance of efficient xylose fermenting yeast strains
- 2011
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Ingår i: Seventh International Conference on Renewable Resources and Biorefineries, Belgium.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Fermentation at large industrial scale poses several challenges for the fermenting microorganism to handle. Thus, for an efficient production it is desirable to have robust and efficient strains which can cope with the specific conditions in the process. For bioethanol production by yeast from lignocellulosic material the substrate for growth constitutes one of the largest challenges due to its mixture of sugars and content of inhibitory compounds. Wild-type strains of Saccharomyces cerevisiae can only convert hexose sugars but not the pentoses, xylose and arabinose, which may be present in lignocellulosic material. However, strains have been genetically modified to allow for xylose conversion, but their performance is needed to be improved in terms of rate and efficiency. During the pre-treatment of lignocellulosic material inhibitory compounds are formed; furans, phenolics and organic acids. In an industrial setting, a robust strain back ground (industrial yeast strains) is a prerequisite, in which earlier pentose fermenting traits should be incorporated and further adaptation to the inhibitory compounds need to follow. In the present project, we have used directed evolution to simultaneously improve the inhibitor tolerance and xylose conversion capability of recombinant yeast strains with an industrial background. Improved yeast strains resulting from several strategies were evaluated and one of the best strains with high ethanol production, good xylose utilization capacity, and low xylitol formation was selected for evaluation in larger scale. Fermentations on pre-treated corn cobs were performed with good results regarding ethanol production and xylose utilization both in process development unit scale (15 l) and demonstration scale (10 m3).
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| 9. |
- Albers, Eva, 1966, et al.
(författare)
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Development of industrial yeast strains for efficient xylose fermentation in lignocellulosic material
- 2012
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Ingår i: 13th International Congress on Yeasts, ICY 2012, August 26-30, Madison, USA.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Fermentation at large industrial scale poses several challenges for the fermenting microorganism to handle. Thus, for an efficient production it is desirable to have robust and efficient strains, which can cope with the specific conditions in the process. For bioethanol production by yeast from lignocellulosic material, one of the largest challenges is the mixture of sugars and the content of inhibitory compounds in the material. Wild-type strains of Saccharomyces cerevisiae can only convert hexose sugars but not the pentoses, xylose and arabinose, which may be present in these materials. However, strains have been genetically modified to allow for xylose conversion, but their performance need to be improved in terms of rate and efficiency. During the pre-treatment of lignocellulosic material the inhibitory compounds are formed; furans, phenolics and organic acids. In an industrial setting, a robust strain back ground (industrial yeast strains) is a prerequisite, in which first pentose fermenting traits should be incorporated and further improvement of the tolerance to inhibitory compounds need to follow. In the present project, we have used directed evolution to simultaneously improve the inhibitor tolerance and xylose conversion capability of recombinant yeast strains with an industrial background. The strains showed increased xylose utilization and ethanol production which was for some strains coupled to decreased xylitol formation. The resulting properties of the strains are highly dependent on the mode of directed evolution applied, which may also give rise to quite a number of clones with different properties.
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| 10. |
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