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- Anasontzis, George E, 1980
(författare)
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Biomass modifying enzymes: From discovery to application
- 2012
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Ingår i: Oral presentation at the Chalmers Life Science AoA conference.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- It has now been realized that the road towards the bio-based economy is a one-way street, leaving gradually the oil-based technology and driving slowly towards a more sustainable society. The current non-biodegradable hydrocarbon fuels and plastics will be replaced by new products which will derive from natural and renewable resources. The synthesis of such biofuels and biochemicals is still challenged by the difficulties to cost efficiently degrade lignocellulosic material to fermentable sugars or to isolate the intact polymers. Biomass degrading and modifying enzymes play an integral role both in the separation of the polymers from the wood network, as well as in their subsequent modification, prior to further product development.Our group interests focus on all levels of applied enzyme research of biomass acting enzymes: Discovery, assay development, production and application. Relevant examples will be provided: What is our strategy for discovering novel microorganisms and enzymes from the tropical forests and grasslands of Vietnam? How do we design novel real-world assays for enzyme activity determination? Which are the bottlenecks in the enzymatic cellulose hydrolysis? How enzymes can be used to produce high added value compounds from biomass?
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| 4. |
- 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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| 5. |
- 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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| 6. |
- Bettiga, Maurizio, 1978, et al.
(författare)
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Yeast physiology studies and metabolic engineering for enhanced robustness
- 2014
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Ingår i: Enzitec 2014- XI Seminário Brasileiro de Tecnologia Enzimática. Barra da Tijuca-Rio de Janeiro, April 14th to 16th, 2014.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The extensive research on second-generation ethanol has paved the way to a new concept of bio-based industry, where lignocellulosic material is the primary source of sugars, to be converted to a number of fuels and chemicals. Sugars are released from cellulose and hemicellulose by pretreatment and hydrolysis steps. Harsh conditions during pretreatment promote the formation of a number of inhibitory compounds, among which weak organic acids, furaldehydes and phenolic compounds. In addition, the product of interest can act as a potent inhibitor. Regardless of the product, robust microorganisms are a prerequisite for the feasibility of lignocellulose-based bioprocesses.Current research carried out by our group focuses on the yeast Saccharomyces cerevisiae and aims at investigating the molecular bases of microbial robustness. Our efforts include the identification of the molecular targets of different classes of fermentation inhibitors aiming at understanding the complex responses of the cells to these compounds. The final goal is to engineer more robust strains. The concept of robustness will be discussed and examples of key features for S. cerevisiae robustness as well as examples of successful engineering to increase robustness will be presented.In particular, during this presentation, the following results will be discussed i) the study of redox and energy metabolism as key determinants of tolerance; ii) conversion routes of in S. cerevisiae as a way of detoxification from phenolic compounds; iii) cell membrane engineering as a strategy to achieve enhanced tolerance to weak acids.
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| 7. |
- Marx, Christian, 1975, et al.
(författare)
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ENGINEERING GLUTATHIONE BIOSYNTHESIS TO ENHANCE REDOX ROBUSTNESS OF Saccharomyces cerevisiae
- 2014
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Ingår i: ISSY31: 31ST INTERNATIONAL SPECIALISED SYMPOSIUM ON YEAST.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The focus for biofuel production shifts to using lignocellulose biomass from forest and agricultural by-products since it does not compete with food and feed production. Polysaccharides must be pretreated to be made accessible to hydrolytic enzymes to generate monomeric sugars for the following fermentation. In this pretreatment step inhibitors of fermenting microorganisms are generated, mainly furan derivates, weak acids and phenolics. Although Saccharomyces cerevisiae is more robust than bacteria, there is demand for improvement and the development of novel yeast strains with increased inhibitor tolerance is highly desirable.Furan derivates and other inhibitors have been shown to induce the formation of reactive oxygen species. Engineering of the redox metabolism of S. cerevisiae in terms of increasing the intracellular levels of glutathione by overexpressing glutathione synthetase GSH1 resulted in increased strain robustness in a simultaneous saccharification and fermentation (SSF) process. Cell survival and final ethanol concentrations were increased in the recombinant strains compared to the wild type in industrial media [Ask et al. 2013].To show a correlation between the intracellular concentration of glutathione and the resulting effect on robustness, strains accumulating different amounts of glutathione will be created. GshF is a bi-functional enzyme found in several bacterial species, that catalyzes the formation of glutathione from its precursors without accumulation of the intermediate product γ- glutamylcysteine and without any relevant feedback inhibition. GshF will be overexpressed in a CEN.PK strain, followed by deletion of the native GSH1 and GSH2 enzymes catalyzing the two-step reaction in S. cerevisiae.
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| 8. |
- Wang, Ruifei, 1985, et al.
(författare)
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Process optimization of multi-feed SSCF
- 2014
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Ingår i: 10th European Symposium on Biochemical Engineering Sciences and 6th International Forum on Industrial Bioprocesses.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Economical production of bio-ethanol from lignocellulosic materials requires an efficient and robust process which enables high-solid fermentation of pretreated lignocellulose to achieve high ethanol fermentation performance. In this work, we design and optimize a high-solid fed-batch simultaneous saccharification and co-fermentation (SSCF) process with a feed of substrate, enzyme and yeast cell for efficient production of ethanol from pretreated wheat straw in both lab and pilot scale. The yeast is prepared by pre-cultivation and adaptation in a semi-continuous cultivation in liquid hydrolysate medium in order to achieve high fermentation capacity. The feeding profiles in both pre-cultivation and SSCF steps are optimized based on a previously developed multi-feed SSCF model [1] in order to maintain high activities of both hydrolytic enzyme and yeast cell resulting in highest biomass yield during pre-cultivation and highest ethanol production efficiency during SSCF process. We also demonstrate scale up of fed-batch SSCF process in a 10 m3 pilot-scale bioreactor. The fed-batch SSCF with an optimized feed of substrate, cell and enzymes reaches high ethanol fermentation performance suggesting it to be a promising process for efficient bioconversion of lignocellulosic materials to ethanol.[1] Wang et al. Bioresour. Technol., 2014
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| 9. |
- Olofsson, Martin, 1975-, et al.
(författare)
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Combined Effects of Nitrogen Concentration and Seasonal Changes on the Production of Lipids in Nannochloropsis oculata
- 2014
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Ingår i: Marine Drugs. - Basel, Switzerland : MDPI AG. - 1660-3397 .- 1660-3397. ; 12:4, s. 1891-1910
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Tidskriftsartikel (refereegranskat)abstract
- Instead of sole nutrient starvation to boost algal lipid production, we addressed nutrient limitation at two different seasons (autumn and spring) during outdoor cultivation in flat panel photobioreactors. Lipid accumulation, biomass and lipid productivity and changes in fatty acid composition of Nannochloropsis oculata were investigated under nitrogen (N) limitation (nitrate:phosphate N:P 5, N:P 2.5 molar ratio). N. oculata was able to maintain a high biomass productivity under N-limitation compared to N-sufficiency (N:P 20) at both seasons, which in spring resulted in nearly double lipid productivity under N-limited conditions (0.21 g L−1 day−1) compared to N-sufficiency (0.11 g L−1 day−1). Saturated and monounsaturated fatty acids increased from 76% to nearly 90% of total fatty acids in N-limited cultures. Higher biomass and lipid productivity in spring could, partly, be explained by higher irradiance, partly by greater harvesting rate (~30%). Our results indicate the potential for the production of algal high value products (i.e., polyunsaturated fatty acids) during both N-sufficiency and N-limitation. To meet the sustainability challenges of algal biomass production, we propose a dual-system process: Closed photobioreactors producing biomass for high value products and inoculum for larger raceway ponds recycling waste/exhaust streams to produce bulk chemicals for fuel, feed and industrial material.
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| 10. |
- Johansson, Nina, 1983
(författare)
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A study of ethylene production via the 2-oxoglutarate dependent pathway in S. cerevisiae
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The detrimental effect of the petroleum industry on the environment combined with the threat of peak oil has driven the exploration for alternative strategies to produce traditional petrochemicals. Biotechnological production could be an alternative, using microorganisms to convert renewable feedstocks into desired products. A microbial based system for production of the traditional petrochemical ethylene has previously been developed through the expression of a bacterial version of the ethylene forming enzyme (EFE), which catalyzes the 2-oxoglutarate dependent ethylene pathway, in the yeast Saccharomyces cerevisiae. This work aims at deepening the understanding of how the EFE functions and investigate the functionality of the S. cerevisiae-EFE cell factory for ethylene production. To this end metabolic modeling, metabolic engineering as well as several cultivation studies have been performed. Alongside this the enzyme has been characterized through structural prediction and enzyme engineering, which has reviled both a structural entity necessary for ethylene forming functionality as well as a number of specific amino acid residues coupled to ethylene formation. Cultivation studies combined with metabolic engineering strategies have shown that balancing of arginine availability is important for optimal ethylene productivity. Further studies have also revealed that maintaining a high oxygenation level is a crucial cultivation factor for optimal ethylene productivity. This can be linked both to the reaction mechanism of the EFE, for which oxygen is a substrate, but also to an increased requirement of NADH re-oxidation when EFE is expressed. It was found that co-expression of heterologous oxidases could help relieve the redox stress and expression of the Aox1 of Histoplasma capsulatum was concluded to increase the ethylene yield with 28 %. To find further metabolic targets for increased ethylene productivity metabolic modeling was performed. The majority of the targets found were involved in supply of the EFE substrate 2-oxogltuarate, however none of the targets evaluated in vivo so far has given any increase in ethylene yields. Through this work important factors for optimal ethylene formation have been revealed, however it has also shown that more work is required before this system is a competitive alternative for ethylene production.
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