| 1. |
- Alriksson, Björn, et al.
(författare)
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Overexpression of Saccharomyces cerevisiae transcription factor and multidrug resistance genes conveys enhanced resistance to lignocellulose-derived fermentation inhibitors
- 2010
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Ingår i: Process Biochemistry. - : Elsevier. - 1359-5113 .- 1873-3298. ; 45:2, s. 264-271
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Tidskriftsartikel (refereegranskat)abstract
- The presence of fermentation inhibitors in lignocellulose hydrolysates is an obstacle for achieving efficient fermentation of lignocellulose hydrolysates to ethanol and other commodities. In this investigation, the possibility of generating more inhibitor-resistant Saccharomyces cerevisiae by genetic engineering was explored. Based on previous results from studies of deletion mutants, three S. cerevisiae genes (ATR1, FLR1, YAP1) involved in multidrug resistance and stress response of yeast were selected for overexpression in three S. cerevisiae strains. The resistance of the transformed strains to lignocellulose-derived fermentation inhibitors and a dilute-acid spruce hydrolysate was evaluated in fermentation experiments. Overexpression of FLR1 resulted in enhanced resistance to the phenolic inhibitor coniferyl aldehyde and the furan aldehyde HMF (5-hydroxymethyl-2-furaldehyde). Overexpression of ATR1 conferred increased resistance to coniferyl aldehyde. Strains overexpressing YAP1, which encodes a transcription factor, displayed increased resistance to coniferyl aldehyde, HMF, and the spruce hydrolysate. An ethanol productivity of 0.17 g ethanol × l−1 × h−1 was achieved for a YAP1-overexpressing transformant cultivated in spruce hydrolysate, whereas a control transformant, which did not overexpress YAP1, only reached a productivity of 0.05 g ethanol × l−1 × h−1.
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| 2. |
- Andersson, Mikael, et al.
(författare)
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Characterization of the Chemical and Functional Stability of DEAE Sepharose Fast Flow
- 1993
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Ingår i: Process Biochemistry. - 1359-5113 .- 1873-3298. ; 28:4, s. 223-230
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Tidskriftsartikel (refereegranskat)abstract
- The release of amines from the ion-exchange groups in DEAE Sepharose® Fast Flow has been studied under static and column conditions. The leakage compounds have been identified and quantified by gas chromatography—mass spectrometry. It was shown that the main leakage product under acidic (pH 1) and basic conditions (pH 14) was N,N,N′,N′-tetraethylethylenediamine. Three other amines were also identified, namely N,N,N′-triethylethylenediamine, diethylaminoethanol and diethylamine. The leakage of amines from DEAE Sepharose Fast Flow treated at pH 1 or 14 for 672 h at 40°C corresponds to a reduction of only 1% of the total ion-exchange capacity.The functional stability of DEAE Sepharose Fast Flow was also studied by separation of a protein mixture during repeated cleaning-in-place treatments with 0·10 m HCl or 1·0 m NaOH. The separation behaviour was unaltered after the gel had been treated for a total contact time of 672 h with 0·10 m HCl or 1·0 m NaOH.The clearance of ethanol from a DEAE Sepharose Fast Flow column stored in a 20% ethanol aqueous solution was also studied.
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| 3. |
- Andersson, Mikael, et al.
(författare)
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The Influence of the Degree of Cross-linking, Type of Ligand and Support on the Chemical Stability of Chromatography Media Intended for protein Purification
- 1998
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Ingår i: Process Biochemistry. - 1359-5113 .- 1873-3298. ; 33:1, s. 47-55
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Tidskriftsartikel (refereegranskat)abstract
- The release of organic compounds from different liquid chromatography media in static conditions has been analysed with a total organic carbon (TOC) analyser. TOC results show that chemical stability increases with the degree of cross-linking in agarose beaded chromatography media and thus extend the working pH-range of the media. Of the unsubstituted chromatography media investigated, Sepharose® 6B, Sepharose CL-6B, Sepharose 4 Fast Flow, Sepharose 6 Fast Flow and Sepharose High Performance, the latter was the most stable medium. Sepharose High Performance releases only about 0·06% of its total carbon content after 1 week in 0·01 m HCl. Agarose beads are more stable to basic conditions (pH 14) compared with acidic conditions (pH 2). From UV spectroscopic and gel filtration results it was found that all Sepharose media release low amounts of 5-(hydroxymethyl)-2-furaldehyde and agarose fragments in acidic conditions. To investigate the effect of different ligands on chemical stability Q Sepharose 6 Fast Flow, DEAE Sepharose 6 Fast Flow, SP Sepharose 6 Fast Flow, CM Sepharose 6 Fast Flow, Phenyl Sepharose 6 Fast Flow, Octyl Sepharose 4 Fast Flow media were also studied under static conditions. In basic conditions it was found that all these chromatography media release carbon compounds to a higher extent than the unsubstituted Sepharose support. In addition, Hofmann elimination of Q and DEAE groups contributes to the decrease in the carbon content of the corresponding anion exchangers. During exposure to acidic conditions (pH 2) the release of carbon compounds was lower than the release from the support to which the ligands were coupled. The exceptions are Octyl Sepharose 4 Fast Flow and SP Sepharose 6 Fast Flow. In the case of Octyl Sepharose 4 Fast Flow, the ligand did not seem to influence chemical stability, whereas the SP group increases the degradation of the Sepharose support. In the case of SP Sepharose 6 Fast Flow the stability in acidic conditions can be improved by increasing the ionic strength. Anion exchangers based on different support polymers (agarose-, polystyrene-, methacrylate- and polyvinyl-based matrixes) were studied under static conditions. Agarose-based anion exchanger was the most stable in basic conditions (pH 14). In acidic conditions (pH 2) the chemical stability was about the same for many different anion exchangers.
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| 4. |
- Antonopoulou, Io, et al.
(författare)
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Optimization of enzymatic synthesis of l-arabinose ferulate catalyzed by feruloyl esterases from Myceliophthora thermophila in detergentless microemulsions and assessment of its antioxidant and cytotoxicity activities
- 2018
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Ingår i: Process Biochemistry. - : Elsevier. - 1359-5113 .- 1873-3298. ; 65, s. 100-108
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Tidskriftsartikel (refereegranskat)abstract
- The feruloyl esterases FaeA1, FaeA2, FaeB1, FaeB2 from Myceliophthora thermophila C1 and MtFae1a from M. thermophila ATCC 42464 were used as biocatalysts for the transesterification of vinyl ferulate (VFA) with l-arabinose in detergentless microemulsions. The effect of parameters such as the microemulsion composition, the substrate concentration, the enzyme load, the pH, the temperature and the agitation was investigated. FaeA1 offered the highest transesterification yield (52.2 ± 4.3%) after 8 h of incubation at 50 °C using 80 mM VFA, 55 mM l-arabinose and 0.02 mg FAE mL−1 in a mixture comprising of 19.8: 74.7: 5.5 v/v/v n-hexane: t-butanol: 100 mM MOPS-NaOH pH 8.0. The ability of l-arabinose ferulate (AFA) to scavenge 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals was significant (IC50 386.5 μM). AFA was not cytotoxic even at high concentrations (1 mM) however was found to be pro-oxidant at concentrations higher than 20 μM when the antioxidant activity was determined with the dichloro-dihydro-fluorescein diacetate (DCFH-DA) assay in human skin fibroblasts.
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| 5. |
- Aragao, Rosa, et al.
(författare)
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Immobilization of Clostridium acetobutylicum DSM 792 as macroporous aggregates through cryogelation for butanol production
- 2014
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Ingår i: Process Biochemistry. - : Elsevier BV. - 1873-3298 .- 1359-5113. ; 49:1, s. 10-18
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Tidskriftsartikel (refereegranskat)abstract
- In this study, a new cell immobilization technique is presented. Cells of Clostridium acetobutylicum DSM 792 form a macroporous aggregate through cryogelation with concomitant crosslinking together with activated polyethyleneimine (PEI) and poly(vinyl alcohol) (PVA). The cell based cryogel presents a highly porous, elastic structure with walls consisting of densely packed crosslinked cells. The immobilization process maintained the viability of cells as new bacterial cells were observed when gel-plugs were incubated in liquid medium, glucose was consumed and solvent production was observed. Solvent production was improved 2.7-fold in immobilized cells in comparison to free cells. It was possible to reuse the gel-plugs 3-5 times in partial or completely fresh medium, reaching a maximum butanol concentration in the broth of 18.2 g/l and yield of 0.41 (g/g) in one of the cycles. The use of cells based cryogels can be a good alternative for improvement of acetone-butanol-ethanol (ABE) process as cells are immobilized in a macroporous structure with low limitations for mass transfer with potential for high yield production. (C) 2013 Elsevier Ltd. All rights reserved.
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| 6. |
- Areskogh, Dimitri, et al.
(författare)
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Immobilisation of laccase for polymerisation of commercial lignosulphonates
- 2011
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Ingår i: Process Biochemistry. - : Elsevier BV. - 1359-5113 .- 1873-3298. ; 46:5, s. 1071-1075
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Tidskriftsartikel (refereegranskat)abstract
- The oxidoreductive enzyme laccase has previously been shown to be able to increase the average molecular weight of lignosulphonatesthrough generation of phenoxy radicals on end groups and the subsequent radical-radical coupling reactions that cross-link individual lignosulphonate molecules. Utilisation of laccases for this purpose is a potential industrial process not only to improve the properties of technical lignosulphonates but also to expand their utilisation to new areas. Immobilisation of the laccase is an interesting technique to enable reusage of the enzyme and thus reduce costs involved with such process. In this work, we demonstrate the potential of immobilised laccase to polymerise technical lignosulphonates. A number of factors that limits re-utilisation of the immobilised catalyst such as lignosulphonate adsorption onto the carrier and laccase deactivation have been identified and are discussed. However, by using a low-porosity support and lower reaction temperatures these problems can be limited.
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| 7. |
- Ask, Magnus, 1983, et al.
(författare)
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Challenges in enzymatic hydrolysis and fermentation of pretreated Arundo donax revealed by a comparison between SHF and SSF
- 2012
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Ingår i: Process Biochemistry. - : Elsevier BV. - 1359-5113 .- 1873-3298. ; 47:10, s. 1452-1459
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Tidskriftsartikel (refereegranskat)abstract
- The perennial herbaceous crop Arundo donax is a potential feedstock for second-generation bioethanol production. In the present work, two different process options were investigated for the conversion of two differently steam-pretreated batches of A. donax. The pretreated raw material was converted to ethanol with a xylose-consuming Saccharomyces cerevisiae strain, VTT C-10880, by applying either separate hydrolysis and fermentation (SHF) or simultaneous saccharification and fermentation (SSF). The highest overall ethanol yield and final ethanol concentration were achieved using SHF (0.27 g g(-1) and 20.6 g L-1 compared to 0.24 g g(-1) and 19.0 g L-1 when SSF was used). The performance of both SHF and SSF was improved by complementing the cellulolytic enzymes with hemicellulases. The higher amount of acetic acid in one of the batches was shown to strongly affect xylose consumption in the fermentation. Only half of the xylose was consumed when batch 1 (high acetic acid) was fermented, compared to that 94% of the xylose was consumed in fermentation of batch 2 (lower acetic acid). Furthermore, the high amount of xylooligomers present in the pretreated materials considerably inhibited the enzymatic hydrolysis. Both the formation of xylooligomers and acetic acid thus need to be considered in the pretreatment process in order to achieve efficient conversion of A. donax to ethanol.
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| 8. |
- Bohn, Irene, et al.
(författare)
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The energy balance in farm scale anaerobic digestion of crop residues at 11-37 degrees C
- 2007
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Ingår i: Process Biochemistry. - : Elsevier BV. - 1873-3298 .- 1359-5113. ; 42:1, s. 57-64
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Tidskriftsartikel (refereegranskat)abstract
- Crop residues can be used for biogas production in farm scale reactors. Use of a process temperature below mesophilic conditions reduces the need for heating as well as investment and operating costs, although it may also reduce the methane yield. In the present study the effect of temperature on net energy output was studied using sugar beet tops and straw as substrates for two pilot-scale reactors. Digestion was found to be stable down to 11 degrees C and optimal methane yield was obtained at 30 degrees C. The methane yield and process performance was studied at 15 degrees C and 30 'C as organic loading rates were increased. It was found that the highest net energy production would be achieved at 30 degrees C with a loading rate of 3.3 kg VS m(-3) day(-1). Running a low-cost process at ambient temperatures would give a net energy output of 60% of that obtained at 30 degrees C. (c) 2006 Elsevier Ltd. All rights reserved.
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| 9. |
- Butler, Samuel J., et al.
(författare)
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Transglycosylation by β-mannanase TrMan5A variants and enzyme synergy for synthesis of allyl glycosides from galactomannan
- 2022
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Ingår i: Process Biochemistry. - : Elsevier BV. - 1359-5113. ; 112, s. 154-166
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Tidskriftsartikel (refereegranskat)abstract
- Retaining β-mannanases are glycoside hydrolases (GHs) that can potentially be applied for synthesis of glycosides by catalysis of transglycosylation reactions. A novel active-site double mutant (R171K/E205D) of the catalytic module (CM) of the family GH5 Trichoderma reesei β-mannanase (TrMan5A) was expressed in Pichia pastoris and purified. TrMan5A, CM and CM-variants R171K and R171K/E205D had pH optima between pH 4.0–5.3 and showed >80 % remaining activity after incubation at 40 °C for 48 h. The enzymes were screened for transglycosylation capacity toward oligomeric and polymeric donor substrates and alcohol acceptors using mass-spectrometry. Hydrolysis and transglycosylation products were analysed by a novel HPLC procedure using an NH2 column. R171K/E205D was superior in reactions with mannotetraose and the acceptor allyl alcohol, it had twice as high propensity for transglycosylation as wild-type TrMan5A. Wild-type TrMan5A produced the highest amounts of allyl β-mannosides (with 1–3 mannosyls) from locust bean galactomannan. Applying enzyme synergy, adding the GH27 guar α-galactosidase to the reaction (to cleave off galactomannan side-groups), gave a 2.1-fold increase of allyl mannosides and simultaneously a significant production of allyl galactopyranoside, increasing overall yield of allyl glycosides 4.4-fold, from 2.2% to 9.8%. The enzymatic synthesis of reactive allyl glycosides opens up for production of novel biomaterials and glycopolymers.
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| 10. |
- Campos, Joana, et al.
(författare)
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Fed-batch strategies for biodetoxification in production of optically pure lactic acid from softwood hydrolysate using Pediococcus acidilactici
- 2023
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Ingår i: Process Biochemistry. - : Elsevier BV. - 1359-5113. ; 125, s. 162-170
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Tidskriftsartikel (refereegranskat)abstract
- Optically pure lactic acid (LA) is important for the development of specialized applications for poly-lactic acid (PLA). To pursue sustainable production, feedstocks such as lignocellulosic biomass need to be investigated. The present study focused on the production of L-LA from softwood hydrolysate with Pediococcus acidilactici TY112. One of the challenges when using this substrate is the presence of inhibitors, such as furfural and 5-hydroxymethylfurfural (HMF), formed during pretreatment. To investigate adaptation, fed-batch experiments on softwood hydrolysate and model media were conducted. Although LA production was still affected by the presence of other inhibitors in the hydrolysate, P. acidilactici TY112 was capable of converting HMF and furfural and partly detoxify both hydrolysate and synthetic media. The strain adapted to the inhibitors present, if fed at a low rate (30 mL·h−1 for model medium with inhibitors and 15 mL·h−1 for softwood hydrolysate, both with 30 g·L−1 glucose and 45 g·L−1 mannose). Regarding carbon source consumption, a feeding rate of 30 mL·h−1 limited the uptake of glucose, leading to improved mannose uptake, with LA yields higher than 0.86 g·g−1. This study shows the potential of P. acidilactici TY112 for the production of L-LA from softwood hydrolysate which is regarded as inhibitory.
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