Browsing by Subject "ENZYMATIC-HYDROLYSIS"

Sort by: Order: Results:

Now showing items 1-13 of 13
  • Dou, Jinze; Chandgude, Vijaya; Vuorinen, Tapani; Bankar, Sandip; Hietala, Sami; Huy Quang Le (2021)
    Aiming to understand the importance of debarking on the controlled utilization of phenolic-rich willow biomass, biobutanol was produced from it by using Clostridium acetobutylicum. Acid-catalysed steam explosion and enzymatic hydrolysis (EH) were investigated before the acetone-butanol-ethanol (ABE) fermentation. The hydrolysable sugar yield and ABE fermentation efficiency were found to decline progressively from willow wood (WW) to HWE WB (hot water extracted willow biomass), WB (willow biomass) and the WW + HWE (willow wood plus the artificial willow bark water extracts), indicating that the pre-removal of water extracts or the bark can significantly improve ABE yield. Notably, the ABE productivity of WW achieved 12.7 g/L at the solvent yield of 31%, and the butanol concentration (i.e. 8.5 g/L) generated by WW is relatively high among the reported lignocellulosic-derived biomass. Additionally, it is hypothesized that under acidic conditions and high temperatures the fructose present in willow water extracts form hydroxymethylfurfural during steam explosion, which then spontaneously condenses with phenolic substances of willow bark to form a solid furanic precipitate. The formed furanic precipitates play inhibitory role in the enzymatic hydrolysis and are thereby deleterious to the ABE fermentation.
  • Mohan-Anupama Pawar , Prashant; Derba-Maceluch, Marta; Chong, Sun-Li; Gomez, Leonardo D.; Miedes, Eva; Banasiak, Alicja; Ratke, Christine; Gaertner, Cyril; Mouille, Gregory; McQueen-Mason, Simon J.; Molina, Antonio; Sellstedt, Anita; Tenkanen, Tiina Maija; Mellerowicz, Ewa J. (2016)
    Cell wall hemicelluloses and pectins are O-acetylated at specific positions, but the significance of these substitutions is poorly understood. Using a transgenic approach, we investigated how reducing the extent of O-acetylation in xylan affects cell wall chemistry, plant performance and the recalcitrance of lignocellulose to saccharification. The Aspergillus niger acetyl xylan esterase AnAXE1 was expressed in Arabidopsis under the control of either the constitutively expressed 35S CAMV promoter or a woody-tissue-specific GT43B aspen promoter, and the protein was targeted to the apoplast by its native signal peptide, resulting in elevated acetyl esterase activity in soluble and wall-bound protein extracts and reduced xylan acetylation. No significant alterations in cell wall composition were observed in the transgenic lines, but their xylans were more easily digested by a beta-1,4-endoxylanase, and more readily extracted by hot water, acids or alkali. Enzymatic saccharification of lignocellulose after hot water and alkali pretreatments produced up to 20% more reducing sugars in several lines. Fermentation by Trametes versicolor of tissue hydrolysates from the line with a 30% reduction in acetyl content yielded similar to 70% more ethanol compared with wild type. Plants expressing 35S: AnAXE1 and pGT43B:AnAXE1 developed normally and showed increased resistance to the biotrophic pathogen Hyaloperonospora arabidopsidis, probably due to constitutive activation of defence pathways. However, unintended changes in xyloglucan and pectin acetylation were only observed in 35S: AnAXE1-expressing plants. This study demonstrates that postsynthetic xylan deacetylation in woody tissues is a promising strategy for optimizing lignocellulosic biomass for biofuel production.
  • Ma, Yibo; Stubb, Jonas; Kontro, Inkeri; Nieminen, Kaarlo; Hummel, Michael; Sixta, Herbert (2018)
    Man-made lignocellulosic fibres were successfully prepared from unbleached birch kraft pulps by using the Ioncell-F technology. Pulps with different lignin content were produced by tailored kraft pulping with varying intensity. The degree of polymerization of the pulps was adjusted by acid-catalyzed hydrolysis and electron beam treatment. All substrates were completely soluble in 1,5-diazabicyclo[4.3.0]non-5-enium acetate ([DBNH] OAc) and the respective solutions were spinnable to yield fibres with good to excellent mechanical properties despite the use of only mildly refined wood pulp. The tensile properties decreased gradually as the lignin concentration in the fibres increased. Changes in the chemical composition also affected the structure and morphology of the fibres. Both the molecular orientation and the crystallinity decreased while the presence of lignin enhanced the water accessibility. The effects of the crystallite size and lignin content on monolayer water adsorption are discussed.
  • Pawar, Prashant Mohan-Anupama; Derba-Maceluch, Marta; Chong, Sun-Li; Gandla, Madhavi Latha; Bashar, Shamrat Shafiul; Sparrman, Tobias; Ahvenainen, Patrik; Hedenström, Mattias; Ozparpucu, Merve; Ruggeberg, Markus; Serimaa, Ritva; Lawoko, Martin; Tenkanen, Maija; Jönsson, Leif J.; Mellerowicz, Ewa J. (2017)
    Background: Lignocellulose from fast growing hardwood species is a preferred source of polysaccharides for advanced biofuels and "green" chemicals. However, the extensive acetylation of hardwood xylan hinders lignocellulose saccharification by obstructing enzymatic xylan hydrolysis and causing inhibitory acetic acid concentrations during microbial sugar fermentation. To optimize lignocellulose for cost-effective saccharification and biofuel production, an acetyl xylan esterase AnAXE1 from Aspergillus niger was introduced into aspen and targeted to cell walls. Results: AnAXE1-expressing plants exhibited reduced xylan acetylation and grew normally. Without pretreatment, their lignocellulose yielded over 25% more glucose per unit mass of wood (dry weight) than wild-type plants. Glucose yields were less improved (+7%) after acid pretreatment, which hydrolyses xylan. The results indicate that AnAXE1 expression also reduced the molecular weight of xylan, and xylan-lignin complexes and/or lignin co-extracted with xylan, increased cellulose crystallinity, altered the lignin composition, reducing its syringyl to guaiacyl ratio, and increased lignin solubility in dioxane and hot water. Lignin-associated carbohydrates became enriched in xylose residues, indicating a higher content of xylo-oligosaccharides. Conclusions: This work revealed several changes in plant cell walls caused by deacetylation of xylan. We propose that deacetylated xylan is partially hydrolyzed in the cell walls, liberating xylo-oligosaccharides and their associated lignin oligomers from the cell wall network. Deacetylating xylan thus not only increases its susceptibility to hydrolytic enzymes during saccharification but also changes the cell wall architecture, increasing the extractability of lignin and xylan and facilitating saccharification.
  • Saastamoinen, Päivi; Mattinen, Maija-Liisa; Hippi, Ulla; Nousiainen, Paula; Sipilä, Jussi; Lille, Martina; Suurnäkki, Anna; Pere, Jaakko (2012)
  • Mattila, Hans Kristian; Kačar, Dina; Mali, Tuulia Leena Elina; Lundell, Taina Kristina (2018)
    The Polyporales phlebioid white rot fungus Phlebia radiata is efficient in decomposing the wood main components, and in producing ethanol from lignocelluloses and waste materials. Based to these qualifications, the fungus was adopted for design of a consolidated bioprocess method to convert wood waste materials into ethanol without pretreatments. Higher ethanol yield was aimed by introducing collaborative fungal cultivations including isolates of Saccharomyces cerevisiae, other yeasts, and a brown rot fungus. Various waste lignocellulose materials such as wheat and barley straw, recycled wood-fiber based core board, recycled construction waste wood, spruce saw dust, and birch wood were applied to represent wood and non-wood waste lignocellulose of different origin, chemical content and structure. In solid-state single cultivations with the white rot fungus P. radiata, both core board and barley straw turned out as suitable substrates for the consolidated bioprocess. Up to 32.4 ± 4.5 g/L of ethanol accumulated in the solid-state core board cultivation in 30 days whereas with barley straw, 7.0 ± 0.01 g/L of ethanol was obtained. Similar concentrations of ethanol were produced in increased-volume and higher gravity bioreactor cultivations without chemical, physical or enzymatic pretreatment. In all, our consolidated method adopting a white rot fungus is a promising and economic alternative for second generation bioethanol production from waste and residual lignocelluloses.
  • Rahikainen, Jenni; Anbarasan, Sasikala; Wahlström, Ronny; Parviainen, Arno; King, Alistair W. T.; Puranen, Terhi; Kruus, Kristiina; Kilpeläinen, Ilkka; Turunen, Ossi; Suurnäkki, Anna (2018)
    BACKGROUNDThis study elaborates the possibility to apply combined ionic liquid (IL) and enzyme treatments for pulp fibre modification. The approach involves swelling of fibre surfaces with IL followed by enzymatic modification of the disrupted fibre surface using carbohydrate active enzymes. RESULTSThe capacity of seven cellulose-dissolving or cellulose-swelling ionic liquids to swell pulp fibres was compared. In addition, thirteen cellulases and five xylanases were screened for their IL tolerance, which determines their applicability in combined or sequential IL-enzyme treatments of fibres. Among the studied ionic liquids, 1-ethyl-3-methylimidazolium dimethylphosphate ([EMIM]DMP) and 1,3-dimethylimidazolium dimethylphosphate ([DMIM]DMP) had the strongest effect on fibre swelling. These solvents were also found to be the least inactivating for the studied enzymes. CONCLUSIONEnzyme compatibility and cellulose-dissolving capability are not two conflicting properties of an ionic liquid. (c) 2017 Society of Chemical Industry
  • Parviainen, A.; Wahlstrom, R.; Liimatainen, U.; Liitia, T.; Rovio, S.; Helminen, J. K. J.; Hyvakko, U.; King, A. W. T.; Suurnakki, A.; Kilpelainen, I. (2015)
    The recyclability of 1,5-diazabicyclo[4.3.0] non-5-enium acetate ([DBNH][OAc]), as a direct dissolution solvent for cellulose, was evaluated during laboratory scale recycling trials. The main objective was to simulate the conditions of a spinning bath from a Lyocell-type air-gap spinning process, called the IONCELL-F process. The saline solution was then concentrated, recycled and reused as many times as possible before cellulose dissolution was no longer possible. The chemical compositions of the ionic liquid and pulp were recorded throughout the experiments. The results of the experiments showed that [DBNH][OAc] can be recycled from aqueous media with an average recovery rate of 95.6 wt% using basic laboratory equipment, without any further process intensification or optimisation. The recycling of the ionic liquid did not change the chemical composition or degree of polymerisation of the recovered pulp but the colour of the regenerated pulps gradually darkened as the recycling times increased. The ionic liquid was found to hydrolyse 6.0-13.6 mol% per cycle, under these conditions. The build-up of the hydrolysis product, 3-( aminopropyl)-2-pyrrolidonium acetate, killed the dissolution feature at between 30.6-45.6 wt% hydrolysis product. The enzymatic digestibility of the regenerated pulp samples was studied with both a monocomponent endoglucanase and a cellulase mixture. The amount of residual [DBNH][OAc] in the regenerated pulps was determined, by both NMR and capillary electrophoresis. Although hydrolysis of the ionic liquid occurs, this study clearly shows potential for industrial application, with appropriate process equipment and recycling conditions.
  • Rytioja, Johanna; Hilden, Kristiina; Di Falco, Marcos; Zhou, Miaomiao; Aguilar-Pontes, Maria Victoria; Sietiö, Outi-Maaria; Tsang, Adrian; de Vries, Ronald; Mäkelä, Miia R. (2017)
    The ability to obtain carbon and energy is a major requirement to exist in any environment. For several ascomycete fungi, (post-)genomic analyses have shown that species that occupy a large variety of habitats possess a diverse enzymatic machinery, while species with a specific habitat have a more focused enzyme repertoire that is well-adapted to the prevailing substrate. White-rot basidiomycete fungi also live in a specific habitat, as they are found exclusively in wood. In this study, we evaluated how well the enzymatic machinery of the white-rot fungus Dichomitus squalens is tailored to degrade its natural wood substrate. The transcriptome and exoproteome of D. squalens were analyzed after cultivation on two natural substrates, aspen and spruce wood, and two non-woody substrates, wheat bran and cotton seed hulls. D. squalens produced ligninolytic enzymes mainly at the early time point of the wood cultures, indicating the need to degrade lignin to get access to wood polysaccharides. Surprisingly, the response of the fungus to the non-woody polysaccharides was nearly as good a match to the substrate composition as observed for the wood polysaccharides. This indicates that D. squalens has preserved its ability to efficiently degrade plant biomass types not present in its natural habitat.
  • Immonen, Mikko; Maina, Ndegwa; Coda, Rossana; Katina, Kati (2021)
    Surplus bread is a major bakery side stream that should be strictly kept within the human food chain to reduce waste and ensure resource efficiency in baking processes. Optimally, surplus bread should be recycled as a dough ingredient, however, this is known to be detrimental to the volume and texture of bread. The purpose of this study was to investigate how gelatinized starch in surplus bread, untreated or enzymatically hydrolyzed, affects dough development, bread volume and textural attributes. Starch was hydrolyzed to various degrees using commercial alpha-amylase and amyloglucosidase. Bread hydrolysates containing different carbohydrate profiles (untreated, 75%, 57%, and 26% starch remaining) were evaluated as dough ingredients. More complete starch hydrolysis resulted in better dough visco-elastic properties and higher dough level, and reduced dough water absorption by 13%. Nonetheless, breads containing hydrolysate with high-malto-oligosaccharides had the lowest intrinsic hardness and similar volume yield when compared to control bread. Furthermore, compared to untreated slurry, the hydrolysate with high-malto-oligosaccharides, reduced crumb hardness by 28% and staling rate by 42%, and increased specific volume by 8%. The present findings show that enzymatic hydrolysis dramatically transforms the impact of gelatinized starch. Thus, by selecting correct bioprocessing approaches, bread recycling performance may be significantly improved.
  • Immonen, Mikko; Ndegwa, Maina H.; Wang, Yaqin; Coda, Rosseana; Katina, Kati (2020)
    Food-grade waste and side streams should be strictly kept in food use in order to achieve sustainable food systems. At present, the baking industry creates food-grade waste as excess and deformed products that are mainly utilized for non-food uses, such as bioethanol production. The purpose of this study was therefore to explore the potential of waste wheat bread recycling for fresh wheat bread production. Waste bread recycling was assessed without further processing or after tailored fermentation with lactic acid bacteria producing either dextran or β-glucan exopolysaccharides. When non-treated waste bread slurry was added to new bread dough, bread quality (specific volume and softness) decreased with increasing content of waste bread addition. In situ EPS-production (dextran and microbial β-glucan) significantly increased waste bread slurry viscosity and yielded residual fructose or glucose that could effectively replace the sugar added for yeast leavening. Furthermore, fermentation acidified waste bread matrix, thus improving the hygienic safety of the process. Bread containing dextran synthesized in situ by Weissella confusa A16 showed good technological quality. The produced dextran compensated the adverse effect of recycled bread on new bread quality attributes by 12% increase in bread specific volume and 37% decrease in crumb hardness. In this study, a positive technological outcome of the bread containing microbial β-glucan was not detected. The waste bread fermented by W. confusa A16 containing dextran appears to enable safe bread recycling with low acidity and minimal quality loss.
  • Tang, Jing; Wennerberg, Krister; Aittokallio, Tero (2015)
    Many biological or chemical agents when combined interact with each other and produce a synergistic response that cannot be predicted based on the single agent responses alone. However, depending on the postulated null hypothesis of non-interaction, one may end up in different interpretations of synergy. Two popular reference models for null hypothesis include the Bliss independence model and the Loewe additivity model, each of which is formulated from different perspectives. During the last century, there has been an intensive debate on the suitability of these synergy models, both of which are theoretically justified and also in practice supported by different schools of scientists. More than 20 years ago, there was a community effort to make a consensus on the terminology one should use when claiming synergy. The agreement was formulated at a conference held in Saariselka, Finland in 1992, stating that one should use the terms Bliss synergy or Loewe synergy to avoid ambiguity in the underlying models. We review the theoretical relationships between these models and argue that one should combine the advantages of both models to provide a more consistent definition of synergy and antagonism.