The Experts below are selected from a list of 219 Experts worldwide ranked by ideXlab platform
Timon T Wyatt - One of the best experts on this subject based on the ideXlab platform.
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Hydrophilins in the filamentous fungus Neosartorya fischeri (Aspergillus fischeri) have protective activity against several types of microbial water stress.
Environmental microbiology reports, 2015Co-Authors: M.r. Van Leeuwen, Timon T Wyatt, Han A. B. Wösten, T. M. Van Doorn, Luis G. Lugones, Jan DijksterhuisAbstract:Hydrophilins are proteins that occur in all domains of life and protect cells and organisms against drought and other stresses. They include most of the late embryogenesis abundant (LEA) proteins and the heat shock protein (HSP) Hsp12. Here, the role of a predicted LEA-like protein (LeamA) and two Hsp12 proteins (Hsp12A and Hsp12B) of Neosartorya fischeri was studied. This filamentous fungus forms ascospores that belong to the most stress-resistant eukaryotic cells described to date. Heterologous expression of LeamA, Hsp12A and Hsp12B resulted in increased tolerance against salt and osmotic stress in Escherichia coli. These proteins were also shown to protect lactate dehydrogenase against dry heat and freeze-thaw cycles in vitro. Deletion of leamA caused diminished viability of sexual ascospores after drought and heat. This is the first report on functionality of Hsp12 and putative LeamA proteins derived from filamentous fungi, and their possible role in N. fischeri ascospore resistance against desiccation, high temperature and osmotic stress is discussed.
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Structural analysis of novel trehalose-based oligosaccharides from extremely stress-tolerant ascospores of Neosartorya fischeri (Aspergillus fischeri)
Carbohydrate research, 2015Co-Authors: Timon T Wyatt, Gerrit J. Gerwig, Johannis P. Kamerling, Han A. B. Wösten, Jan DijksterhuisAbstract:Different fungi, including the genera Neosartorya, Byssochlamys and Talaromyces, produce (asco)spores that survive pasteurization treatments and are regarded as the most stress-resistant eukaryotic cells. Here, the NMR analysis of a series of trehalose-based oligosaccharides, being compatible solutes that are accumulated to high levels in ascospores of the fungus Neosartorya fischeri, is presented. These oligosaccharides consist of an α,α-trehalose backbone, extended with one [α-D-Glcp-(1 → 6)-α-D-Glcp-(1 ↔ 1)-α-D-Glcp; isobemisiose], two [α-D-Glcp-(1 → 6)-α-D-Glcp-(1 → 6)-α-D-Glcp-(1 ↔ 1)-α-D-Glcp] or three [α-D-Glcp-(1 → 6)-α-D-Glcp-(1 → 6)-α-D-Glcp-(1 → 6)-α-D-Glcp-(1 ↔ 1)-α-D-Glcp] glucose units. The tetra- and pentasaccharide, dubbed neosartose and fischerose, respectively, have not been reported before to occur in nature.
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Functionality and prevalence of trehalose‐based oligosaccharides as novel compatible solutes in ascospores of Neosartorya fischeri (Aspergillus fischeri) and other fungi
Environmental Microbiology, 2014Co-Authors: Timon T Wyatt, M. Richard Van Leeuwen, Elena A. Golovina, Edward A. Palumbo, Alex E.e. Verkennis, Nicole L Snyder, Folkert A. Hoekstra, Eric J Kuenstner, C.m. Visagie, John E. HallsworthAbstract:Ascospores of Neosartorya, Byssochlamys and Talaromyces can be regarded as the most stress-resistant eukaryotic cells. They can survive exposure at temperatures as high as 85°C for 100 min or more. Neosartorya fischeri ascospores are more viscous and more resistant to the combined stress of heat and desiccation than the ascospores of Talaromyces macrosporus which contain predominantly trehalose. These ascospores contain trehalose-based oligosaccharides (TOS) that are novel compatible solutes, which are accumulated to high levels. These compounds are also found in other members of the genus Neosartorya and in some other genera within the order Eurotiales that also include Byssochlamys and Talaromyces. The presence of oligosaccharides was observed in species that had a relatively high growth temperature. TOS glasses have a higher glass transition temperature (Tg ) than trehalose, and they form a stable glass with crystallizing molecules, such as mannitol. Our data indicate that TOS are important for prolonged stabilization of cells against stress. The possible unique role of these solutes in protection against dry heat conditions is discussed.
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Functionality and prevalence of trehalose-based oligosaccharides as novel compatible solutes in ascospores of Neosartorya fischeri (Aspergillus fischeri) and other fungi
Environmental microbiology, 2014Co-Authors: Timon T Wyatt, Elena A. Golovina, Edward A. Palumbo, Alex E.e. Verkennis, Nicole L Snyder, Folkert A. Hoekstra, Eric J Kuenstner, C.m. Visagie, M. Richard Van Leeuwen, John E. HallsworthAbstract:Ascospores of Neosartorya, Byssochlamys and Talaromyces can be regarded as the most stress-resistant eukaryotic cells. They can survive exposure at temperatures as high as 85°C for 100 min or more. Neosartorya fischeri ascospores are more viscous and more resistant to the combined stress of heat and desiccation than the ascospores of Talaromyces macrosporus which contain predominantly trehalose. These ascospores contain trehalose-based oligosaccharides (TOS) that are novel compatible solutes, which are accumulated to high levels. These compounds are also found in other members of the genus Neosartorya and in some other genera within the order Eurotiales that also include Byssochlamys and Talaromyces. The presence of oligosaccharides was observed in species that had a relatively high growth temperature. TOS glasses have a higher glass transition temperature (Tg ) than trehalose, and they form a stable glass with crystallizing molecules, such as mannitol. Our data indicate that TOS are important for prolonged stabilization of cells against stress. The possible unique role of these solutes in protection against dry heat conditions is discussed.
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A decrease in bulk water and mannitol and accumulation of trehalose and trehalose-based oligosaccharides define a two-stage maturation process towards extreme stress resistance in ascospores of Neosartorya fischeri (Aspergillus fischeri)
Environmental microbiology, 2014Co-Authors: Timon T Wyatt, Elena A. Golovina, John E. Hallsworth, Han A. B. Wösten, Richard Van Leeuwen, Jan DijksterhuisAbstract:Fungal propagules survive stresses better than vegetative cells. Neosartorya fischeri, an Aspergillus teleomorph, forms ascospores that survive high temperatures or drying followed by heat. Not much is known about maturation and development of extreme stress resistance in fungal cells. This study provides a novel two-step model for the acquisition of extreme stress resistance and entry into dormancy. Ascospores of 11- and 15-day-old cultures exhibited heat resistance, physiological activity, accumulation of compatible solutes and a steep increase in cytoplasmic viscosity. Electron spin resonance spectroscopy indicated that this stage is associated with the removal of bulk water and an increase of chemical stability. Older ascospores from 15- to 50-day-old cultures showed no changes in compatible solute content and cytoplasmic viscosity, but did exhibit a further increase of heat resistance and redox stability with age. This stage was also characterized by changes in the composition of the mixture of compatible solutes. Mannitol levels decreased and the relative quantities of trehalose and trehalose-based oligosaccharides increased. Dormant ascospores of N. fischeri survive in low-water habitats. After activation of the germination process, the stress resistance decreases, compatible solutes are degraded and the cellular viscosity drops. After 5 h, the hydrated cells enter the vegetative stage and redox stability has decreased notably.
Jan Dijksterhuis - One of the best experts on this subject based on the ideXlab platform.
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Comparing thermal inactivation to a combined process of moderate heat and high pressure: Effect on ascospores in strawberry puree
International journal of food microbiology, 2020Co-Authors: R.a.h. Timmermans, Hasmik Hayrapetyan, Martijntje Vollebregt, Jan DijksterhuisAbstract:High pressure processing is a mild preservation process that inactivates pathogenic and spoilage micro-organisms in food products, but preserves the fresh characteristics of a product. Compared to untreated product, an enhanced shelf life is obtained during refrigerated storage. Knowledge on the use of high pressure pasteurisation aimed for ambient storage is limited. The aim of this research was to investigate if a combination of high pressure and moderate heat could be used to produce a shelf-stable high-acid fruit product. Ascospores of the heat resistant fungi Talaromyces macrosporus and Aspergillus fischeri were added to fresh strawberry puree that served as a model system. The effect of the processing steps and storage at ambient temperature for 2 weeks was studied on viability of the ascospores. A preheating step at 69 °C/2 min resulted in full or partial activation of A. fischeri and T. macrosporus spores, respectively. The pressure build-up by the process without any holding time resulted in additional activation of spores. A combination of moderate heat (maximum 85-90 °C) and high pressure (500-700 MPa) for holding times up to 13 min inactivated these highly resistant spores much faster than a heat treatment alone. At Tmax = 85 °C and 600 MPa the spores of T. macrosporus and A. fischeri were inactivated by 5.0 and 5.5 log10 after 13 and 7 min, respectively. At Tmax = 85 °C the heat treatment alone did not reduce the viability of these spores up to 60 min of treatment. At Tmax = 90 °C the holding time of the combined pressure-heat treatment could be reduced to obtain the same degree of inactivation of the heat resistant fungi. In addition, treated and untreated ascospores in strawberry puree were stored for 14 days at room temperature to evaluate delayed outgrowth of spores. Untreated ascospores of A. fischeri were activated by storage in the puree. However, at conditions combining high pressure ≥ 600 MPa with Tmax ≥ 85 °C for 13 min, heat resistant fungi were successfully inactivated. This research showed that a combination of moderate heat and pressure can drastically improve the effectiveness to inactivate heat-resistant ascospores in a high-acid fruit product compared to a heat treatment, potentially resulting in a better product quality.
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Hydrophilins in the filamentous fungus Neosartorya fischeri (Aspergillus fischeri) have protective activity against several types of microbial water stress.
Environmental microbiology reports, 2015Co-Authors: M.r. Van Leeuwen, Timon T Wyatt, Han A. B. Wösten, T. M. Van Doorn, Luis G. Lugones, Jan DijksterhuisAbstract:Hydrophilins are proteins that occur in all domains of life and protect cells and organisms against drought and other stresses. They include most of the late embryogenesis abundant (LEA) proteins and the heat shock protein (HSP) Hsp12. Here, the role of a predicted LEA-like protein (LeamA) and two Hsp12 proteins (Hsp12A and Hsp12B) of Neosartorya fischeri was studied. This filamentous fungus forms ascospores that belong to the most stress-resistant eukaryotic cells described to date. Heterologous expression of LeamA, Hsp12A and Hsp12B resulted in increased tolerance against salt and osmotic stress in Escherichia coli. These proteins were also shown to protect lactate dehydrogenase against dry heat and freeze-thaw cycles in vitro. Deletion of leamA caused diminished viability of sexual ascospores after drought and heat. This is the first report on functionality of Hsp12 and putative LeamA proteins derived from filamentous fungi, and their possible role in N. fischeri ascospore resistance against desiccation, high temperature and osmotic stress is discussed.
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Structural analysis of novel trehalose-based oligosaccharides from extremely stress-tolerant ascospores of Neosartorya fischeri (Aspergillus fischeri)
Carbohydrate research, 2015Co-Authors: Timon T Wyatt, Gerrit J. Gerwig, Johannis P. Kamerling, Han A. B. Wösten, Jan DijksterhuisAbstract:Different fungi, including the genera Neosartorya, Byssochlamys and Talaromyces, produce (asco)spores that survive pasteurization treatments and are regarded as the most stress-resistant eukaryotic cells. Here, the NMR analysis of a series of trehalose-based oligosaccharides, being compatible solutes that are accumulated to high levels in ascospores of the fungus Neosartorya fischeri, is presented. These oligosaccharides consist of an α,α-trehalose backbone, extended with one [α-D-Glcp-(1 → 6)-α-D-Glcp-(1 ↔ 1)-α-D-Glcp; isobemisiose], two [α-D-Glcp-(1 → 6)-α-D-Glcp-(1 → 6)-α-D-Glcp-(1 ↔ 1)-α-D-Glcp] or three [α-D-Glcp-(1 → 6)-α-D-Glcp-(1 → 6)-α-D-Glcp-(1 → 6)-α-D-Glcp-(1 ↔ 1)-α-D-Glcp] glucose units. The tetra- and pentasaccharide, dubbed neosartose and fischerose, respectively, have not been reported before to occur in nature.
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A decrease in bulk water and mannitol and accumulation of trehalose and trehalose-based oligosaccharides define a two-stage maturation process towards extreme stress resistance in ascospores of Neosartorya fischeri (Aspergillus fischeri)
Environmental microbiology, 2014Co-Authors: Timon T Wyatt, Elena A. Golovina, John E. Hallsworth, Han A. B. Wösten, Richard Van Leeuwen, Jan DijksterhuisAbstract:Fungal propagules survive stresses better than vegetative cells. Neosartorya fischeri, an Aspergillus teleomorph, forms ascospores that survive high temperatures or drying followed by heat. Not much is known about maturation and development of extreme stress resistance in fungal cells. This study provides a novel two-step model for the acquisition of extreme stress resistance and entry into dormancy. Ascospores of 11- and 15-day-old cultures exhibited heat resistance, physiological activity, accumulation of compatible solutes and a steep increase in cytoplasmic viscosity. Electron spin resonance spectroscopy indicated that this stage is associated with the removal of bulk water and an increase of chemical stability. Older ascospores from 15- to 50-day-old cultures showed no changes in compatible solute content and cytoplasmic viscosity, but did exhibit a further increase of heat resistance and redox stability with age. This stage was also characterized by changes in the composition of the mixture of compatible solutes. Mannitol levels decreased and the relative quantities of trehalose and trehalose-based oligosaccharides increased. Dormant ascospores of N. fischeri survive in low-water habitats. After activation of the germination process, the stress resistance decreases, compatible solutes are degraded and the cellular viscosity drops. After 5 h, the hydrated cells enter the vegetative stage and redox stability has decreased notably.
Paramasamy Gunasekaran - One of the best experts on this subject based on the ideXlab platform.
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Optimization of biobleaching of paper pulp in an expanded bed bioreactor with immobilized alkali stable xylanase by using response surface methodology.
Bioresource technology, 2008Co-Authors: Sundar Rajan Senthilkumar, Chandraraj Krishnan, Michael J. Dempsey, Paramasamy GunasekaranAbstract:Purified alkali stable xylanase from Aspergillus fischeri was immobilized on polystyrene beads using diazotization method. An expanded bed bioreactor was developed with these immobilized beads to biobleach the paper pulp in continuous mode. Response surface methodology was applied to optimize the biobleaching conditions. Temperature (°C), flow rate of pulp (ml/min) and concentration of the pulp (%) were selected as variables in this study. Optimal conditions for biobleaching process were reaction temperature 60 °C, flow rate of 2 ml/min and 5% (w/v) of pulp. The kappa number reduced from 66 in the unbleached pulp to 20 (reduction of 87%). This system proves to be a better option for the conventional chlorine based pulp bleaching.
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Optimization of medium composition for alkali-stable xylanase production by Aspergillus fischeri Fxn 1 in solid-state fermentation using central composite rotary design.
Bioresource technology, 2005Co-Authors: Sundar Rajan Senthilkumar, K. Chandra Raj, Balasubramaniem Ashokkumar, Paramasamy GunasekaranAbstract:Response surface methodology and central composite rotary design (CCRD) was employed to optimize a fermentation medium for the production of alkali-stable cellulase-free xylanase by Aspergillus fischeri in solid-state fermentation at pH 9.0 with wheat bran as substrate. The four variables involved in this study were sodium nitrite, potassium dihydrogen phosphate, magnesium sulphate and yeast extract. The statistical analysis of the results showed that, in the range studied, only sodium nitrite had a significant effect on xylanase production. The optimized medium containing (in g/l) NaNO(2)-7.0, K2HPO(4)-1.0, MgSO(4)-0.5 and yeast extract-5.0 resulted in 1.9-fold increased level of alkali-stable xylanase (1024 U/g wheat bran) production compared to initial level (540 U/g) after 72 h of fermentation, whereas its value predicted by the quadratic model was 931 U/g. The level of protease activity was considerably decreased in optimized medium, thus helping to preserve the xylanase activity and demonstrating another advantage of applying statistical experimental design.
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Purification and characterization of a low molecular weight endoxylanase from solid-state cultures of alkali-tolerant Aspergillus fischeri
Biotechnology Letters, 2004Co-Authors: Sundar Rajan Senthilkumar, Balasubramaniem Ashokkumar, Krishnan Chandra Raj, Paramasamy GunasekaranAbstract:A low molecular weight, alkaline-stable endoxylanase (XylB) was purified to homogeneity from solid-state culture of Aspergillus fischeri Fxn1. XylB had a molecular mass of 13 kDa which is the lowest of reported xylanases. Optimal activity was at pH 6 and 55 °C. XylB was stable from pH 4.5 to 10 and up to 60 °C. It was non-glycosylated. The apparent K _m and V _max values of XylB on birch wood xylan were 0.53 mg ml^−1 and 0.2 mmol min^−1 mg^−1, respectively. The activity of XylB was not inhibited by Cd^2+, Zn^2+, Co^2+, EDTA, iodoacetamide, β-mercaptoethanol and acetic anhydride but strongly inhibited by 10 mm of N -bromosuccinimide, Hg^2+, Pb^2+ and p -hydroxymercuric benzoate. XylB is an endoxylanase since it hydrolysed xylan resulting the formation of xylo-oligomers but not of xylose residues.
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Purification and characterization of a low molecular weight endoxylanase from solid-state cultures of alkali-tolerant Aspergillus fischeri.
Biotechnology letters, 2004Co-Authors: Sundar Rajan Senthilkumar, Balasubramaniem Ashokkumar, Krishnan Chandra Raj, Paramasamy GunasekaranAbstract:A low molecular weight, alkaline-stable endoxylanase (XylB) was purified to homogeneity from solid-state culture of Aspergillus fischeri Fxn1. XylB had a molecular mass of 13 kDa which is the lowest of reported xylanases. Optimal activity was at pH 6 and 55 degrees C. XylB was stable from pH 4.5 to 10 and up to 60 degrees C. It was non-glycosylated. The apparent K(m) and V(max) values of XylB on birch wood xylan were 0.53 mg ml(-1) and 0.2 mmol min-1 mg-1, respectively. The activity of XylB was not inhibited by Cd2+, Zn2+, Co2+, EDTA, iodoacetamide, beta-mercaptoethanol and acetic anhydride but strongly inhibited by 10 mm of N-bromosuccinimide, Hg2+, Pb2+ and p-hydroxymercuric benzoate. XylB is an endoxylanase since it hydrolysed xylan resulting the formation of xylo-oligomers but not of xylose residues.
John E. Hallsworth - One of the best experts on this subject based on the ideXlab platform.
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Functionality and prevalence of trehalose‐based oligosaccharides as novel compatible solutes in ascospores of Neosartorya fischeri (Aspergillus fischeri) and other fungi
Environmental Microbiology, 2014Co-Authors: Timon T Wyatt, M. Richard Van Leeuwen, Elena A. Golovina, Edward A. Palumbo, Alex E.e. Verkennis, Nicole L Snyder, Folkert A. Hoekstra, Eric J Kuenstner, C.m. Visagie, John E. HallsworthAbstract:Ascospores of Neosartorya, Byssochlamys and Talaromyces can be regarded as the most stress-resistant eukaryotic cells. They can survive exposure at temperatures as high as 85°C for 100 min or more. Neosartorya fischeri ascospores are more viscous and more resistant to the combined stress of heat and desiccation than the ascospores of Talaromyces macrosporus which contain predominantly trehalose. These ascospores contain trehalose-based oligosaccharides (TOS) that are novel compatible solutes, which are accumulated to high levels. These compounds are also found in other members of the genus Neosartorya and in some other genera within the order Eurotiales that also include Byssochlamys and Talaromyces. The presence of oligosaccharides was observed in species that had a relatively high growth temperature. TOS glasses have a higher glass transition temperature (Tg ) than trehalose, and they form a stable glass with crystallizing molecules, such as mannitol. Our data indicate that TOS are important for prolonged stabilization of cells against stress. The possible unique role of these solutes in protection against dry heat conditions is discussed.
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Functionality and prevalence of trehalose-based oligosaccharides as novel compatible solutes in ascospores of Neosartorya fischeri (Aspergillus fischeri) and other fungi
Environmental microbiology, 2014Co-Authors: Timon T Wyatt, Elena A. Golovina, Edward A. Palumbo, Alex E.e. Verkennis, Nicole L Snyder, Folkert A. Hoekstra, Eric J Kuenstner, C.m. Visagie, M. Richard Van Leeuwen, John E. HallsworthAbstract:Ascospores of Neosartorya, Byssochlamys and Talaromyces can be regarded as the most stress-resistant eukaryotic cells. They can survive exposure at temperatures as high as 85°C for 100 min or more. Neosartorya fischeri ascospores are more viscous and more resistant to the combined stress of heat and desiccation than the ascospores of Talaromyces macrosporus which contain predominantly trehalose. These ascospores contain trehalose-based oligosaccharides (TOS) that are novel compatible solutes, which are accumulated to high levels. These compounds are also found in other members of the genus Neosartorya and in some other genera within the order Eurotiales that also include Byssochlamys and Talaromyces. The presence of oligosaccharides was observed in species that had a relatively high growth temperature. TOS glasses have a higher glass transition temperature (Tg ) than trehalose, and they form a stable glass with crystallizing molecules, such as mannitol. Our data indicate that TOS are important for prolonged stabilization of cells against stress. The possible unique role of these solutes in protection against dry heat conditions is discussed.
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A decrease in bulk water and mannitol and accumulation of trehalose and trehalose-based oligosaccharides define a two-stage maturation process towards extreme stress resistance in ascospores of Neosartorya fischeri (Aspergillus fischeri)
Environmental microbiology, 2014Co-Authors: Timon T Wyatt, Elena A. Golovina, John E. Hallsworth, Han A. B. Wösten, Richard Van Leeuwen, Jan DijksterhuisAbstract:Fungal propagules survive stresses better than vegetative cells. Neosartorya fischeri, an Aspergillus teleomorph, forms ascospores that survive high temperatures or drying followed by heat. Not much is known about maturation and development of extreme stress resistance in fungal cells. This study provides a novel two-step model for the acquisition of extreme stress resistance and entry into dormancy. Ascospores of 11- and 15-day-old cultures exhibited heat resistance, physiological activity, accumulation of compatible solutes and a steep increase in cytoplasmic viscosity. Electron spin resonance spectroscopy indicated that this stage is associated with the removal of bulk water and an increase of chemical stability. Older ascospores from 15- to 50-day-old cultures showed no changes in compatible solute content and cytoplasmic viscosity, but did exhibit a further increase of heat resistance and redox stability with age. This stage was also characterized by changes in the composition of the mixture of compatible solutes. Mannitol levels decreased and the relative quantities of trehalose and trehalose-based oligosaccharides increased. Dormant ascospores of N. fischeri survive in low-water habitats. After activation of the germination process, the stress resistance decreases, compatible solutes are degraded and the cellular viscosity drops. After 5 h, the hydrated cells enter the vegetative stage and redox stability has decreased notably.
Sundar Rajan Senthilkumar - One of the best experts on this subject based on the ideXlab platform.
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Optimization of biobleaching of paper pulp in an expanded bed bioreactor with immobilized alkali stable xylanase by using response surface methodology.
Bioresource technology, 2008Co-Authors: Sundar Rajan Senthilkumar, Chandraraj Krishnan, Michael J. Dempsey, Paramasamy GunasekaranAbstract:Purified alkali stable xylanase from Aspergillus fischeri was immobilized on polystyrene beads using diazotization method. An expanded bed bioreactor was developed with these immobilized beads to biobleach the paper pulp in continuous mode. Response surface methodology was applied to optimize the biobleaching conditions. Temperature (°C), flow rate of pulp (ml/min) and concentration of the pulp (%) were selected as variables in this study. Optimal conditions for biobleaching process were reaction temperature 60 °C, flow rate of 2 ml/min and 5% (w/v) of pulp. The kappa number reduced from 66 in the unbleached pulp to 20 (reduction of 87%). This system proves to be a better option for the conventional chlorine based pulp bleaching.
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Optimization of medium composition for alkali-stable xylanase production by Aspergillus fischeri Fxn 1 in solid-state fermentation using central composite rotary design.
Bioresource technology, 2005Co-Authors: Sundar Rajan Senthilkumar, K. Chandra Raj, Balasubramaniem Ashokkumar, Paramasamy GunasekaranAbstract:Response surface methodology and central composite rotary design (CCRD) was employed to optimize a fermentation medium for the production of alkali-stable cellulase-free xylanase by Aspergillus fischeri in solid-state fermentation at pH 9.0 with wheat bran as substrate. The four variables involved in this study were sodium nitrite, potassium dihydrogen phosphate, magnesium sulphate and yeast extract. The statistical analysis of the results showed that, in the range studied, only sodium nitrite had a significant effect on xylanase production. The optimized medium containing (in g/l) NaNO(2)-7.0, K2HPO(4)-1.0, MgSO(4)-0.5 and yeast extract-5.0 resulted in 1.9-fold increased level of alkali-stable xylanase (1024 U/g wheat bran) production compared to initial level (540 U/g) after 72 h of fermentation, whereas its value predicted by the quadratic model was 931 U/g. The level of protease activity was considerably decreased in optimized medium, thus helping to preserve the xylanase activity and demonstrating another advantage of applying statistical experimental design.
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Purification and characterization of a low molecular weight endoxylanase from solid-state cultures of alkali-tolerant Aspergillus fischeri
Biotechnology Letters, 2004Co-Authors: Sundar Rajan Senthilkumar, Balasubramaniem Ashokkumar, Krishnan Chandra Raj, Paramasamy GunasekaranAbstract:A low molecular weight, alkaline-stable endoxylanase (XylB) was purified to homogeneity from solid-state culture of Aspergillus fischeri Fxn1. XylB had a molecular mass of 13 kDa which is the lowest of reported xylanases. Optimal activity was at pH 6 and 55 °C. XylB was stable from pH 4.5 to 10 and up to 60 °C. It was non-glycosylated. The apparent K _m and V _max values of XylB on birch wood xylan were 0.53 mg ml^−1 and 0.2 mmol min^−1 mg^−1, respectively. The activity of XylB was not inhibited by Cd^2+, Zn^2+, Co^2+, EDTA, iodoacetamide, β-mercaptoethanol and acetic anhydride but strongly inhibited by 10 mm of N -bromosuccinimide, Hg^2+, Pb^2+ and p -hydroxymercuric benzoate. XylB is an endoxylanase since it hydrolysed xylan resulting the formation of xylo-oligomers but not of xylose residues.
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Purification and characterization of a low molecular weight endoxylanase from solid-state cultures of alkali-tolerant Aspergillus fischeri.
Biotechnology letters, 2004Co-Authors: Sundar Rajan Senthilkumar, Balasubramaniem Ashokkumar, Krishnan Chandra Raj, Paramasamy GunasekaranAbstract:A low molecular weight, alkaline-stable endoxylanase (XylB) was purified to homogeneity from solid-state culture of Aspergillus fischeri Fxn1. XylB had a molecular mass of 13 kDa which is the lowest of reported xylanases. Optimal activity was at pH 6 and 55 degrees C. XylB was stable from pH 4.5 to 10 and up to 60 degrees C. It was non-glycosylated. The apparent K(m) and V(max) values of XylB on birch wood xylan were 0.53 mg ml(-1) and 0.2 mmol min-1 mg-1, respectively. The activity of XylB was not inhibited by Cd2+, Zn2+, Co2+, EDTA, iodoacetamide, beta-mercaptoethanol and acetic anhydride but strongly inhibited by 10 mm of N-bromosuccinimide, Hg2+, Pb2+ and p-hydroxymercuric benzoate. XylB is an endoxylanase since it hydrolysed xylan resulting the formation of xylo-oligomers but not of xylose residues.
