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The interdomain electron transfer (IET) between the catalytic flavodehydrogenase domain and the electron-transferring cytochrome domain of cellobiose dehydrogenase (CDH) plays an essential role in biocatalysis, biosensors and biofuel cells, as well as in its natural function as an auxiliary enzyme of lytic polysaccharide monooxygenase. We investigated the mobility of the cytochrome and dehydrogenase domains of CDH, which is hypothesised to limit IET in solution by small angle X-ray scattering (SAXS). CDH from Myriococcum thermophilum (syn. Crassicarpon hotsonii, syn. Thermothelomyces myriococcoides) was probed by SAXS to study the CDH mobility at different pH and in the presence of divalent cations. By comparison of the experimental SAXS data, using pair-distance distribution functions and Kratky plots, we show an increase in CDH mobility at higher pH, indicating alterations of domain mobility. To further visualise CDH movement in solution, we performed SAXS-based multistate modelling. Glycan structures present on CDH partially masked the resulting SAXS shapes, we diminished these effects by deglycosylation and studied the effect of glycoforms by modelling. The modelling shows that with increasing pH, the cytochrome domain adopts a more flexible state with significant separation from the dehydrogenase domain. On the contrary, the presence of calcium ions decreases the mobility of the cytochrome domain. Experimental SAXS data, multistate modelling and previously reported kinetic data show how pH and divalent ions impact the closed state necessary for the IET governed by the movement of the CDH cytochrome domain.

Copper-dependent lytic polysaccharide monooxygenases (LPMOs) classified in Auxiliary Activity (AA) families are considered indispensable as synergistic partners for cellulolytic enzymes to saccharify recalcitrant lignocellulosic plant biomass. In this study, we characterized two fungal oxidoreductases from the new AA16 family. We found that MtAA16A from Myceliophthora thermophila and AnAA16A from Aspergillus nidulans did not catalyze the oxidative cleavage of oligo-and polysaccharides. Indeed, the MtAA16A crystal structure showed a fairly LPMO-typical histidine brace active site, but the cellulose-acting LPMO-typical flat aromatic surface parallel to the histidine brace region was lacking. Further, we showed that both AA16 proteins are able to oxidize low-molecular-weight reductants to produce H2O2. The oxidase activity of the AA16s substantially boosted cellulose degradation by four AA9 LPMOs from M. thermophila (MtLPMO9s) but not by three AA9 LPMOs from Neurospora crassa (NcLPMO9s). The interplay with MtLPMO9s is explained by the H2O2-producing capability of the AA16s, which, in the presence of cellulose, allows the MtLPMO9s to optimally drive their peroxygenase activity. Replacement of MtAA16A by glucose oxidase (AnGOX) with the same H2O2-producing activity could only achieve less than 50% of the boosting effect achieved by MtAA16A, and earlier MtLPMO9B inactivation (6 h) was observed. To explain these results, we hypothesized that the delivery of AA16produced H2O2 to the MtLPMO9s is facilitated by protein-protein interaction. Our findings provide new insights into the functions of copper-dependent enzymes and contribute to a further understanding of the interplay of oxidative enzymes within fungal systems to degrade lignocellulose.

Copper-dependent lytic polysaccharide monooxygenases (LPMOs) classified in Auxiliary Activity (AA) families are considered indispensable as synergistic partners for cellulolytic enzymes to saccharify recalcitrant lignocellulosic plant biomass. In this study, we characterized two fungal oxidoreductases from the new AA16 family. We found that MtAA16A from Myceliophthora thermophila and AnAA16A from Aspergillus nidulans did not catalyze the oxidative cleavage of oligo-and polysaccharides. Indeed, the MtAA16A crystal structure showed a fairly LPMO-typical histidine brace active site, but the cellulose-acting LPMO-typical flat aromatic surface parallel to the histidine brace region was lacking. Further, we showed that both AA16 proteins are able to oxidize low-molecular-weight reductants to produce H2O2. The oxidase activity of the AA16s substantially boosted cellulose degradation by four AA9 LPMOs from M. thermophila (MtLPMO9s) but not by three AA9 LPMOs from Neurospora crassa (NcLPMO9s). The interplay with MtLPMO9s is explained by the H2O2-producing capability of the AA16s, which, in the presence of cellulose, allows the MtLPMO9s to optimally drive their peroxygenase activity. Replacement of MtAA16A by glucose oxidase (AnGOX) with the same H2O2-producing activity could only achieve less than 50% of the boosting effect achieved by MtAA16A, and earlier MtLPMO9B inactivation (6 h) was observed. To explain these results, we hypothesized that the delivery of AA16produced H2O2 to the MtLPMO9s is facilitated by protein-protein interaction. Our findings provide new insights into the functions of copper-dependent enzymes and contribute to a further understanding of the interplay of oxidative enzymes within fungal systems to degrade lignocellulose.

Biological control agents are a promising niche to replace chemical pesticides for treating plant pathogens in agriculture. A potential biocontrol agent is the microparasitic fungi Clonostachys rosea which has the ability to attack various plant pathogens such as other fungi and nematodes. One key feature in the interaction between mycoparasite and prey is degradation of the fungal cell wall where cell wall degrading enzymes are important. One cell wall degrading enzyme is cellobiose dehydrogenase of which it has been found a high number of genes for in C. rosea compared to other mycoparasites. The reason for these many cellobiose dehydrogenase genes being present in C. rosea is what this study aimed to find out. To do so, the different cellobiose dehydrogenase proteins 001, 002, 003 and 004 were successfully expressed in Pichia pastoris. The 003 protein had significantly higher expression levels and were further purified with size exclusion chromatography where some of the resulting purified protein was used to set up a crystallization screen. Unfortunately, no crystals have been formed so far. The enzymatic activity against lactose, cellobiose and laminaribiose of all produced cellobiose dehydrogenase proteins were also analyzed using a 2,6-dichloroindophenol activity assay. The proteins 001 and 002 showed a low activity against lactose and cellobiose whereas the other protein showed no activity for the tested conditions. That these proteins have developed variations in their activities may be one reason for why they are all still existing.

Biological control agents are a promising niche to replace chemical pesticides for treating plant pathogens in agriculture. A potential biocontrol agent is the microparasitic fungi Clonostachys rosea which has the ability to attack various plant pathogens such as other fungi and nematodes. One key feature in the interaction between mycoparasite and prey is degradation of the fungal cell wall where cell wall degrading enzymes are important. One cell wall degrading enzyme is cellobiose dehydrogenase of which it has been found a high number of genes for in C. rosea compared to other mycoparasites. The reason for these many cellobiose dehydrogenase genes being present in C. rosea is what this study aimed to find out. To do so, the different cellobiose dehydrogenase proteins 001, 002, 003 and 004 were successfully expressed in Pichia pastoris. The 003 protein had significantly higher expression levels and were further purified with size exclusion chromatography where some of the resulting purified protein was used to set up a crystallization screen. Unfortunately, no crystals have been formed so far. The enzymatic activity against lactose, cellobiose and laminaribiose of all produced cellobiose dehydrogenase proteins were also analyzed using a 2,6-dichloroindophenol activity assay. The proteins 001 and 002 showed a low activity against lactose and cellobiose whereas the other protein showed no activity for the tested conditions. That these proteins have developed variations in their activities may be one reason for why they are all still existing.

Celobioza – dehidrogenaza poreklom iz Phanerochaete chrysosporium, gljive bele truleži, pripada ekstracelularnim oksidoredukcionim enzimima i katalizuje oksidaciju β – 1,4 – glikozidno vezanih oligosaharida poput celobioze i laktoze. Oksidacijom laktoze dolazi do formiranja laktobionske kiseline koja pronalazi veliku primenu u farmaceutskoj i kozmetičkoj industriji gde se koristi prilikom distribucije lekova i za hidrataciju kože kao sastavni deo različitih krema, gde zajedno sa hijaluronskom kiselinu ima ulogu u smanjenju bora.Celobioza – dehidrogenaza prilikom oksidacije laktoze ili celobioze, kao prirodnih supstrata, katalizuje redukciju jednog dvoelektronskog ili dva jednoelektronska akceptora elektrona. Jedan od najkorišćenijih dvoelektronskih akceptora elektrona je upravo dihlor fenol indofenol (DCIP), dok jednoelektronski akceptori elektrona mogu biti citohrom c, ABTS, ali i Fe3+ i Mn3+ joni. Redukcijom Fe3+ jona u prisustvu molekulskog kiseonika dolazi do formiranja vodonik peroksida i posredstvom Fentonove reakcije do generisanja hidroksil radikala.Polazeći od ove činjenice, iskoristili smo upravo Fentonovu reakciju za razvoj fluorescentnog eseja za visoko efikasnu pretragu biblioteka gena celobioza – dehidrogenaze, baziranog na detekciji proizvedenih hidroksil radikala fluorogenom probom aminofenil – fluoresceinom (APF).Primena celobioza – dehidrogenaze u konstruisanju biosenzora i biogorivnih ćelija leži upravo u njenoj sposobnosti da katalizuje oksidaciju laktoze, celobioze i β – 1,4 – vezanih oligosaharida do odgovarajućih laktona koji potom spontano hidrolizuju do aldonskih kiselina. Enzimi koji nalaze primenu u konstruisanju biosenzora i biogorivnih ćelija, moraju da zadovoljavaju nekoliko kriterijuma,odnosno moraju da imaju veliku osetljivost i supstratnu specifičnost, ali i da pokazuju povećanu stabilnost..., Cellobiose dehydrogenase from Phanerochaete chrysosporium, a white rot fungus, belongs to the extracellular oxidoreductive group of enzymes and catalyzes the oxidation of the β – 1,4 – glycoside bond of oligosaccharides such as cellobiose and lactose. During oxidation of lactose, formation of lactobionic acid occurs which has many applications in pharmaceutical and cosmetic industry. Such applications include the distribution of medicine, a component responsible for skin hydration and when combined with hyaluronic acid as an agent against wrinkles.During oxidation of lactose or cellobiose by cellobiose dehydrogenase, reduction catalysis occurs of one two electron or two one electron acceptors. One of the most utilized two electron acceptors is DCIP, while one electron acceptors are usually cytochrome c, ABTS, Fe3+ and Mn3+ ions. During reduction of Fe3+ ions in the presence of molecular oxygen, H2O2 is formed and due to the Fenton reaction formation of hydroxyl radicals occurs. Due to this occurrence we wanted to use the Fenton reaction in order to develop a fluorescent assay based on the production of hydroxyl radicals and the fluorescence of aminophenyl fluorescein (APF). This would allow us to efficiently analyze cellobiose dehydrogenase gene libraries.With this fact in mind, the Fenton reaction was used to develop a fluorescent assay for the high throughput screening of cellobiose dehydrogenase genes, based on the detection of hydroxyl radicals with the fluorescent probe APF.The possible application of cellobiose dehydrogenase in the construction of various biosensors and biofuel cells is due the its ability to catalyze the oxidation of lactose, cellobiose and similar β – 1,4 – oligosaccharides do their corresponding lactones which then spontaneously hydrolyze to aldonic acids. Enzymes used in suchapplications need to satisfy certain criteria, such as exceptional sensitivity, substrate selectivity, stability and activity...

Celobioza – dehidrogenaza poreklom iz Phanerochaete chrysosporium, gljive bele truleži, pripada ekstracelularnim oksidoredukcionim enzimima i katalizuje oksidaciju β – 1,4 – glikozidno vezanih oligosaharida poput celobioze i laktoze. Oksidacijom laktoze dolazi do formiranja laktobionske kiseline koja pronalazi veliku primenu u farmaceutskoj i kozmetičkoj industriji gde se koristi prilikom distribucije lekova i za hidrataciju kože kao sastavni deo različitih krema, gde zajedno sa hijaluronskom kiselinu ima ulogu u smanjenju bora.Celobioza – dehidrogenaza prilikom oksidacije laktoze ili celobioze, kao prirodnih supstrata, katalizuje redukciju jednog dvoelektronskog ili dva jednoelektronska akceptora elektrona. Jedan od najkorišćenijih dvoelektronskih akceptora elektrona je upravo dihlor fenol indofenol (DCIP), dok jednoelektronski akceptori elektrona mogu biti citohrom c, ABTS, ali i Fe3+ i Mn3+ joni. Redukcijom Fe3+ jona u prisustvu molekulskog kiseonika dolazi do formiranja vodonik peroksida i posredstvom Fentonove reakcije do generisanja hidroksil radikala.Polazeći od ove činjenice, iskoristili smo upravo Fentonovu reakciju za razvoj fluorescentnog eseja za visoko efikasnu pretragu biblioteka gena celobioza – dehidrogenaze, baziranog na detekciji proizvedenih hidroksil radikala fluorogenom probom aminofenil – fluoresceinom (APF).Primena celobioza – dehidrogenaze u konstruisanju biosenzora i biogorivnih ćelija leži upravo u njenoj sposobnosti da katalizuje oksidaciju laktoze, celobioze i β – 1,4 – vezanih oligosaharida do odgovarajućih laktona koji potom spontano hidrolizuju do aldonskih kiselina. Enzimi koji nalaze primenu u konstruisanju biosenzora i biogorivnih ćelija, moraju da zadovoljavaju nekoliko kriterijuma,odnosno moraju da imaju veliku osetljivost i supstratnu specifičnost, ali i da pokazuju povećanu stabilnost..., Cellobiose dehydrogenase from Phanerochaete chrysosporium, a white rot fungus, belongs to the extracellular oxidoreductive group of enzymes and catalyzes the oxidation of the β – 1,4 – glycoside bond of oligosaccharides such as cellobiose and lactose. During oxidation of lactose, formation of lactobionic acid occurs which has many applications in pharmaceutical and cosmetic industry. Such applications include the distribution of medicine, a component responsible for skin hydration and when combined with hyaluronic acid as an agent against wrinkles.During oxidation of lactose or cellobiose by cellobiose dehydrogenase, reduction catalysis occurs of one two electron or two one electron acceptors. One of the most utilized two electron acceptors is DCIP, while one electron acceptors are usually cytochrome c, ABTS, Fe3+ and Mn3+ ions. During reduction of Fe3+ ions in the presence of molecular oxygen, H2O2 is formed and due to the Fenton reaction formation of hydroxyl radicals occurs. Due to this occurrence we wanted to use the Fenton reaction in order to develop a fluorescent assay based on the production of hydroxyl radicals and the fluorescence of aminophenyl fluorescein (APF). This would allow us to efficiently analyze cellobiose dehydrogenase gene libraries.With this fact in mind, the Fenton reaction was used to develop a fluorescent assay for the high throughput screening of cellobiose dehydrogenase genes, based on the detection of hydroxyl radicals with the fluorescent probe APF.The possible application of cellobiose dehydrogenase in the construction of various biosensors and biofuel cells is due the its ability to catalyze the oxidation of lactose, cellobiose and similar β – 1,4 – oligosaccharides do their corresponding lactones which then spontaneously hydrolyze to aldonic acids. Enzymes used in suchapplications need to satisfy certain criteria, such as exceptional sensitivity, substrate selectivity, stability and activity...

Celobioza – dehidrogenaza poreklom iz Phanerochaete chrysosporium, gljive bele truleži, pripada ekstracelularnim oksidoredukcionim enzimima i katalizuje oksidaciju β – 1,4 – glikozidno vezanih oligosaharida poput celobioze i laktoze. Oksidacijom laktoze dolazi do formiranja laktobionske kiseline koja pronalazi veliku primenu u farmaceutskoj i kozmetičkoj industriji gde se koristi prilikom distribucije lekova i za hidrataciju kože kao sastavni deo različitih krema, gde zajedno sa hijaluronskom kiselinu ima ulogu u smanjenju bora. Celobioza – dehidrogenaza prilikom oksidacije laktoze ili celobioze, kao prirodnih supstrata, katalizuje redukciju jednog dvoelektronskog ili dva jednoelektronska akceptora elektrona. Jedan od najkorišćenijih dvoelektronskih akceptora elektrona je upravo dihlor fenol indofenol (DCIP), dok jednoelektronski akceptori elektrona mogu biti citohrom c, ABTS, ali i Fe3+ i Mn3+ joni. Redukcijom Fe3+ jona u prisustvu molekulskog kiseonika dolazi do formiranja vodonik peroksida i posredstvom Fentonove reakcije do generisanja hidroksil radikala. Polazeći od ove činjenice, iskoristili smo upravo Fentonovu reakciju za razvoj fluorescentnog eseja za visoko efikasnu pretragu biblioteka gena celobioza – dehidrogenaze, baziranog na detekciji proizvedenih hidroksil radikala fluorogenom probom aminofenil – fluoresceinom (APF). Primena celobioza – dehidrogenaze u konstruisanju biosenzora i biogorivnih ćelija leži upravo u njenoj sposobnosti da katalizuje oksidaciju laktoze, celobioze i β – 1,4 – vezanih oligosaharida do odgovarajućih laktona koji potom spontano hidrolizuju do aldonskih kiselina. Enzimi koji nalaze primenu u konstruisanju biosenzora i biogorivnih ćelija, moraju da zadovoljavaju nekoliko kriterijuma, odnosno moraju da imaju veliku osetljivost i supstratnu specifičnost, ali i da pokazuju povećanu stabilnost..., Cellobiose dehydrogenase from Phanerochaete chrysosporium, a white rot fungus, belongs to the extracellular oxidoreductive group of enzymes and catalyzes the oxidation of the β – 1,4 – glycoside bond of oligosaccharides such as cellobiose and lactose. During oxidation of lactose, formation of lactobionic acid occurs which has many applications in pharmaceutical and cosmetic industry. Such applications include the distribution of medicine, a component responsible for skin hydration and when combined with hyaluronic acid as an agent against wrinkles. During oxidation of lactose or cellobiose by cellobiose dehydrogenase, reduction catalysis occurs of one two electron or two one electron acceptors. One of the most utilized two electron acceptors is DCIP, while one electron acceptors are usually cytochrome c, ABTS, Fe3+ and Mn3+ ions. During reduction of Fe3+ ions in the presence of molecular oxygen, H2O2 is formed and due to the Fenton reaction formation of hydroxyl radicals occurs. Due to this occurrence we wanted to use the Fenton reaction in order to develop a fluorescent assay based on the production of hydroxyl radicals and the fluorescence of aminophenyl fluorescein (APF). This would allow us to efficiently analyze cellobiose dehydrogenase gene libraries. With this fact in mind, the Fenton reaction was used to develop a fluorescent assay for the high throughput screening of cellobiose dehydrogenase genes, based on the detection of hydroxyl radicals with the fluorescent probe APF. The possible application of cellobiose dehydrogenase in the construction of various biosensors and biofuel cells is due the its ability to catalyze the oxidation of lactose, cellobiose and similar β – 1,4 – oligosaccharides do their corresponding lactones which then spontaneously hydrolyze to aldonic acids. Enzymes used in such applications need to satisfy certain criteria, such as exceptional sensitivity, substrate selectivity, stability and activity...

Graphite electrodes were modified with triangular (AuNTrs) or spherical (AuNPs) nanoparticles and further modified with fructose dehydrogenase (FDH). The present study reports the effect of the shape of these nanoparticles (NPs) on the catalytic current of immobilized FDH pointing out the different contributions on the mass transfer-limited and kinetically limited currents. The influence of the shape of the NPs on the mass transfer-limited and the kinetically limited current has been proved by using two different methods: a rotating disk electrode (RDE) and an electrode mounted in a wall jet flow-through electrochemical cell attached to a flow system. The advantages of using the wall jet flow system compared with the RDE system for kinetic investigations are as follows: no need to account for substrate consumption, especially in the case of desorption of enzyme, and studies of product-inhibited enzymes. The comparison reveals that virtually identical results can be obtained using either of the two techniques. The heterogeneous electron transfer (ET) rate constants (k(S)) were found to be 3.8 +/- 0.3 s(-1) and 0.9 +/- 0.1 s(-1), for triangular and spherical NPs, respectively. The improvement observed for the electrode modified with AuNTrs suggests a more effective enzyme-NP interaction, which can allocate a higher number of enzyme molecules on the electrode surface

Cellobiose dehydrogenase (CDH) from Phanerochaete chrysosporium can be used in lactobionic acid production, biosensor for lactose, biofuel cells, lignocellulose degradation, and wound-healing applications. To make it a better biocatalyst, CDH with higher activity in an immobilized form is desirable. For this purpose, CDH was expressed for the first time on the surface of S. cerevisiae EBY100 cells in an active form as a triple mutant tmCDH (D20N, A64T, V592M) and evolved further for higher activity using resazurin-based fluorescent assay. In order to decrease blank reaction of resazurin with yeast cells and to have linear correlation between enzyme activity on the cell surface and fluorescence signal, the assay was optimized with respect to resazurin concentration (0.1 mM), substrate concentration (10mMlactose and 0.08mMcellobiose), and pH (6.0). Using optimized assay an error prone PCR gene library of tmCDH was screened. Two mutants with 5 (H5) and 7 mutations (H9) were found having two times higher activity than the parent tmCDH enzyme that already had improved activity compared to wild type CDH whose activity could not be detected on the surface of yeast cells.

Cellobiose dehydrogenase (CDH) can be used in industry for lactobionic acid production, as a part of biosensors for disaccharides and in wound healing. In fungi it is involved in lignocellulose degradation. CDH gene from Phanerochaete chrysosporium has been cloned in pYES2 plasmid for extracellular expression and protein engineering in yeast Saccharomyces cerevisiae InvSC1 for the first time. A CDH gene library was generated using error-prone PCR and screened by spectrophotometric enzymatic assay based on 2,6-dichloroindophenol reduction detection in microtiter plates. Several mutants with increased activity and specificity towards lactose and cellobiose were found, purified and characterized in detail. Recombinant CDH enzymes showed a broad molecular weight between 120 and 150 KDa due to hyper-glycosylation and the best S137 N mutant showed 2.2 times increased k cat and 1.5 and 2 times increased specificity constant for lactose and cellobiose compared to the wild type enzyme. pH optimum of mutants was not changed while thermostability of selected mutants improved and S137 N mutant retained 30% of it's original activity after 15 min at 70 °C compared to 10% of activity that the wild type enzyme retained. Mutants M65S and S137 N showed also 1.6 and 1.5 times increased productivity of hydrogen peroxide in the presence of 30 mM lactose compared to the wild type.

Cellobiose dehydrogenase (CDH) from Phanerochaete chrysosporium can be used in lactobionic acid production, biosensor for lactose, biofuel cells, lignocellulose degradation, and wound-healing applications. To make it a better biocatalyst, CDH with higher activity in an immobilized form is desirable. For this purpose, CDH was expressed for the first time on the surface of S. cerevisiae EBY100 cells in an active form as a triple mutant tmCDH (D20N, A64T, V592M) and evolved further for higher activity using resazurin-based fluorescent assay. In order to decrease blank reaction of resazurin with yeast cells and to have linear correlation between enzyme activity on the cell surface and fluorescence signal, the assay was optimized with respect to resazurin concentration (0.1 mM), substrate concentration (10mMlactose and 0.08mMcellobiose), and pH (6.0). Using optimized assay an error prone PCR gene library of tmCDH was screened. Two mutants with 5 (H5) and 7 mutations (H9) were found having two times higher activity than the parent tmCDH enzyme that already had improved activity compared to wild type CDH whose activity could not be detected on the surface of yeast cells.

Cellobiose dehydrogenase (CDH) can be used in industry for lactobionic acid production, as a part of biosensors for disaccharides and in wound healing. In fungi it is involved in lignocellulose degradation. CDH gene from Phanerochaete chrysosporium has been cloned in pYES2 plasmid for extracellular expression and protein engineering in yeast Saccharomyces cerevisiae InvSC1 for the first time. A CDH gene library was generated using error-prone PCR and screened by spectrophotometric enzymatic assay based on 2,6-dichloroindophenol reduction detection in microtiter plates. Several mutants with increased activity and specificity towards lactose and cellobiose were found, purified and characterized in detail. Recombinant CDH enzymes showed a broad molecular weight between 120 and 150 KDa due to hyper-glycosylation and the best S137 N mutant showed 2.2 times increased k cat and 1.5 and 2 times increased specificity constant for lactose and cellobiose compared to the wild type enzyme. pH optimum of mutants was not changed while thermostability of selected mutants improved and S137 N mutant retained 30% of it's original activity after 15 min at 70 °C compared to 10% of activity that the wild type enzyme retained. Mutants M65S and S137 N showed also 1.6 and 1.5 times increased productivity of hydrogen peroxide in the presence of 30 mM lactose compared to the wild type.

Cellobiose dehydrogenase (CDH) can be used in industry for lactobionic acid production, as a part of biosensors for disaccharides and in wound healing. In fungi it is involved in lignocellulose degradation. CDH gene from Phanerochaete chrysosporium has been cloned in pYES2 plasmid for extracellular expression and protein engineering in yeast Saccharomyces cerevisiae InvSC1 for the first time. A CDH gene library was generated using error-prone PCR and screened by spectrophotometric enzymatic assaybased on 2,6-dichloroindophenol reduction detection in microtiter plates. Several mutants with increased activity and specificity towards lactose and cellobiose were found, purified and characterized in detail. Recombinant CDH enzymes showed a broad molecular weight between 120 and 150 KDa due to hyperglycosylation and the best S137N mutant showed 2.2 times increased kcat and 1.5 and 2 times increased specificity constant for lactose and cellobiose compared to the wild type enzyme. pH optimum of mutants was not changed while thermostability of selected mutants improved and S137N mutant retained 30% of it’s original activity after 15 minutes at 70oC compared to 10% of activity that the wild type enzyme retained. Mutants M65S and S137N showed also 1.6 and 1.5 times increased productivity of hydrogen peroxide in the presence of 30mM lactose compared to the wild type.

Cellobiose dehydrogenase (CDH) from Phanerochaete chrysosporium can be used in lactobionic acid production, biosensor for lactose, biofuel cells, lignocellulose degradation, and wound-healing applications. To make it a better biocatalyst, CDH with higher activity in an immobilized form is desirable. For this purpose, CDH was expressed for the first time on the surface of S. cerevisiae EBY100 cells in an active form as a triple mutant tmCDH (D20N, A64T, V592M) and evolved further for higher activity using resazurin-based fluorescent assay. In order to decrease blank reaction of resazurin with yeast cells and to have linear correlation between enzyme activity on the cell surface and fluorescence signal, the assay was optimized with respect to resazurin concentration (0.1 mM), substrate concentration (10mMlactose and 0.08mMcellobiose), and pH (6.0). Using optimized assay an error prone PCR gene library of tmCDH was screened. Two mutants with 5 (H5) and 7 mutations (H9) were found having two times higher activity than the parent tmCDH enzyme that already had improved activity compared to wild type CDH whose activity could not be detected on the surface of yeast cells.

Cellobiose dehydrogenase (CDH) can be used in industry for lactobionic acid production, as a part of biosensors for disaccharides and in wound healing. In fungi it is involved in lignocellulose degradation. CDH gene from Phanerochaete chrysosporium has been cloned in pYES2 plasmid for extracellular expression and protein engineering in yeast Saccharomyces cerevisiae InvSC1 for the first time. A CDH gene library was generated using error-prone PCR and screened by spectrophotometric enzymatic assay based on 2,6-dichloroindophenol reduction detection in microtiter plates. Several mutants with increased activity and specificity towards lactose and cellobiose were found, purified and characterized in detail. Recombinant CDH enzymes showed a broad molecular weight between 120 and 150 KDa due to hyperglycosylation and the best S137N mutant showed 2.2 times increased kcat and 1.5 and 2 times increased specificity constant for lactose and cellobiose compared to the wild type enzyme. pH optimum of mutants was not changed while thermostability of selected mutants improved and S137N mutant retained 30% of it’s original activity after 15 minutes at 70oC compared to 10% of activity that the wild type enzyme retained. Mutants M65S and S137N showed also 1.6 and 1.5 times increased productivity of hydrogen peroxide in the presence of 30mM lactose compared to the wild type.

Graphite electrodes were modified with triangular (AuNTrs) or spherical (AuNPs) nanoparticles and further modified with fructose dehydrogenase (FDH). The present study reports the effect of the shape of these nanoparticles (NPs) on the catalytic current of immobilized FDH pointing out the different contributions on the mass transfer-limited and kinetically limited currents. The influence of the shape of the NPs on the mass transfer-limited and the kinetically limited current has been proved by using two different methods: a rotating disk electrode (RDE) and an electrode mounted in a wall jet flow-through electrochemical cell attached to a flow system. The advantages of using the wall jet flow system compared with the RDE system for kinetic investigations are as follows: no need to account for substrate consumption, especially in the case of desorption of enzyme, and studies of product-inhibited enzymes. The comparison reveals that virtually identical results can be obtained using either of the two techniques. The heterogeneous electron transfer (ET) rate constants (k(S)) were found to be 3.8 +/- 0.3 s(-1) and 0.9 +/- 0.1 s(-1), for triangular and spherical NPs, respectively. The improvement observed for the electrode modified with AuNTrs suggests a more effective enzyme-NP interaction, which can allocate a higher number of enzyme molecules on the electrode surface

Cellobiose dehydrogenase (CDH) from Phanerochaete chrysosporium can be used in lactobionic acid production, biosensor for lactose, biofuel cells, lignocellulose degradation, and wound-healing applications. To make it a better biocatalyst, CDH with higher activity in an immobilized form is desirable. For this purpose, CDH was expressed for the first time on the surface of S. cerevisiae EBY100 cells in an active form as a triple mutant tmCDH (D20N, A64T, V592M) and evolved further for higher activity using resazurin-based fluorescent assay. In order to decrease blank reaction of resazurin with yeast cells and to have linear correlation between enzyme activity on the cell surface and fluorescence signal, the assay was optimized with respect to resazurin concentration (0.1 mM), substrate concentration (10mMlactose and 0.08mMcellobiose), and pH (6.0). Using optimized assay an error prone PCR gene library of tmCDH was screened. Two mutants with 5 (H5) and 7 mutations (H9) were found having two times higher activity than the parent tmCDH enzyme that already had improved activity compared to wild type CDH whose activity could not be detected on the surface of yeast cells.

Cellobiose dehydrogenase (CDH) can be used in industry for lactobionic acid production, as a part of biosensors for disaccharides and in wound healing. In fungi it is involved in lignocellulose degradation. CDH gene from Phanerochaete chrysosporium has been cloned in pYES2 plasmid for extracellular expression and protein engineering in yeast Saccharomyces cerevisiae InvSC1 for the first time. A CDH gene library was generated using error-prone PCR and screened by spectrophotometric enzymatic assay based on 2,6-dichloroindophenol reduction detection in microtiter plates. Several mutants with increased activity and specificity towards lactose and cellobiose were found, purified and characterized in detail. Recombinant CDH enzymes showed a broad molecular weight between 120 and 150 KDa due to hyper-glycosylation and the best S137 N mutant showed 2.2 times increased k cat and 1.5 and 2 times increased specificity constant for lactose and cellobiose compared to the wild type enzyme. pH optimum of mutants was not changed while thermostability of selected mutants improved and S137 N mutant retained 30% of it's original activity after 15 min at 70 °C compared to 10% of activity that the wild type enzyme retained. Mutants M65S and S137 N showed also 1.6 and 1.5 times increased productivity of hydrogen peroxide in the presence of 30 mM lactose compared to the wild type.

Graphite electrodes were modified with triangular (AuNTrs) or spherical (AuNPs) nanoparticles and further modified with fructose dehydrogenase (FDH). The present study reports the effect of the shape of these nanoparticles (NPs) on the catalytic current of immobilized FDH pointing out the different contributions on the mass transfer-limited and kinetically limited currents. The influence of the shape of the NPs on the mass transfer-limited and the kinetically limited current has been proved by using two different methods: a rotating disk electrode (RDE) and an electrode mounted in a wall jet flow-through electrochemical cell attached to a flow system. The advantages of using the wall jet flow system compared with the RDE system for kinetic investigations are as follows: no need to account for substrate consumption, especially in the case of desorption of enzyme, and studies of product-inhibited enzymes. The comparison reveals that virtually identical results can be obtained using either of the two techniques. The heterogeneous electron transfer (ET) rate constants (k(S)) were found to be 3.8 +/- 0.3 s(-1) and 0.9 +/- 0.1 s(-1), for triangular and spherical NPs, respectively. The improvement observed for the electrode modified with AuNTrs suggests a more effective enzyme-NP interaction, which can allocate a higher number of enzyme molecules on the electrode surface

Cellobiose dehydrogenase (CDH) can be used in industry for lactobionic acid production, as a part of biosensors for disaccharides and in wound healing. In fungi it is involved in lignocellulose degradation. CDH gene from Phanerochaete chrysosporium has been cloned in pYES2 plasmid for extracellular expression and protein engineering in yeast Saccharomyces cerevisiae InvSC1 for the first time. A CDH gene library was generated using error-prone PCR and screened by spectrophotometric enzymatic assaybased on 2,6-dichloroindophenol reduction detection in microtiter plates. Several mutants with increased activity and specificity towards lactose and cellobiose were found, purified and characterized in detail. Recombinant CDH enzymes showed a broad molecular weight between 120 and 150 KDa due to hyperglycosylation and the best S137N mutant showed 2.2 times increased kcat and 1.5 and 2 times increased specificity constant for lactose and cellobiose compared to the wild type enzyme. pH optimum of mutants was not changed while thermostability of selected mutants improved and S137N mutant retained 30% of it’s original activity after 15 minutes at 70oC compared to 10% of activity that the wild type enzyme retained. Mutants M65S and S137N showed also 1.6 and 1.5 times increased productivity of hydrogen peroxide in the presence of 30mM lactose compared to the wild type.

Cellobiose dehydrogenase (CDH) from Phanerochaete chrysosporium can be used in lactobionic acid production, biosensor for lactose, biofuel cells, lignocellulose degradation, and wound-healing applications. To make it a better biocatalyst, CDH with higher activity in an immobilized form is desirable. For this purpose, CDH was expressed for the first time on the surface of S. cerevisiae EBY100 cells in an active form as a triple mutant tmCDH (D20N, A64T, V592M) and evolved further for higher activity using resazurin-based fluorescent assay. In order to decrease blank reaction of resazurin with yeast cells and to have linear correlation between enzyme activity on the cell surface and fluorescence signal, the assay was optimized with respect to resazurin concentration (0.1 mM), substrate concentration (10mMlactose and 0.08mMcellobiose), and pH (6.0). Using optimized assay an error prone PCR gene library of tmCDH was screened. Two mutants with 5 (H5) and 7 mutations (H9) were found having two times higher activity than the parent tmCDH enzyme that already had improved activity compared to wild type CDH whose activity could not be detected on the surface of yeast cells.

Cellobiose dehydrogenase (CDH) can be used in industry for lactobionic acid production, as a part of biosensors for disaccharides and in wound healing. In fungi it is involved in lignocellulose degradation. CDH gene from Phanerochaete chrysosporium has been cloned in pYES2 plasmid for extracellular expression and protein engineering in yeast Saccharomyces cerevisiae InvSC1 for the first time. A CDH gene library was generated using error-prone PCR and screened by spectrophotometric enzymatic assay based on 2,6-dichloroindophenol reduction detection in microtiter plates. Several mutants with increased activity and specificity towards lactose and cellobiose were found, purified and characterized in detail. Recombinant CDH enzymes showed a broad molecular weight between 120 and 150 KDa due to hyperglycosylation and the best S137N mutant showed 2.2 times increased kcat and 1.5 and 2 times increased specificity constant for lactose and cellobiose compared to the wild type enzyme. pH optimum of mutants was not changed while thermostability of selected mutants improved and S137N mutant retained 30% of it’s original activity after 15 minutes at 70oC compared to 10% of activity that the wild type enzyme retained. Mutants M65S and S137N showed also 1.6 and 1.5 times increased productivity of hydrogen peroxide in the presence of 30mM lactose compared to the wild type.

Featured Application Developed fluorescent assay and expression system can be used for obtaining improved cellobiose dehydrogenase whole cell biocatalysts for lactobionic acid production and building of biosensors and biofuel cells. Cellobiose dehydrogenase (CDH) from Phanerochaete chrysosporium can be used in lactobionic acid production, biosensor for lactose, biofuel cells, lignocellulose degradation, and wound-healing applications. To make it a better biocatalyst, CDH with higher activity in an immobilized form is desirable. For this purpose, CDH was expressed for the first time on the surface of S. cerevisiae EBY100 cells in an active form as a triple mutant tmCDH (D20N, A64T, V592M) and evolved further for higher activity using resazurin-based fluorescent assay. In order to decrease blank reaction of resazurin with yeast cells and to have linear correlation between enzyme activity on the cell surface and fluorescence signal, the assay was optimized with respect to resazurin concentration (0.1 mM), substrate concentration (10 mM lactose and 0.08 mM cellobiose), and pH (6.0). Using optimized assay an error prone PCR gene library of tmCDH was screened. Two mutants with 5 (H5) and 7 mutations (H9) were found having two times higher activity than the parent tmCDH enzyme that already had improved activity compared to wild type CDH whose activity could not be detected on the surface of yeast cells.

Cellobiose dehydrogenase (CDH, EC 1.1.99.18) from Phanerochaete chrysosporium belongs to a group of oxidoreductases and has the ability to degrade different components of woody plants. CDH is secreted by wood degrading, phytopathogenic and saprotrophic fungi and this widespread appearance implies hers important function and makes her an important enzyme for applications in industrial and biotechnological processes, as well as biosensors and biofuel cells. CDH is also used in industry for bleaching cotton and in food industry for lactose detection. CDH is monomeric enzyme consisting of two domains, flavin domain containing FAD as cofactor and smaller hem b containing cytochrome domain, connected via flexible linker. Physiological role of CDH is reflected in the degradation of cellulose and lignin in cooperation with other cellulolytic enzymes, because CDH catalyzes oxidation of celobiose (Glc - β - 1,4 Glc) and other β - 1,4 - linked disaccharides and oligosaccharides to the corresponding lactons. Enzymes used in biosensors and for bleaching cotton should have high stability, especially toward reactive oxygen species. In order to improve oxidative stability of CDH, we have mutated CDH and tested its stability in presence of hydrogen peroxide. After successful cloning of the CDH gene in pYES2 vector, saturation mutagenesis was used to make library mutants where tree methionine residues were mutated. Residual activity of mutants was measured after the enzyme incubation in 0.3 M hydrogen peroxide for 0, 2 and 6h. After analysis of large number of mutants, it was observed that three mutants are showing higher oxidative stability compared to the wild - type enzyme. Residual activities of these mutants after 6 hour incubation in the hydrogen peroxide were over 50%, whereas wild-type has 30%. Selected mutants were expressed in S. cerevisiae and purified on DEAE column. Purity and activity of the enzymes were detected on the electrophoresis gel, oxidative stability of purifi

Cellobiose dehydrogenase (CDH) is a sugar oxidizing enzyme secreted by various species of wood degrading fungi to assist the process of wood degradation. It can oxidise analytically relevant sugars as cellobiose, lactose or glucose leading to a gain of two electrons per sugar molecule. CDH consists of a flavin containing catalytic domain (DH) and a haem containing electron mediating domain (CYT). CDH is able to directly communicate with electrode surfaces via the CYT delivering its gained electrons making it a suitable candidate for the construction of mediatorless biosensors and biofuel cell anodes being applicable either for the detection of sugars or for the generation of electricity out of sugar containing solutions. In the present thesis the ability of CDH to electrically communicate with silver, gold and graphite electrode surfaces was investigated and employed mainly by electrochemical techniques as cyclic voltammetry and square wave voltammetry and was complemented by spectroscopic techniques. The central finding is the ability of cations to enhance the electro-catalytic activity of CDH. Especially divalent cations as Ca2+ were found to increase the internal electron transfer (IET) from the DH to the electron mediating CYT leading to higher current outputs. The effect was ascribed to a yet unknown, transient, electrostatic interaction of Ca2+ with negative charges present on the DH and CYT decreasing their repulsion leading to a faster IET. Similar effects were observed for CDH electrodes premodified with immobilised polycations as polyethylenimine (PEI) or polydiallyldimethylammonium chloride (PDADMAC) or premodified with PEI covered gold nanoparticles. The polycations were found to enhance the enzyme load onto electrode surfaces by electrostatic interactions but were also suggested to increase the IET comparable to Ca2+. The beneficial effect of cations and polycations on the electro-catalytic activity of CDH was employed to construct various biosensors to

Enzymatic fuel cells (EFCs) are bioelectronic devices based on redox enzymes, which convert chemical energy into electrical energy via biochemical reactions. A major difficulty to overcome is to successfully connect (using e.g., immobilization) the enzymes to the electrode surface. Since the immobilization process often stabilizes the enzyme, the electrode surface and the enzyme/electrode interface is of utmost importance for both the efficiency and stability of the EFC. In this work several different means of establishing the enzyme/electrode connection have been investigated.In order to construct a device that utilizes direct electron transfer the electrode surfaces were modified with nanostructures and, in some designs, self-assembled monolayers of thiols. The performance of the electrodes was evaluated by electrochemical methods, including potential sweeps and chronopotentiometry. Catalytic constants could be calculated mathematically by combining electrochemical methods with surface characterization methods, such as quartz crystal microbalance with dissipation and ellipsometry. All the fuel cells covered by this thesis are based on direct electron transfer processes. All designs also oxidize carbohydrates and reduce oxygen using cellobiose dehydrogenase and multi-copper oxidase, respectively.Our results revealed that the use of particular thiol had the capability to electrically connect cellobiose dehydrogenase to the electrode, equalling the commonly used two-thiol system. Both designs reached similar current densities, Le., about 20 jiA cm 2 with 5 mM lactose and the enzyme immobilized on thiolated gold nanoparticles (AuNPs). Both Bilirubin oxidase and Trichaptum abietinum Laccase could be directly immobilized on gold nanoparticles and current densities of up to 180 pA cm 2 were achieved. The 9- fold difference in currents with BOx and CDH reveals that the bioanode in this system requires more improvement to match the biocathode in performance. Upon doser ins

peer-reviewed, Here for the first time, we detail self-contained (wireless and self-powered) biodevices with wireless signal transmission. Specifically, we demonstrate the operation of self-sustained carbohydrate and oxygen sensitive biodevices, consisting of a wireless electronic unit, radio transmitter and separate sensing bioelectrodes, supplied with electrical energy from a combined multi-enzyme fuel cell generating sufficient current at required voltage to power the electronics. A carbohydrate/oxygen enzymatic fuel cell was assembled by comparing the performance of a range of different bioelectrodes followed by selection of the most suitable, stable combination. Carbohydrates (viz. lactose for the demonstration) and oxygen were also chosen as bioanalytes, being important biomarkers, to demonstrate the operation of the self-contained biosensing device, employing enzyme-modified bioelectrodes to enable the actual sensing. A wireless electronic unit, consisting of a micropotentiostat, an energy harvesting module (voltage amplifier together with a capacitor), and a radio microchip, were designed to enable the biofuel cell to be used as a power supply for managing the sensing devices and for wireless data transmission. The electronic system used required current and voltages greater than 44 mu A and 0.57 V, respectively to operate; which the biofuel cell was capable of providing, when placed in a carbohydrate and oxygen containing buffer. In addition, a USB based receiver and computer software were employed for proof-of concept tests of the developed biodevices. Operation of bench-top prototypes was demonstrated in buffers containing different concentrations of the analytes, showcasing that the variation in response of both carbohydrate and oxygen biosensors could be monitored wirelessly in real-time as analyte concentrations in buffers were changed, using only an enzymatic fuel cell as a power supply., PUBLISHED, peer-reviewed

Enzymatic fuel cells (EFCs) are bioelectronic devices based on redox enzymes, which convert chemical energy into electrical energy via biochemical reactions. A major difficulty to overcome is to successfully connect (using e.g., immobilization) the enzymes to the electrode surface. Since the immobilization process often stabilizes the enzyme, the electrode surface and the enzyme/electrode interface is of utmost importance for both the efficiency and stability of the EFC. In this work several different means of establishing the enzyme/electrode connection have been investigated.In order to construct a device that utilizes direct electron transfer the electrode surfaces were modified with nanostructures and, in some designs, self-assembled monolayers of thiols. The performance of the electrodes was evaluated by electrochemical methods, including potential sweeps and chronopotentiometry. Catalytic constants could be calculated mathematically by combining electrochemical methods with surface characterization methods, such as quartz crystal microbalance with dissipation and ellipsometry. All the fuel cells covered by this thesis are based on direct electron transfer processes. All designs also oxidize carbohydrates and reduce oxygen using cellobiose dehydrogenase and multi-copper oxidase, respectively.Our results revealed that the use of particular thiol had the capability to electrically connect cellobiose dehydrogenase to the electrode, equalling the commonly used two-thiol system. Both designs reached similar current densities, Le., about 20 jiA cm 2 with 5 mM lactose and the enzyme immobilized on thiolated gold nanoparticles (AuNPs). Both Bilirubin oxidase and Trichaptum abietinum Laccase could be directly immobilized on gold nanoparticles and current densities of up to 180 pA cm 2 were achieved. The 9- fold difference in currents with BOx and CDH reveals that the bioanode in this system requires more improvement to match the biocathode in performance. Upon doser ins, Paper III in dissertation as manuscript with title "Electroactive biomaterial based on enzymatic catalysis and physical factors affecting its performance"

The present paper features an exciting time in the late 1980s when I, as a visiting scientist, had the privilege to participate in the early and very exciting development of the in vivo redox-polymer-wired glucose sensor in Professor Adam Heller's laboratory at the Department of Chemical Engineering at University of Texas at Austin. This story is followed by an overview of the research my visit initiated at Uppsala University. In collaboration with Swedish colleagues, we explored a few of the many possibilities to form new biosensors by utilizing Prof. Heller's concept of cross-linked redox-polymer/redox-enzyme electrodes.

Pyranose dehydrogenases (PDHs) are extracellular flavin-dependent oxidoreductases secreted by litter-decomposing fungi with a role in natural recycling of plant matter. All major monosaccharides in lignocellulose are oxidized by PDH at comparable yields and efficiencies. Oxidation takes place as single-oxidation or sequential double-oxidation reactions of the carbohydrates, resulting in sugar derivatives oxidized primarily at C2, C3 or C2/3 with the concomitant reduction of the flavin. A suitable electron acceptor then reoxidizes the reduced flavin. Whereas oxygen is a poor electron acceptor for PDH, several alternative acceptors, e.g., quinone compounds, naturally present during lignocellulose degradation, can be used. We have determined the 1.6-Å crystal structure of PDH from Agaricus meleagris. Interestingly, the flavin ring in PDH is modified by a covalent mono- or di-atomic species at the C(4a) position. Under normal conditions, PDH is not oxidized by oxygen; however, the related enzyme pyranose 2-oxidase (P2O) activates oxygen by a mechanism that proceeds via a covalent flavin C(4a)-hydroperoxide intermediate. Although the flavin C(4a) adduct is common in monooxygenases, it is unusual for flavoprotein oxidases, and it has been proposed that formation of the intermediate would be unfavorable in these oxidases. Thus, the flavin adduct in PDH not only shows that the adduct can be favorably accommodated in the active site, but also provides important details regarding the structural, spatial and physicochemical requirements for formation of this flavin intermediate in related oxidases. Extensive in silico modeling of carbohydrates in the PDH active site allowed us to rationalize the previously reported patterns of substrate specificity and regioselectivity. To evaluate the regioselectivity of D-glucose oxidation, reduction experiments were performed using fluorinated glucose. PDH was rapidly reduced by 3-fluorinated glucose, which has the C2 position accessible fo, QC 20130213

The cost of cellulose degrading enzymes is still a major barrier to the economical production of liquid fuels from lignocellulose. Fungi play a central role in the degradation of plant biomass in terrestrial environments. They use a wide variety of secreted enzymes to break down biopolymers present in the plant cell wall. Here I report on the mechanisms of cellulose degradation used by Neurospora crassa, a model genetic organism, and Myceliopthora thermophila, a thermophilic fungus. Enzymes important for the degradation process were identified using a combination of transcriptomics, proteomics, genetics, and biochemistry. A key result from this work is that, in N. crassa and many other fungi, oxidative enzymes play a critical role in the depolymerization of cellulose. In contrast to the accepted models of oxidative cellulose degradation, via non-specific hydroxyl radical species, I found that in N. crassa, an oxidoreductase and several copper oxidases bind to cellulose and hydroxylate the substrate at specific positions leading to cleavage of the glycosidic bonds. This mode of action is orthogonal to that of traditional hydrolases and if used optimally in conjunction with other cellulases, could reduce the required enzyme loading for lignocellulose saccharification by 2-4 fold.

The cost of cellulose degrading enzymes is still a major barrier to the economical production of liquid fuels from lignocellulose. Fungi play a central role in the degradation of plant biomass in terrestrial environments. They use a wide variety of secreted enzymes to break down biopolymers present in the plant cell wall. Here I report on the mechanisms of cellulose degradation used by Neurospora crassa, a model genetic organism, and Myceliopthora thermophila, a thermophilic fungus. Enzymes important for the degradation process were identified using a combination of transcriptomics, proteomics, genetics, and biochemistry. A key result from this work is that, in N. crassa and many other fungi, oxidative enzymes play a critical role in the depolymerization of cellulose. In contrast to the accepted models of oxidative cellulose degradation, via non-specific hydroxyl radical species, I found that in N. crassa, an oxidoreductase and several copper oxidases bind to cellulose and hydroxylate the substrate at specific positions leading to cleavage of the glycosidic bonds. This mode of action is orthogonal to that of traditional hydrolases and if used optimally in conjunction with other cellulases, could reduce the required enzyme loading for lignocellulose saccharification by 2-4 fold.

Pyranose dehydrogenase (PDH) is a flavin-dependant sugar oxidoreductase found in the family Agaricaceae, basidiomycetes that degrade lignocellulose-rich forest litter, and is catalytically related to the fungal enzymes pyranose 2-oxidase and cellobiose dehydrogenase. It has broad substrate specificity and displays similar activities with most sugar constituents of lignocellulose including disaccharides and oligosaccharides, a number of (substituted) quinones, and metal ions are suitable electron acceptors rather than molecular oxygen. In contrast to pyranose 2-oxidase and cellobiose dehydrogenase, which oxidize regioselectively at C-2 and C-1, respectively, PDH is capable of oxidation on C-1 to C-4 as well as double oxidations, depending on the nature of the substrate. This makes it a very interesting enzyme for biocatalytic applications, as many of the reaction products are otherwise unaccessible by chemical or enzymatic means. PDH was characterized in detail in a limited number of fungi, and the first encoding genes were isolated only recently. We report here, for the first time, the heterologous expression of one of these genes, encoding the major PDH protein in Agaricus meleagris, in the filamentous fungi Aspergillus nidulans, and Aspergillus niger., QC 20140821

We report on the fabrication and characterisation of the very first direct electron transfer-based glucose/oxygen biofuel cell (BFC) operating in neutral glucose-containing buffer and human serum. Corynascus thermophilus cellobiose ehydrogenase and Myrothecium verrucaria bilirubin oxidase were used as anodic and cathodic bioelements, respectively. Thefollowing characteristics of the mediator-, separator- and membrane-less, a priori, non-toxic and simple miniature BFC, was obtained: an open-circuit voltage of 0.62 and0.58 V, a maximum power density of ca. 3 and 4 lW cm–2 at 0.37 and 0.19 V of cell voltage, in phosphate buffer and human serum, respectively.

We report on the fabrication and characterisation of the very first direct electron transfer-based glucose/oxygen biofuel cell (BFC) operating in neutral glucose-containing buffer and human serum. Corynascus thermophilus cellobiose ehydrogenase and Myrothecium verrucaria bilirubin oxidase were used as anodic and cathodic bioelements, respectively. Thefollowing characteristics of the mediator-, separator- and membrane-less, a priori, non-toxic and simple miniature BFC, was obtained: an open-circuit voltage of 0.62 and0.58 V, a maximum power density of ca. 3 and 4 lW cm–2 at 0.37 and 0.19 V of cell voltage, in phosphate buffer and human serum, respectively.

The catalytic properties and the inter-domain electron transfer of cellobiose dehydrogenase (CDH) from the ascomycete fungus Myriococcum thermophilum adsorbed on graphite and thiol (SAM) modified gold electrodes were investigated using cyclic voltammetry, flow injection amperometry and UV-Vis spectroelectrochemistry. The fabrication and characterisation of a noncompartmentalised, mediator and cofactor free glucose–oxygen biofuel cell well-operating in glucose-containing buffers and human blood serum was performed. The biofuel cell was based on adsorbed enzymes exhibiting direct bioelectrocatalysis, viz. CDH from Dichomera saubinetii and Corynascus thermophilus used as anodic bioelements and laccase (Lc) from Trametes hirsuta and bilirubin oxidase (BOD) from Myrothecium verrucaria used as cathodic bioelements, respectively. Different bacterial strains of E. coli and B. subtilis were immobilised on the electrode surface and tested for electrical communication using soluble and polymeric mediators. In the case of E. coli, the introduction of cytochromes in the inner membrane facilitated the electrochemical communication when using artificial mediators, while in the case of B. subtilis, the results demonstrated that mediators did not have to pass the cytosolic membrane to bring about an efficient electronic communication between bacterial cells with a thick cell wall and electrodes.

Sugar oxidoreductases such as cellobiose dehydrogenase or pyranose oxidase are widespread enzymes among fungi, whose biological function is largely speculative. We investigated a similar gene family in the mushroom Agaricus meleagris and its expression under various conditions. Three genes (named pdh1, pdh2 and pdh3) putatively encoding pyranose dehydrogenases were isolated. All three genes displayed a conserved structure and organization, and the respective cDNAs contained ORFs translating into polypeptides of 602 or 600 amino acids. The N-terminal sections of all three genes encode putative signal peptides consistent with the enzymes extracellular secretion. We cultivated the fungus on different carbon sources and analyzed the mRNA levels of all three genes over a period of several weeks using real-time RT-PCR. The glyceraldehyde-3-phosphate dehydrogenase gene from A. meleagris was also isolated and served as reference gene. pdh2 and pdh3 are essentially transcribed constitutively, whereas pdh1 expression is upregulated upon exhaustion of the carbon source; pdh1 appears to be additionally regulated under conditions of oxygen limitation. These data are consistent with an assumed role in lignocellulose degradation., QC 20100525

We purified an extracellular pyranose dehydrogenase (PDH) from the basidiomycete fungus Agaricus xanthoderma using ammonium sulfate fractionation and ion-exchange and hydrophobic interaction chromatography. The native enzyme is a monomeric glycoprotein (5% carbohydrate) containing a covalently bound FAD as its prosthetic group. The PDH polypeptide consists of 575 amino acids and has a molecular mass of 65 400 Da as determined by MALDI MS. On the basis of the primary structure of the mature protein, PDH is a member of the glucose-methanol-choline oxidoreductase family. We constructed a homology model of PDH using the 3D structure of glucose oxidase from Aspergillus niger as a template. This model suggests a novel type of bi-covalent flavinylation in PDH, 9-S-cysteinyl, 8-alpha-N3-histidyl FAD. The enzyme exhibits a broad sugar substrate tolerance, oxidizing structurally different aldopyranoses including monosaccharides and oligosaccharides as well as glycosides. Its preferred electron donor substrates are D-glucose, D-galactose, L-arabinose, and D-xylose. As shown by in situ NMR analysis, D-glucose and D-galactose are both oxidized at positions C2 and C3, yielding the corresponding didehydroaldoses (diketoaldoses) as the final reaction products. PDH shows no detectable activity with oxygen, and its reactivity towards electron acceptors is rather limited, reducing various substituted benzoquinones and complexed metal ions. The azino-bis-(3-ethylbenzthiazolin-6-sulfonic acid) cation radical and the ferricenium ion are the best electron acceptors, as judged by the catalytic efficiencies (k(cat)/K-m). The enzyme may play a role in lignocellulose degradation., QC 20100525

Pycnoporus strains were used as model to understand the role of laccases in the in vivo decolourisation of three anthraquinonic dyes. The decolourisation capability of Pycnoporus sanguineus MUCL 41582 (PS7), which produces laccases as the main oxidative enzyme, was assayed and compared with the decolourisation capability of a control strain, Pycnoporus cinnabarinus MUCL 39533 (PC330) described as laccase-deficient strain. In absence of dye, laccase activity was observed during the trophophase and the idiophase with PS7, while no laccase activity was observed with PC330. Acid Blue 62 (ABu62), Acid Blue 281 (ABu281) and Reactive Blue 19 (RBu 19) caused an increase in laccase activity and surprisingly laccase activity was detected with PC330. In vitro, oxidation of all three anthraquinones by a laccase preparation was obtained to a lesser extent than the whole cell process; suggesting that other factor(s) could be required for a complete decolourisation. As the time space of laccase production in the tested fungi was not perfectly coincidental with the decolourisation process, the activity of cellobiose dehydrogenase (CDH) was monitored. Present early in the broth during the growth of the fungi, CDH displayed in vitro a synergism with laccases in the decolourisation of ABu62, and an antagonism with laccases in the decolourisation of ABu281 and RBu19. (c) 2006 Elsevier Inc. All rights reserved.

Cellobiose dehydrogenase, the only currently known extracellular flavocytochrome. is formed not only by a number of wood-degrading but also by various phytopathogenic fungi. This inducible enzyme participates in early events of lignocellulose degradation, as investigated in several basidiomycete fungi at the transcriptional and translational level. However, its role in the ascomycete fungi is not yet obvious. Comprehensive sequence analysis of CDH-encoding genes and their translational products reveals significant sequence similarities along the entire sequences and also a common domain architecture. All known cellobiose dehydrogenases fall into two related subgroups. Class-I members are represented by sequences from basidiomycetcs whereas class-II comprises longer, more complex sequences from ascomycete fungi. Cellobiose dehydrogenase is typically a monomeric protein consisting of two domains joined by a protease-sensitive linker region. Each larger (dehydrogenase) domain is flavin-associated while the smaller (cytochrome) domains are haem-binding. The latter shorter domains are unique sequence motifs for all currently known flavocytochromes. Each cytochrome domain of CDH can bind a single haem b as prosthetic group. The larger dehydrogenase domain belongs to the glucose-methanol-choline (GMC) oxidoreductase superfamily - a widespread flavoprotein evolutionary line. The larger domains can be further divided into a flavin-binding subdomain and a substrate-binding subdomain. In addition, the class-II (but not class-I) proteins can possess a short cellulose-binding module of type I at their C-termini. All the cellobiose dehydrogenases oxidise cellobiose, cellodextrins, and lactose to the corresponding lactones using a wide spectrum of different electron acceptors. Their flexible specificity serves as a base for the development of possible biotechnological applications., QC 20100525

Pyranose2-oxidase(P2Ox) participates in fungal lignin degradation by producing the H2O2 needed for lignin-degrading peroxidases. The enzyme oxidizes cellulose- and hemicellulose-derived aldopyranoses at C2 preferentially, but also on C3, to the corresponding ketoaldoses. To investigate the structural determinants of catalysis, covalent flavinylation, substrate binding, and regios-electivity, wild-type and mutant P2Ox enzymes were produced and characterized biochemically and structurally. Removal of the histidyl-FAD linkage resulted in a catalytically competent enzyme containing tightly, but noncovalently bound FAD. This mutant (H167A) is characterized by a 5-fold lower k(cat), and a 35-mV lower redox potential, although no significant structural changes were seen in its crystal structure. In previous structures of P2Ox, the substrate loop (residues 452-457) covering the active site has been either disordered or in a conformation incompatible with carbohydrate binding. We present here the crystal structure of H167A in complex with a slow substrate, 2-fluoro-2-deoxy-D-glucose. Based on the details of 2-fluoro-2-deoxy-D-glucose binding in position for oxidation at C3, we also outline a probable binding mode for D-glucose positioned for regioselective oxidation at C2. The tentative determinant for discriminating between the two binding modes is the position of the O6 hydroxyl group, which in the C2-oxidation mode can make favorable interactions with Asp(452) in the substrate loop and, possibly, a nearby arginine residue (Arg(472)). We also substantiate our hypothesis with steady-state kinetics data for the alanine replacements of Asp(452) and Arg(472) as well as the double alanine 452/472 mutant., QC 20100525

The enzymatic degradation of cellulose is an important process in nature. This thesis has focused on the degradation of cellulose by enzymes from two cellulose-degrading fungi, Hypocrea jecorina and Phanerochaete chrysosporium, including both the action of the individual enzymes and their synergistic interplay. The end-preference of cellobiohydrolases on crystalline cellulose was studied. Cellobiohydrolases belonging to glycosyl hydrolase (GH) family 7 were found to hydrolyse cellulose processively, starting from the reducing end of the cellulose chain. End-labelled cellulose can serve as a tool for functional classification of cellulases. The synergy mechanism between endoglucanases and cellobiohydrolases was studied using substrates with different physical properties derived from bacterial cellulose. A new mechanism for synergism between endo- and exoacting enzymes was proposed whereby endoglucanases, in addition to creating nicks in amorphous parts of cellulose, thereby making new starting-points for processively acting cellobiohydrolases, also “polish” the cellulose surface by removing shorter chains from cellulose surface. A new small endoglucanase belonging to the GH12 family was isolated and characterised. The proposed role of this enzyme is to make the cellulose in wood more accessible to other cellulases. Oxygen conversion by cellobiose dehydrogenase was studied. Hydrogen peroxide produced by cellobiose dehydrogenase can be decomposed even by traces of certain metal ions into a hydroxyl radical and a hydroxyl ion. As an example, reduced metal ions will be continuously regenerated by cellobiose dehydrogenase, which thus stimulates the degradation. Interactions between GH7 family cellobiohydrolases and o-nitrophenyl cellobioside were studied by fluorescence spectroscopy and kinetic tests. o-nitrophenyl cellobioside was used as indicator ligand to determine the dissociation constants for cellobiose binding to catalytically inactive Cel7A mutants by displacemen

The enzymatic degradation of cellulose is an important process in nature. This thesis has focused on the degradation of cellulose by enzymes from two cellulose-degrading fungi, Hypocrea jecorina and Phanerochaete chrysosporium, including both the action of the individual enzymes and their synergistic interplay. The end-preference of cellobiohydrolases on crystalline cellulose was studied. Cellobiohydrolases belonging to glycosyl hydrolase (GH) family 7 were found to hydrolyse cellulose processively, starting from the reducing end of the cellulose chain. End-labelled cellulose can serve as a tool for functional classification of cellulases. The synergy mechanism between endoglucanases and cellobiohydrolases was studied using substrates with different physical properties derived from bacterial cellulose. A new mechanism for synergism between endo- and exoacting enzymes was proposed whereby endoglucanases, in addition to creating nicks in amorphous parts of cellulose, thereby making new starting-points for processively acting cellobiohydrolases, also “polish” the cellulose surface by removing shorter chains from cellulose surface. A new small endoglucanase belonging to the GH12 family was isolated and characterised. The proposed role of this enzyme is to make the cellulose in wood more accessible to other cellulases. Oxygen conversion by cellobiose dehydrogenase was studied. Hydrogen peroxide produced by cellobiose dehydrogenase can be decomposed even by traces of certain metal ions into a hydroxyl radical and a hydroxyl ion. As an example, reduced metal ions will be continuously regenerated by cellobiose dehydrogenase, which thus stimulates the degradation. Interactions between GH7 family cellobiohydrolases and o-nitrophenyl cellobioside were studied by fluorescence spectroscopy and kinetic tests. o-nitrophenyl cellobioside was used as indicator ligand to determine the dissociation constants for cellobiose binding to catalytically inactive Cel7A mutants by displacemen

The enzymatic degradation of cellulose is an important process in nature. This thesis has focused on the degradation of cellulose by enzymes from two cellulose-degrading fungi, Hypocrea jecorina and Phanerochaete chrysosporium, including both the action of the individual enzymes and their synergistic interplay. The end-preference of cellobiohydrolases on crystalline cellulose was studied. Cellobiohydrolases belonging to glycosyl hydrolase (GH) family 7 were found to hydrolyse cellulose processively, starting from the reducing end of the cellulose chain. End-labelled cellulose can serve as a tool for functional classification of cellulases. The synergy mechanism between endoglucanases and cellobiohydrolases was studied using substrates with different physical properties derived from bacterial cellulose. A new mechanism for synergism between endo- and exoacting enzymes was proposed whereby endoglucanases, in addition to creating nicks in amorphous parts of cellulose, thereby making new starting-points for processively acting cellobiohydrolases, also “polish” the cellulose surface by removing shorter chains from cellulose surface. A new small endoglucanase belonging to the GH12 family was isolated and characterised. The proposed role of this enzyme is to make the cellulose in wood more accessible to other cellulases. Oxygen conversion by cellobiose dehydrogenase was studied. Hydrogen peroxide produced by cellobiose dehydrogenase can be decomposed even by traces of certain metal ions into a hydroxyl radical and a hydroxyl ion. As an example, reduced metal ions will be continuously regenerated by cellobiose dehydrogenase, which thus stimulates the degradation. Interactions between GH7 family cellobiohydrolases and o-nitrophenyl cellobioside were studied by fluorescence spectroscopy and kinetic tests. o-nitrophenyl cellobioside was used as indicator ligand to determine the dissociation constants for cellobiose binding to catalytically inactive Cel7A mutants by displacemen

The enzymatic degradation of cellulose is an important process in nature. This thesis has focused on the degradation of cellulose by enzymes from two cellulose-degrading fungi, Hypocrea jecorina and Phanerochaete chrysosporium, including both the action of the individual enzymes and their synergistic interplay. The end-preference of cellobiohydrolases on crystalline cellulose was studied. Cellobiohydrolases belonging to glycosyl hydrolase (GH) family 7 were found to hydrolyse cellulose processively, starting from the reducing end of the cellulose chain. End-labelled cellulose can serve as a tool for functional classification of cellulases. The synergy mechanism between endoglucanases and cellobiohydrolases was studied using substrates with different physical properties derived from bacterial cellulose. A new mechanism for synergism between endo- and exoacting enzymes was proposed whereby endoglucanases, in addition to creating nicks in amorphous parts of cellulose, thereby making new starting-points for processively acting cellobiohydrolases, also “polish” the cellulose surface by removing shorter chains from cellulose surface. A new small endoglucanase belonging to the GH12 family was isolated and characterised. The proposed role of this enzyme is to make the cellulose in wood more accessible to other cellulases. Oxygen conversion by cellobiose dehydrogenase was studied. Hydrogen peroxide produced by cellobiose dehydrogenase can be decomposed even by traces of certain metal ions into a hydroxyl radical and a hydroxyl ion. As an example, reduced metal ions will be continuously regenerated by cellobiose dehydrogenase, which thus stimulates the degradation. Interactions between GH7 family cellobiohydrolases and o-nitrophenyl cellobioside were studied by fluorescence spectroscopy and kinetic tests. o-nitrophenyl cellobioside was used as indicator ligand to determine the dissociation constants for cellobiose binding to catalytically inactive Cel7A mutants by displacemen

The enzymatic degradation of cellulose is an important process in nature. This thesis has focused on the degradation of cellulose by enzymes from two cellulose-degrading fungi, Hypocrea jecorina and Phanerochaete chrysosporium, including both the action of the individual enzymes and their synergistic interplay. The end-preference of cellobiohydrolases on crystalline cellulose was studied. Cellobiohydrolases belonging to glycosyl hydrolase (GH) family 7 were found to hydrolyse cellulose processively, starting from the reducing end of the cellulose chain. End-labelled cellulose can serve as a tool for functional classification of cellulases. The synergy mechanism between endoglucanases and cellobiohydrolases was studied using substrates with different physical properties derived from bacterial cellulose. A new mechanism for synergism between endo- and exoacting enzymes was proposed whereby endoglucanases, in addition to creating nicks in amorphous parts of cellulose, thereby making new starting-points for processively acting cellobiohydrolases, also “polish” the cellulose surface by removing shorter chains from cellulose surface. A new small endoglucanase belonging to the GH12 family was isolated and characterised. The proposed role of this enzyme is to make the cellulose in wood more accessible to other cellulases. Oxygen conversion by cellobiose dehydrogenase was studied. Hydrogen peroxide produced by cellobiose dehydrogenase can be decomposed even by traces of certain metal ions into a hydroxyl radical and a hydroxyl ion. As an example, reduced metal ions will be continuously regenerated by cellobiose dehydrogenase, which thus stimulates the degradation. Interactions between GH7 family cellobiohydrolases and o-nitrophenyl cellobioside were studied by fluorescence spectroscopy and kinetic tests. o-nitrophenyl cellobioside was used as indicator ligand to determine the dissociation constants for cellobiose binding to catalytically inactive Cel7A mutants by displacemen