Search

Sunflower and rapeseed meals are agro-industrial coproducts that contain high amount of phenolics (1–4 % dry matter), mostly as esters of caffeic acid (CA) and sinapic acid (SA), respectively. The enzymatic hydrolysis of the ester bonds enables to recover the corresponding free phenolic acids that are bioactive compounds and platform molecules for various applications in green chemistry. Here we aimed to find the best route for producing free CA and SA by applying various fungal carboxylic ester hydrolases from recombinant Aspergillus niger strains either directly on crude meal or on their phenolic extracts obtained by methanolic extraction. Two types of meals were studied: (i) industrial (commercial) meals (I-meals), produced by a process that includes cooking at 95–100 °C and steam desolventizing at 105–107 °C, and (ii) non-industrial meals (NI-meals) obtained at pilot-scale with much milder heat treatment, that offer a higher total phenolic content. CA release through hydrolysis of sunflower meal (SFM) was successfully achieved with A. niger type-B feruloyl esterase (AnFaeB) and chlorogenic acid esterase (ChlE). Maximal amount of free CA released was of 54.0 ± 1.1 to 59.8 ± 2.1 μmol/g defatted dry matter (DDM) from I-SFM (94–100% hydrolysis yield) against 42.0 ± 1.1 to 52.3 ± 0.2 μmol/g DDM (59–73% hydrolysis yield) from NI- SFM in which CA release was hampered by a phenolic oxidation side-reaction, seemingly due to meal endogenous polyphenol oxidase activities. AnFaeB and ChlE hydrolysis of phenolic extracts from NI-SFM increased the CA amount obtained to 55.0–68.1 μmol/g DDM (77–95% hydrolysis yield). In all cases, AnFaeB showed broader specificity towards SFM caffeoyl quinic acid isomers than ChlE. In particular, ChlE did not hydrolyze 3-O-caffeoylquinic acid. The maximal amount of free SA released by AnFaeA hydrolysis was 41.3 ± 0.3 μmol/g DDM from NI-SFM (50% hydrolysis yield) and 32.3 ± 0.4 μmol/g DDM from the phenolic extract (64% hydrolysis yield), with AnFaeA also having sinapine transesterification activity that led to the synthesis of 1,2-di-O-sinapoyl-β-D-glucose. Finally, of all the substrates tested for enzymatic hydrolysis in our conditions, I-RSM and NI-SFM extract showed the best compromise between initial total phenolic content, hydrolysis yields and amounts of CA/SA released.

The purpose of this work was to optimize the pretreatment process of wheat straw by Polyporus brumalis_BRFM985 in order to improve carbohydrate accessibility for more efficient bioconversion. Indeed, there is growing demands to develop sustainable routes for lignocellulosic feedstocks valorization into value‐added products in energy, chemicals, materials, and animal feed fields. To be achieved, implementation of cheap and ecofriendly biomass pretreatment processes is necessary. In this frame, white rot basidiomycetes, well known for their ability to degrade lignin efficiently and selectively, are of great interest. The pretreatment of wheat straw by Polyporus brumalis_BRFM985 was performed in packed bed bioreactor and optimized using response surface methodology. The four pretreatment parameters optimized were metals addition (Cu, Mn, and Fe), time of culture, initial water content, and temperature. Multicriteria optimization highlighted that wheat straw pretreatment by Polyporus brumalis_ BRFM985 in the presence of metals with high initial water content of 3.6 g H2O/g at 27°C for 15–16 days led to an improvement of carbohydrate accessibility with minimal matter loss.

International audience; Rapeseed meal is a cheap and abundant raw material, particularly rich in phenolic compounds of biotechnological interest. In this study, we developed a two-step bioconversion process of naturally occurring sinapic acid (4-hydroxy-3,5-dimethoxycinnamic acid) from rapeseed meal into canolol by combining the complementary potentialities of two filamentous fungi, the micromycete Aspergillus niger and the basidiomycete Neolentinus lepideus. Canolol could display numerous industrial applications because of its high antioxidant, antimutagenic and anticarcinogenic properties. In the first step of the process, the use of the enzyme feruloyl esterase type-A (named AnFaeA) produced with the recombinant strain A. niger BRFM451 made it possible to release free sinapic acid from the raw meal by hydrolysing the conjugated forms of sinapic acid in the meal (mainly sinapine and glucopyranosyl sinapate). An amount of 39 nkat AnFaeA per gram of raw meal, at 55 °C and pH 5, led to the recovery of 6.6 to 7.4 mg of free sinapic acid per gram raw meal, which corresponded to a global hydrolysis yield of 68 to 76% and a 100% hydrolysis of sinapine. Then, the XAD2 adsorbent (a styrene and divinylbenzene copolymer resin), used at pH 4, enabled the efficient recovery of the released sinapic acid, and its concentration after elution with ethanol. In the second step, 3-day-old submerged cultures of the strain N.lepideus BRFM15 were supplied with the recovered sinapic acid as the substrate of bioconversion into canolol by a non-oxidative decarboxylation pathway. Canolol production reached 1.3 g/L with a molar yield of bioconversion of 80% and a productivity of 100 mg/L day. The same XAD2 resin, when used at pH 7, allowed the recovery and purification of canolol from the culture broth of N. lepideus. The two-step process used mild conditions compatible with green chemistry.

Directeur de l'ouvrage : Arnaud Diemer Directeur de l'ouvrage : Florian Diericks Directeur de l'ouvrage : Ganna Gladkykh Directeur de l'ouvrage : Manuel E Morales Directeur de l'ouvrage : Tim Parrique Directeur de l'ouvrage : Julian Torres Auteur de l'ouvrage : Arnaud Diemer Directeur de l'ouvrage : Arnaud Diemer Directeur de l'ouvrage : Florian Diericks Directeur de l'ouvrage : Ganna Gladkykh Directeur de l'ouvrage : Manuel E Morales Directeur de l'ouvrage : Tim Parrique Directeur de l'ouvrage : Julian Torres Auteur de l'ouvrage : Arnaud DiemerDirecteur de l'ouvrage : Arnaud DiemerDirecteur de l'ouvrage : Florian DiericksDirecteur de l'ouvrage : Ganna GladkykhDirecteur de l'ouvrage : Manuel E MoralesDirecteur de l'ouvrage : Tim ParriqueDirecteur de l'ouvrage : Julian TorresAuteur de l'ouvrage : Arnaud Diemer; Exploration of fungal biodiversity for the deconstruction of lignocellulosic biomass and the implementation of new biosynthetic pathways for green chemistry. European Union and Sustainable Development: Challenges and Prospects

International audience; The competitiveness of the second-generation bioethanol by biotechnological process requires an effective and quantitative control of biochemical reactions. In this study, the potential of isothermal calorimetry technique to measure heat and kinetics of a non-homogeneous substrate enzymatic hydrolysis is intended. Using this technique, optimum temperature of the enzymes used for lignocellulosic molecules hydrolysis was determined. Thus, the amount of substrate-to-enzyme ratio was highlighted as an important parameter of the hydrolysis yield. Furthermore, a new enzymes' cocktail efficiency consisting of a mix of cellulases and cellobiose dehydrogenase (CDH) was qualified by this technique. The results showed that this cocktail allowed the production of a high amount of gluconic acid that could improve the attractiveness of these second-generation biofuels. From the set of experiments, the hydrolysis heat of wheat straw was derived and a meaningful value of -32.2 +/- 3.2 J g(-1) (gram reducing sugars product) is calculated. Then, isothermal measurements were used to determine kinetic constants of the cellulases and CDH mix on wheat straw. Results showed that this enzyme cocktail has an optimal rate at 45 A degrees C in the range of temperatures tested (40-55 A degrees C).

Second generation bioethanol, i.e., ethanol from lignocellulosic biomass is envisaged as a renewable source of transport fuel in the next years to complement or replace the first generation and the fossil fuel. At present, the most economic solution seems to be the enzymatic way that produces fermentable sugars from cellulose and hemicellulose. To make this process commercially viable, several improvements are needed to enhance the process. Currently, stocks of biomass are constituted by available agro-industrial residues such as corn stover and straws, wood and wood processing residues and dedicated crops such as miscanthus and other grasses. The biological process for converting the lignocellulose to fuel ethanol requires: a pretreatment to liberate cellulose and hemicellulose from their complex with lignin, a depolymerization of the carbohydrate polymers to produce free sugars, and a fermentation of mixed hexose and pentose sugars to produce ethanol. Pretreatment must be cost effective and must be adapted to the type of biomass. They must not produce high amount of inhibitors such as 5-hydroxymethyl furfural, even if different technique are currently available to detoxify fermentation broths. Saccharification by enzymes and fermentation should be conducted separately (SHF) or simultaneously (SSF). Integration of the process the development of cofermentation of pentoses produced through the pretreatment of the biomass (SSCF). Progress in genetic engineering allows us to consider the development of Consolidated BioProcesses (CBP) in which a single microbial strain is able to ferment polysaccharides to produce ethanol in one step. The economic viability of ethanol recovery from the fermentation mash depends of the overall process, as distillation heat balance is dependant of ethanol concentration. The future of ethanol from biomass is widely dependent on the oil price and on the political will of the different countries.

At the beginning of 2016, first generation bioethanol still contributes to the majority of the 25 billion of gallons’ bioethanol produced worldwide, with the United States and Brazil producing approximately 85 % of the global production predominantly based on corn and sugarcane, respectively. However, concerns over the long-term sustainability of first generation bioethanol, such as the impacts on land use, water resource, the potential contamination of soils with the distillation residues, and the competition for food and feed production is frequently highlighted. Current fuel ethanol research and development strives to minimize these negative externalities. The fundamental role that process design plays during the development of cost-effective technologies is evaluated through the modification of the major pathways in first generation ethanol synthesis. In this context, the central role that better performing enzymes and microorganisms play in the intensity and integration of the process, such as the typical example of simultaneous saccharification and fermentation from starchy material in first generation facilities is acknowledged. Compensating ethanol production costs by the integrated valorization of energy and by-products for feed and green chemistry in a typical biorefinery concept are striking outputs of the first generation ethanol real scale experiment. Finally, rather than a mistake, first generation bioethanol should be considered as the first step that made it possible to gain the necessary experience for the successful implementation of the future greener generations biofuels from the field to the tank, starting with second generation lignocellulosic that is now coming on the market. In this context, integrated biorefineries are a promising way to diversify the usable feedstocks, leading to reduced facilities size and optimized supply-chains, to valorize more efficiently bagasse’s from sugarcane and corn stover or even to exploit the potential of microalgae to capture the carbon dioxide that is produced during the fermentation steps. Major stakeholders in bioenergy production are taking advantage of the large-scale successful development of first generation bioethanol, using the most promising processing schemes for next generation facilities, although the industry is still facing uncertainties with respect to its economic viability and longevity.

Rapeseed and sunflower are two of the world's major oilseeds. Rapeseed and sunflower meal (RSM and SFM), the by-products of oil extraction, are produced in large quantities. They are mainly composed of proteins, lignocellulosic fibres and minerals. They were initially used as a protein complement in animal feed rations and sometimes as fertilizer or as combustible source. More recently, new alternatives to these traditional uses have been developed that draw on the structure and physicochemical properties of RSM and SFM, which are plentiful sources of nitrogen and carbon nutrients. This feature, together with their cheapness and ready availability, supports the cultivation of various microorganisms in both submerged cultures and solid-state fermentation. Recent studies have thus emphasized the potential utilisation of RSM and SFM in fermentative processes, including saccharification and production of enzymes, antibiotics, antioxidants and other bio-products, opening new challenging perspectives in white biotechnology applications.

Paper production requires fibres to be refined, meaning mechanically treated to present sufficient bonding potential. As it is a highly energy consuming stage, various charges of cellulase as a pre-treatment were investigated to reduce the energy consumption and improve paper properties. The enzyme was added during pulp slushing and conditions of treatment were chosen to be compatible with an industrial application. Results obtained after low consistency disc refining of a softwood bleached kraft pulp were compared at a given drainage index. Enzymatically-treated samples showed a better development of fibrillation leading to a stronger paper. Moreover, fibre swelling was significantly improved. The impact of cellulase charge added to the pulp was identified. However, for all cellulase charges tested, fibre intrinsic resistance was lowered. Consequently fibres became shorter and tear index dropped. A solution was found by applying a milder treatment consisting in reducing refining intensity. This was a way to limit the intense fibre cutting at high refining levels. Moreover, by treating pulp with cellulase, it became possible to reduce refining intensity by 33%, keeping breaking length similar to control.

Laccase–mediator systems have the disadvantage that the mediator is expensive and potentially toxic. In this work, we used N-hydroxyacetanilide (NHA) in combination with laccase for the first time to bleach eucalypt pulp and found it to be a very promising, advantageous alternative to 1-hydroxybenzotriazole (HBT) as mediator. Thus, NHA is efficiently oxidized by laccase to a radical that absorbs light at 350 nm. Also, NHA is a better substrate for laccase than is HBT. An innovative result is that the enzyme is inactivated to a similar extent by both mediators under the typical treatment conditions of the bleaching step (L). This adverse effect, however, is strongly reduced in the presence of pulp. Moreover, the laccase–NHA system is as efficient as the laccase–HBT system in reducing the kappa number of eucalyptus pulp. Using a xylanase pretreatment or unbleached pulp boosts kappa number reduction and bleaching with the laccase–mediator system. Based on the results of cyclic voltammetry tests, NHA has a slightly lower redox potential than HBT, which further supports use of the former; also, unlike HBT, NHA is oxidized in a reversible, pH-dependent manner. Interestingly, the laccase–NHA system provides more efficient bleaching of eucalyptus pulp at pH 5 than it does at pH 4.

International audience; Background: Lactic acid is the building block of poly-lactic acid (PLA), a biopolymer that could be set to replace petroleum-based plastics. To make lactic acid production cost-effective, the production process should be carried out at low pH, in low-nutrient media, and with a low-cost carbon source. Yeasts have been engineered to produce high levels of lactic acid at low pH from glucose but not from carbohydrate polymers (e.g. cellulose, hemicellulose, starch). Aspergilli are versatile microbial cell factories able to naturally produce large amounts of organic acids at low pH and to metabolize cheap abundant carbon sources such as plant biomass. However, they have never been used for lactic acid production. Results: To investigate the feasibility of lactic acid production with Aspergillus, the NAD-dependent lactate dehydrogenase (LDH) responsible for lactic acid production by Rhizopus oryzae was produced in Aspergillus brasiliensis BRFM103. Among transformants, the best lactic acid producer, A. brasiliensis BRFM1877, integrated 6 ldhA gene copies, and intracellular LDH activity was 9.2 x 10(-2) U/mg. At a final pH of 1.6, lactic acid titer reached 13.1 g/L (conversion yield: 26%, w/w) at 138 h in glucose-ammonium medium. This extreme pH drop was subsequently prevented by switching nitrogen source from ammonium sulfate to Na-nitrate, leading to a final pH of 3 and a lactic acid titer of 17.7 g/L (conversion yield: 47%, w/w) at 90 h of culture. Final titer was further improved to 32.2 g/L of lactic acid (conversion yield: 44%, w/w) by adding 20 g/L glucose to the culture medium at 96 h. This strain was ultimately able to produce lactic acid from xylose, arabinose, starch and xylan. Conclusion: We obtained the first Aspergillus strains able to produce large amounts of lactic acid by inserting recombinant ldhA genes from R. oryzae into a wild-type A. brasiliensis strain. pH regulation failed to significantly increase lactic acid production, but switching nitrogen source and changing culture feed enabled a 1.8-fold increase in conversion yields. The strain produced lactic acid from plant biomass. Our findings make A. brasiliensis a strong contender microorganism for low-pH acid production from various complex substrates, especially hemicellulose.

The Lavandula genus, which includes lavender (Lavandula angustifolia) and lavandin (L. angustifolia x Lavandula latifolia), is cultivated worldwide for its essential oils, which find applications in perfumes, cosmetics, food processing and, more recently, in aromatherapy products. The chemical composition of lavender and lavandin essential oils, usually produced by steam distillation from the flowering stems, is characterized by the presence of terpenes (e.g. linalool and linalyl acetate) and terpenoids (e.g. 1,8-cineole), which are mainly responsible for their characteristic flavour and their biological and therapeutic properties. Lavender and lavandin distilled straws, the by-products of oil extraction, were traditionally used for soil replenishment or converted to a fuel source. They are mineral- and carbon-rich plant residues and, therefore, a cheap, readily available source of valuable substances of industrial interest, especially aroma and antioxidants (e.g. terpenoids, lactones and phenolic compounds including coumarin, herniarin, alpha-bisabolol, rosmarinic and chlorogenic acids). Accordingly, recent studies have emphasized the possible uses of lavender and lavandin straws in fermentative or enzymatic processes involving various microorganisms, especially filamentous fungi, for the production of antimicrobials, antioxidants and other bioproducts with pharmaceutical and cosmetic activities, opening up new challenging perspectives in white biotechnology applications.

The potential of fungal pretreatment to improve fermentable sugar yields from wheat straw or Miscanthus was investigated. We assessed 63 fungal strains including 53 white-rot and 10 brown-rot fungi belonging to the Basidiomycota phylum in an original 12 day small-scale solid-state fermentation (SSF) experiment using 24-well plates. This method offers the convenience of one-pot processing of samples from SSF to enzymatic hydrolysis. The comparison of the lignocellulolytic activity profiles of white-rot fungi and brown-rot fungi showed different behaviours. The hierarchical clustering according to glucose and reducing sugars released from each biomass after 72 h enzymatic hydrolysis splits the set of fungal strains into three groups: efficient, no-effect and detrimental-effect species. The efficient group contained 17 species belonging to seven white-rot genera and one brown-rot genus. The yield of sugar released increased significantly (max. 62%) compared with non-inoculated controls for both substrates.

Aims: Tyrosinase production by Pycnoporus cinnabarinus and Pycnoporus sanguineus was screened among 20 strains originating from various geographical areas, particularly from tropical environments. The tyrosinase from the most efficient strain was purified and characterized and tested for food additive applications. Methods and Results: Monophenolase and diphenolase activities of tyrosinase were measured from cell lysate from the 20 Pycnoporus strains, for 8–10 days of cultivation. The strain P. sanguineus CBS 614.73 showed the highest productivity (45·4 and 163·6 U g−1 protein per day for monophenolase and diphenolase respectively). P. sanguineus CBS 614.73 tyrosinase was purified from concentrated cell lysate, anion‐exchange, size‐exclusion and hydroxyapatite chromatography, with a final yield of 2% and a purification factor of 35–38. The pure enzyme was a monomere with a molecular mass of 45 kDa and it showed four isoforms or isoenzymes with pI between 4·5–5. No N‐glycosylation was found. The N‐terminal amino acid sequence was IVTGPVGGQTEGAPAPNR. The enzyme was shown to be almost fully active in a pH range of 6–7, in a large temperature range (30–70°C), and was stable below 60°C. The main kinetic constants were determined. The tyrosinase was able to convert p‐tyrosol and p‐coumaric acid into hydroxytyrosol and caffeic acid, respectively, and it could also catalyse the cross‐linking formation of a model protein. Conclusions: Among the genus Pycnoporus, known for the production of laccase, the strain P. sanguineus CBS 614.73 was shown to produce one other phenoloxidase, a new monomeric tyrosinase with a specific activity of 30 and 84 U mg−1 protein for monophenolase and diphenolase respectively. Significance and Impact of the Study: This study identified P. sanguineus CBS 614.73 as a potential producer of a tyrosinase which demonstrated effectiveness in the synthesis of antioxidant molecules and in protein cross‐linking.

Background Filamentous fungi are well known for their ability to degrade lignocellulosic biomass and have a natural ability to convert certain products of biomass degradation, for example glucose, into various organic acids. Organic acids are suggested to give a competitive advantage to filamentous fungi over other organisms by decreasing the ambient pH. They also have an impact on the ecosystem by enhancing weathering and metal detoxification. Commercially, organic acids can be used as chemical intermediates or as synthons for the production of biodegradable polymers which could replace petroleum-based or synthetic chemicals. One of the advantages of filamentous fungi as biotechnological production platforms for synthetic biology is their ability to degrade vegetal biomass, which is a promising feedstock for the biotechnological production of organic acids. The Fungal Culture Collection of the International Centre of Microbial Resources (CIRM-CF), curated by our laboratory, contains more than 1600 strains of filamentous fungi, mainly Basidiomycetes and Ascomycetes. The natural biodiversity found in this collection is wide, with strains collected from around the world in different climatic conditions. This collection is mainly studied to unravel the arsenal of secreted lignocellulolytic enzymes available to the fungi in order to enhance biomass degradation. While the fungal biodiversity is a tremendous reservoir for “green” molecules production, its potentiality for organic acids production is not completely known. Results In this study, we screened 40 strains of Ascomycota and 26 strains of Basidiomycota, representing the distribution of fungal diversity of the CIRM-CF collection, in order to evaluate their potential for organic acid and ethanol production, in a glucose liquid medium. We observed that most of the filamentous fungi are able to grow and acidify the medium. We were also able to discriminate two groups of filamentous fungi considering their organic acid production at day 6 of incubation. This first group represented fungi co-producing a wide variety of organic acids and ethanol at concentrations up to 4 g.L−1 and was composed of all the Aspergilli and only 3 other Ascomycota. The second group was composed of the remaining Ascomycota and all the Basidiomycota which produced mainly ethanol. Among the Basidiomycota, two strains produced oxalic acid and one strain produced gluconic and formic acid. Six strains of Aspergillus producing high concentrations of oxalic, citric and gluconic acids, and ethanol were selected for metabolism analysis. Conclusion These results illustrate the versatility in metabolites production among the fungal kingdom. Moreover, we found that some of the studied strains have good predispositions to produce valuable molecules. These strains could be of great interest in the study of metabolism and may represent new models for synthetic biology or consolidated bioprocessing of biomass. Electronic supplementary material The online version of this article (doi:10.1186/s40694-014-0001-z) contains supplementary material, which is available to authorized users.

A novel highly active phosphatidylglycerol-phosphatidylinositol transfer protein (PG/PI-TP) was isolated from a cell-free extract of Aspergillus oryzae LMTC 2.14 grown on lecithin fractions as sole carbon source. A protocol for the extraction of the cytosolic PG/PI-TP that supports an extrapolation at industrial scale has been developed allowing the recovery of the active protein with high performance. Mycelium was harvested using a membrane press filter. A study of the cake permeability and compressibility which reflects the resistance of the cake to flow of liquid through pores was achieved in order to select the optimal working pressure (4×105 Pa). Mycelium disruption was achieved using a high-pressure homogenizer, with semi-continuous recycle. Two passes were necessary for an optimal recovery of PG/PI-TP. Removal of cell debris by filtration needed the use of 60 g l−1 Harbolite as filter aid. In the present growth conditions, mycelial intracellular lipid content was particularly high (≈40% of the mycelial dry weight) leading to major problems during chromatographic steps. In order to remove lipids, the crude extract was treated with hexane. Under these conditions, the crude extract was significantly clarified without loss of PG/PI-TP activity. As molecular filtration is not a suitable first chromatographic step in industry, ion-exchange chromatography was performed as a pre-purification step. Under these conditions, a recovery of 52% active PG/PI-TP was obtained, i.e. an improvement of 3.47-fold compared with previous work at labscale level.

Manganese peroxidase (MnP) production was performed in a airlift bioreactor in which Phanerochaete chrysosporium I-1512, an MnP hypersecretory strain, was immobilized on a stainless steel mesh. Production was scaled up from a 2.5-L bench scale to a 100-L bioreactor. The yield of MnP was increased 2-fold and reached 6600 U L(-1). These results indicate the feasibility of MnP production on a medium scale, which promises sufficient MnP availability for its use in pulp bleaching at industrial scale.

Monokaryotic Pycnoporus cinnabarinus strains were obtained from the dikaryotic strain I-938. One of these, designated MK18, consistently produced high laccase activity. In cultures of MK18 and I-938 where ferulic acid was added as laccase inducer, laccase activity was enhanced about 2.5-fold reaching 3400 U/l for the MK18 strain. Laccase was purified to homogeneity and under the selected growth conditions, only one isoform of the enzyme was produced. The N-terminal sequence was similar to the amino terminal sequence of laccase II from Trametes versicolor. The enzyme was stable at 60 ∘C for more than 1 h.

The biodegradation of phenanthrene and benzo[a]pyrene was assayed in liquid and wet sand cultures in the presence of five filamentous fungi. In the controls, 85% volatilisation of phenanthrene occurred within 28 days in liquid cultures while it was only 50% in wet sand. In the later system, remaining phenanthrene and benzo[a]pyrene amounted to 6–51 and 53–92% of their initial levels, respectively, according to the strains. Then, wet sand used as a screening tool evidenced Trametes versicolor and Cunninghamella elegans as the most efficient polycyclic aromatic hydrocarbons degraders among ten strains. © Rapid Science Ltd. 1998

The biotransformation of benzo[a]pyrene by purified extracellular laccase of Pycnoporus cinnabarinus was investigated in bench scale reactors. The reaction required the presence of exogenous mediator ABTS. Most of 95% of the substrate was converted within 24 hours. The enzyme preparation oxidised the substrate mainly to benzo[a]pyrene 1,6- 3,6- and 6,12-quinones in a 2/1/1 ratio after 24 h incubation.

Two wheat straw pulps (Kraft pulp and Chemimechanical pulp (CMP)) were treated with a crude enzymatic extract containing mainly manganese dependent peroxidase. The extract was prepared from the culture supernatant of a hypersecretory strain of Phanerochaete chrysosporium. Enzymatic treatment was applied to an unbleached pulp suspension (2% w/v). Lactate buffer (pH4.5) was used to regulate the pH at the MnP optimum activity and to stabilize the diffusing oxidative agent (Mn 3+ ). The enzymatic treatment was applied for 4 hours only. so as to ensure compatibility with industrial processes. After this treatment, the kappa number of unbleached Kraft pulp was reduced by about 50% and the consumption of bleaching reagent was subsequently reduced to the same extent. As with unbleached CMP, the enzymatic treatment substantially enhanced the physical properties of the pulps. In all the cases studied. transmission electron microscopy showed that structural changes had occurred in the treated fibres as compared with untreated samples. The main modification appeared to be a superficial defibrillation, which was sometimes accompanied by extensive delamination depending upon the extent to which the straw had been destructured by previous chemical and mechanical treatments.

The genome of the coprophilic ascomycete Podospora anserina encodes 33 different genes encoding copper-dependent lytic polysaccharide monooxygenases (LPMOs) from glycoside hydrolase family 61 (GH61). In this study, two of these enzymes ( P. anserina GH61A [ Pa GH61A] and Pa GH61B), which both harbored a family 1 carbohydrate binding module, were successfully produced in Pichia pastoris . Synergistic cooperation between Pa GH61A or Pa GH61B with the cellobiose dehydrogenase (CDH) of Pycnoporus cinnabarinus on cellulose resulted in the formation of oxidized and nonoxidized cello-oligosaccharides. A striking difference between Pa GH61A and Pa GH61B was observed through the identification of the products, among which were doubly and triply oxidized cellodextrins, which were released only by the combination of Pa GH61B with CDH. The mass spectrometry fragmentation patterns of these oxidized products could be consistent with oxidation at the C-6 position with a geminal diol group. The different properties of Pa GH61A and Pa GH61B and their effect on the interaction with CDH are discussed in regard to the proposed in vivo function of the CDH/GH61 enzyme system in oxidative cellulose hydrolysis.

Pycnoporus cinnabarinus laccase and a chimeric laccase-CBM were applied in softwood kraft pulp biobleaching in the presence of 1-hydroxybenzotriazole (HBT). The presence of CBM could enhance the laccase biobleaching potential as a decrease in the enzymatic charge and chlorine dioxide consumption, as well as an increase in pulp brightness were observed. Laccase/HBT treatment could be improved by increasing oxygen pressure from 1 to 3bar and pulp consistency from 5% to 10%. Conversely, under the same conditions, no improvement of laccase-CBM/HBT treatment was observed, indicating a different behavior of both systems. However, laccase-CBM/HBT treatment led to a better preservation of pulp properties. This effect was probably due to fiber surface modifications involving the action of the CBM. Transmission electron microscopy examination of pulp fibers indicated a retention of laccase-CBM inside the pulp fibers due to CBM binding and an increased external microfibrillation of the fibers due to enzymatic treatments.

A number of microorganisms, bacteria and filamentous fungi, are able to degrade lignocellulosic components to various extents. However, only a few ones can degrade lignins, among which wood-rotting fungi. White-rot fungi, the most frequent ones, mineralize cell wall components (cellulose, hemicelluloses and lignins) and extensively degrade lignins, which results in a bleached aspect of decayed wood. Fungal lignin degradation involves secreted heme-peroxidases and laccases that use oxidants as electron acceptors (H2O2 and O2). The three main heme-peroxidases are lignin peroxidases, manganese peroxidases and versatile peroxidases. Lignin and versatile peroxidases are able to oxidize non-phenolic lignin units. By contrast, manganese peroxidase needs diffusible Mn-chelated ions and mainly degrades lignin units with free phenolic groups. Other peroxidases have been recently found, such as dye peroxidases with potential applications in bioremediation and other industrial processes. Peroxidases need the cooperation of other oxidases such as glyoxal or aryl-alcohol oxidases to produce hydrogen peroxide. The recent availability of complete fungal genomes opens innovative opportunities to annotate lignocellulolytic gene families. Phylogenetic approaches are unique tools to comparatively analyse these data and predict or infer gene function. The increasing number of putative lignin-degrading enzymes emerging from genome analyses requires the development of high-throughput expression systems to meet the demands of industries. Several expression systems have been developed to produce more efficient recombinant ‘ligninases’ and auxiliary enzymes. Fungi and yeasts are useful hosts for the production of recombinant enzymes, but only a few ones are devoted to ligninase production. In this review, we give a survey of the main fungal and enzymatic actors of lignin degradation before discussing the phylogenetic inference strategy used to predict lignocellulolytic enzymes and reviewing the recombinant production of these enzymes in fungal hosts.

Fusarium verticillioides secretes enzymes (secretome), some of which might be potentially useful for saccharification of lignocellulosic biomass since supplementation of commercial cellulases from Trichoderma reesei with the F. verticillioides secretome improved the enzymatic release of glucose, xylose and arabinose from wheat straw by 24%, 88% and 68%, respectively. Determination of enzymatic activities revealed a broad range of hemicellulases and pectinases poorly represented in commercial cocktails. Proteomics approaches identified 57 proteins potentially involved in lignocellulose breakdown among a total of 166 secreted proteins. This analysis highlighted the presence of carbohydrate-active enzymes (CAZymes) targeting pectin (from glycoside hydrolase families GH5, GH27, GH28, GH43, GH51, GH54, GH62, GH88 and GH93, polysaccharide lyase family PL4 and carbohydrate esterase family CE8) and hemicelluloses (from glycoside hydrolase families GH3, GH10, GH11, GH30, GH39, GH43 and GH67). These data provide a first step towards the identification of candidates to supplement T. reesei enzyme preparations for lignocellulose hydrolysis.

Background Cellobiose dehydrogenase (CDH) is an extracellular hemoflavoenzyme produced by lignocellulose-degrading fungi including Pycnoporus cinnabarinus. We investigated the cellulolytic system of P. cinnabarinus, focusing on the involvement of CDH in the deconstruction of lignocellulosic biomass. Results First, P. cinnabarinus growth conditions were optimized for CDH production. Following growth under cellulolytic conditions, the main components secreted were cellulases, xylanases and CDH. To investigate the contribution of P. cinnabarinus secretome in saccharification processes, the Trichoderma reesei enzymatic cocktail was supplemented with the P. cinnabarinus secretome. A significant enhancement of the degradation of wheat straw was observed with (i) the production of a large amount of gluconic acid, (ii) increased hemicellulose degradation, and (iii) increased overall degradation of the lignocellulosic material. P. cinnabarinus CDH was heterologously expressed in Pichia pastoris to obtain large amounts of pure enzyme. In a bioreactor, the recombinant CDH (rCDH) expression level reached 7800 U/L. rCDH exhibited values of biochemical parameters similar to those of the natural enzyme, and was able to bind cellulose despite the absence of a carbohydrate-binding module (CBM). Following supplementation of purified rCDH to T. reesei enzymatic cocktail, formation of gluconic acid and increased hemicellulose degradation were observed, thus confirming the previous results observed with P. cinnabarinus secretome. Conclusions We demonstrate that CDH offers an attractive tool for saccharification process enhancement due to gluconic acid production from raw lignocellulosic material.

Surface microlayer samples were collected with a rotating device at eight stations in a coastal area, and examined, with their related bulk waters, for their organic matter composition. At each station, sampling operations were conducted inside and outside slicks. With the exception of pigments, all the examined groups of compounds, particularly hydrocarbons and anionic detergents, exhibit accumulation in surface microlayer; enrichment is higher in samples collected inside slicks than outside. A decrease of the surface tension measurements is linked to the accumulation of organic matter in the slicks. In surface microlayers, the major part of the identified organic fraction, consists of carbohydrates and proteinaceous compounds rather than lipids. As far as could be deduced from an estimation of lipid, sugar- and protein-carbon, half the recorded particulate organic carbon weight is of an unidentified complex form. The study of hydrolysis kinetics of the carbohydrate particulate fraction shows that the organic matter is in a less condensed form in surface microlayers than in bulk water samples. A close relationship appears between pollutant accumulation and the lowering of surface tension in slicks. This has a direct consequence: the dampening effect on waves which smooths the surface of the sea, making slicks observable features of pollutant accumulation.

International audience; Endo β-1,4-mannanases (β-mannanases, EC 3.2.1.78), belonging to CAZy GH5 and GH26 families, catalyze the hydrolysis of structurally different mannans. In this study, the mannanase encoding gene of Aspergillus aculeatus VN was expressed in Aspergillus niger D15#26 using pAN 52-4 vector, under the control of PgpdA promoter and TtrpC terminator. In order to improve the hydrolytic capacity of this GH5 on lignocellulosic substrate, the family 1 carbohydrate-binding module (CBM1) of Aspergillus niger cellobiohydrolase B was artificially fused at the C-terminal end of this enzyme with a natural linker. Both mannanase and mannanase–CBM genes were successfully expressed in A. niger D15#26, producing proteins with molecular masses of 54 and 79 kDa, respectively. The Michaelis–Menten constants, pH activity profiles and temperature optima of three enzymes (wild-type mannanase, recombinant mannanase and recombinant mannanase–CBM) were similar, but the fused mannanase–CBM enzyme was more thermostable. Cross-comparison of the three enzymes for softwood hydrolysis in association with Trichoderma reesei enzymatic cocktail showed that mannanase–CBM improved the glucose yield compared to wild-type and recombinant mannanases

Background Mannans are key components of lignocellulose present in the hemicellulosic fraction of plant primary cell walls. Mannan endo-1,4-β-mannosidases (1,4-β-D-mannanases) catalyze the random hydrolysis of β-1,4-mannosidic linkages in the main chain of β-mannans. Biodegradation of β-mannans by the action of thermostable mannan endo-1,4-β-mannosidase offers significant technical advantages in biotechnological industrial applications, i.e. delignification of kraft pulps or the pretreatment of lignocellulosic biomass rich in mannan for the production of second generation biofuels, as well as for applications in oil and gas well stimulation, extraction of vegetable oils and coffee beans, and the production of value-added products such as prebiotic manno-oligosaccharides (MOS). Results A gene encoding mannan endo-1,4-β-mannosidase or 1,4-β-D-mannan mannanohydrolase (E.C. 3.2.1.78), commonly termed β-mannanase, from Aspergillus niger BK01, which belongs to glycosyl hydrolase family 5 (GH5), was cloned and successfully expressed heterologously (up to 243 μg of active recombinant protein per mL) in Pichia pastoris. The enzyme was secreted by P. pastoris and could be collected from the culture supernatant. The purified enzyme appeared glycosylated as a single band on SDS-PAGE with a molecular mass of approximately 53 kDa. The recombinant β-mannanase is highly thermostable with a half-life time of approximately 56 h at 70°C and pH 4.0. The optimal temperature (10-min assay) and pH value for activity are 80°C and pH 4.5, respectively. The enzyme is not only active towards structurally different mannans but also exhibits low activity towards birchwood xylan. Apparent Km values of the enzyme for konjac glucomannan (low viscosity), locust bean gum galactomannan, carob galactomannan (low viscosity), and 1,4-β-D-mannan (from carob) are 0.6 mg mL-1, 2.0 mg mL-1, 2.2 mg mL-1 and 1.5 mg mL-1, respectively, while the kcat values for these substrates are 215 s-1, 330 s-1, 292 s-1 and 148 s-1, respectively. Judged from the specificity constants kcat/Km, glucomannan is the preferred substrate of the A. niger β -mannanase. Analysis by thin layer chromatography showed that the main product from enzymatic hydrolysis of locust bean gum is mannobiose, with only low amounts of mannotriose and higher manno-oligosaccharides formed. Conclusion This study is the first report on the cloning and expression of a thermostable mannan endo-1,4-β-mannosidase from A. niger in Pichia pastoris. The efficient expression and ease of purification will significantly decrease the production costs of this enzyme. Taking advantage of its acidic pH optimum and high thermostability, this recombinant β-mannanase will be valuable in various biotechnological applications.

International audience; Pycnoporus cinnabarinus laccase was fused to the C-terminal linker and carbohydrate binding module (CBM) of Aspergillus niger cellobiohydrolase B (CBHB). The chimeric enzyme of molecular mass 100 kDa was successfully produced in A. niger. Laccase-CBM was further purified to determine its main biochemical properties. The Michaelis-Menten constant and pH activity profile were not modified, but the chimeric enzyme was less thermostable than either the P. cinnabarinus laccase or the recombinant laccase produced in the same strain. Laccase-CBM was able to bind to a cellulosic substrate and, to a greater extent, to softwood kraft pulp. Binding to the pulp was shown to be mainly time and temperature-dependent. Laccase-CBM was further investigated for its softwood kraft pulp biobleaching potential and compared with the P. cinnabarinus laccase. Addition of a CBM was shown to greatly improve the delignification capabilities of the laccase in the presence of 1-hydroxybenzotriazole (HBT). In addition, ClO2 reduction using 5 U of chimeric enzyme per gram of pulp was almost double than that observed using 20 U of P. cinnabarinus laccase per gram of pulp. We demonstrated that conferring a carbohydrate binding capability to the laccase could significantly enhance its biobleaching properties

Abstract Proteomic analysis was performed to determine and differentiate the composition of the secretomes of Phanerochaete chrysosporium CIRM-BRFM41, a peroxidase hypersecretory strain grown under ligninolytic conditions and on softwood chips under biopulping conditions. Extracellular proteins from both cultures were analyzed by bidimensional gel electrophoresis and matrix-assisted laser desorption/ionization time-of-flight tandem mass spectrometry. A total of 37 spots were identified. The secretome in liquid synthetic medium comprised mainly peroxidases, while several wood-degrading enzymes and enzymes involved in fungal metabolism were detected in biopulping cultures on softwood. This prompted an analysis of the impact of secretome modulation in the presence of softwood chips. Biotreated wood was submitted to kraft cooking and chemical bleaching using chlorine dioxide. The fungal pre-treatment led to a significant increase in pulp yield and a better bleachability of the pulp. This bleachability improvement could be explained by the production of specific lignocellulose-degrading enzymes.

Background Due to its capacity to produce large amounts of cellulases, Trichoderma reesei is increasingly been researched in various fields of white biotechnology, especially in biofuel production from lignocellulosic biomass. The commercial enzyme mixtures produced at industrial scales are not well characterized, and their proteinaceous components are poorly identified and quantified. The development of proteomic methods has made it possible to comprehensively overview the enzymes involved in lignocellulosic biomass degradation which are secreted under various environmental conditions. Results The protein composition of the secretome produced by industrial T. reesei (strain CL847) grown on a medium promoting the production of both cellulases and hemicellulases was explored using two-dimensional electrophoresis and MALDI-TOF or LC-MS/MS protein identification. A total of 22 protein species were identified. As expected, most of them are potentially involved in biomass degradation. The 2D map obtained was then used to compare the secretomes produced by CL847 and another efficient cellulolytic T. reesei strain, Rut-C30, the reference cellulase-overproducing strain using lactose as carbon source and inducer of cellulases. Conclusion This study provides the most complete mapping of the proteins secreted by T. reesei to date. We report on the first use of proteomics to compare secretome composition between two cellulase-overproducing strains Rut-C30 and CL847 grown under similar conditions. Comparison of protein patterns in both strains highlighted many unexpected differences between cellulase cocktails. The results demonstrate that 2D electrophoresis is a promising tool for studying cellulase production profiles, whether for industrial characterization of an entire secretome or for a more fundamental study on cellulase expression at genome-wide scale.

Sea water and sediment samples taken near the coasts of Hyeres bay (France) were used for anionic surfactant titrations with surface and bottom waters and the finest part of sediments. The capacity for surfactant degradation by the ‘in situ’ microflora was evaluated. By using a selective plating technique 26 strains able to utilize anionic surfactant were isolated from the selected bacterial communities. Their ability to degrade anionic surfactant was verified according to the biodegradation standard method. Isolated strains were characterized by morphological and physiological properties using API 20 NE micro-method. All tested strains were Gram negative, strictly aerobic, rod or helical shaped. Their weak utilization of phenolic substrates suggests that they degrade preferentially the alkyl chain of the surfactant molecule. Biodegradation was more efficient with bacterial communities rather than with any isolated strains. Such observations indicate that complete mineralization involves several other so far non-isolated strains which complete the degradation initiated by the isolated strains.

We investigated the paraffinic hydrocarbon composition of cell suspensions of Euphorbia characias L. grown in different regimes of carbon and energy supply. Heterotropic (H), photomixotrophic (PM) and photoautotrophic (PA) cell suspensions were compared to leaves. Alkane compositions varied greatly both quantitatively and qualitatively according to the mode of culture. PM and H cells had indentical gaussian-like hydrocarbon distributions, with maxima around C 27 or C 28 compounds, while PA cells and leaf hydrocarbons were enriched in odd carbon chain-length compounds, especially C 29 , C 31 and C 33 In long-term cultivated suspensions, total hydrocarbon amounts of PM and PA cells were about 5% and 6% that of leaf, respectively, and PA suspensions presented a major enrichment of all odd carbon chain-length compounds. Minor differences were observed between the growth phases of PM as well as PA cells. On the other hand, major differences appeared between these two modes of culture and were amplified along subcultures, indicating that the paraffinic hydrocarbon composition was directly related to the mode of culture. We discuss the possible origins of these alkane patterns.

International audience; Laccase production by the strain Pycnoporus cinnabarinus ss3 was studied in a solid-state culture on sugar-cane bagasse using chemical compounds as inducers (ethanol, methanol, veratryl alcohol and ferulic acid). Laccase productions were about 5- to 8.5-fold higher than non-induced cultures. Liquid-culture experiments with 14C-labeled ethanol were conducted. Ninety-eight percent of the initial amount of 14C from ethanol was recovered as 14CO2, 14C-biomass and soluble 14C-compounds (mainly ethanol). The amount of 14C in the biomass was only 6.8% of the total carbon consumed by P. cinnabarinus, in absence of maltose, representing only 2.8% of added ethanol (1.1% and 1.6% in presence of maltose, respectively). Ethanol was poorly used as carbon and energy sources for P. cinnabarinus growth and other carbon sources present in the liquid medium (yeast extract and sodium tartrate) were preferentially degraded. Time-courses of laccase activity and gene expression were monitored in column in presence or in absence of ethanol vapors. Analyses showed a perfect correlation between the activity and the amount of transcript. After 16 days of ethanol ventilation through the column, the ethanol flow was stopped. Immediately, both laccase activity and gene expression decreased, but started to increase again as soon as the ventilation was restored. In parallel, the effect of ethanol on protease activity in P. cinnabarinus was measured. Presence of ethanol led to an inhibition of protease activity. Therefore ethanol plays a regulatory role on two elements (gene-expression and protease-activity levels) that are both in favor of an increase in laccase production by the fungus

International audience; A new tyrosinase-encoding gene (2,204 bp) and the corresponding cDNA (1,857 nucleotides) from the white-rot fungus Pycnoporus sanguineus BRFM49 were cloned. This gene consisted of seven exons and six introns and encoded a predicted protein of 68 kDa, exceeding the mature tyrosinase by 23 kDa. P. sanguineus tyrosinase cDNA was over-expressed in Aspergillus niger, a particularly suitable fungus for heterologous expression of proteins of biotechnological interest, under the control of the glyceraldehyde-3-phosphate-dehydrogenase promoter as strong and constitutive promoter. The glucoamylase preprosequence of A. niger was used to target the secretion. This construction enabled the production of recombinant tyrosinase in the extracellular medium of A. niger. The identity of the purified recombinant protein was confirmed by N-terminal amino acid sequencing. The maturation process was shown to be effective in A. niger, and the recombinant enzyme was fully active, with a molecular mass of 45 kDa. The best transformant obtained, A. niger D15#26-e, produced extracellular tyrosinase activities of 534 and 1,668 U l−1 for monophenolase and diphenolase, respectively, which corresponded to a protein yield of ca. 20 mg l−1.

International audience; The focus of this study was to improve conditions of use of fungal lignocellulolytic enzymes for conversion of lignocellulosic biomass to fermentable sugars for the production of bioethanol. Wheat straw was pre-treated by acid treatment with diluted sulfuric acid followed by steam explosion. Several enzymatic treatments implementing hydrolases (cellulases and xylanases from Trichoderma reesei, recombinant feruloyl esterase (FAE) from Aspergillus niger and oxidoreductases (laccases from Pycnoporus cinnabarinus) were investigated to the saccharification of exploded wheat straw. A synergistic effect between cellulases, FAE and xylanase was proven under a critical enzymatic concentration (10 U/g of cellulases, 3 U/g of xylanase and 10 U/g of FAE). The yield of enzymatic hydrolysis was enhanced by increasing the temperature from 37 °C to 50 °C and addition of a non-ionic surfactant, Tween 20. Optimisation of enzymatic hydrolyses allowed the use of lower quantities of enzymes and improved the cost effectiveness of the process

International audience; We propose a new process using a vapor phase bioreactor (VPB) to simultaneously (i) delignify sugar-cane bagasse, a residue of sugar production that can be recycled in paper industry, and (ii) produce laccase, an enzyme usable to bleach paper pulp. Ethanol vapor, used as laccase inducer, was blown up through a VPB packed with bagasse and inoculated with Pycnoporus cinnabarinus ss3, a laccase-hyperproducing fungal strain. After 28 days, the laccase activity in the ethanol-treated bagasse was 80-fold higher (80 U gds-1) and the bagasse delignification percentage was 12-fold (12%) higher than in the reference samples produced in the absence of ethanol, corresponding to a high overall pulp yield of 96.1%. In the presence of ethanol, the total soluble phenols amount was 2.5-fold (3 mg FA gds-1) higher than that without ethanol. Six monomeric phenols were detected: p-coumaric (4-hydroxyphenyl-2-propenoic), ferulic (4-hydroxy-3-methoxyphenyl-2-propenoic), syringic (4-hydroxy-3,5-dimethoxybenzoic), vanillic (4-hydroxy-3-methoxybenzoic) and 4-hydroxybenzoic acids, and 2-methoxyhydroquinone. Higher concentrations of phenolic compounds were observed when ethanol vapor was added, confirming a more efficient bagasse delignification. After 28 days, the fungal-treated bagasse (with ethanol addition) was pulped and refined. For a freeness of 81 mL CSF, this processing required 50% less energy than with untreated bagasse (without inoculation and ethanol addition), which indicated a significant potential economy for the pulp and paper industry. Handsheets were made from pulp obtained after fungal-treated and untreated bagasse. Comparison of bagasse-pulp characteristics for freeness of 35 and 181 mL CSF showed an average increment by 35% for tensile index and breaking strength and length. VPB allowed a simultaneous production of laccase (90 U gds-1, after pressing of the bagasse) that improved the overall profitability of the process.

Tyrosinases are type-3 copper proteins involved in the initial step of melanin synthesis. These enzymes catalyse both the o-hydroxylation of monophenols and the subsequent oxidation of the resulting o-diphenols into reactive o-quinones, which evolve spontaneously to produce intermediates, which associate in dark brown pigments. In fungi, tyrosinases are generally associated with the formation and stability of spores, in defence and virulence mechanisms, and in browning and pigmentation. First characterized from the edible mushroom Agaricus bisporus because of undesirable enzymatic browning problems during postharvest storage, tyrosinases were found, more recently, in several other fungi with relevant insights into molecular and genetic characteristics and into reaction mechanisms, highlighting their very promising properties for biotechnological applications. The limit of these applications remains in the fact that native fungal tyrosinases are generally intracellular and produced in low quantity. This review compiles the recent data on biochemical and molecular properties of fungal tyrosinases, underlining their importance in the biotechnological use of these enzymes. Next, their most promising applications in food, pharmaceutical and environmental fields are presented and the bioengineering approaches used for the development of tyrosinase-overproducing fungal strains are discussed.

Phanerochaete chrysosporium has been found to preferentially metabolize vanillic acid using a reduction pathway which leads to vanillyl alcohol via vanillin. In order to prevent vanillin transformation into unwanted vanillyl alcohol, the ability of different adsorbents to adsorb vanillin was investigated. XAD-2 resin was shown to be very efficient and selective for vanillin. When applied to the culture medium of P. chrysosporium, the resin trapped the vanillin, which prevented the transformation of vanillin into vanillyl alcohol.

International audience; The influence of gaseous ethanol addition as inducer of laccase produced by Pycnoporus cinnabarinus ss3 in a biofilter packed with sugarcane bagasse was investigated. Gaseous-ethanol concentration up to 13.3 g m -3 allowed an important increment of laccase activity. Maximum of laccase production of 90 U g -1 dry support, which was 45 times higher than that without ethanol, was obtained for a concentration of about 7 gethanol m -3 (ethanol concentration in the liquid phase of 31 g L- 1). At this concentration, the maximum laccase activity was reached after 14 days, and then remained steady for 15 days. For other gaseous-ethanol concentrations, enzyme activity reached a maximum after 6–9 days, and then decreased. In spite of the inhibitory effect of ethanol on P. cinnabarinus ss3 growth, it provides an opportunity to improve the production of laccases. It is noteworthy that to obtain highest laccase production, ethanol vapours have to be added at the beginning of the experiment at a low air flow-rate of 40 mL min -1. A gradient of laccase activity down along the column was observed and correlated with gaseous-ethanol concentrations.

International audience; Three laccases, a natural form and two recombinant forms obtained from two different expression hosts, were characterized and compared for paper pulp bleaching. Laccase from Pycnoporus cinnabarinus, a well known lignolytic fungus, was selected as a reference for this study. The corresponding recombinant laccases were produced in Aspergillus oryzae and A. niger hosts using the lacI gene from P. cinnabarinus to develop a production process without using the expensive laccase inducers required by the native source. In flasks, production of recombinant enzymes by Aspergilli strains gave yields close to 80 mg l–1. Each protein was purified to homogeneity and characterized, demonstrating that the three hosts produced proteins with similar physico-chemical properties, including electron paramagnetic resonance spectra and N-terminal sequences. However, the recombinant laccases have higher Michaelian (K m) constants, suggesting a decrease in substrate/enzyme affinity in comparison with the natural enzyme. Moreover, the natural laccase exhibited a higher redox potential (around 810 mV), compared with A. niger (760 mV) and A. oryzae (735 mV). Treatment of wheat straw Kraft pulp using laccases expressed in P. cinnabarinus or A. niger with 1-hydroxybenzotriazole as redox mediator achieved a delignification close to 75%, whereas the recombinant laccase from A. oryzae was not able to delignify pulp. These results were confirmed by thioacidolysis. Kinetic and redox potential data and pulp bleaching results were consistent, suggesting that the three enzymes are different and each fungal strain introduces differences during protein processing (folding and/or glycosylation).

International audience; AIMS: Laccase production by the monokaryotic strain Pycnoporus cinnabarinus ss3 was studied using ethanol as inducer in the culture medium. METHODS AND RESULTS: The effect of ethanol was tested at 10, 20, 30, 35 and 45 g l-1 and compared with that of ferulic acid, known until now as the most efficient inducer for laccase expression by P. cinnabarinus ss3. In the presence of 35 g l-1 ethanol, laccase activity (266 600 U l-1) and productivity (19 000 U l-1 day-1) were nine and fivefold higher compared with ferulic acid-induced cultures, and 155- and 65-fold higher compared with non-induced cultures, respectively. In vivo, ethanol added to the culture medium of P. cinnabarinus ss3 favoured a continuous and high expression of laccase gene. Under these conditions, P. cinnabarinus ss3 produced preferentially the isoenzyme LAC I. Ethanol added in vitro to the purified P. cinnabarinus ss3 laccase typically inhibited the enzymatic activity. CONCLUSIONS: In spite of an initial inhibitory effect on mycelial growth, ethanol was shown to be a very strong inducer for laccase expression by P. cinnabarinus ss3 allowing an average yield of 1-1.5 g l-1 laccase. SIGNIFICANCE AND IMPACT OF THE STUDY: This study identified P. cinnabarinus ss3 as an outstanding producer of laccase in the presence of ethanol as inducer. Ethanol is an inexpensive agricultural by-product and the process is simple to scale-up for industrial production.

Laboratory experiments were conducted to study the potential of adding gaseous toluene, as a readily degradable carbon source, to enhance phenanthrene mineralization in polluted soil (1,000 mg/kg(dry soil)) aged for 400 days. Experiments were conducted in 0.5-L column reactors packed with a mixture of (80:20 w(wet)/w(wet)) spiked soil and vermiculite and fed with 1 g m(-3)reactor h(-1) toluene load in air. Removal efficiencies of 100% for toluene and greater than 95% for phenanthrene were obtained in 190 h. Evolved CO2 showed that phenanthrene mineralization increased from 39% to 86% in columns treated with gaseous toluene. Phthalic acid was identified as the principal soluble intermediate, which accumulated when no toluene was added. Increased phenanthrene uptake and mineralization with toluene can be attributed to increased biomass and the induction of enzymes involved in the intermediate mineralization. In microcosm experiments, phthalic acid mineralization increased from 19% to 81% within 50 h in the presence of toluene. Experiments with 14C-labeled phenanthrene confirmed the enhancement of phenanthrene mineralization from 45% to 83% in 385 h with toluene as a second carbon source. The results indicate thatthe addition of an appropriate gaseous cosubstrate could be an adequate strategy to enhance mineralization of PAHs in soil.

A well-known industrial fungus for enzyme production, Aspergillus niger, was selected to produce the feruloyl esterase FAEA by homologous overexpression for pulp bleaching application. The gpd gene promoter was used to drive FAEA expression. Changing the nature and concentration of the carbon source nature (maltose to glucose; from 2.5 to 60 g l-1), improved FAEA activity 24.5-fold and a yield of 1 g l-1 of the corresponding protein in the culture medium was achieved. The secreted FAEA was purified 3.5-fold to homogeneity in a two-step purification procedure with a recovery of 69%. The overproduced protein was characterised and presented properties in good agreement with those of native FAEA. The recombinant FAEA was tested for wheat straw pulp bleaching, with or without a laccase mediator system and xylanase. Best results were obtained using a bi-sequential process with a sequence including xylanase, FAEA and laccase, and yielded very efficient delignification - close to 75% - and a kappa number of 3.9. This is the first report on the potential application of recombinant FAEA in the pulp and paper sector. Chemicals/CAS: hemicellulose, 63100-39-0, 63100-40-3, 9034-32-6; laccase, 80498-15-3; xylan endo 1,3 beta xylosidase, 37278-89-0, 9025-55-2; Carboxylic Ester Hydrolases, EC 3.1.1.-; Endo-1,4-beta Xylanases, EC 3.2.1.8; feruloyl esterase, EC 3.1.1.73; Laccase, EC 1.10.3.2; Recombinant Proteins

Laccase isozymes from the white-rot basidiomycete fungi Trametes versicolor and Pycnoporus cinnabarinus were purified to apparent iso-electric homogeneity and crystallised. T. versicolor laccase crystallises in two crystal forms, both with the orthorhombic space group P2 1 2 1 2 1 , which diffract to 1.9 and 2.95 A resolution, respectively. The crystals of P. cinnabarinus laccase belong to the monoclinic space group C2 and diffract to at least 2.2 A resolution. All the laccase crystals are suitable for X-ray structure determination and contain a full complement of copper ions.

The development and use of biotechnology in the pulp and paper industry started in the early 1970s and depends mainly on the production of inexpensive biocatalysts in enormous volumes and weights for industrial applications. Some biotechnical processes have already been implemented in the industry, such as bio-bleaching with xylanases, pitch reduction with lipases, and enzymatic deinking. This chapter discusses the potential of laccases in softwood–hardwood high-yield pulping and bleaching. It is suggested that laccase is an interesting alternative to enhance thermomechanical pulp quality and boosting peroxide bleaching. Depending on the enzymatic treatment conditions and the fungus used to produce them, the results are more or less interesting. Some energy savings could be envisaged with laccase treatment of wood chips. Introducing a pre-bleaching stage with laccase without mediator in the oxidizing bleaching sequence could reduce production costs: about 15 % of the peroxide could be saved to reach the same level of brightness in a shorter time than by the conventional bleaching. Some additional experiments are needed to verify some results, to optimize the different treatments, and to understand what are the involved mechanisms and reactions.