Thesis (M.S.)--Rutgers University, 2009. / "Graduate Program in Plant Biology." Includes bibliographical references (p. 45-48).

The purpose of this study was to utilise lignin as a partial substitute for phenol in PF resins. To achieve this, initially brown rot lignin was produced by a bioconversion technique. During the course of the study, it became clear that the production of brown rot lignin had a limited success. Since brown rot lignin could not be obtained in sufficient quantity and purity by a bioconversion method, other alternative lignin production methods, as well as commercially available lignin, were chosen; namely production of lignin from black liquor and Alcell® (organosolv) lignin. Before performing production of resin formulations, the lignin sources were characterised in terms of reactivity and physical properties of lignins. Both lignins had a similar reactivity, but organosolv lignin was found to be more pure, with a low ash content. Since isolation of lignin from black liquor in laboratory conditions is more complex and requires more time, it was decided to use organosolv lignin for subsequent production of lignin-based reSIns. The lignin was introduced to the resin in two different ways. The first method was the replacing of a certain percentage of phenol with lignin (as supplied) directly into resins. In the second method, lignin was modified prior to resin manufacture by phenolation. Different degrees of phenol substitution (from 5% to 60%) were tried for the production of lignin-based resins. Bond qualities of lignin-phenol-formaldehyde (LPF) , phenolated-ligninformaldehyde, commercial phenol-formaldehyde (PF _com) and laboratory made phenol-formaldehyde (PF _made) resins were assessed by using an Automatic Bonding Evaluation System (ABES), prior to production of particleboards, in order to eliminate some of the poor quality resins. The effect of press temperature and time on bond strength appeared to be highly significant, as the lignin substitution levels increased. Up to 30% phenol substitution was achieved without sacrificing bond strength. The bond strength values of phenolated-lignin-formaldehyde resins were similar to commercial phenol-formaldehyde and laboratory made phenolformaldehyde resins, but better than the LPF resins. It was apparent that resins containing a high level of lignin substitution gave the poorest bond strength values. From these results, some of the resins were eliminated, prior to particleboard production. In order to evaluate the quality of lignin-based resins, particleboards were produced and mechanical and physical tests performed. Effect of press platen temperature (140°C, 160°C, 180°C) and press cycle time (5 min, 8 min, IS min) on the mechanical properties of particleboard, produced by using lignin-based resins, were investigated. It was found that particleboards bonded with up to 30% lignin content resins gave similar mechanical and physical properties to commercial phenolformaldehyde resin, as long as a sufficient heating regime and time were applied.

Copper tolerant brown rot fungi are able to depolymerize the structure of wood treated with copper or organic wood preservatives. This research used quantitative polymerase chain reaction (qRT-PCR) combined with RNA-seq to explore what genes of the brown-rot fungus, Fibroporia radiculosa, are expressed when the fungus is overcoming the wood preservatives and decaying the wood. The preliminary study of ACQ-treated wood indicated that the hydrogen peroxide needed for wood decay to proceed may come from AAOX (aryl alcohol oxidase), with oxalate regulation by ODC2 (oxalate decarboxylase), and copper regulation by COP (copper resistance P-type ATPase pump). The principal study measured the expression of ten genes at early, mid, and late stages of decay in wood treated with azole, copper, quat, ACQ, CA, plus untreated. Both AAOX and LCC (laccase) were often expressed at their highest levels early in the decay stages, thus either one or both could be involved in early Fenton chemistry. Expression levels of ICL (isocitrate lyase) and GLOXDH (glyoxylate dehydrogenase) were also highest in early decay stages. Of great interest was the complete lack of expression of the COP gene on copper-treated wood at any decay stage. The most surprising and significant result is the impact the quat-treatment had on the metabolism of the fungus, and lack of impact of the azole-treatment. This research indicates that it is the quat that provides the greatest inhibition of F. radiculosa, more so than the copper. Based on RNA Seq, the total number of genes that were up- or down-regulated on the copper-treatment was 473, with 293 on the quat-treatment, and 185 on the azole-treatment. There were a number of genes with unknown protein functions highly expressed. These data distinctly show that gene expression profiles of F. radiculosa are altered by different wood preservative compositions and the duration of wood decay. These genes and this data needs further analysis and study in order to meet the long term goal of understanding the mechanism of copper-tolerance inFibroporia radiculosa.

Thesis (PhD(Agric))--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: Postharvest decay of stone fruit in the Western Cape province of South Africa is caused primarily by Botrytis cinerea (grey mould) and Monilinia laxa (brown rot). Little is known about the relative importance and seasonal occurrence of the two pathogens in nectarine and plum orchards, the mode of penetration of fruits by M laxa, latency and subsequent disease expression by the latter pathogen. These aspects were investigated in this study. By sampling from the Unifruco Quality Evaluation Scheme and from 11 stone fruit orchards, observations were made over a 3-year period of the occurrence of grey mould and brown rot in the major stone fruit regions. Botrytis cinerea was found to be the most important pathogen causing blossom blight and postharvest decay on stone fruit. The pathogen was most prominent on early- and mid-season culti~ars. Brown rot was exclusively caused by M laxa and no evidence was found that M fructicoZa had been introduced into the region. Monilina laxa was most prominent on the later maturing cultivars. Botrytis cinerea blossom infection did not contribute directly to postharvest decay. Both surface inoculum and latent infection consistently occurred on fruit in each orchard, although at fluctuating levels. Disease expression on developing fruit was not governed by the amount of B. cinerea occurring on fruit surfaces, but by the ability of fruit to resist disease expression. The amount of B. cinerea on fruits was generally higher during spring than during summer. Monilinia laxa occurred sporadically on the blossoms of late-maturing cultivars. Immature fruit were generally pathogen-free and disease expression occurred on maturing fruit only. These findings suggest that conidia of M laxa are generally produced in orchards when fruits are approaching maturity and can penetrate and infect maturing fruit only. The behaviour of airborne M laxa conidia was subsequently studied on nectarine (cultivar Flamekist) and plum (cultivar Laetitia) fruit. For these studies, an inoculation method that simulates natural infection by airborne conidia was used. Fruit at pit hardening, 2 wk before harvest, harvest stage and after cold storage (nectarines 4 wk at -o.soC followed by 1 wk at 23°C at ±56% RH; plums 10 days at .....().5°C,18 days at 7.5°C followed by 1 wk at 23°C at ±56% RH) were dusted with dry conidia of M laxa in a settling tower. The fruits were incubated for periods ranging from 3 to 48 h at high relative humidity (2':93%, humid fruit) or covered with a film of water (wet fruit). Behaviour of the solitary conidia was examined with an epifluorescence microscope on skin segments stained in a differential stain containing fluorescein diacetate, aniline blue and blankophor. The ability of solitary conidia to colonise the fruit surface, penetrate fruit skins and to induce disease expression was determined by using a differential set of tests. For these tests, fruit were surface-sterilised (30 s in 70% ethanol) or left Unsterile. From each group, fruit were selected for isolation (skin segment test), immersed in a 3% paraquat solution (paraquat-treated fruit test) or left untreated (sound fruit test). 1be findings demonstrated that solitary conidia of M laxa behaved consistently on plum and nectarine fruit surfaces: appressorium formation and direct penetration was not observed on any of the fruit surfaces and germ tubes penetrated fruit predominantly through stomata, lenticels and microfissures in the fruit skin. The monitoring of airborne conidia revealed subtle effects of the fruits on the behaviour of solitary germlings, which could not be seen when using conidial suspensions. On both fruit types, no deleterious effect was seen on conidial and germling survival when fruit were kept humid at pit hardening, 2 wk before harvest and harvest. However, conidial and germling survival were drastically reduced by prolonged wet incubation of fruits. The findings on disease expression in the skin segment, paraquat-treated fruit and sound fruit tests clearly showed that the skin of both nectarine and plum fruits were not penetrated at the pit hardening stage, latent infections were not established and fruitsreacted resistant to disease expression. These facets on both fruit types were furthermore unaffected by wetness. The barrier capacity of the fruit skin of the two stone fruit types however differed drastically later in the season. On nectarine, fruit skins were more readily penetrated and disease expression became more pronounced when fruit approached maturity. Penetration and disease expression on ripening nectarine fruit were furthermore greatly influenced by wetness. Maturing plum fruit, on the other hand, did not display the drastic change in the barrier capacity of fruit skins as observed on nectarine. The influence of wetness on infection and disease expression was also less pronounced than on nectarine. In fact, plum fruit remained asymptomatic in the sound fruit test after inoculation and humid incubation at the 2 wk before harvest stage, harvest stage and after cold storage. Plum fruit at these stages only developed disease after a prolonged period (~12 h) of wet incubation. The paraquat fruit test revealed that these fruits became more susceptible to latent infection, but they were not as susceptible as nectarine. Collectively, these findings indicate that M. laxa fruit rot epidemics on plum and nectarine are driven by inoculum levels on fruit approaching maturity and by weather conditions prevailing during the preharvest and harvest period. However, the barrier capacity of plum skins is considerably more effective than that of nectarine fruit. Wounds would therefore play an important role in the epidemiology of M. laxa on plum fruit. Infection of fresh wounds by airborne M. laxa conidia, and by conidia and germlings that have established on fruits, was therefore investigated. Plum fruit (cultivar Laetitia) at pit hardening, 2 wk before harvest, harvest stage and after cold storage were dusted with dry conidia of M. laxa in a settling tower.- Infection of rionwounded fruit and of fresh wounds by \ the airborne conidia on dry, humid and wet plum fruit surfaces, and by conidia and germlings that have been established on fruits under the wetness regimes was then investigated. Nonwounded immature and mature fruit remained mostly asymptomatic, whereas nonwounded cold stored fruit decayed readily. Wounding drastically increased infection by airborne conidia. Immature fruits were less susceptible to wound infection by the airborne conidia than mature fruits. Conidia dispersed freshly were more successful in infecting fresh wounds than conidia that were deposited, or germlings that established, on fruit surfaces 4 days prior to wounding. This decrease in infectivity was especially pronounced on humid and even more on wet incubated fruit. This study clearly showed that in order to reduce. the incidence of brown rot, inoculum levels on fruit approaching maturity should be reduced by sanitation practices and fungicide applications. Furthermore, it is essential to protect fruits, especially. near-mature fruits, from being wounded. / AFRIKAANSE OPSOMMING: EPIDEMIOLOGIE VAN MONILINIA LAXA OP NEKTARIEN EN PRUIM: INFEKSIE VAN VRUGTE DEUR KONIDIA OPSOMMING Naoesverrotting van steenvrugte in die Wes-Kaap provinsie van Suid-Afrika word hoofsaaklik veroorsaak deur Botrytis cinerea (vaalvrot) en Monilinia laxa (bruinvrot). Min is bekend oor die relatiewe belang en seisoenale voorkoms van hierdie patogene in nektarienen pruimboorde, asook oor die infeksieweg, latensie en daaropvolgende siekte-uitdrukking van M laxa. Hierdie aspekte is in dié studie nagevors. \ \ Monsters IS oor 'n 3-jaar periode van die Unifruco Kwaliteitsevalueringskema, en ook van 11 steenvrugboorde verkry. Die voorkoms van vaalvrot en bruinvrot in die hoof steenvrugareas is so bepaal. Botrytis cinerea was die belangrikste patogeen wat betref bloeiselversenging en naoesverrotting. Verder was hierdie patogeen ook meer prominent op die vroeë- en middel-seisoen kultivars. Bruinvrot is uitsluitlik deur M Iaxa veroorsaak en geen aanduiding omtrent die moontlike voorkoms van M fructicola in Suid-Afrika is waargeneem nie. Monilinia laxa was meer prominent op die laat-seisoen kultivars. Botrytis cinerea bloeiselinfeksie het nie direk bygedra tot naoesverrotting nie. Beide oppervlakkige inokulum en latente infeksie het deurgaans, maar wel teen wisselende hoeveelhede, op vrugte in die onderskeie boorde voorgekom. Siekte-uitdrukking op ontwikkelende vrugte is egter nie beinvloed deur die hoeveelheid B. cinerea op die vrug nie, maar eerder deur die vermoë van die vrug om siekte-uitdrukking te onderdruk. Die hoeveelheid B. cinerea op vrugte was verder hoër gedurende lente as gedurende somer. Monilinia laxa het slegs sporadies op die bloeisels van laat-seisoen kultivars voorgekom. Groen vrugte was in die algemeen vry van die patogeen en siekte-uitdrukking het slegs op ryp vrugte plaasgevind. Hierdie bevindinge dui daarop dat M laxa in boorde hoofsaaklik op ryper vrugte geproduseer word. Hierdie swam infekteer ook net ryp vrugte. Die gedrag van luggedraagde M laxa conidia is bestudeer op nektarien- (kultivar Flamekist) en pruimvrugte (kultivar Laetitia). 'n Inokulasie-metode wat natuurlike infeksie deur luggedraagde konidia simuleer, is vir hierdie studies gebruik. Vrugte van die pitverharding-, twee weke voor oes-, oesstadium, asook koud-opgebergde vrugte (nektariene, 4 weke by -o.soe gevolg met 1 week by 23°C en ±56% RH; pruime, 10 dae by -O.5°e, 18 dae by 7.Soe gevolg deur 1 week by 23°C en ±56% RH), is met droë konidia in 'n inokulasietoring geïnokuleer. Die vrugte is vir periodes wat gewissel het van 3 tot 48 h geïnkubeer by hoë relatiewe humiditeit (~93% RH, vogtige vrugte), of dit is bedek met'n film water (nat vrugte). Die gedrag van die enkelspore (konidia) op die vrugoppervlak is met 'n epifluorisensiemikroskoop bestudeer. Skilsegmente is gekleur in 'n kleurstof, bevattende fluorisein diasetaat, analien-blou en blankofor. Die vermoë van die enkelspore om die vrugoppervlak te koloniseer, te penetreer en om siekte-uitdrukking te induseer, is met 'n differensiële stel toetse bepaal. Vir hierdie toetse is die vrugte oppervlakkig gesteriliseer (30 s in 70% etanol), of nie-steriel gelaat. In elke groep is vrugte geneem vir isolasie (skilsegment-to\~ts), of gedoop in "n 3% parakwat-oplossing (parakwat vrugtoets), of\, onbehandeld gelaat (onbehandelde vrugtoets ). Die. bevindinge het op die soortgelyke gedrag van M laxa enkelspore op die verskillende vrugsoorte gedui: appressoria en direkte penetrasie is nie waargeneem nie, en kiembuise het die vrugte hoofsaaklik deur huidmondjies, lentiselle en mikro-krakies .in die vrugskil gepenetreer. Deur luggedraagde spore te bestudeer, is sekere subtiele effekte van die vrug op die gedrag van enkelspore op die vrugoppervlak waargeneem. Op beide vrugtipes is geen nadelige effek op konidiurn- en kiembuisoorlewing opgemerk wanneer die vrugte onder hoë vogtoestande geïnkubeer is. Konidiurn- en kiembuisoorlewing is egter drasties verlaag hoe langer die vrugte onder nat toestande geïnkubeer is. Die bevindinge van die skilsegment-, parakwat en onbehandelde vrugtoetse het duidelik daarop gewys dat die vrugskil van nektarien en pruim nie gepenetreer is tydens die pitverhardingstadium nie, latente infeksies is nie gevorm nie, en die vrugte was bestand teen siekte-uitdrukking. Hierdie fasette op beide vrugtipes is ook nie beinvloed deur inkubasie-natheid nie. Die beskermingskapasiteit van die vrugskil van hierdie steenvrugtipes het egter drasties verskil later in die seisoen. Nektarien-vrugskille is meer geredelik gepenetreer en siekte-uitdrukking het toegeneem met rypwording. Penetrasie en siekteuitdrukking is verder in 'n groot mate deur inkubasie-natheid bevoordeel. Rypwordende pruime het egter nie so In drasties verandering in die beskermingskapasiteit van die vrugskil getoon nie. Die invloed van inkubasie-natheid op infeksie en siekte-uitdrukking was ook minder opsigtelik as op nektarien. Pruimvrugte van die twee weke voor oes-, oesstadium, en , koud-opgebergde pruime, wat onder hoë vog geïnkubeer is, het simptoomloos in die onbehandelde vrugtoets gebly. Vrugte van hierdie stadia het slegs simptome ontwikkel na periodes van langer as 12 h onder nat toestande. Die parakwat-behandelde vrugtoets het egter gewys dat die pruimvrugte meer vatbaar vir latente infeksies raak, maar steeds nie so vatbaar soos die nektarienvrugte nie. Gesamentlik dui hierdie bevindinge daarop <41tM laxa bruinvrot epidemies op pruim en nektarien afhanklik is van inokulumvlakke op rypwordende vrugte, asook die weerstoestande gedurende die vooroes- en oesstadia. Die beskermingskapasiteit van pruim vrugskille was egter aansienlik meer effektief as dié van nektarien vrugte. Wonde op vrugte sal dus 'n groter rol speel in die epidemiologic van M laxa op pruim. Infeksie van vars wonde deur luggedraagde M laxa konidia, en deur konidia en kiembuise wat reeds op die vrugoppervlak gevestig is, is gevolglik bestudeer. Pruimvrugte (kultivar Laetitia) van die pitverharding-, twee weke voor oes-, oesstadium, asook koud- \ \ opgebergde vrugte is in 'n inokulasie-toring geïnokuleer met droë M laxa konidia. .Infeksie , , van nie-gewonde vrugte en van vars wonde deur luggedraagde konidia op droë, vogtige en nat pruim vrugoppervlaktes, asook deur konidia en kiembuise wat reeds op die vrugoppervlak onder hierdie toestande gevestig is, is bepaal. Nie-gewonde groen tot ryp vrugte het meestal simptoomloos gebly, terwyl koud-opgebergde ryp vrugte wel verrot het. Wonde .het die hoeveelheid infeksie deur luggedraagde spore drasties vermeerder. Konidia wat geïnokuleer is op vrugte met vars wonde, was meer in staat om hierdie wonde te infekteer as konidia en kiembuise wat 4 dae voor wonding gevestig is. Hierdie afname in infektiwiteit was meer sigbaar op die vogtige, maar veral die nat vrugte. Hierdie studie het duidelik gewys dat inokulumvlakke op rypwordende vrugte verlaag moet word deur sanitasie-praktyke en fungisiedtoedienings. Dit is verder belangrik om vrugte, veral rypwordende vrugte, teen wonding te beskerm.

O objetivo deste trabalho foi avaliar se as enzimas secretadas pelo fungo de decomposição parda Gloeophyllum trabeum podem atuar como auxiliares às celulases comerciais na hidrólise de substratos celulósicos oxidados. Para isto foi realizada a oxidação de celulose microcristalina Avicel mediante reação de Fenton (Fe+2, H2O2) e tratamento com CuSO4. O substrato oxidado foi caracterizado e posteriormente foi determinado o efeito desta modificação sobre a eficiência hidrolítica de enzimas comerciais (Celluclast/Novozym) e sobre misturas destas enzimas comerciais suplementadas com extrato enzimático obtido de G. trabeum. As reações realizadas com Avicel indicaram que ambos tratamentos químicos foram efetivos para modificar grupos funcionais presentes na celulose. A caracterização fisicoquímica dos substratos oxidados permitiu concluir que o tratamento Fenton gerou transformações mais intensas na celulose do que o tratamento com CuSO4. O análise dos hidrolisados ácidos das amostras oxidadas por Fenton mediante espectrometria de massas (GC-MS) confirmou que a oxidação ocorre principalmente no C1. As hidrólises enzimáticas utilizando preparações com diferentes cargas das enzimas comerciais apresentaram uma diminuição significativa da conversão de celulose quando as amostras são tratadas com o reagente Fenton. Por outro lado, a celulose oxidada gerada pelo tratamento com CuSO4 ainda é eficientemente hidrolisada pelas enzimas. As duas amostras de celulose Avicel oxidadas também foi hidrolisada utilizando misturas de enzimas comerciais e extratos enzimáticos de G. trabeum. Em todas as condições ensaiadas a suplementação da mistura reacional com extratos enzimáticos do fungo de decomposição parda G. trabeum diminuíram a eficiência de hidrólise enzimática da celulose oxidada. O emprego do dobro de carga enzimática de enzimas comerciais permitiu recuperar os níveis de hidrólise observados na celulose in natura. / The goal of this work was to evaluate whether enzymes produced by the brown-rot fungus Gleophyllum trabeum would be able to act as auxiliary enzymes of commercial cellulases during the enzymatic hydrolysis of oxidized cellulose. To reach this goal an oxidation of microcrystalline-cellulose (Avicel) was performed by two differente reaction systems: Fenton reaction (Fe2+, H2O2) or CuSO4 treatments. The oxidized subtracts were characterized and the effect of cellulose modification on the hydrolytic efficiency of commercial enzymes, supplemented or not with the enzymes recovered from a G. trabeum culture, was determined. The Avicel treatment by the oxidative systems resulted in cellulose structural changes as evidenced by infrared spectroscopy, viscosity measurements and chemical characterization by HPLC and GC/MS chromatography of the monomers recovered after acid hydrolysis. The physicochemical characterization of the oxidized celluloses allowed to conclude that the transformation of the cellulose was more intense when Fenton treatment was used as compared with the CuSO4 treatment. The analysis of the acid hydrolysates by GC-MS indicated that the oxidation by Fenton reaction occurred mainly at the C1 of the cellulose chain, resulting in gluconic acid in the acid hydrolysates. A meaningful decrease of the cellulose conversion was observed when Fetnon-treated samples were submitted to enzymatic hydrolysis using different amounts of commercial enzymes. On the other hand, the CuSO4-oxidized cellulose was still efficiently hydrolyzed by high enzyme dosages. The oxidized Avicel substrates were also hydrolyzed using a mixture of the commercial enzymes with enzymes recovered from G. trabeum cultures. At all tested conditions, the supplementation of the reaction mixture with enzymatic extracts from G. trabeum decreased the enzymatic hydrolysis efficiency. Nevertheless, the normal levels of enzymatic hydrolysis were recovered when the commercial enzymes dosage two-fold increased.

O objetivo deste trabalho foi avaliar se as enzimas secretadas pelo fungo de decomposição parda Gloeophyllum trabeum podem atuar como auxiliares às celulases comerciais na hidrólise de substratos celulósicos oxidados. Para isto foi realizada a oxidação de celulose microcristalina Avicel mediante reação de Fenton (Fe+2, H2O2) e tratamento com CuSO4. O substrato oxidado foi caracterizado e posteriormente foi determinado o efeito desta modificação sobre a eficiência hidrolítica de enzimas comerciais (Celluclast/Novozym) e sobre misturas destas enzimas comerciais suplementadas com extrato enzimático obtido de G. trabeum. As reações realizadas com Avicel indicaram que ambos tratamentos químicos foram efetivos para modificar grupos funcionais presentes na celulose. A caracterização fisicoquímica dos substratos oxidados permitiu concluir que o tratamento Fenton gerou transformações mais intensas na celulose do que o tratamento com CuSO4. O análise dos hidrolisados ácidos das amostras oxidadas por Fenton mediante espectrometria de massas (GC-MS) confirmou que a oxidação ocorre principalmente no C1. As hidrólises enzimáticas utilizando preparações com diferentes cargas das enzimas comerciais apresentaram uma diminuição significativa da conversão de celulose quando as amostras são tratadas com o reagente Fenton. Por outro lado, a celulose oxidada gerada pelo tratamento com CuSO4 ainda é eficientemente hidrolisada pelas enzimas. As duas amostras de celulose Avicel oxidadas também foi hidrolisada utilizando misturas de enzimas comerciais e extratos enzimáticos de G. trabeum. Em todas as condições ensaiadas a suplementação da mistura reacional com extratos enzimáticos do fungo de decomposição parda G. trabeum diminuíram a eficiência de hidrólise enzimática da celulose oxidada. O emprego do dobro de carga enzimática de enzimas comerciais permitiu recuperar os níveis de hidrólise observados na celulose in natura. / The goal of this work was to evaluate whether enzymes produced by the brown-rot fungus Gleophyllum trabeum would be able to act as auxiliary enzymes of commercial cellulases during the enzymatic hydrolysis of oxidized cellulose. To reach this goal an oxidation of microcrystalline-cellulose (Avicel) was performed by two differente reaction systems: Fenton reaction (Fe2+, H2O2) or CuSO4 treatments. The oxidized subtracts were characterized and the effect of cellulose modification on the hydrolytic efficiency of commercial enzymes, supplemented or not with the enzymes recovered from a G. trabeum culture, was determined. The Avicel treatment by the oxidative systems resulted in cellulose structural changes as evidenced by infrared spectroscopy, viscosity measurements and chemical characterization by HPLC and GC/MS chromatography of the monomers recovered after acid hydrolysis. The physicochemical characterization of the oxidized celluloses allowed to conclude that the transformation of the cellulose was more intense when Fenton treatment was used as compared with the CuSO4 treatment. The analysis of the acid hydrolysates by GC-MS indicated that the oxidation by Fenton reaction occurred mainly at the C1 of the cellulose chain, resulting in gluconic acid in the acid hydrolysates. A meaningful decrease of the cellulose conversion was observed when Fetnon-treated samples were submitted to enzymatic hydrolysis using different amounts of commercial enzymes. On the other hand, the CuSO4-oxidized cellulose was still efficiently hydrolyzed by high enzyme dosages. The oxidized Avicel substrates were also hydrolyzed using a mixture of the commercial enzymes with enzymes recovered from G. trabeum cultures. At all tested conditions, the supplementation of the reaction mixture with enzymatic extracts from G. trabeum decreased the enzymatic hydrolysis efficiency. Nevertheless, the normal levels of enzymatic hydrolysis were recovered when the commercial enzymes dosage two-fold increased.

M. Tech. Agriculture / Brown rot caused by Monilinia laxa is the main pre and postharvest disease of peaches; it affects the shelf life and marketability of peaches. Increasing consumer concern regarding food safety makes it necessary to search for natural environmentally friendly alternative products for postharvest disease control. The objective of this study is to develop an environmentally friendly essential oil technology for the control of brown rot (M. laxa) in peaches at postharvest stage to replace the currently used synthetic fungicide (Iprodione)

L’utilisation de matériaux d’origine végétale dans les bâtiments thermiquement performants pose la question de la pérennité des ouvrages principalement à cause de la dégradation fongique. Postia placenta est une espèce des champignons provoquant la pourriture brune, qui est la plus destructrice pour les constructions en bois.Ce travail se concentre sur l’observation et la modélisation de la croissance de Postia placenta à trois échelles successives : l'arborescence du mycélium (échelle discrète), la croissance en milieu libre (échelle continue) et la croissance en milieu encombré (échelle macroscopique). L’observation expérimentale de la croissance de Postia placenta utilise un microscope confocal à balayage laser pour quantifier les différentes mécanismes et obtenir les paramètres de croissance. A partir de cette observation, un modèle discret capable de générer un mycélium de forme extrêmement similaire à celle observée a été imaginé, développé et validé. Ensuite, à partir des profils de biomasse moyennés selon le rayon des mycéliums simulés par le modèle discret, un modèle continu basé sur une équation de réaction diffusion a été identifié pour décrire l’évolution de la concentration de biomasse fongique. Ce modèle continu offre la possibilité de la transition de l’échelle locale vers l’échelle macroscopique. Pour cela, des simulations de la prolifération en environnement encombré sont obtenues à l'aide du modèle continu. Par prise de moyenne, les champs spatio-temporels obtenus permettent de déterminer les paramètres d'un modèle continu similaire, mais valable à l'échelle macroscopique, sur un milieu fictif qui prend en considération la morphologie des obstacles. / The use of bio-based materials in thermally efficient buildings raises the question of the sustainability mainly due to fungal degradation. Among the wood-decay fungi, Postia placenta is one of the most common brown rot fungi, which are the most destructive due to their rapid decaying mechanisms. This work focused on the experimental observation and the modeling of fungal growth at three successive scales: the mycelial network (discrete scale), mycelial growth in homogeneous media (continuous scale) and mycelial growth in porous media (macroscopic scale).The experimental observation of the growth of Postia placenta was performed using confocal laser scanning microscopy to quantify the different growth mechanisms and obtain the growth parameters. A discrete model has been derived from this observation and is capable of generating mycelial networks extremely similar to the observed ones. A continuous formulation based on a reaction diffusion equation was developed from the radial biomass density of a mycelial network obtained in the discrete model. This continuous formulation was then used to derive an equivalent macroscale model able to account for fungal development in porous media. Simulations were performed on various periodic porous media. The parameters of the macroscale model was identified on the macroscopic fields obtained by averaging the local field over one periodic unit cell.

No description available.