Pectinases and cellulases from plum curculio larvae: Possible causes of apple and plum fruit abscission

Plum curculio larvae, Conotrachelus nenuphar (Herbst) (Coleoptera: Curculionidae), were assayed for pectic and cellulolytic enzymes. Larvae produce at least five pectic enzymes:pectin methyl-esterase, endo-polymethylgalacturonase, endo-polygalacturonase, pectin methyl-trans-eliminase, and polygalacturonate-trans-eliminase. Larvae also produce cellulase. Enzymes are released as larvae feed and are capable of causing fruit tissue maceration. One or more of these enzymes may be responsible for the premature abscission of plums and apples infested with plum curculio larvae.

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Résumé Les larves de Conotrachelus nenuphar, le Plum curculio ont été testées par la recherche des enzymes pectinolytiques et cellulolytiques. Ces larves produisent au moins cinq enzymes pectinases: pectine methyl-esterase, endo-polymethylgalacturonase, endo-polygalacturonase, pectine methyl trans-eliminase, et polygalacturonate-trans-eliminase. Elles produisent aussi de la cellulase. Les enzymes sont libérées alors que les larves se nourrissent et sont capables de provoquer une macération du tissu des fruits. Une ou plusieurs de ces enzymes peuvent être responsables de la chute prématurée des prunes et des pommes infestées par des larves de Plum curculio.

     

Extracellular enzyme activities during cassava fermentation for ‘fufu’ production

Amylase and pectin methyl esterase activities increased rapidly during the early period of the fermentation of cassava for fufu production, attaining their peak activities after 12 and 24h, respectively. Cellulase activity was lower and approximately constant for most of the fermentation period.     

Esterases in the mosquito Culex pipiens pipiens L.: Formal genetics and polymorphism of adult esterases

The genetics of two esterase loci active in autogenous adults of the mosquito Culex pipiens pipiens L. has been studied by means of starch gel electrophoresis. Three alleles at the Est-1 locus and eight at the Est-2 locus are described. Both loci have a null allele. Active alleles are codominant and there is no hybrid enzyme in heterozygotes. The Est-1 locus codes esterases preferentially hydrolyzing -naphthylacetate and the Est-2 locus esterases preferentially hydrolyzing -naphthylacetate. Strains homozygous for both loci were selected. Linkage studies of the two loci have shown that they are not sex linked but are linked to each other, the crossover frequency being 8.6%. The polymorphism of two laboratory and two natural populations is described for both loci. Phenotypic distributions are in good agreement with Hardy-Weinberg expectations.This work was conducted at the Université des Sciences et Techniques du Languedoc (Laboratoire de Génétique Expérimentale des Populations), Montpellier, France, in partial fulfillment of the requirements for the degree of Docteur de spécialité.     

Etude écologique comparée des populations d'ostracodes dans deux étangs de pisciculture en haute Belgique

The populations of Ostracods inhabiting two ponds have been studied. One of the ponds is left in its natural state and is of an oligotrophic type; the other one is fertilized once a year mainly with lime and calcium phosphate. Moreover the water feeding the last one is neutralized by a regular addition of calcium carbonate.Comparison of the densities of Ostracods shows that this fertilization has a positive action on the abundance of these crustaceans. Spatial distribution of the Ostracods is of the aggregative type. Specific composition is similar in both ponds but for some scarce species.Specific diversity suggests a higher organization level in communities inhabiting the natural pond. The diversity index H Of Shannon-Weaver shows a rather parallel seasonal fluctuation in both biotopes.

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Travail effectué au Laboratoire d'Hydrobiologie de l'Institut royal des Sciences naturelles de Belgique (Directeur de recherches G. Marlier) et au Laboratoire d'Ecologie générale et expérimentale de l'Université Catholique de Louvain (Professeur Ph. Lebrun).     

The role of Bacillus species in the fermentation of cassava

Cassava dough inoculum is added to grated cassava in order to achieve a modification of texture during fermentation into the fermented cassava meal, agbelima. The microflora of two different types of inocula and subsequently inoculated cassava mash at 0, 24 and 48 h of fermentation were examined in order to determine the mechanism responsible for the breakdown of cassava tissue. Bacillus spp. occurred in high numbers, 10₇–10₈ cfu g_-1, in both types of inocula and persisted throughout the cassava dough fermentation. Bacillus spp. found were B. subtilis , B. mycoides , B. pumilus , B. cereus , B. amyloliquefaciens and B. licheniformis , with B. subtilis accounting for more than half of Bacillus isolates. All Bacillus isolates produced a wide spectrum of enzymes and showed similar enzymatic activities but only B. pumilus , B. licheniformis and B. amyloliquefaciens produced linamarase. Some isolates produced the tissue degrading enzymes polygalacturonase and pectin esterase and nearly all isolates hydrolysed starch. All isolates showed cellulase activity and were able to disintegrate cassava tissue. When cassava pieces were incubated in amylase, cellulase, pectin esterase and polygalacturonase solutions, only pieces in cellulase solution were dissolved revealing that the breakdown of cassava dough texture during fermentation with the inocula examined is brought about by Bacillus spp. through cellulase activity.     

Microbiological and Biochemical Characterization of Cassava Retting, a Traditional Lactic Acid Fermentation for Foo-Foo (Cassava Flour) Production

The overall kinetics of retting, a spontaneous fermentation of cassava roots performed in central Africa, was investigated in terms of microbial-population evolution and biochemical and physicochemical parameters. During the traditional process, endogenous cyanogens were almost totally degraded, plant cell walls were lysed by the simultaneous action of pectin methylesterase and pectate lyase, and organic acids (C(inf2) to C(inf4)) were produced. Most microorganisms identified were found to be facultative anaerobes which used the sugars (sucrose, glucose, and fructose) present in the roots as carbon sources. After 24 h of retting, the fermentation reached an equilibrium that was reproducible in all the spontaneous fermentations studied. Lactic acid bacteria were largely predominant (over 99% of the total flora after 48 h) and governed the fermentation. The epiphytic flora was first replaced by Lactococcus lactis, then by Leuconostoc mesenteroides, and finally, at the end of the process, by Lactobacillus plantarum. These organisms produced ethanol and high concentrations of lactate, which strongly acidified the retting juice. In addition, the rapid decrease in partial oxygen pressure rendered the process anaerobic. Strict anaerobes, such as Clostridium spp., developed and produced the volatile fatty acids (mainly butyrate) responsible, together with lactate, for the typical flavor of retted cassava. Yeasts (mostly Candida spp.) did not seem to play a significant role in the process, but their increasing numbers in the last stage of the process might influence the flavor and the preservation of the end products.     

Cell wall metabolism in fruit softening and quality and its manipulation in transgenic plants

Excessive softening is the main factor limiting fruit shelf life and storage. Transgenic plants modified in the expression of cell wall modifying proteins have been used to investigate the role of particular activities in fruit softening during ripening, and in the manufacture of processed fruit products. Transgenic experiments show that polygalacturonase (PG) activity is largely responsible for pectin depolymerization and solubilization, but that PG-mediated pectin depolymerization requires pectin to be de-methyl-esterified by pectin methylesterase (PME), and that the PG -subunit protein plays a role in limiting pectin solubilization. Suppression of PG activity only slightly reduces fruit softening (but extends fruit shelf life), suppression of PME activity does not affect firmness during normal ripening, and suppression of -subunit protein accumulation increases softening. All these pectin-modifying proteins affect the integrity of the middle lamella, which controls cell-to-cell adhesion and thus influences fruit texture. Diminished accumulation of either PG or PME activity considerably increases the viscosity of tomato juice or paste, which is correlated with reduced polyuronide depolymerization during processing. In contrast, suppression of -galactosidase activity early in ripening significantly reduces fruit softening, suggesting that the removal of pectic galactan side-chains is an important factor in the cell wall changes leading to ripening-related firmness loss. Suppression or overexpression of endo-(1\to4)-d-glucanase activity has no detectable effect on fruit softening or the depolymerization of matrix glycans, and neither the substrate nor the function for this enzyme has been determined. The role of xyloglucan endotransglycosylase activity in softening is also obscure, and the activity responsible for xyloglucan depolymerization during ripening, a major contributor to softening, has not yet been identified. However, ripening-related expansin protein abundance is directly correlated with fruit softening and has additional indirect effects on pectin depolymerization, showing that this protein is intimately involved in the softening process. Transgenic work has shown that the cell wall changes leading to fruit softening and textural changes are complex, and involve the coordinated and interdependent activities of a range of cell wall-modifying proteins. It is suggested that the cell wall changes caused early in ripening by the activities of some enzymes, notably -galactosidase and ripening-related expansin, may restrict or control the activities of other ripening-related enzymes necessary for the fruit softening process.     

Antisense transgenesis of tobacco with a flax pectin methylesterase affects pollen ornamentation

Summary. Antisense transgenesis of tobacco (Nicotiana tabacum) with a partial flax (Linum usitatissimum L.) pectin methylesterase (Lupme3) cDNA sequence yielded plants with altered pollen content. Moreover, the characteristically sculptured cell wall surrounding the pollen grains was modified in transgenic tobacco plants: the wavy ornamentation was dramatically reduced, suggesting the involvement of the demethylation of pectin in the pollen cell wall-specific structure. Germination of pollen was decreased and the pollen tube surface aspect was also different in transgenic plants.Correspondence and reprints: Laboratoire de Biotechnologies et Physiologie Végétales, Faculté des Sciences, Université de Picardie Jules Verne, 33 rue Saint-Leu, 80039 Amiens Cedex, France.     

Données sur la distribution des éléments biogènes dans l'estuaire du Tamar, à Plymouth

Résumé Le Tamar possède un estuaire à circulation d'eau typique (pas de mélange des eaux) mais présentant encore à ce point de vue, certaines particularités qu'il convient d'approfondir.Les quelques facteurs écologiques (température, transparence, salinité, phosphates et silicates) étudiés dans la zone la plus salée (de eu- à mésohaline) de l'estuaire montrent des variations importantes qui se réfléteront probablement dans la distribution du phytoplancton. La distribution des phosphates pose un certain nombre de problèmes et notamment celui de leur plus faible teneur en surface. Il conviendra de compléter cette étude préliminaire par des recherches sur la distribution des nitrates et l'exploration des zones oligohaline et limnétique.

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Summary A typical water circulation pattern (no mixing of fresh and sea waters) is demonstrated in the Tamar estuary, however a few particular points still are to be elucidated.The ecological factors (temperature, transparence, salinity, inorganic phosphate and silicate) studied in the lower reaches of the estuary show some important variations.It is emphasized that an exceptionally low amount of inorganic phosphate is found at the surface or the subsurface.

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Assistant au Laboratoire de Botanique systématique et Ecologie de l'Université Libre de Bruxelles. Boursier de l'U.N.E.S.C.O., stagiaire au Laboratoire de la Marine Biological Association of the U.K., Plymouth.     

Molecular cloning and nucleotide sequence of the pectin methyl esterase gene of Erwinia chrysanthemi B374

The gene encoding pectin methyl esterase (pme) has been cloned from Erwinia chrysanthemi B374. Expression of pme in Escherichia coli allowed the enzyme to be characterized. Pectin methyl esterase (PME) was found to have an apparent molecular weight of 36,000 Daltons and an isoelectric point of approximately 9.9. The structural gene was sequenced and consists of a 1098-bp open reading frame encoding a polypeptide of 39,318 Daltons, which includes an amino-terminal signal peptide. The isolation of the Erwinia gene provides a simple method for the production of PME free from depolymerizing pectinases thereby extending its potential uses.     

Infrastructure superficielle de la vésicule vitelline et du sac péricardique de l'embryon de Poecilia reticulata (Poisson Téléostéen)

Résumé Le microscope électronique à balayage montre l'existence d'un réseau complexe de microcrêtes à la surface de la vésicule vitelline et du sac péricardique de l'embryon de Poecilia reticulata. Cette étude permet également de préciser la localisation, l'aspect et la répartition des «cellules à chlorure» et de proposer un schéma tridimensionel de l'organisation infrastructurale de la paroi de la vésicule vitelline. Un choc osmotique détermine rapidement un mouvement d'étalement des cellules épithéliales sur la surface apicale libre des «cellules à chlorure». La signification de ces résultats est discutée en rapport avec le problème de l'osmorégulation embryonnaire chez les Poissons, en particulier chez les Cyprinodontes vivipares de la famille des Poeciliidae.

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Ultrastructure of the yolk sac and pericardial sac surface in the embryo of the teleost Poecilia reticulata

Summary A complex network of microridges is revealed by scanning electron microscopical examination of the yolk sac and embryonic pericardial sac surface of Poecilia reticulata. This study also specifies the localization, aspect and distribution of the chloride cells. A tridimensional diagram of the ultrastructural organization of the yolk sac wall is suggested. Osmotic stress quickly induces an overlapping of adjacent epithelial cells on the free apical surface of the chloride cells. These findings are discussed in relation to the problem of embryonic osmoregulation in fishes and especially in viviparous Poeciliids.

Nous exprimons notre gratitude à Mme Neumann, Directeur du Laboratoire de Micropaléontologie de l'Université Paris VI, qui nous a permis d'utiliser le microscope électronique à balayage qui a servi à cette étude. Nos remerciements s'adressent aussi à Melle Aubry et à M. Saussé pour leur concours technique. — Les observations en microscopie électronique en transmission ont été effectuées au Laboratoire de Microscopie électronique appliquée à la Biologie du C.N.R.S.     

Cholinesterases from plant tissue: v. Cholinesterase is not pectin esterase

Several properties of the cholinesterase from Phaseolus aureus Roxb. and of pectin (methyl) esterases from both Phaseolus aureus and Lycopersicon esculentum (L.) Mill. are contrasted. Cholinesterase activity is inhibited by all of the concentrations of NaCl tested, from 0.05 m to 0.9 m, a property which differs sharply from published data pertaining to pectin esterase. Although crude preparations of cholinesterase contain pectin esterase activity, further purification by gel filtration of the cholinesterase results in a nearly complete elimination of the pectin esterase activity. The activity of neither the pectin esterase from Lycopersicon esculentum nor that from Phaseolus aureus is affected by 25 μm neostigmine, a potent inhibitor of the cholinesterase activity extracted from Phaseolus aureus.     

Characterization of the solid-state fermentation of cassava

The solid-state fermentation of cassava (Mannlhot esculenta Crantz) was characterized by determining pH and biological oxygen demand (BOD). The results showed a strong association (=0.73) between pH of the fermenting slurry and that of the waste llquor. BOD of the liquor decreased as fermentation progressed. After 96 h fermentation, BOD was about 6×10² mg/l. Progress of cassava fermentation can probably be determined indirectly by following the changes in the pH and BOD profiles of the liquor.

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Résumé La fermentation en milleu solide du manioc (Mannihot esculenta Crantz) a été caractérisée en déterminant le pH et la demande biolgique en oxygène (DBO). Les résultats montrent une forte corrélation (=0.73) entre le pH de la pâte en fermentation et celui de la liquer résiduaire. La DBO de la liqueur décroît au fur et à mesure que la fermentation progresse. Après 96hh de fermentation, la DBO était de 6×10² mg/l. L'avancement de la fermentation du manioc peut probablement être déterminée indirectement ectement en sulvant l'évolution des profiles en pH et en DBO de la liqueur.

     

Production of extracellular pectinase enzymes by a mutant (Pol6) of Penicillium occitanis

Summary Penicillium occitanis strain Pol6, a mutant developed for hyperproduction of cellulase and pectinase enzymes was used for the study of extracellular pectinase production when pectins from different sources (apple and citrus) and with varying degree of esterification (DE) were used as inducers. Highly esterified citrus pectins were found to be suitable substrates for polygalacturonase, pectinase and pectin methyl esterase production, while low esterified citrus pectin favoured pectin lyase (PL) production. Apple pectins induced other hydrolytic enzymes (e.g., -1,3-glucanase, -glucosidase, -galactosidase), in addition to pectolytic enzymes. Moreover, the combination of high and low esterified citrus pectins induced the production of a complete pectinase complex. The extent of degradation of the substrate and the affinity for PL decreased with decreasing DE irrespective of the source. There was no evidence of PL activity in this strain. No significant effect of cations (Ca⁺⁺, Mn⁺⁺, Na⁺) on PL activity was observed. However, EDTA (100 mm) inhibited 50% of the activity, when tested on highly esterified (rapid set citrus) pectin. Offprint requests to: S. Jain     

Xenobiotic induction of esterases in cultures of the yeast-like symbiont from the cigarette beetle

By using the l-naphthyl acetate assay system, we found that xenobiotics can induce increased esterase activity in cultures of the yeast-like symbiont, Symbiotaphrina kochii Jurzitza ex. W. Gams and v. Arx, of the cigarette beetle, Lasioderma serricorne L.. The activities expressed as percent of solvent control are as follows: flavone, 184.2%; griseofulvin, 115.8%; cis(–)--pinene, 111.4%; and malathion, 114.0%. Gel electrophoresis showed new enzymes are induced by three of the compounds tested. Thus, the yeast responds in a manner consistent with detoxification enzyme regulation common in insects and microorganisms.

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Résumé En utilisant une méthode de dosage avec le l-naphtyle-acétate, nous avons trouvé que des substances xénobiotiques peuvent induire une augmentation de l'activité estérase dans des cultures du symbionte de type levure, Symbiotaphrina kochii Jurzitza, ex W. Gams & v. Arx, de L. serricorne. Le solvant ayant servi de témoin, a constitué la référence à partir de laquelle ont été calculés les pourcentages obtenus: flavone 184,2%; griséofluvine, 115,8%; cis(–)--pinène, 111,4%; malathion, 114,0%. L'électrophorèse sur gel de polyacrylamine a montré que les nouvelles enzymes sont induites par 3 des substances examinées. Ainsi, la levure réagit d'une façon compatible avec la régulation enzymatique de la détoxification commune aux insectes et aux microorganismes.

     

The ectopic expression of a pectin methyl esterase inhibitor increases pectin methyl esterification and limits fungal diseases in wheat

Cell wall pectin methyl esterification can influence plant resistance because highly methyl-esterified pectin can be less susceptible to the hydrolysis by pectic enzymes such as fungal endopolygalacturonases (PG). Pectin is secreted into the cell wall in a highly methyl-esterified form and, here, is de-methyl esterified by pectin methyl esterase (PME). The activity of PME is controlled by specific protein inhibitors called PMEI; consequently, an increased inhibition of PME by PMEI might modify the pectin methyl esterification. In order to test the possibility of improving wheat resistance by modifying the methyl esterification of pectin cell wall, we have produced durum wheat transgenic lines expressing the PMEI from Actinidia chinensis (AcPMEI). The expression of AcPMEI endows wheat with a reduced endogenous PME activity, and transgenic lines expressing a high level of the inhibitor showed a significant increase in the degree of methyl esterification. These lines showed a significant reduction of disease symptoms caused by the fungal pathogens Bipolaris sorokiniana or Fusarium graminearum. This increased resistance was related to the impaired ability of these fungal pathogens to grow on methyl-esterified pectin and to a reduced activity of the fungal PG to hydrolyze methyl-esterified pectin. In addition to their importance for wheat improvement, these results highlight the primary role of pectin despite its low content in the wheat cell wall.     

The medicinal value of the mushroomGrifola

This review contains the most recent information on the various substances isolated and Identified in the maitake mushroomGrifola, their source and significance. The majority of the references concern the anti-tumour polysaccharides that have been extracted from fruiting bodies and mycelia, but certain species can also act as metabolic regulators and contain enzymes, essential amino acids, lipids and vitamins. The use of edible fungi in the development and application of beneficial biological activities ofters an advantage in that the active principle is safe and can be tolerated by humans. Cultivation of such edible mushrooms would provide an adequate supply but is unnescessary if mycelial cultures grown in large-scale fermentations can produce the same active principle. It is hoped that this article will be infromative as the search continues for new uses for edible fungi and for educating the public about their potential value.

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Résumé Cette revue contient l'information la plus récente sur les diverses substances isolées et identifiées du champignon maitake,Grifola, leur origine et leur signification. La majorité des références concerne les polysaccharides anti-tumoraux qui ont été extraits des corps fructifères et des mycelia mais certaines espèces peuvent aussi agir en tant que régulateurs métaboliques et contiennent des enzymes, des acides aminés essentiels, des lipides et des vitamines. L'utilisation de moisissures comestibles dans le développement et l'application d'activités biologiques bénéfiques offre l'avantage du principe actif sain et toléré par les humains. La culture de tels champignons comestibles procurerait la quantité adéquate de principe actif mais n'est pas nécessaire si les cultures myceliennes, cultivées par fermentation à grande échelle peuvent produire le même principe actif. On espère que cet article sera informatif, comme la recherche continue pour de nouvelles utilisations de moisissures comestibles et pour l'éducation du public au sujet de leur valeur potentielle.

     

Crop storage losses in southern Nigeria caused by the activities of micro-organisms

Summary In the southern part of Nigeria, maize, cassava, and yam are the major food crops grown, and they constitute an important source of carbohydrate in the diet of the inhabitants of the area. There are various traditional methods for storage of these crops and all have been shown to lead to storage losses both quantitatively and qualitatively. Micro-organism, especially the fungi, are important as agents of deterioration and spoilage of these crops during storage. Factors that influence the infestation and growth of micro-organisms in these crops during storage are many with moisture being especially significant. To aid in their preservation, cassava and yams are usually processed into more shelf-stable products such as garri and fufu from cassava as well as yam chips and fluor from yam. All these processed products, in spite of their relatively shelf-stable nature, are still subject to microbial infection if improperly handled and stored. It is concluded that much work needs to be done in Nigeria to improve storage conditions.

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Résumé Dans le Sud du Nigéria, le maïs, le manioc et la patate douce sont les récoltes alimentaires majeures, et celles-ci constituent une source importante d'hydrates de carbone dans l'alimentation des habitants locaux. Il y a plusieurs méthodes traditionnelles pour le stockage de ces récoltes et toutes ont révélé conduire à des pertes tant quantitatives que qualitatives par stockage. Les microorganismes, particulièrement les moisissures, sont d'importants agents de détérioration et d'avarie de ces récoltes pendant le stockage. De nombreux facteurs influencent l'infection par et la croissance des microorganismes dans ces récoltes durant le stockage, particulièrement l'humidité. Pour améliorer leur conservation, le manioc et la patate douce sont en général transformées en produits stables à conserver en rayonnage comme le garri et le fufu de manioc ou encore les chips et la farine de patate douce. Tous ces produits transformés, malgré leur aptitude à la conservation en rayannage, sont néanmoins sujets à l'infection microbienne lorsqu'ils sont manipulés et conservés de manière impropre. Il faut en conclure que beaucoup de travail reste à faire au Nigéria pour améliorer les conditions de stockage.El maíz, la mandioca y el ñame son los cultivos, destinados a la alimentación, más importantes del sur de Nigeria, constituyendo la principal fuente de carbohidratos para los habitantes del area. Todos los métodos de almacenamiento tradicionales de estos cultivos producen perdidas tanto cuantitativas como cualitativas. Los microorganismos, especialmente los hongos, son agentes importantes de este deterioro. Son muchos los factores que influyen en la infestación y crecimiento de los microorganismos durante el almacenamiento de dichas cosechas, siendo la húmedad especialmente importante. Para mejorar su conservación la mandioca y el ñame se transforman en productos más estables tales como fufu y garri en el caso de la mandioca, y harina y rodajas cocinadas (chips) en del ñame. Todos estos productos transformados, a pesar de su naturaleza relativamente estable, están todavía sujetos a infección microbiana si se manipulan o almacenan de forma inadecuada. Se concluye que restan por hacer muchos trabajos para poder mejorar las condiciones de almacenamiento en Nigeria.

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Paper based on a presentation made at the VII International Conference on the Global Impacts of Applied Microbiology, Helsinki, 12–16.8.1985.     

Influence of environmental conditions on the production of pectinesterase and polygalacturonase byAspergillus niger

Summary A pectinesterase- and polygalacturonase-producer strain ofAspergillus niger showed a diauxic growth when cultivated in a medium containing pectin as the carbon source. Diauxie was suppressed by adding yeast extract to the medium. The specific production of polygalacturonase was decreased by increasing the initial concentration of pectin, while that of pectinesterase was enhanced with up to 15 g pectin/l. Yeast extract increased the production of biomass but decreased that of the enzymes. The temperature of incubation (25 to 40°C) did not affect the production of biomass or that of polygalacturonase, but production of pectinesterase was markedly affected, 30°C being the optimal temperature.

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Influence de la composition du milieu et les conditions des cultures sur la production de pectinestérase et polygalacturonase par Aspergillus niger

Résumé Aspergillus niger que produit pectinestérase et polygalacturonase, quand est developpé dans un milieu avec pectine comme source de carbone a presenté le phenomene de diauxie. Cela ne succedait pas quand le milieu avait aussi extrait de levure dans sa composition. L'effect de la concentration initiale de pectine sur la production specifique des enzymes des cellules (unité d'enzyme g^–1 de cellules poid sec) a été différent selon la phase du developpement de la culture, sugérant une rélation étroite parmi la synthèse des enzymes et l'état physiologique des cellules. L'augmentation de la concentration de pectine a troublé beaucoup la production spécifique de polygalacturonase. Au contraire, jusqu'à une concentration de 15 g/l a augmenté la synthèse de pectinestérase. La grandeur et structure des pellets ont changé avec la variation de la concentration de pectine, ces modifications peuvent avoir eu influence sur les valeurs des coefficients de transfert de masse et en conséquence sur la cinétique de production des enzymes. L'augmentation de la concentration iniciale d'extrait de levure dans le milieu que contenait pectine comme source de carbone a augmenté la production de biomasse, mais a baisse la synthèse des enzymes surtout celle de pectinestérase. Températures parmi 25°C et 40°C n'ont pas modifié la production de biomasse et non plus polygalacturonase. Au contraire la production de pectinesterase a été bien différente selon la température utilisé ayant un optimum de 30°C.

     

The effect of juvenile hormone and its antagonists on JH esterase activity in Tenebrio molitor

The hemolymph juvenile hormone esterase (JHE) and general carboxyl esterase activities in Tenebrio molitor show independent development-associated changes during larval-pupal and pupal-adult metamorphoses. JHE activity was high in pharate pupae and early pupae. Unlike in lepidopteran pupae that have been studied thus far, JH had no effect on JHE activity in pupae and pharate adults of Tenebrio. A JH antagonist, ethyl 4,2,tert butyl carboxy n benzoate (ETB), and 20-hydroxyecdysone had no effect on JHE activity. These observations suggest that although JHE activity in Tenebrio is precisely regulated during larval-pupal metamorphosis, JH and molting hormone do not appear to be involved in its regulation and that the proximate cues that influence JHE activity in Tenebrio pupae are different from that of lepidopterans.

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Résumé Les activités JHE (estérase juvénile hormone) de l'hémolymphe et carboxyl estérase générale de T. molitor changent indépendamment du développement pendant les métamorphoses larve-nymphe et nymphe-adulte. L'activité JHE est élevée chez les prénymphe et les jeunes nymphes. Contrairement aux chrysalides de papillons, JH n'a pas d'effet sur l'activité JHE chez les nymphes et les préadultes de Tenebrio. Un antagoniste de JH, l'éthyl 4,2,tert butyl carboxy n benzoate (ETB), 20-hydroxyecdysone et le précocène 2-agent anti-allate chez plusieurs insectes-, n'ont aucun effet sur l'activité JHE. Ces observations suggèrent que, bien que l'activité JHE chez T. molitor soit ajustée avec précision pendant la métamorphose larvo-nymphale, JH et hormone de mue ne paraissent pas être impliquées dans sa régulation et que les signaux immédiats, qui influent sur l'activité JHE de la nymphe de T. molitor, diffèrent de ceux des Lépidoptères.