Production of laccase without inducer by Chaetomium species isolated from Chettaba forest situated in the East of Algeria

A positive laccase strain which showed a positive reaction with guaïacol was isolated from Chettaba Forest, which is situated in Constantine, the East of Algeria. It was identified as Chaetomium species (Ref 051A) according to the morphological and ribosomal internal transcribed spacer (ITS) DNA genomic sequence analysis. Laccase activity was determined by using 2,2-azinobis(3- ethylbenzthiazoline-6-sulfonate) diammonium salt (ABTS) as a substrate. Its highest activity was achieved by using potato dextrose broth (PDB) as a culture medium. Metal ion CuSO4 had no positive effect on laccase production. The laccase activity obtained in submerged fermentation (20 L) was higher than that produced in Erlenmeyer flask (500 ml). The study of pH and temperature effects showed that pH optimum was 5 and 6, and temperature was 35°C. Laccase produced by Chaetomium spp. can be used in industrial production.Keywords: Chaetomium species, guaïcol, laccase, 2,2-azinobis(3- ethylbenzthiazoline-6-sulfonate) diammonium salt (ABTS), submerged fermentatio

MANUFACTURING OF KIVUGUTO MILK AND STABILITY IN STORAGE UNDER REFRIGERATION

The kivugutomilk was processed in a 20 liters bioreactor with three bacteria previously selected in kivuguto traditional milk. The work aimed to study the association of three bacteria previously selected in traditional kivuguto in order to reproduce it in a controlled fermentation, and thereafter to understand its stability during storage under refrigeration. Postacidification, viability, proteolysis, flavor compounds as well as rheological characteristics were monitored for 36 days. The ph decreases from 4.54 to 4.45 and the titratable acidity grew from 73°d to 79°d. The final biomass after storage was 0.60 108 cfu.g-1 which is far higher than the recommended 106 cells.g-1before consumption. The proteolysis was at a range of 3.0 to 7.0 mg.l-1of lysine equivalent, which is too low so that it can’t produce bitter peptides. The evolution of flavor compounds in storage showed that no change found with 3-methylbutan-1-ol, acetic acid and furan-2(5h)-one, whilst pentan-1-ol and furanmethan-2-ol increased slightly upon 24 days’ storage. The complex viscosity decreased from 4 - 5.3 pas before storage to 2.9 - 4.0 pas corresponding respectively to the ratio g''/g' of about 0.3-0.4 with a very low variation. These data allowed the production and the good preservation of kivuguto milk at 4°c on 36 days

MANUFACTURING OF KIVUGUTO MILK AND STABILITY IN STORAGE UNDER REFRIGERATION

The kivugutomilk was processed in a 20 liters bioreactor with three bacteria previously selected in kivuguto traditional milk. The work aimed to study the association of three bacteria previously selected in traditional kivuguto in order to reproduce it in a controlled fermentation, and thereafter to understand its stability during storage under refrigeration. Postacidification, viability, proteolysis, flavor compounds as well as rheological characteristics were monitored for 36 days. The ph decreases from 4.54 to 4.45 and the titratable acidity grew from 73°d to 79°d. The final biomass after storage was 0.60 108 cfu.g-1 which is far higher than the recommended 106 cells.g-1before consumption. The proteolysis was at a range of 3.0 to 7.0 mg.l-1of lysine equivalent, which is too low so that it can’t produce bitter peptides. The evolution of flavor compounds in storage showed that no change found with 3-methylbutan-1-ol, acetic acid and furan-2(5h)-one, whilst pentan-1-ol and furanmethan-2-ol increased slightly upon 24 days’ storage. The complex viscosity decreased from 4 - 5.3 pas before storage to 2.9 - 4.0 pas corresponding respectively to the ratio g''/g' of about 0.3-0.4 with a very low variation. These data allowed the production and the good preservation of kivuguto milk at 4°c on 36 days

Comparison of explant responses treated with leachate and leonardite sources of humic substances during in vitro rooting of woody plants.

As heterogeneous mixtures of compounds resulting from the physical, chemical and microbiological transformations of organic residues, humic substances (HS) are mostly recognized for their biostimulation of plant growth that firstly involve the root development and architecture before further putative improvement of nutrients uptakes. To avoid the interferences currently reported from external origins, the successive steps of rooting have been carried out using shoots and isolated leaves of birch and alder vitro-plants. Extracts issued from landfill leachate (LHS) has been compared to a stable formulation from leonardite ("Humifirst" 12% humic acid 3% and fulvic acid) commercialized by TRADECORP company's (HHS). Chemical analysis showed that LHS source typically contain much higher N (mainly as ammonium (93%) and chloride concentration than HHS. Used at low concentration (10 ppm) during root induction/initiation phase, both HS sources may be slightly unfavorable to the root formation (21% of reduction in primary root number) of alder but not of birch. While, in root elongation phase, there is an increase in the primary root length and lateral root number. The direct effects of HS on in vitro root development vary from one species to another depending on the root treatment stage. Results showed that both explants type response are equivalent in the development of a complete rooting system

Accelerated storage testing of freeze-dried Pseudomonas fluorescens BTP1, BB2 and PI9 strains

Freeze-dried cultures of Pseudomonas fluorescens are used in agriculture and microbiological industry. However, P. fluorescens is very susceptible to damage during freeze-drying and subsequent storage and it would be useful to increase culture viability during storage. The viability of freeze-dried P. fluorescens strains (BTP1, PI9 and BB2) was evaluated by using the Arrhenius model. This model was described by measuring the reaction rate constants (D or k) and temperature sensitivity of rate constant (z or Ea). The freeze-dried P. fluorescens strains were stored in glass tubes at 60, 37 and 4°C for 8 h, 28 days and two months, respectively. D value decreased or k increased with an increase of the storage temperature. By comparing their decimal reduction time (D), we observed that BB2 strain was more resistant than BTP1 and PI9 at 37 and 60°C. The activation energy of all P. fluorescens strains were not significantly different and thermal inactivation may occur by the same mechanism. Thus, it was possible to compare rate constants of survival for the freeze-dried P. fluorescens strains. These results will be useful to the development of improved reference materials and samples held in culture collections.Key words: Arrhenius model, accelerated storage testing (AST), freeze-drying, storage stability

Assessment of the physiological and biochemical characterization of a Lactic acid bacterium isolated from chicken faeces in sahelian region

The aim of this work was the examination of the microbiological and technological properties of a lactic acid bacterium (CWBI-B623) isolated from chicken faeces in sahelian region (Burkina Faso). The strain CWBI-B623 is a Gram positive rod, asporogenous, catalase-positive, facultatively anaerobic, non motile and mesophilic. The analysis showed that it produce L(+)-lactic acid via homofermentative pathway and it was able to ferment an important number of the carbohydrates of API 50CHL system. The 16S-rDNAsequence analysis revealed that the isolate was phylogenetically a member of the genus Lactobacillus and formed a subline within the Lactobacillus casei cluster. The minimal inhibitory concentration of CWBI-B623 for bile salts was higher than 1% and the survival rates to acidity with pH 3.0 and pH 2.5 were 26 and 1.2%, respectively. CWBI-B623 is an Lactobacillus casei species based on its physiological and biochemical properties and it could be a good candidate for probiotic formulations.Key words: Lactic acid bacteria, Lactobacillus, probiotic, biodiversity

Utilisation d’un bio-réacteur scale-down pour la production de lipase à partir de Yarrowia lipolytica

Les résultats obtenus au niveau de fermenteur de laboratoire et de volume industriel sont souvent différents à cause de la diminution de l’efficacité d’homogénéisation (substrats, oxygène dissous …etc.) du réacteur lorsque le volume augmente tels que. Dans cette optique, le fermenteur scale-down peut être utilisé. Il s’agit d’un système permettant de représenter à petite échelle les conditions de mélange des réacteurs de taille industrielle. Les lipases microbiennes sont stables dans de nombreux solvants organiques et ne requièrent pas de co-facteur pour être actives. Leurs domaines d'application sont très vastes et variés. Pour la production de la lipase, la levure non conventionnelle présente de nombreuses potentialités. A ce propos, Yarrowia lipolytica est le microorganisme le plus important vu qu’il produit les lipases à l’échelle industrielle. Pour des raisons économiques, les conditions de culture (pH, dispersion liquide-liquide, aération, …etc.) lors de la production de la lipase, doivent être optimalisées. Ce poster présente les résultats de l’effet de l’extrapolation sur la production de lipase à partir de Yarrowia lipolytica en mode batch avec un milieu de production optimisé (Destain et al., 2005). Les effets de la concentration en oxygène dissous, la dispersion liquide-liquide et les gradients de pH, qui sont affectés par le mélange du milieu de culture, sont présentés dans ce poster. Dans cette optique, plusieurs dispositifs scale-down ont été utilisés. Ceux-ci permettent de reproduire à l’échelle du laboratoire les hétérogénéités rencontrées à l’échelle industrielle

The Resistance to Freeze-Drying and to Storage Was Determined as the Cellular Ability to Recover Its Survival Rate and Acidification Activity

The protective effects of the fatty acid composition and membrane action of the acidification activity of two strains of Lactobacillus kept at 20°C were studied. The addition of sorbitol, monosodium glutamate and glycerol during storage is causing the decline of acidification and increased concentrations of unsaturated fatty acids observed in both strains. The addition of sorbitol and monosodium glutamate does not alter the fatty acid composition, whatever the strain, but increases the resistance to freeze-drying of L. plantarum CWBI-B1419 and improves survival during storage. The addition of these preservatives and decreased activity of acidification improves the ratio unsaturated. These results indicate that the survival during storage and freeze-drying resistance are closely related to the composition of membrane fatty acids. This behaviour can be interpreted as an adaptation of L. plantarum B1419-CWBI supplemented by cryoprotectant additives such as sorbitol or monosodium glutamate sorbitol and monosodium glutamate as an additive. L. plantarum CWBI-B1419 presents a greater adaptation to culture conditions than L. paracasei ssp. paracasei LMG9192T