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See detailEffects of glycerol on Pseudomonas fluorescens BTP1 freeze-dried
Mputu Kanyinda, Jean-Noël ULg; Pierart, C.; Weekers, F. et al

in International Journal of Biotechnology and Biochemistry. (2012), 8(2), 245-258

The storage stability of freeze-dried powders was studied by parameters such as loss of viability on the Plate Count Agar (PCA). Powder with glycerol (PG) contains 8.4x1010cfu/g before storage 1 ... [more ▼]

The storage stability of freeze-dried powders was studied by parameters such as loss of viability on the Plate Count Agar (PCA). Powder with glycerol (PG) contains 8.4x1010cfu/g before storage 1.1x1010cfug after 3 months at 4°C and 6.0x108cfu/g after 3 months at 20°C. The concentration of soluble proteins (mg/g) decrease during storage at 4°C from 3.77 to 0.80 after 90 days; and the ratios of unsaturated to saturated fatty acids (C18:3/C16:0 and C18:2/C16:0) decrease respectively from 0.05 to 0.04 and 0.007 to 0.004 after 3 months at 4°C. This ratio characterises the membrane fluidity. Powder without glycerol (PS) contains 1.1x1010 cfu/g before storage and 1.4 x 108 cfu/g after 3 months at 4°C and 1.4 x 107 cfu/g after 3 months at 20°C. The concentration of soluble proteins (mg/g) decrease during storage at 4°C from 4.08 to 0.42 after 90 days, the glutathione concentration decrease during storage at 4°C from 2.2 to 1.4. The beneficial effect of glycerol on fatty acid composition during freezedrying is shown and the ratios of unsaturated to saturated fatty acids (C18:2/C16:0 and C18:3/C16:0) decrease respectively from 0.019 to 0.004 and 0.054 to 0.036 after 90 days storage at 4°C. Analysis by flow cytometry was used to assess the physiological state in which cells are at the end of freeze-drying. We found 13.5% live cells, 36.1% dead cells and 50.4% cells in an intermediate state for powder with glycerol (PG) after freeze-drying. These results shows that glycerol play an important role in Pseudomonas fluorescens BTP1 desiccation during freeze-drying, by maintaining a degree of viability after freeze-drying and during storage. [less ▲]

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See detailImpact of Protective Compounds on the Viability, Physiological State and Lipid Degradation of FreezeDried Pseudomonas Fluorescens BTP1 during Storage
Mputu Kanyinda, Jean-Noël ULg; Pierart, C.; Weekers, F. et al

in International Journal of Biotechnology and Biochemistry (2012), 8(4), 17-26

The drying of bacteria remains a major alternative in order to keep them long term. After centrifugation, the bacterial pellet of Pseudomonas fluorescensBTP1 was divided in two fractions one with ... [more ▼]

The drying of bacteria remains a major alternative in order to keep them long term. After centrifugation, the bacterial pellet of Pseudomonas fluorescensBTP1 was divided in two fractions one with protecting compounds (2% glycerol or 5% maltodextrine) and one without and freeze-dried. After freeze drying, powders were sealed in aluminium bag under vacuum and stored at 4 or 20°C. The parameters such as viability, the conductivity and the ratio of polyunsaturated fatty acids/saturated fatty acids were used to investigate the viability of freeze-dried powders during storage. For example cell concentration of powder with glycerol (PG) at CFU/g before storage is 4.109 and after 7 month 2.108 at 4°C and 3,5.107 at 20°C). The ratio of polyunsaturated fatty acids/saturated fatty acids decrease in function of time (e.g. at 4°C the ratios of C18:3 and C18:2 by C16:0 decreases respectively of 0,013 to 0,001 and 0,05 to 0,03 after 60 days of storage). In the present study, flow cytometric analysis was applied to evaluate the state in which the cells are at the end of storage time. We compared the survival results of bacteria obtained by plate count with the flow cytometric analysis results. [less ▲]

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See detailAn enhanced process for the production of a highly purified extracellular lipase in the non-conventional yeast Yarrowia lipolytica
Turki, S.; Ayed, A.; Chalghoumi, N. et al

in Applied Biochemistry and Biotechnology (2010), 160(5), 1371-1385

Yarrowia lipolytica LgX64.81 is a non-genetically modified mutant that was previously identified as a promising microorganism for extracellular lipase production. In this work, the development of a fed ... [more ▼]

Yarrowia lipolytica LgX64.81 is a non-genetically modified mutant that was previously identified as a promising microorganism for extracellular lipase production. In this work, the development of a fed-batch process for the production of this enzyme in this strain was described. A lipolytic activity of 2,145 U/mL was obtained after 32 h of batch culture in a defined medium supplemented with 10 g/L of tryptone, an enhancer of lipase expression. To maximize the volumetric productivity, two different fed-batch strategies had been investigated. In comparison to batch process, the intermittent fed-batch strategy had not improved the volumetric lipase productivity. In contrast, the stepwise feeding strategy combined with uncoupled cell growth and lipase production phases resulted in a 2-fold increase in the volumetric lipase productivity, namely, the lipase activity reached 10,000 U/mL after 80 h of culture. Furthermore, this lipase was purified to homogeneity by anion exchange chromatography on MonoQ resin followed by gel filtration on Sephacryl S-100. This process resulted in an overall yield of 72% and a 3.5-fold increase of the specific lipase activity. The developed process offers a great potential for an economic production of Lip2 at large scale in Y. lipolytica LgX64.81. © 2009 Humana Press. [less ▲]

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See detailIsolation of bioactive peptides from tryptone that modulate lipase production in Yarrowia lipolytica
Turki, Souassen; Ben Kraeim, Ines; Weekers, F. et al

in Bioresource Technology (2009), 100

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See detailSelection of a cold-adapted bacterium for bioremediation of wastewater at low temperatures
Gratia, E.; Weekers, F.; Margesin, R. et al

in Extremophiles : Life Under Extreme Conditions (2009), 13(5), 763-8

Amongst more than 1000 isolates collected in various cold environments, the strain Arthrobacter psychrolactophilus Sp 31.3 has been selected for its ability to grow and to produce exoenzymes at low ... [more ▼]

Amongst more than 1000 isolates collected in various cold environments, the strain Arthrobacter psychrolactophilus Sp 31.3 has been selected for its ability to grow and to produce exoenzymes at low temperatures, its inability to grow at 37 degrees C, its non-halophilic character and its growth versatility on various media. This non-pathogenic strain displays a strong resistance to desiccation and storage at room temperature and is suitable for the production of freeze-dried bacterial starters. When grown in a synthetic wastewater at 10 degrees C, the strain induces a complete clarification of the turbid medium and efficiently hydrolyses proteins, starch and lipids in the broth. Furthermore, this strain has a remarkable capacity to improve the biodegradability of organic compounds in wastewater as indicated by a BOD(5)/COD ratio of 0.7. [less ▲]

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See detailCulture And Spray-Drying Of Tsukamurella Paurometabola C-924: Stability Of Formulated Powders
Hernandez, A.; Weekers, F.; Mena, J. et al

in Biotechnology Letters (2007), 29(11),

The nematocidal agent, Tsukamurella paurometabola C-924, was cultured in a 300 l bioreactor. Spray-dried formulations of this microorganism were prepared using sucrose. At an outlet temperature 628C ... [more ▼]

The nematocidal agent, Tsukamurella paurometabola C-924, was cultured in a 300 l bioreactor. Spray-dried formulations of this microorganism were prepared using sucrose. At an outlet temperature 628C, survival rates between 12 and 85% were reached with sucrose up to 10% (w/w). The stability study of the powders showed that the best storage condition was at 48C under vacuum. A new method for the calculation of cell death order for bacteria stored at low temperatures was developed. Powders stored under vacuum showed an Arrhenius behavior in relation to cell death kinetics. [less ▲]

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See detailProduction and down-stream processing of an extracellular lipase from the yeast Yarrowia lipolytica
Fickers, Patrick ULg; Ongena, MARC ULg; Destain, Jacqueline ULg et al

in Enzyme & Microbial Technology (2006), 38(6), 756-759

Lipase constitutes an interesting class of enzyme with many biotechnological applications. However, the development of a fruitful process must be set up to obtained a product compatible with the ... [more ▼]

Lipase constitutes an interesting class of enzyme with many biotechnological applications. However, the development of a fruitful process must be set up to obtained a product compatible with the industrial and commercial needs. Here, we report the development of such a process for the extracellular lipase secreted by the yeast Yarrowia lipolytica. The enzyme production, carried out in a 2000 L bioreactor, led to a lipase activity of approximately 1100 U mL(-1) after 53 h of fermentation. The post-culture treatment, consisting of a centrifugation, a filtration and an ultra-filtration steps, led to 15-fold volume reduction and a 8-fold increased of the lipase activity. Finally, addition of 12% of milk powder and 3% of gum arabic before spray-drying dehydration led to a stable powder with a lipolytic activity of 37,500 U g D.W.(-1). (c) 2005 Elsevier Inc. All rights reserved. [less ▲]

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See detailUtilization of methyloleate in production of microbial lipase
Destain, Jacqueline ULg; Fickers, Patrick ULg; Weekers, F. et al

in Applied Biochemistry and Biotechnology (2005), 121(Spring), 269-277

In this article, we report the development and optimization of an industrial culture medium for the production of extracellular lipase in the yeast Yarrowia lipolytica. Until now olive oil in combination ... [more ▼]

In this article, we report the development and optimization of an industrial culture medium for the production of extracellular lipase in the yeast Yarrowia lipolytica. Until now olive oil in combination with glucose was used as the carbon source and inducer for the production of lipase. Our results demonstrate that methyloleate, a cheap hydrophobic compound, could efficiently substitute olive oil as the inducer and carbon source for lipase production. A new process of lipase production was developed yielding a twofold increase in the level of production compared with the levels in previous reports. [less ▲]

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See detailMicrobial inoculation for improving the growth and health of micropropagated strawberry
Vestberg, Mauritz; Kukkonen, Sanna; Saari, K. et al

in Applied Soil Ecology (2004), 27(3), 243-258

Multimicrobial inoculation has been proposed as a way of protecting plants against environmental stress and increasing the sustainability of plant production. To study these possibilities in a ... [more ▼]

Multimicrobial inoculation has been proposed as a way of protecting plants against environmental stress and increasing the sustainability of plant production. To study these possibilities in a micropropagation system, microplants of strawberry, Fragaria x ananssa, were inoculated or left uninoculated with five microorganisms (Glomus mosseae BEG29, Bacillus subtilis M3, Trichoderma harzianum DB11, Pseudomonas fluorescens C7rl2 and Gliocladium catenulatum Gliomix(R)), used either singly or in dual mixtures in the presence or absence of the strawberry diseases crown rot (Phytophthora cactorum) and red stele (P. fragariae). Finnish light Sphagnum peat was used as the growth substrate in the experiments. Seven experiments were performed as two to three months pot experiments in greenhouses of research laboratories in Finland and Belgium and in a nursery in Finland. In most experiments, the inoculated microorganims were detected at sufficient densities four weeks after inoculation. Exceptions were T harzianum and G. mosseae which were detected at insufficient densities in several experiments. This might have been due to the biological and/or nutritional properties of the peat. None of the microorganisms or their mixtures caused significant growth-promoting effects in more than two experiments. Dual inoculation did not increase growth more than inoculation with single organisms. B. subtilis was the most promising growth promoting microorganism. Most of the microbial treatments decreased crown rot shoot symptoms as well as the numbers of oospores in the roots when the experiment was performed in autumn. In the summer experiment with conditions more favourable for strawberry growth, no disease control was obtained, but some of the microorganisms increased the severity of crown rot. No microbial treatment decreased shoot symptoms of red stele, but the degree of root necrosis was slightly decreased by B. subtilis and G. mosseae + G. catenulatum. The numbers of oospores of P. fragariae in strawberry roots were not decreased by any treatment, but several treatments increased them. Both growth promotion and disease control considered, the single microorganisms T harzianum, G. catenulatum and B. subtilis as well as the mixture T harzianum + G. catenulatum were the most promising treatments in this study. However, the great variation between experiments indicates that more studies are needed for optimization of the whole plant-substrate-microorganism system. The importance of microbial inoculation for ensuring subsequent growth in the field also needs to be studied. (C) 2004 Elsevier B.V. All rights reserved. [less ▲]

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See detailUtilization of methyloleate in the production of Yarrowia lipolytica.
Destain, Jacqueline ULg; Moreau, B.; Weekers, F. et al

Poster (2004, May)

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See detailAn approach to desication-tolerant bacteria in starter culture production
Weekers, F.; Jacques, Ph.; Mergeay, M. et al

in Engineering and manufacturing for biotechnology (2001)

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See detailDissemination of catabolic plasmids among desiccation-tolernt bacteria in soil microcosms.
Weekers, F.; Rodriguez, Ch.; Jacques, P. et al

Poster (2000, March 31)

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See detailDesiccation-tolerance : an advantage for the biotechnological applications of bacteria
Weekers, F.; Jacques, Ph.; Springael, D. et al

Poster (1999, July)

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See detailImproving The Catabolic Functions Of Desiccation-Tolerant Soil Bacteria
Weekers, F.; Jacques, P.; Springael, D. et al

in Applied Biochemistry and Biotechnology (1999), 77-9

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See detailImproving the catabolic functions in desiccation-tolerant soil bacteria in view of their use in bioaugmentation.
Weekers, F.; Jacques, Ph.; Springael, D. et al

Poster (1998, May 08)

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See detailImproving the catabolic functions in dessication-tolerant soil bacteria in view of their use in bioaugmentation
Weekers, F.; Jacques, Ph.; Springael, D. et al

Poster (1998, May)

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See detailEffect Of Drying On Bioremediation Bacteria Properties
Weekers, F.; Jacques, P.; Springael, D. et al

in Applied Biochemistry and Biotechnology (1998), 70-2

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See detailEffect of drying and long term conservation on bioremediation properties of Rhodococcus erythropolis
Weekers, F.; Jacques, P.; Springael, D. et al

in Mededelingen van de Faculteit Landbouwkundige en Toegepaste Biologische Wetenschappen (Rijksuniversiteit te Gent) (1997), 62/4b

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