Process control measures are of critical importance which guard against process instability of an... more Process control measures are of critical importance which guard against process instability of anaerobic digestion. By introducing perturbations in an up-flow anaerobic filter reactor fed with olive mill wastewaters (OMWs), reliable parameters that could suggest process imbalance were determined. The reactor was operated for a period of 10 days at 37 • C and at an HRT of 23 days corresponding to a loading rate of 0.75 g COD l -1 per day. Changing the organic loading rate (OLR), hydraulic retention time (HRT) and temperature lead to reactor performance failure. A decrease in biogas production and methane yield was observed together with an accumulation of VFAs such as acetate, propionate, butyrate, isobutyrate, and valerate. Significant concentrations of butyrate, isobutyrate, and valerate accumulated when acetate and propionate concentrations were very high. The pH at the bottom of the reactor, where substrates were introduced, showed a low pH value (acid), whereas no such change was observed at the top of the reactor. Valerate accumulation was shown to be the most toxic of all VFAs but an accumulation of propionate, butyrate and acetate also inhibited the functioning of the reactor.
Decolourization and detoxification of a textile industry effluent by laccase from Trametes trogii... more Decolourization and detoxification of a textile industry effluent by laccase from Trametes trogii in the presence and the absence of laccase mediators was investigated. Laccase alone was not able to decolourize the effluent efficiently even at the highest enzyme concentration tested: less than 10% decolourization was obtained with 9 U/mL reaction mixture. To enhance effluent decolourization, several potential laccase mediators were tested at concentrations ranging from 0 to 1 mM. Most potential mediators enhanced decolourization of the effluent, with 1-hydroxybenzotriazol (HBT) being the most effective. The effect of several physico-chemical parameters that could influence enzyme activity, such as pH, temperature and dye concentration was tested. Optimal decolourization occurred with 20% effluent at pH 5, a temperature of 50 • C, and in the presence of 1 mM HBT. The toxicities of crude, laccase-HBT treated and laccase-acetosyringone treated effluent were evaluated using the Microtox assay. Only laccase-acetosyringone treated effluent was not toxic; crude and laccase-HBT treated effluent retained toxicity.
Isolation and characterization of a plant growth‑promoting rhizobacterium strain MD36 that promotes barley seedlings and growth under heavy metals stress
A white-rot basidiomycete, isolated from decayed acacia wood (from Northwest of Tunisia) and iden... more A white-rot basidiomycete, isolated from decayed acacia wood (from Northwest of Tunisia) and identified as Trametes trogii, was selected in a broad plate screening because of its ability to degrade commercial dyes. In liquid cultures using a glucose-peptone medium, the sole ligninolytic activity detected was laccase. The highest laccase levels were obtained in presence of CuSO 4 as inducer (around 20000 U/l). Two isoenzymes, were purified using anion-exchange and size-exclusion chromatographies. Both isoenzymes are monomeric proteins, with M w around 62 kDa and isoelectric points of 4.3 and 4.5, showing similar stability at pH and temperature, optimum pH and substrate specificity. The highest oxidation rate was obtained at pH 2 and 2.5 for ABTS and DMP, respectively. They were stable up to 50 • C for 24 h and the stability was higher at alkaline pH. Activity increased by the addition of 10 mM Ni, Mo or Mn but it was not affected by Cd, Al, Li and Ca. Identical N-terminal sequences were determined in both laccases. The crude enzyme, as well as the purified laccase, was able to decolorize dyes from the textile industry.
Malachite green decolourization and detoxification by the laccase from a newly isolated strain of Trametes sp
International Biodeterioration & Biodegradation, Jul 1, 2009
The decolourization and detoxification of the triarylmethane dye Malachite green (MG) by laccase ... more The decolourization and detoxification of the triarylmethane dye Malachite green (MG) by laccase from Trametes sp. were investigated. The laccase decolorized efficiently the dye down to 97% of 50 mg L− 1 initial concentration of MG when only 0.1 U mL− 1 of laccase ...
Etude de la dégradation de compsés aromatiques par des bactéries anaérobies d'un digesteur méthanogène alimenté par des margines d'olives
Les etudes microbiologiques visant a mettre en evidence les populations microbiennes impliquees d... more Les etudes microbiologiques visant a mettre en evidence les populations microbiennes impliquees dans la degradation anaerobie de la matiere organique, et plus particulierement des composes aromatiques lors de la digestion anaerobies des margines d'huileries d'olives, ont ete jusqu'a ce jour limitees aux consortiums methanogenes. Le but de ce travail est d'isoler des nouvelles bacteries anaerobies et les caracteriser par la suite sur le plan physiologique, biochimique et phylogenetique. Cette etude est la premiere a decrire l'isolement de cultures pures de bacteries anaerobies strictes, capables de degrader les composes aromatiques avec (souche sr1) ou sans clivage du cycle aromatique (souches sr3 et sr12) a partir de ce type d'effluent agro-industriel. Nous avons isole egalement du meme environnement, deux bacteries anaerobies strictes qui degradent respectivement le xylane (clostridium xylanovorans) et les acides amines (clostridium peptidovorans). Les transformations des composes aromatiques par les souches sr3 (clostridium methoxybenzovorans) et sr12 (eubacterium aggregans) sont des reactions de demethoxylation. L'activite demethoxylase a ete mise en evidence dans des suspensions et dans les extraits cellulaires de ces deux souches. La souche sr3 a la particularite de demethoxyler une large gamme de composes aromatiques methoxyles, sans tenir compte du nombre ou de la position des groupements methoxyles sur le cycle aromatique, alors que la souche sr12 realise des demethoxylations specifiques des composes possedant des groupements methoxyles en position ortho sur le cycle aromatique, par rapport a un autre groupement methoxyle ou hydroxyle. Les composes hydroxyles obtenus apres demethoxylation ne sont pas utilises par les deux bacteries. La souche sr1 (sporobacterium olearium) qui appartient a un nouveau genre, a la capacite de demethoxyler les composes aromatiques trimethoxyles et de cliver le cycle aromatique des composes trihydroxyles formes. Nous avons egalement montre que l'ouverture du cycle aromatique est realisee via la voie du phloroglucinol. L'activite demethoxylase a ete mesuree dans les extraits cellulaires et dans des suspensions cellulaires. Cette demethoxylase n'est active qu'en presence d'atp et d'un milieu tres reduit. Les resultats de ce travail ont contribue a ameliorer les connaissances sur la population bacterienne impliquee dans la degradation des margines d'olive. Les nouvelles bacteries isolees pourraient etre utilisees pour ameliorer l'efficacite de la degradation des margines dans le digesteur ou dans le sol. L'o-demethylase presente chez les souches sr1, sr3 et sr12 pourrait etre utilisee dans l'industrie pour la biotransformation de composes aromatiques d'origine naturelle.
Two proteolytic bacteria Bacillus pumilus and Bacillus cereus were isolated from an aerobic tanne... more Two proteolytic bacteria Bacillus pumilus and Bacillus cereus were isolated from an aerobic tannery effluent treatment tank. Both strains were characterized and used for the treatment of unhairing wastewater during batch experiments. Chemical oxygen demand (COD), biomass production and protease activity were determined during the incubation period. The maximum COD removals were of 41 and 44% after 10 days incubation in B. cereus and B. pumilus, respectively. Optimum pH and temperature for protease and keratinase production by both strains were also investigated. Results showed that the optimum temperature and pH of protease production in the cultures of B. pumilus and B. cereus were of 30˚C and 9.0, respectively. Under these optimum conditions, proteolytic activities were 283.8 and 515.8 U/mL in the cultures of B. cereus and B. pumilus, respectively. Optimum keratinase production by cultures of both bacteria occurred at the same temperature and pH of the protease production.
Fifteen mesophilic bacteria with high C x cellulase activities were isolated and purified from a ... more Fifteen mesophilic bacteria with high C x cellulase activities were isolated and purified from a mixed-culture enriched from a flower stalks-vegetable waste co-composting system. A CMCase test showed that the enzyme activity of these isolates ranged from 7.9 to 28.0 U ml ؊1 . Although filter paper degrading capability was low in single culture, significant synergetic cellulose degradation were detected in four groups of mixed cultures, their degradation rates were 23.5%, 26.3%, 19.4% and 24.5%, respectively. Study of morphological and physiological characters of five predominant isolates which possess high CMCase and had positive effect on synergetic cellulose degradation in mixed culture system showed that two of them were closely related to Bacillus pasteurii and Bacillus cereus, whereas the rest belong to the genus Halobacillus, Aeromicrobium and Brevibacterium, respectively.
International Journal of Systematic and Evolutionary Microbiology, 2003
A facultatively denitrifying bacterium, strain K601 T , was isolated at 30 ˚C from a municipal se... more A facultatively denitrifying bacterium, strain K601 T , was isolated at 30 ˚C from a municipal sewage plant on cyclohexanol as sole carbon source and nitrate as electron acceptor. Under aerobic conditions this strain used acetate, fumarate, lactate, pyruvate, crotonate, indole, glucose, vanillate, 4-hydroxybenzoate, m-cresol, o-cresol and p-cresol. Under denitrifying conditions the strain used cyclohexanol, cyclohexanone, 1,3-cyclohexanedione, 2-cyclohexenone, 1,3-cyclohexanediol (cis and trans), monocarboxylic acids (C 2 -C 7 ), adipate, pimelate, 5-oxocaproate, citrate, 2-oxoglutarate, succinate, malate, crotonate, lactate, pyruvate and fumarate. Cells were short rods, 0 . 6 mm wide and 1-2 mm long, motile, non-spore-forming, Gram-negative, and catalase-and oxidase-positive. Strain K601 T used nitrate, nitrite and oxygen as electron acceptors, but not sulfate, sulfite or fumarate. The DNA G+C content of strain K601 T was 66 mol%. Phylogenetic analysis, based on 16S rDNA sequencing, showed that strain K601 T represents a separate lineage of the family Comamonadaceae in the b-subclass of Proteobacteria. Based on the high 16S rDNA sequence divergence and phenotypic characteristics, the name Alicycliphilus denitrificans gen. nov., sp. nov. is proposed for this strain. The type strain is K601 T (5DSM 14773 T 5CIP 107495 T ).
Remazol Brilliant Blue R decolourization by the laccase from Trametes trogii
Chemosphere, Aug 1, 2006
The decolourization of the recalcitrant dye RBBR by the culture filtrate of Trametes trogii and i... more The decolourization of the recalcitrant dye RBBR by the culture filtrate of Trametes trogii and its isolated laccase was investigated. Both filtrates from Cu-induced cultures as well as purified laccase decolourized the dye RBBR. The purified laccase decolourized the dye down to 97% of 100 mg l(-1) initial concentration of RBBR when only 0.2U ml(-1) of laccase was used in the reaction mixture. The effects of different physicochemical parameters were tested and optimal decolourization rates occurred at pH 5 and at a temperature of 50 degrees C. Decolourization of RBBR occurred in the presence of metal ions which could be found in textile industry effluents. Of all the metal ions tested, FeCl2 was the most inhibiting for the decolourization. HBT was shown to have no effect on the decolourization of RBBR at low concentration, while at a concentration of 5 mM it slightly inhibited decolourization. The presence of aromatic compounds was found to be inhibiting for the decolourization at a concentration of 10 mM, but not at 0.1 mM, while at 1 mM only ortho-diphenols were inhibiting. Probing the effect of methanol it was found that higher concentrations caused a decrease in the decolourization rate of RBBR. The effect of laccase inhibitors on the decolourization of RBBR was tested with L-cysteine, SDS and EDTA. It was demonstrated that L-cysteine was the most inhibiting substrate for the decolourization while SDS was only inhibiting at 10 mM concentration and ETDA was not inhibiting at all tested concentrations.
Journal of Chemical Technology & Biotechnology, Dec 1, 2009
BACKGROUND: This study concerns the assessment of laccase stability during textile industry efflu... more BACKGROUND: This study concerns the assessment of laccase stability during textile industry effluent treatment by laccase in the presence of a mediator RESULTS: The effects of 1-hydroxybenzotriazole (HBT) and textile wastewater on the stability of a crude laccase prepared from cultures of Trametes trogii during the process of textile industry effluent decolourization were determined. HBT was essential for decolourization of effluent by laccase. Decolourization efficiency decreased when effluent was repeatedly added to the reaction mixture, suggesting inhibition of laccase during the process. Stability of the laccase was not affected by different concentrations of effluent, but inactivation was proportional to HBT concentration. CONCLUSION: Experimental results showed that a redox mediator such as HBT was required for high decolourization rate of textile industry effluent; however free radicals generated from this compound inactivated the laccase used in the process.
Fast activated charcoal prepurification of <i>Fusarium solani</i> <i>β</i>-glucosidase for an efficient oleuropein bioconversion
Preparative Biochemistry & Biotechnology, Nov 3, 2016
Fungal β-glucosidases were extensively studied regarding their various potential biotechnology ap... more Fungal β-glucosidases were extensively studied regarding their various potential biotechnology applications. Here, we report the selection of Fusarium solani strain producing high yield of β-glucosidase activity. The effect of some factors on β-glucosidase production was studied including: Initial pH, medium composition, concentration of carbon and nitrogen sources, and particle size of raw substrates. The optimal enzyme production was obtained with 4 units of pH. The highest β-glucosidase activity was produced on 4% wheat bran (WB) as raw carbon sources, reaching 5 U/mL. A positive correlation between WB particle size and the β-glucosidase production level was settled. The last one was enhanced to 13.60 U/mL in the presence of 0.5% (w/v) of ammonium sulfate. Interestingly, the activated charcoal was used as an inexpensive reagent enabling a rapid and efficient purification prior step that improved the enzyme-specific activity. Eventually, F. solani β-glucosidase acts efficiently during the bioconversion process of oleuropein. Indeed, 82.5% of oleuropein was deglycosylated after 1 hr at 40°C. Altogether, our data showed that the β-glucosidase of F. solani has a potential application to convert oleuropein to ameliorate food quality.
Azo dyes decolourization by the laccase from<i>Trametes trogii</i>
Journal of The Textile Institute, Jan 7, 2016
Dye decolourizing potential of laccase obtained from the white rot fungus Trametes trogii was stu... more Dye decolourizing potential of laccase obtained from the white rot fungus Trametes trogii was studied for two reactive dyes; namely Reactive Black 5 (diazoic) and Reactive Violet 5 (monoazoic). The presence of a redox mediator as 1-hydroxybenzotriazole (HBT) was found to be essential for the decolourization of the said two dyes. The optimization of the decolourization process using experimental design was studied with three variables: dye (25, 50, 100 mg/L), enzyme (0.1; 0.5; 1 U/mL) and redox mediator (0.1; 0.5; 1 mM) concentrations. Results of this investigation revealed that the optimum concentrations of dye, enzyme and HBT for the degradation of the Reactive Black 5 (RB5) were 25 mg/L, 1U/mL and 1 mM, respectively, for a maximum decolourization about 93%. However, the optimum concentrations for Reactive Violet 5 (RV5) were found to be 25 mg/L, 0.5 U/mL and 0.5 mM, for a total removal of the dye. The apparent capacity of this laccase to decolourize azo dyes make it a suitable candidate for further applications in biobleaching and the treatment of textile effluents.
Application of response surface methodology to optimize decolourization of dyes by the laccase-mediator system
Journal of Environmental Management, Oct 1, 2012
Response surface methodology (RSM) was applied to optimize the decolourization of 3 dyes belongin... more Response surface methodology (RSM) was applied to optimize the decolourization of 3 dyes belonging to 3 dye families such as reactive black 5 (diazoic), indigo carmine (indigoid) and aniline blue (anthraquinonic). Crude laccase from Trametes trogii and the laccase-mediator 1-hydroxybenzotriazole (HBT) were used in this study. Box-Behnken design using RSM with six variables namely pH, temperature, enzyme concentration, HBT concentration, dye concentration and incubation time was used in this study to optimize significant correlation between the effects of these variables on the decolourization of reactive black 5 (RB5), indigo carmine (IC) and aniline blue (AB). The optimum of pH, temperature, laccase, HBT, RB5 and reaction time were 4.5, 0.5 U ml(-1), 0.5 mM, 100 mg ml(-1) and 150 min respectively, for a maximum decolourization of RB5 (about 92.92% ± 7.21). Whereas, the optimum decolourization conditions of both IC (99.76% ± 7.75) and AB (98.44% ± 10) were: pH 4.5, temperature of 45 °C, enzyme concentration of 0.1 U ml(-1) and 0.5 U ml(-1), HBT concentration of 0.9 mM and 0.5 mM, dye concentration of 60 mg l(-1) and reaction time of 150 and 90 min, respectively. The experimental values were in good agreement with the predicted ones and the models were highly significant, the correlation coefficient (R(2)) being 0.864, 0.663 and 0.776 for RB5, IC and AB, respectively. In addition, when the kinetic parameters for the three dyes decolourization were calculated according to Hannes-Wolf plot, the following values were obtained: Km of 268.4, 47.94 and 44.64 mg l(-1) then V(max) of 35.58, 10.43 and 9.23 mg l(-1) min for the RB5, IC and AB decolourizations by laccase, respectively.
Efficient bioethanol production from date palm (Phoenix dactylifera L.) sap by a newly isolated Saccharomyces cerevisiae X19G2
Process Biochemistry, 2021
Abstract In this research, 54 newly isolated strains of yeast from various microhabitats were scr... more Abstract In this research, 54 newly isolated strains of yeast from various microhabitats were screened in order to explore their potential for bioethanol production through bioconversion of date palm sap (DPS), as a renewable raw material. The highest ethanol concentration of 58.7 ± 0.23 g/L was achieved by the newly selected Saccharomyces cerevisiae strain X19G2 under anaerobic conditions. The effects of nitrogen supplementation, inoculum size and incubation temperature on bioethanol production from DPS by this strain were investigated. Bioethanol yield (0.43 ± 0.01 g/g consumed sugars) and ethanol productivity (1.49 ± 0.11 g/L·h) increased significantly when a mixture of ammonium sulfate and yeast extract (1:1) were used as nitrogen sources at 30 °C. Subsequently, batch and fed-batch (FB) fermentation were performed in a 2 L bioreactor. The highest ethanol yield was achieved in the FB experiment, reaching 0.48 g/g consumed sugars, which corresponded to over 90 % of the maximum theoretical yield. Based on these findings, the minimum bioethanol production potential using DPS was estimated to be approximately 11000 L per hectare of palm trees. This study indicated that DPS is a highly promising feedstock for bioethanol production by the yeast S. cerevisiae strain X19G2 with economic benefits for industrial scale production.
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