Decolorization and partial mineralization of a polyazo dye by Bacillus firmus immobilized within tubular polymeric gel

The degradation of C.I. Direct red 80, a polyazo dye, was investigated using Bacillus firmus immobilized by entrapment in tubular polymeric gel. This bacterial strain was able to completely decolorize 50 mg/L of C.I. Direct red 80 under anoxic conditions within 12 h and also degrade the reaction intermediates (aromatic amines) during the subsequent 12 h under aerobic conditions. The tubular gel harboring the immobilized cells consisted of anoxic and aerobic regions integrated in a single unit which was ideal for azo dye degradation studies. Results obtained show that effective dye decolorization (97.8%), chemical oxygen demand (COD) reduction (91.7%) and total aromatic amines removal were obtained in 15 h with the immobilized bacterial cell system whereas for the free cells, a hydraulic residence time of 24 h was required for an equivalent performance in a sequential anoxic and aerobic process. Repeated-batch experiments indicate the immobilized cells could decolorize C.I. Direct red 80 and reduce medium COD in five successive batch runs with enhanced activity obtained after each consecutive run, thus suggesting its stability and potential for repeated use in wastewater treatment. UV–visible spectrophotometry and HPLC analysis were used to confirm the partial mineralization of the dye. Data from this study could be used as a reference for the development of effective industrial scale biotechnological process for the removal of dyes and their metabolites in textile wastewater

Optimization of the production of ß-carotene from molasses by Blakeslea trispora: A statistical approach

The effect of pretreatment of molasses, nitrogen sources, natural oils, fatty acids, anti-oxidant, precursors, and mixtures of the above substances on ß-carotene production by Blakeslea trispora in shake flask culture was investigated. Also, a central composite design was employed to determine the maximum ß-carotene concentration at optimum values for the process variables (linoleic acid, kerosene, antioxidant). The highest concentration of the carotenoid pigment was obtained in molasses solution treated with invertase. Corn steep liquor and yeast extract at concentrations of 5.0% and 0.5% (w/v), respectively, increased slightly the concentration of ß-carotene, while the natural oils, fatty acids, and precursors (except kerosene) did not improve the production of pigment when they were added separately to the medium. On the other hand, the mixture of linoleic acid, kerosene and antioxidant increased significantly the concentration of ß-carotene. The fit of the model was found to be good. Linoleic acid, kerosene and antioxidant had a strong linear effect on ß-carotene concentration. The concentration of ß-carotene was significantly affected by linoleic acid-antioxidant and kerosene-antioxidant interactions as well as by the negative quadratic effects of these variables. The interaction between linoleic acid-kerosene had no significant linear effect. Maximum ß-carotene concentration (790.0 mg dm-3) was obtained in culture grown in molasses solution supplemented with linoleic acid (30.74g dm-3), kerosene (27.79g dm-3) and antioxidant (10.22g dm-3). © 2002 Society of Chemical Industry

Optimization of the production of beta-carotene from molasses by Blakeslea trispora: a statistical approach

WOS: 000177228900011The effect of pretreatment of molasses, nitrogen sources, natural oils, fatty acids, antioxidant, precursors, and mixtures of the above substances on beta-carotene production by Blakeslea trispora in shake flask culture was investigated. Also, a central composite design was employed to determine the maximum beta-carotene concentration at optimum values for the process variables (linoleic acid, kerosene, antioxidant). The highest concentration of the carotenoid pigment was obtained in molasses solution treated with invertase. Corn steep liquor and yeast extract at concentrations of 5.0% and 0.5% (w/v), respectively, increased slightly the concentration of beta-carotene, while the natural oils, fatty acids, and precursors (except kerosene) did not improve the production of pigment when they were added separately to the medium. On the other hand, the mixture of linoleic acid, kerosene and antioxidant increased significantly the concentration of beta-carotene. The fit of the model was found to be good. Linoleic acid, kerosene and antioxidant had a strong linear effect on beta-carotene concentration. The concentration of beta-carotene was significantly affected by linoleic acid-antioxidant and kerosene-antioxidant interactions as well as by the negative quadratic effects of these variables. The interaction between linoleic acid-kerosene had no significant linear effect. Maximum P-carotene concentration (790.0 mg dm(-3)) was obtained in culture grown in molasses solution supplemented with linoleic acid (30.74 g dm(-3)), kerosene (27.79 g dm(-3)) and antioxidant (10.22 g dm(-3)). (C) 2002 Society of Chemical Industry

Effect of biomass pre-treatment and solvent extraction on β-carotene and lycopene recovery from Blakeslea trispora cells

The production of carotenoids from Blakeslea trispora cells in a synthetic medium has been reported, with the main products being β-carotene, lycopene, and γ-carotene. The effect of biomass pretreatment and solvent extraction on their selective recovery is reported here. Eight solvents of class II and III of the International Conference of Harmonization: ethanol, methanol, acetone, 2-propanol, pentane, hexane, ethyl acetate, and ethyl ether, and HPLC analysis were used for the evaluation of their selectivities towards the three main carotenoids with regard to different biomass pre-treatment. The average Cmax values (maximum concentration of caronoids in a specific solvent) were estimated to 16 mg/L with the five out of eight solvents investigated, whereas methanol, pentane, and hexane gave lower values of 10, 11, and 9 mg/L, respectively. The highest carotenoid yield was obtained in the case of wet biomass, where 44-56% is recovered with one solvent and three extractions and the rest is recovered only after subsequent treatment with acetone; thus, four extractions of 2.5 h are needed. Two extractions of 54 min are enough to recover carotenoids from dehydrated biomass, with the disadvantage of a high degree of degradation. Our results showed that, for maximum carotenoid recovery, ethyl ether, 2-propanol, and ethanol could be successfully used with biomass without prior treatment, whereas fractions enriched in β-carotene or lycopene can be obtained by extraction with the proper solvent, thus avoiding degradation due to time-consuming processes