Uptake of reactive textile dyes by Aspergillus foetidus

An isolated fungus, Aspergillus foetidus was found to effectively decolorize media containing azo reactive dyes namely, Drimarene dyes. The extent of color removal was greater than 95% within 48 h of growth of the fungus. The entire color was found to be strongly bioadsorbed to the rapidly settling fungal biomass pellets without undergoing significant biotransformation. Our investigations reveal that the process of decolorization is concomitant with the exponential growth phase of the fungus and has requirement for a biodegradable substrate such as glucose. The fungus was also able to decolorize media containing mixture of dyes to an extent of 85% within 72 h of growth. Kinetic analyses of fungal decolorization indicate that the process is time dependent and follows first order kinetics with respect to initial concentration of dye. The rates of color uptake (k values) decrease to a significant extent with increasing initial concentrations of dye. The fungus was able to grow and decolorize media in the presence of 5 ppm of chromium and 1% sodium chloride. An alternate and cheaper carbon source such as starch supported the growth and decolorization process. These results suggest that dye uptake process mediated by A. foetidus has a potential for large-scale treatment of textile mill discharges.     

Kinetic modeling and equilibrium studies during cadmium biosorption by dead Sargassum sp. biomass

A basic investigation on the removal of cadmium(II) ions from aqueous solutions by dead Sargassum sp. was conducted in batch conditions. The influence of different experimental parameters; initial pH, shaking rate, sorption time, temperature and initial concentrations of cadmium ions on cadmium uptake was evaluated. Results indicated that cadmium uptake could be described by the Langmuir adsorption model, being the monolayer capacity negatively affected with an increase in temperature. Analogously, the adsorption equilibrium constant decreased with increasing temperature. The kinetics of the adsorption process followed a second-order adsorption, with characteristic constants increasing with increasing temperature. Activation energy of biosorption could be calculated as equal to 10 kcal/mol. The biomass used proved to be suitable for removal of cadmium from dilute solutions. Its maximum uptake capacity was 120 mg/g. It can be considered an optimal result when compared to conventional adsorbing materials. Thus Sargassum sp. has great potential for removing cadmium ions especially when concentration of this metal is low in samples such as wastewater streams.     

Kinetic modeling for the biosorption of copper by pretreated Aspergillus niger biomass

In this present work, a kinetic model for biosorption of copper was developed considering the possibility of different forms of functional groups being present on the surface of the biomass prepared from Aspergillus niger. Results showed that metal uptake by A. niger was a mass transfer driven process, requiring only 30min to achieve 70% adsorption efficiency. Copper sorption by A. niger was influenced by the biomass dose, initial metal ion concentration, and pH of the solution. The Langmuir and Freundlich adsorption isotherms were used to describe the behavior of the system at different pH. The retention capacity of the biomass was determined at pH 6.0 to be equal to 23.62mg/g of biomass. The pretreatment with formalin improved the uptake of metal ion.     

红树林混合菌群协同降解偶氮染料活性黑5脱色性能研究

通过对福建省龙海市海门岛红树林保护区的近海沉积物样品进行富集驯化,得到了能够协同降解偶氮染料活性黑5的混合菌群HMD9-Q7。经过生化试验和16S rDNA序列分析,鉴定该混合菌群主要由越南蔷薇菌（Rossellomorea vietnamensis）、转化异源物食烷菌（Alcanivorax xenomutans）和近海生微泡菌（Microbulbifer maritimus）组成。与单一菌株相比较,混合菌群具有显著的脱色效果,可能因其菌株之间存在着相互协同促进作用。该混合菌群对含20~100 mg/L浓度的活性黑5均产生脱色作用。混合菌群HMD9-Q7可以广泛利用外加碳源和氮源,如葡萄糖、硝酸铵、牛肉膏等;NaCl浓度在5~30 g/L范围内都可对活性黑5进行脱色;在pH 7和温度30℃条件下脱色率最高。在最优条件下,该混合菌群在60 h内对活性黑5的脱色率可达到85%~90%。该新型混合菌群主要通过生物降解途径来实现对活性黑5的脱色。随着降解反应的发生,活性黑5的最大吸收峰逐渐变小直至完全消失,降解产物吸收峰位于近紫外光区。     

A new approach to study the decolorization of complex reactive dye bath effluent by biosorption technique

This work focused on the development of a practical biosorbent for the decolorization of textile effluents. The fermentation waste, Corynebacterium glutamicum biomass, when decarboxylated and immobilized in polysulfone matrix performed well in decolorization of simulated reactive dye bath effluent comprised of four different reactive dyes and other auxiliary chemicals. The regeneration of polysulfone-immobilized C. glutamicum was successful with the aid of 0.01 M NaOH as the eluant, which enabled the biosorbent to maintain consistent decolorization efficiency for up to 25 cycles. An up-flow packed column loaded with polysulfone-immobilized biomass performed well in the continuous treatment of Remazol effluent. Samples collected after 14 h of column operation revealed almost zero color and TOC. The column was also able to decrease the TDS level from 55,840 to 33,480 mg/L. Column regeneration experiments revealed that the biosorbent was able to continuously treat Remazol effluent over ten cycles, with more than 90.6% decolorization efficiency.     

Computational identification and analysis of the key biosorbent characteristics for the biosorption process of reactive black 5 onto fungal biomass

The performances of nine biosorbents derived from dead fungal biomass were investigated for their ability to remove Reactive Black 5 from aqueous solution. The biosorption data for removal of Reactive Black 5 were readily modeled using the Langmuir adsorption isotherm. Kinetic analysis based on both pseudo-second-order and Weber-Morris models indicated intraparticle diffusion was the rate limiting step for biosorption of Reactive Black 5 on to the biosorbents. Sorption capacities of the biosorbents were not correlated with the initial biosorption rates. Sensitivity analysis of the factors affecting biosorption examined by an artificial neural network model showed that pH was the most important parameter, explaining 22%, followed by nitrogen content of biosorbents (16%), initial dye concentration (15%) and carbon content of biosorbents (10%). The biosorption capacities were not proportional to surface areas of the sorbents, but were instead influenced by their chemical element composition. The main functional groups contributing to dye sorption were amine, carboxylic, and alcohol moieties. The data further suggest that differences in carbon and nitrogen contents of biosorbents may be used as a selection index for identifying effective biosorbents from dead fungal biomass.     

Kinetic studies on the aggregation of Aspergillus niger conidia

Morphology has a crucial effect on productivity and the supply of substrate for cultures of filamentous fungi. However, cultivation parameters leading to the desired morphology are often chosen empirically as the mechanisms governing the processes involved are usually unknown. For coagulating microorganisms like Aspergillus niger the morphological development is considered to start with the aggregation of conidia right after inoculation. To elucidate the mechanism of this process, kinetic studies were carried out using an in-line particle size analyzer. Based on the data obtained from these experiments a model for conidial aggregation is proposed in this article. It consists of two separate aggregation steps. The first one takes place immediately after inoculation, but only leads to a small decrease of total particle concentration. Most suspended conidia aggregate after a second aggregation step triggered by germination and hyphal growth. Aggregation velocity of this second phase is linearly dependent on the particle growth rate.     

Lanthanum biosorption by a Pseudomonas sp.: equilibrium studies and chemical characterization

Lanthanum biosorption by a Pseudomonas sp. was characterized in terms of equilibrium metal loading, model fitting, kinetics, effect of solution pH, lanthanum–bacteria interaction mechanism and recovery of sorbed metal. Lanthanum sorption by the bacterium was rapid and optimum at pH 5.0 with equilibrium metal loading as high as 950 mg g⁻¹ biomass dry wt. Scatchard model and potentiometric titration suggested the presence of at least two types of metal-binding sites, corresponding to a strong and a weak binding affinity. The chemical nature of metal–microbe interaction has been elucidated employing FTIR spectroscopy, energy dispersive X-ray analysis (EDX) and X-ray diffraction analysis (XRD). FTIR spectroscopy and XRD analysis revealed strong involvement of cellular carboxyl and phosphate groups in lanthanum binding by the bacterial biomass. EDX and the elemental analysis of the sorption solution ascertained the binding of lanthanum with the bacterial biomass via displacement of cellular potassium and calcium. Transmission electron microscopy exhibited La accumulation throughout the bacterial cell with some granular deposits in cell periphery and in cytoplasm. XRD confirmed the presence of LaPO₄ crystals onto the bacterial biomass after La accumulation for a long period. A combined ion-exchange–complexation–microprecipitation mechanism could be involved in lanthanum accumulation by the biomass. Almost 98% of biomass-bound La could be recovered using CaCO₃ as the desorbing agent.     

Different bioreactor configurations for the decolourisation of the azo dye reactive black 5 by Geotrichum sp. CCMI 1019

Decolourisation of the azo dye Reactive Black 5 by Geotrichum sp. CCMI 1019 was studied using stirred tank reactors (STR) and two types of bubble columns (porous plate (PP) bubble column and aeration tube (AT) bubble column). For the bubble columns, the k_La increased with the gas fractional hold-up (ε_G) and the aeration rate. A linear relationship between ε_G and superficial gas velocity was obtained for all reactors. At same aeration rates, the PP bubble columns showed higher k_La and hold-up values than the AT bubble column. In the STRs, large and dense aggregates were formed which adhered to surfaces whereas bubble columns gave smaller and less compact pellets.

Manganese peroxidase and laccase were detected in the extracellular media in all reactors. However, laccase was only detected after the onset of decolourisation, suggesting that additional enzymes may be involved. Mn peroxidase activity was detected (about 46 U/ml) in both the STRs and AT bubble columns but higher values (110 U/ml) were obtained with the PP bubble columns.

Out of the three reactor systems studied, the AT bubble columns gave the most favourable results for Reactive Black 5 decolourisation. Rapid and complete colour removal was obtained throughout the visible spectrum. Bubble columns are simple in design as well as operation and may be useful for the bioremediation of textile wastewater.     

Different bioreactor configurations for the decolourisation of the azo dye reactive black 5 by Geotrichum sp. CCMI 1019

Decolourisation of the azo dye Reactive Black 5 by Geotrichum sp. CCMI 1019 was studied using stirred tank reactors (STR) and two types of bubble columns (porous plate (PP) bubble column and aeration tube (AT) bubble column). For the bubble columns, the k_La increased with the gas fractional hold-up (ε_G) and the aeration rate. A linear relationship between ε_G and superficial gas velocity was obtained for all reactors. At same aeration rates, the PP bubble columns showed higher k_La and hold-up values than the AT bubble column. In the STRs, large and dense aggregates were formed which adhered to surfaces whereas bubble columns gave smaller and less compact pellets.

Manganese peroxidase and laccase were detected in the extracellular media in all reactors. However, laccase was only detected after the onset of decolourisation, suggesting that additional enzymes may be involved. Mn peroxidase activity was detected (about 46 U/ml) in both the STRs and AT bubble columns but higher values (110 U/ml) were obtained with the PP bubble columns.

Out of the three reactor systems studied, the AT bubble columns gave the most favourable results for Reactive Black 5 decolourisation. Rapid and complete colour removal was obtained throughout the visible spectrum. Bubble columns are simple in design as well as operation and may be useful for the bioremediation of textile wastewater.     

Optimization of the growth parameters of Aspergillus foetidus

The batch production of gluconic acid in the presence of glucose, sucrose and molasses was investigated using free mycelia of Aspergillus foetidus NRRL 337 in shake flasks. Eight growth parameters were chosen as independent variables. The temperature, pH, substrate type and initial concentrations, inoculum percentage and shake rate directly affected the specific microorganism growth and gluconic acid production rates. The optimum temperature and initial pH values were found to be 33°C and five to six, respectively. The maximum specific growth and gluconic acid production rates were established as 57 g/dm³ of glucose, 75 g/dm³ of sucrose and 150 g/dm³ of molasses. The optimum values of the shake rate, inoculum percentage and initial ammonium nitrate concentration were determined as 100 1/min, 0.5% and 1.5 g/dm³, respectively. The maximum gluconic acid concentrations corresponding to these initial substrate concentrations were observed to be 8.3 g/dm³, 17.4 g/dm³ 37.0 g/dm³, respectively. The optimum specific microbial growth and gluconic acid production rates were found as 0.0145 1/h and 0.0375 g/g × h, respectively, for the fermentation conditions of S_Go = 57 g/dm³, T = 28°C, initial pH = 6.5, N = 84 1/min, A = 0.5 g/dm³ and I = 0.5%.     

Production of amylase by Aspergillus foetidus on rice flour medium and characterization of the enzyme

M ichelena , V.V. & C astillo , F.J. 1984. Production of amylase by Aspergillus foetidus on rice flour medium and characterization of the enzyme. Journal of Applied Bacteriology 56 , 395–407.
Aspergillus foetidus ATCC 10254 was selected from nine starch-utilizing microorganisms for its high amylolytic activity. This mould produced high levels of extracellular α-amylase in rice starch medium and degraded the available starch efficiently. Optimal conditions for enzyme production on 2.0% rice medium included 28C, initial pH of 6.6, and supplementations with 0.02% NaNO₂, 0.08% KH₂PO₄, and 0.08% corn steep liquor. Eleven-fold purification of the enzyme was obtained after ammonium sulphate and ethanol precipitations from spent medium. The molecular weight was estimated at 41 500. Optimum pH and temperature for enzyme activity were 5.0 and 45C. Michaelis-Menten constants were 1.14 mg/ml on amylopectin, 2.19 mg/ml on soluble starch and 7.65 mg/ml on amylose. Amylose produced substrate inhibition while glucose or maltose did not inhibit the enzyme. This α-amylase may be used as a saccharifying enzyme for rice starch. Aspergillus foetidus ATCC 10254 also presents a potential for treatment of starch-containing waste waters.     

Production of amylase by Aspergillus foetidus on rice flour medium and characterization of the enzyme

Aspergillus foetidus ATCC 10254 was selected from nine starch-utilizing microorganisms for its high amylolytic activity. This mould produced high levels of extracellular alpha-amylase in rice starch medium and degraded the available starch efficiently. Optimal conditions for enzyme production on 2.0% rice medium included 28 degrees C, initial pH of 6.6, and supplementations with 0.02% NaNO2, 0.08% KH2PO4, and 0.08% corn steep liquor. Eleven-fold purification of the enzyme was obtained after ammonium sulphate and ethanol precipitations from spent medium. The molecular weight was estimated at 41 500. Optimum pH and temperature for enzyme activity were 5.0 and 45 degrees C. Michaelis-Menten constants were 1.14 mg/ml on amylopectin, 2.19 mg/ml on soluble starch and 7.65 mg/ml on amylose. Amylose produced substrate inhibition while glucose or maltose did not inhibit the enzyme. This alpha-amylase may be used as a saccharifying enzyme for rice starch. Aspergillus foetidus ATCC 10254 also presents a potential for treatment of starch-containing waste waters.     

Kinetic studies on the specificity of chelate-iron uptake in Aspergillus.

Three strains of the fungus Aspergillus, Aspergillus quadricinctus (E. Yuill), A. fumigatus (Fresenius), and A. melleus (Yukawa), each producing different iron-chelating compounds during iron-deficient cultivation, were used for 55Fe3+ uptake measurements. Iron from chelates of the ferrichrome-type family was taken up by young mycelia of all strains tested, irrespective of the ferrichrome-type compound these strains predominantly produce in low-iron cultures. Ferrichrysin-producing strains, however, seem to favor ferrichrysin iron uptake, whereas ferrichrome, ferricrocin, and even ferrirubin showed similar iron transport properties in all of these strains. Compared to iron uptake from ferrichrome-type compounds (Km approximately 4 uM) iron uptake from fusigen revealed completely different kinetic values (Km approximately 50 to 80 muM). Iron from exogenous chelates, e.g., from coprogen produced by Neurospora crassa for ferrioxamine B produced by Streptomyces pilosus, can obviously not be taken up by Aspergillus, confirming the pronounced specificity of chelate-iron transport in fungi.     

Bioaccumulation and biosorption of chromium by Aspergillus niger MTCC 2594

Chromium toxicity is of prime concern due to chrome tanning processes in the leather sector. Chrome tanning results in the discharge of toxic levels of chromium causing pollution hazards. Chromium levels of Cr(III) and Cr(VI) were high above permissible limits in chrome samples after chrome tanning. The potential of Aspergillus niger MTCC 2594 to accumulate chromium as well as its biosorption capacity is investigated in this study. Bioaccumulation of Cr(III) and Cr(VI) in the spent chrome liquor has resulted in a 75-78% reduction of the initial Cr content in 24-36 h. A. niger biomass is found to be very effective in the biosorption of Cr(III) and Cr(VI) in spent chrome liquor. Maximum adsorption of 83% for biosorption of Cr(III) at 48 h and 79% of Cr(VI) at 36 h in spent chrome liquor is observed. The biosorption characteristics fit well with Langmuir and Freundlich isotherms and the adsorption parameters are evaluated. The biosorption of Cr also follows Lagergren kinetics. A. niger biomass is effectively used for the biosorption of chromium with 79-83% Cr removal in 36-48 h.     

Sequential batch culture studies for the decolorisation of reactive dye by Coriolus versicolor

The white rot fungus Coriolus versicolor could decolorise reactive dye Remazol Brilliant Violet to almost 90%. The fungal mycelia removed color as well as COD up to 95% and 75%, respectively, in a batch reactor. Decolorising activity was observed during the repeated reuse of the fungus. It was possible to substantially increase the dye decolorising activity of the fungus by carefully selecting the operational conditions such as media composition, age of fungus and nitrogen source. The fungal pellets could be used for eight cycles during the long term operation, where medium and dye was replenished at the end of each cycle and the fungus was recycled. Presence of a nitrogen source and nutrient content of media played an important role in sustaining the decolorisation activity of the fungus. The form of nitrogen source (e.g. peptone vs. urea) was also important to maintain the decolorising activity with peptone showing better decolorisation.