BIOSORPTION OF CHROMIUM (VI) BY A MUTATED STRAIN OF Bacillus cereus M116

The removal of chromium, a highly toxic metal causing environmental pollution from dilute aqueous solution, was studied in the present work using growing and washed cells of a mutant strain of Bacillus cereus (M116) isolated from tannery waste. Particularly, the effects of pH, temperature, metal ion concentration and contact time on removal of chromium werestudied. About 40% chromium removal, was observed by growing cells of the selected strain at pH 6.5, temperature 30o±1oC, inoculum size 3%, medium volume 50 ml/250 ml Erlenmeyer flask, and initial chromium concentration 50 ppm. Usingresting cells 98.02% and 78.34% chromium removal was possible with initial chromium concentration of 25 and 50 ppm, respectively, at pH 3.0, temperature 25-35oC and 2.73 g/L biomass concentration. It was found that the overall adsorption process was best described by pseudo-second order kinetics. Freundlich and Langmuir adsorption models were found suitablefor describing the short-term biosorption of chromium (VI). IR spectral analysis of the biomass was carried out to find out the functional groups responsible for chromium (VI) biosorption

Biosorption of Cu(II) by immobilized biomass of Bacillus cereus M¹₁₆ from aqueous solution

629-634Biosorption of Cu(II) ion from aqueous solution was studied using Bacillus cereus M1 16 immobilized in calcium alginate and agar agar gel in batch mode. Uptake of metal was very fast initially and equilibrium was attained within 240 min. Sorption data conformed well to both Freundlich and Langmuir isotherm model. Highest Cu(II) uptake (87.32%) by selected biomass (3.09 g/l, dry wt) immobilized in 3% calcium alginate occurred at 30°C, 120 rpm when initial copper concentration was 50 mg/l

Production of lipase in a fermentor using a mutant strain of <i>Corynebacterium </i>species: Its partial purification and immobilization

202-207Extracellular Corynebacterium lipase was produced using a 2.5 L Chemap ferrnentor using 1300 ml fermentation medium at temperature 33°C, agitator speed 50 rpm, aeration rate 1 VVM having KLa 16.21hr-l. Crude lipase was purified by salting out method followed by dialysis and immobilized using calcium alginate gel matrix followed by glutaraldehyde cross linking Purification process increased specific activity of enzyme from 2.76 to 114.7 IU/mg. Activity of immobilized enzyme was 107.31IU/mg. Optimum temperature for purified and immobilized enzyme activity were 65° and 50°C respectively. Optimum pH was 8.0 in both the cases, Km and Vmax value for purified lipase were 111.1 μmol/min and 14.7% respectively. Ca2+ (5 mM) was found to be stimulator for enzyme activity. Immobilized lipase retained 68.18% of the original activity when stored for 40 days

Purification and immobilization of an <i style="">Aspergillus terreus</i> xylanase: Use of continuous fluidized bed column reactor

163-168An Aspergillus terreus extracellular xylanase produced by solid state fermentation was purified and characterized. A 6.4 fold purified xylanase was obtained by ammonium sulphate (in 30-40% saturation) precipitation followed by dialysis. Molecular weight of the xylanase was 67.0 kDa as estimated by SDS-PAGE. The enzyme was immobilized in barium alginate gel. Both free and immobilized enzyme showed maximum activity at pH 5.5 and 60°C (8.0 IU/mg & 5.25 IU/mg, respectively) and were most stable at pH 5.5 and thermostable up to 55°C. Co2+ stimulated free enzyme activity (9.27 IU/mg) and Mg2+ stimulated activity of immobilized enzyme (5.54 IU/mg). Vmax and Km for free and immobilized xylanases were 6.6 mole/mg/min, 0.75% and 1.25 mole/mg/min, 0.625%, respectively. 23.4% conversion of substrate (0.1% birchwood xylan) was possible in 7 h using a continuous fluidized bed column reactor under the following conditions: bed height 16 cm, temperature 40°C, and dilution rate 4.09 h-1

Study of phenol biodegradation by an indigenous mixed consortium of bacteria

227-233The potential of a mixed consortium of bacteria has been isolated from the soil of the East Calcutta Wetlands, the major waste treatment and recovery site of Kolkata, for degradation of phenol, a representative of phenolic compounds has been investigated. The mixed culture is first acclimatized to higher phenol concentrations in the mineral salt (MS) media and then its behaviour for degradation of phenol has been studied. The mixed culture successfully degrades phenol till 200 mg/L and then undergoes substrate inhibition at 400 mg/L. At still higher phenol concentration of 800 mg/L this mixed culture shows an anomalous behaviour by degrading phenol at a higher rate as compared to lesser phenol concentration by overcoming the substrate inhibition effect. The bacterial growth curve also follows the same pattern which indicates the observation. By the kinetic modeling of the substrate inhibition biokinetic constants are calculated which conform to experimentally observed values. For the phenol degradation and growth studies, Haldane model and Yano and Koga model are found to be the most efficient kinetic models respectively

Continuous removal of chromium from tannery wastewater using activated sludge process—Determination of kinetic parameters

32-36The activated sludge has been acclimatized with chromium (VI) ions from 5 mg/L to 20 mg/L. It is observed that the chromium removal percentage, COD removal and mixed liquor suspended solid (MLSS) decrease with the increase in dilution rate. Maximum food to microorganisms ratio (F/M) is found to be 0.19. When initial metal ion concentration increases from 5 mg/L to 20 mg/L, the chromium removal decreases from 95.58% to 63.85% (dilution rate 0.041h-1)

Isolation and identification of alkaline thermostable lipase producing microorganism, cultural conditions, nutritional requirements and some properties of crude enzyme

818-824A bacterial strain isolated from spoiled coconut and identified as Corynebacterium species was found capable of producing alkaline thermostable extracellular lipase. Lipase activity of the strain was increased 2.3 -fold by mutagenic technique using a chemical mutagen NTG (N-methyl-N/-nitro-N-nitrosoguanidine). Optimum temperature, time and pH for enzyme substrate reaction were found to be 60°C, 10 min and 8.0 respectively. Common surfactants have no or very little inhibitory effects on the activity of enzyme, whereas bile salts are inhibitory. The maximum lipase production was achieved at 33°C, pH 8.0 on 72 hr of fermentation. Optimum age and volume of inoculum were 24 hr and 2% respectively. Superior carbon and nitrogen sources for lipase production were starch (2%), ammonium chloride (nitrogen level 0.100g/100ml) and peptone (nitrogen level 0.320g / 100 ml) in combination respectively. The optimum C/N ratio was found to be 4.76 :1. Glycerol and oil when used as sole sources of carbon low levels of enzyme was produced. The maximum enzyme activity obtained was 28.0 IU/ml

Immobilization of β-galactosidase from <i style="mso-bidi-font-style:normal">Enterobacter cloacae</i>:<i style="mso-bidi-font-style:normal"> </i>Characterization and its use in the continuous production of low lactose milk

523-530Immobilization of β-galactosidase from Enterobacter cloacae was carried out using barium alginate gel (2%). Maximum activity (39.33 IU/mg) of the immobilized enzyme was observed at pH 9.0 and temperature 50oC. The immobilized enzyme was found to be stable in pH range 8.5-9.5 and temperature range 4-50oC. The enzyme activity was stimulated by only Ca2+, Mn2+ and EDTA at 0.5 mM concentration. Immobilized enzyme was used for the preparation of low lactose milk in a jacketed packed bed column reactor (height 150 mm, internal diam 22 mm). At 89 mm bed height and dilution rate 4.30 h-1, 61.25 and 46.67% conversion of lactose were observed using lactose (4%) solution and milk (lactose content 4.2%) as substrate, respectively

Extracellular laccase from <i>Pleurotus sajor-caju</i>: Fermentative conditions and influence of nitrogenous sources

230-235The present paper describes the production of extracellular laccase, a lignolytic enzyme, through fermentation of molasses salt medium (MSM) by Pleurotus sajor-caju, an edible mushroom, under stationary condition. MSM supported better growth of the fungus as well as laccase production compared to the other two media used, viz., whey and potato dextrose broth. Both laccase and edible biomass production attained the maximum value after 15 d of fermentation and depended on the fungal species, physico-chemical conditions of fermentation, and nature and composition of the fermentation media. Increase in laccase and biomass production to the extent of 9.1-48.0% and 4.2-76.4%, respectively was achieved by supplementing the medium with different organic and inorganic nitrogen sources. The positive effects of supplementation of MSM with nitrogen sources on enzyme production resulted from higher biomass yield. About 2.5-fold increase in laccase activity was obtained in comparison with the non-optimized medium. The results establish the importance of P. sajor-caju for the production of lignolytic extracellular enzyme, laccase