Debabrata Bera

Studies on Cr(VI), Pb(II) and Cu(II) adsorption-desorption using calcium alginate as biopolymer

Abstract The aim of this study was to investigate the Cr(VI), Pb(II) and Cu(II) biosorption potential of calcium alginate from aqueous solution and to screen a variety of desorbing agents, in order to access the efficiency of desorption and regeneration of the biosorbent in multiple sorption-desorption cycles. Calcium alginate beads was found to remove heavy metal ions efficiently from aqueous solution with selectivity in the order of Cr(VI)>Cu(II)> Pb(II).The biosorption of metal ions by calcium alginate beads decreased as the initial concentration of metal ions increased in the medium. The maximum heavy metal ions adsorbed was found to be 238,154,120 mg/g calcium alginate beads for Cr(VI), Cu(II) and Pb(II) respectively. The maximum uptake of metal ions was obtained at pH 2.0. Above pH 2.0, biosorption of metal ions by calcium alginate beads was found to be relatively constant for Pb(II) and Cu(II) ions, biosorption of Cr(VI) still increased upto pH 3.0 having 86% removal efficiency. At temperature 35°C, the biosorption of metal ions was found to be highest, with increase or decrease in temperature resulted in a decrease in the metal ions uptake capacity. The sorption data of all three metal ions conformed well the Langmuir isotherm. The bound metal ions could be eluted successfully using 0.1 M EDTA. The successive sorption-desorption studies employing calcium alginate beads indicated that the beads could be regenerated without showing the significant loss in adsorption capacity even after second cycle of adsorption -desorption. The results suggest that calcium alginate beads can be used as a biosorbent for an efficient removal of heavy metal ions from aqueous solution.

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 (M 1 16 ) isolated from tannery waste. Particularly, the effects of pH, temperature, metal ion concentration and contact time on removal of chromium were studied. About 40% chromium removal, was observed by growing cells of the selected strain at pH 6.5, temperature 30 o ±1 o C, inoculum size 3%, medium volume 50 ml/250 ml Erlenmeyer flask, and initial chromium concentration 50 ppm. Using resting 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 25-35 o C 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 suitable for 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.

Osmotic dehydration of Litchi using sucrose solution: effect of mass transfer.

Minimal processing techniques like osmodehydration have been finding a significant place in post-harvest practices of fruits and vegetables. Osmodehydration is adopted for extending shelf life of certain fruits. The overall effectiveness of the process is determined by process parameters affecting the mass transfer phenomena. In the present study this technique has been extensively applied on Litchi (Litchi chinensisSonn), a sub-tropical fruit. The process has been effectively modeled and the findings of the result suggest that sugar concentration and temperature significantly influence the process. Developed model could adequately predict the equilibrium point. The effective diffusion coefficients for water loss and solid gain obtained for the process ranged from 0.23 to 0.348×10-10 m2s-1 for water loss and from 0.0428 to 0.0721×10-10 m2s-1 respectively.

Enzymes- An Existing and Promising Tool of Food Processing Industry

BACKGROUND The enzyme catalyzed process technology has enormous potential in the food sectors as indicated by the recent patents studies. It is very well realized that the adaptation of the enzyme catalyzed process depends on the availability of enzyme in affordable prices. OBJECTIVE Enzymes may be used in different food sectors like dairy, fruits & vegetable processing, meat tenderization, fish processing, brewery and wine making, starch processing and many other. Commercially only a small number of enzymes are used because of several factors including instability of enzymes during processing and high cost. METHOD More and more enzymes for food technology are now derived from specially selected or genetically modified microorganisms grown in industrial scale fermenters. Enzymes with microbial source have commercial advantages of using microbial fermentation rather than animal and plant extraction to produce food enzymes. CONCLUSION At present only a relatively small number of enzymes are used commercially in food processing. But the number is increasing day by day and field of application will be expanded more and more in near future. The purpose of this review is to describe the practical applications of enzymes in the field of food processing.

Mycosynthesized Nanoparticles: Role in Food Processing Industries

Green synthesis of nanoparticles (NPs) is an evolving branch of nanotechnology. The use of fungi for the synthesis of NPs is referred to as mycosynthesis of metal NPs. Fungal endophytes have been recognized as important sources of a variety of structurally novel active secondary metabolites with anticancer, antimicrobial, and other biological activities. This mode of synthesis of metal nanoparticles is gaining more importance owing to its simplicity, rapid rate of synthesis of NP of attractive and diverse morphologies, and elimination of elaborate maintenance of cell cultures and eco-friendliness. Presently, the researchers are looking into the development of cost-effective procedures for producing reproducible, stable, and biocompatible metal NPs using fungal cultures. The present chapter is an exhaustive overview that assesses the role of fungi in the synthesis of nanoparticles, the mechanism involved in the synthesis, the effect of different factors on the reduction of metal ions in developing low-cost techniques for the synthesis, and recovery of nanoparticles. Finally, the application of nanoparticles in food processing industries, i.e., antimicrobial mechanisms, etc., has also been discussed.