Biosorption of Cr(VI) by free and immobilized Pediastrum boryanum biomass: equilibrium, kinetic, and thermodynamic studies

15th International Symposium on Toxicity Assessment (ISTA) -- JUL 03-08, 2011 -- City Univ Hong Kong, Hong Kong, PEOPLES R CHINAWOS: 000306790200053PubMed ID: 22374187The biosorption of Cr(VI) from aqueous solution has been studied using free and immobilized Pediastrum boryanum cells in a batch system. The algal cells were immobilized in alginate and alginate-gelatin beads via entrapment, and their algal cell free counterparts were used as control systems during biosorption studies of Cr(VI). The changes in the functional groups of the biosorbents formulations were confirmed by Fourier transform infrared spectra. The effect of pH, equilibrium time, initial concentration of metal ions, and temperature on the biosorption of Cr(VI) ion was investigated. The maximum Cr(VI) biosorption capacities were found to be 17.3, 6.73, 14.0, 23.8, and 29.6 mg/g for the free algal cells, and alginate, alginate-gelatin, alginate-cells, and alginate-gelatin-cells at pH 2.0, which are corresponding to an initial Cr(VI) concentration of 400 mg/L. The biosorption of Cr(VI) on all the tested biosorbents (P. boryanum cells, alginate, alginate-gelatin, and alginate-cells, alginate-gelatin-cells) followed Langmuir adsorption isotherm model. The thermodynamic studies indicated that the biosorption process was spontaneous and endothermic in nature under studied conditions. For all the tested biosorbents, biosorption kinetic was best described by the pseudo-second-order model.PROCORE-France/Hong Kong Joint Res Scheme, Croucher Fdn, KC Wong Educ Fd

Long-term storage of a number of microorganism species using different cryoprotectants

This study aims to generate a microalgae culture collection, and ensure the long-term survival of this collection by prolonging the period when the isolated microalgae and other microorganism cultures can be preserved. The microalgae cultures included four microalgae species (Chlorella vulgaris Beyerinck [Beijerinck], Klebsormidium subtile (Kützing) Mikhailyuk, Glaser, Holzinger & Karsten, Microcoleus autumnalis (Gomont) Strunecky, Komárek & J.R. Johansen and Synechococcus bigranulatus Skuja), two bacteria species (Staphylococcus aureus and Escherichia coli) and two fungi species (Aspergillus Niger and Pénicillium sp.). The study applied a cryopreservation protocol at -80°C directly to each of the species. The cryoprotective agents used in the study were dimethyl sulfoxide (DMSO), glycerol and skimmed milk at a final concentration of 5% for the microalgae in addition to an application without any cryoprotectant at all. The cryoprotectant agents used for this procedure were 15% final glycerol concentration for the bacteria and 10% skimmed milk for the fungi. After six months, the strains of C. vulgaris (93%), S. bigranulatus (83%) and M autumnalis (80%) showed higher viability rates in glycerol, while the strain of K. subtile (93%) showed higher viability rates in skimmed milk. The recovery ratio of E. coli, S. aureus, A. Niger and Pénicillium sp. were found to be 5.10, 3.23, 1.98 and 2.67 log CFU/ml, respectively. © by PSP

Characterization of silver nanoparticle produced by Pseudopediastrum boryanum (Turpin) E. Hegewald and its antimicrobial effects on some pathogens

WOS: 000489337200054The aim of this research was to investigate the antimicrobial activity of silver nanoparticles (AgNPs) biosynthesized by Pseudopediastrum boryanum (Turpin) E. on several human pathogen microorganisms. AgNPs were isolated from P. boryanum. The biosynthesis of AgNPs was carried out using a UV-visible spectrophotometer and FTIR spectroscopy analysis. The antimicrobial activity of AgNPs was evaluated against various pathogen microorganisms using the well diffusion method, and MIC was estimated by qualitative experimentation by microbroth dilution method. The antimicrobial activities of AgNPs at three different concentrations (1 mM, 2 mM and 3 mM) were measured using the diameter of the inhibition zone (DIZ) of the pathogen microorganisms. AgNPs demonstrated various antimicrobial effects on pathogen microorganisms at different concentrations. The highest antimicrobial activity was determined in Proteus vulgaris [DIZ = 30 +/- 0.2 mm (2 and 3 mM)], followed by Candida parapsilosis (M006) [DIZ = 25 +/- 0.1 mm (3 mM)], followed by Pseudomonas aeruginosa [DIZ = 20 mm (2 and 3 mM)] and Candida parapsilosis (M006) [DIZ = 20 mm (1 and 2 mM)]. The lowest antibacterial effects of AgNPs were observed on Aeromonas hydrophila [DIZ = 5 +/- 0.1 mm (3 mM)], Staphylococcus epidermidis [DIZ = 5 +/- 0.1 mm (1 mM)], Candida parapsilosis [DIZ = 5 +/- 0.1 mm (2 mM)] and Candida albicans [DIZ = 5 +/- 0.1 mm (3 mM)]. Gram-negative bacteria Proteus mirabilis, Enterobacter aerogenes, Salmonella typhimurium, Shigella dysenteriae, Escherichia coli and Serratia marcescens and Gram-positive bacteria Listeria monocytogenes and Enterococcus faecalis exhibited no zone of inhibition. Our results confirm that AgNPs biosynthesized from P. boryanum may be used as an effective antimicrobial agent against human pathogens