Chemical Research Papers - Academia.edu (original) (raw)

In this work, a brewer’s yeast strain was used to remove heavy metals from a synthetic effluent. The solid–liquid separation process was carried out using the flocculation ability of the strain. The yeast strain was able to sediment in... more

In this work, a brewer’s yeast strain was used to remove heavy metals from a synthetic effluent. The solid–liquid separation process was carried out using the flocculation ability of the strain. The yeast strain was able to sediment in the presence of Cu2+, Ni2+, Zn2+, Cd2+ and Cr3+, which evidences that the flocculation can be used as a cheap and natural separation process for an enlarged range of industrial effluents. For a biomass concentration higher than 0.5 g/l, more than 95% of the cells were settled after 5 min; this fact shows that the auto-aggregation of yeast biomass is a rapid and efficient separation process. Cells inactivated at 45 °C maintain the sedimentation characteristics, while cells inactivated at 80 °C lose partially (40%) the flocculation.The passage of metal-loaded effluent through a series of sequential batches allowed, after the second batch, the reduction of the Ni2+concentration in solution for values below the legal limit of discharge of wastewater in natural waters (2 mg/l); this procedure corresponds to a removal of 91%. A subsequent batch had a marginal effect on Ni2+ removal (96%).Together, the results obtained suggest that the use of brewing flocculent biomass looks a promising alternative in the bioremediation of metal-loaded industrial effluents since the removal of the heavy metals and cell separation are simultaneously achieved.

An expression system based on Escherichia coli and the T5 promoter allowed the overproduction of a his-tagged rhamnulose-1-phosphate aldolase (RhuA; EC 4.1.2.19), an enzyme with applications in the production of deoxyazasugars and... more

An expression system based on Escherichia coli and the T5 promoter allowed the overproduction of a his-tagged rhamnulose-1-phosphate aldolase (RhuA; EC 4.1.2.19), an enzyme with applications in the production of deoxyazasugars and deoxysugars compounds. Shake flask and bioreactor cultivation with E coli M15 (pQErham) were performed under different media and inducing conditions for RhuA expression. A Defined Medium (DM) with glucose as carbon source gave a high volumetric and enzyme productivity (3460 AU dm−3 and 288 AU dm−3 h−1 respectively) compared with Luria–Bertoni (LB) medium (2292 AU dm− 3 and 255 AU dm−3 h−1). The minimum quantity of (isopropyl-β-D-thiogalactoside) IPTG for optimal induction was estimated in 18–20 µmol IPTG gDCW−1. The highest volumetric production of RhuA (8333 AU dm−3) was obtained when IPTG was added in the late log-phase. No significant differences were found in specific RhuA activity for induction temperatures of 30 and 37 °C. An effective two-step purification process comprising affinity chromatography and gel permeation has been developed (overall recovery 66.5%). These studies provide the basis for the further development of an integrated process for recombinant RhuA production suitable for biotransformation applications. Copyright © 2003 Society of Chemical Industry

One-pot synthesis of the title compound (1) is achieved from tert-butyl allyl ether (2) and the N'(4-methylbenzenesulfonyl) (4-methylphenoxy) imidoyl azide (3) in high yield. The energy barrier of nitrogen interconversion of the title... more

One-pot synthesis of the title compound (1) is achieved from tert-butyl allyl ether (2) and the N'(4-methylbenzenesulfonyl) (4-methylphenoxy) imidoyl azide (3) in high yield. The energy barrier of nitrogen interconversion of the title compound (1) was investigated by dynamic NMR. The free energies of activation (A G‡) are 11.11 kcal/mol ( Tc = 238 K) and 11.30 kcal/mol ( Tc = 242 K) in acetone-d6 and chloroform-d, respectively, and are attributed to nitrogen inversion of aziridine ring nitrogen.

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