Maximization of uricase production in a column bioreactor through response surface methodology-based optimization.

Uricase (EC 1.7.3.3) is an oxidoreductase enzyme that is widely exploited for diagnostic and treatment purposes in medicine. This study focuses on producing recombinant uricase fromE. coliBL21 in a bubble column bioreactor (BCB) and finding the optimal conditions for maximum uricase activity. The three most effective variables on uricase activity were selected through the Plackett-Burman design from eight different variables and were further optimized by the central composite design of the response surface methodology (RSM). The selected variables included the inoculum size (%v/v), isopropylß-d-1-thiogalactopyranoside (IPTG) concentration (mM) and the initial pH of the culture medium. The activity of uricase, the final optical density at 600 nm wavelength (OD600) and the final pH were considered as the responses of this optimization and were modeled. As a result, activity of 5.84 U·ml-1and a final OD600of 3.42 were obtained at optimum conditions of 3% v/v inoculum size, an IPTG concentration of 0.54 mM and a pH of 6.0. By purifying the obtained enzyme using a Ni-NTA agarose affinity chromatography column, 165 ± 1.5 mg uricase was obtained from a 600 ml cell culture. The results of this study show that BCBs can be a highly effective option for large-scale uricase production.

Bioleaching of indium from spent light-emitting diode monitors and selective recovery followed by solvent extraction.

The spent light emitting diode (LED) monitors are one of the fastest-growing waste streams that could provide indium, an essential element for the industry. This study presents a comprehensive strategy for indium extraction from spent LED monitors, including bioleaching followed by solvent extraction, stripping, and precipitation. Effects of A. thiooxidans and A. ferrooxidans inoculum percentage in mixed culture, pulp density, and time on indium, aluminum, and strontium bioleaching were investigated. In this regard, at optimized inoculum percentages (1.5 and 0.5% (v/v) of A. ferrooxidans and A. thiooxidans, respectively) and pulp density (60 g/L) at initial pH of 2, approximately 100% indium recovery was obtained in 18 days. The solubilized indium in the bioleaching solution has been extracted by the organic solvent of 20% (v/v) D2EHPA in kerosene. Following extraction, the stripping step was carried out to recover indium rather than iron selectively. The effect of two-phase contact time and aqueous to organic phase volume ratio in the extraction step and the acid type and concentration in the stripping step on indium and iron recovery percentages have been evaluated. For indium extraction, the optimum ratio of aqueous to organic phase volume and time were determined as 1 and 30 min, respectively, recovering 91.5% of indium. Using 5 M sulfuric acid has also resulted in an efficient stripping process. Finally, sodium hydroxide performed indium precipitation and a final precipitate of 94% (w/w) indium was obtained.

Complete bioleaching of Co and Ni from spent batteries by a novel silver ion catalyzed process.

In the present work, bioleaching of two valuable metals of cobalt (Co) and nickel (Ni) from spent lithium-ion batteries (LIBs) of laptop by Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans through a novel adaptation procedure was investigated. Different bioleaching methods including A. ferrooxidans and A. thiooxidans spent medium, A. ferrooxidans one-step and two-step bioleaching were carried out. The effect of silver ion on the bioleaching of Co and Ni in these methods was evaluated. Moreover, a novel strain adaptation approach to the toxic solid content of the battery powder was chosen, which resulted in a very short adaptation time and bioleaching (2 days). Even though silver ion did not have a significant effect on the spent medium method, it had an increasing effect of 26% and 7%, for Co and Ni recovery, respectively, on two-step bioleaching with silver ion-adapted A. ferrooxidans, in gradual addition of the battery powder. The highest extraction results in the spent medium method were 45.2% and 71.5% for Co and Ni, respectively, and a very high extraction yield of 99.95% for these metals was achieved in a short time of only 3 days by two-step bioleaching with gradual addition of the solid content and in the presence of Ag+. KEY POINTS: • Mixed spent medium of acidophilic bacteria resulted in higher Ni and Co extraction. • Adaptation to Ag+ has enhanced the strain capability for Co and Ni extraction. • With Ag+ presence, Co and Ni extraction reached 99.95% in two-step bioleaching.

The Effectiveness of MOFs for the Removal of Pharmaceuticals from Aquatic Environments: A Review Focused on Antibiotics Removal.

There is an increasing level of various pollutants and their persistence in aquatic environments. The improper use of antibiotics and their inefficient metabolism in organisms result in their release into aquatic environments. Antibiotic abuse has led to hazardous effects on human health. Thereby, efficient removal of pharmaceuticals, particularly antibiotics, from wastewater and contaminated water bodies is greatly interested in international research communities. Metal-organic framework (MOF) materials, as a hybrid group of material containing metallic center and organic linkers, offer a porous structure that is highly efficient for removing different pollutants from contaminated water and wastewater streams. This article aims to review the recent advancement in using MOF-based adsorbents and catalysts for the removal of pharmaceuticals, especially antibiotics, from polluted water. Applying MOFs-based structures for removing antibiotics using photocatalytic removal and adsorptive removal techniques will be discussed and evaluated in this review paper. Various MOF-based materials such as functionalized MOFs, MOF-based composites, magnetic MOF-based composites, MOFs templated-metal oxide catalysts for removing pharmaceuticals, personal care products, and antibiotics from contaminated aqueous media are discussed. Furthermore, effective operational parameters on the adsorption, adsorption mechanisms, adsorption isotherms, and thermodynamic parameters are explained and discussed. Finally, in the concluding remarks, the challenges and future outlooks of using MOFs-based adsorbents and catalysts for removing antibiotics are summarized.