Corynebacterium strain SH09 separated from a silver mine was used for biosorption and bioreduction of diamine silver complex. The biosorption of the diamine silver complex was better than that of silver ions and the maximum of the former was about 350 (mg Ag) (g dried biomass) −1 . After dried cells of SH09 were resuspended in the aqueous solution of diamine silver complex in the dark at 60• C for more than 72 h, transmission electron microscopy (TEM) observations showed that a large quantity of black particles whose diameter ranged from 10 to 15 nm were formed on the cell wall. The particles were identified as being silver nanoparticles by X-ray diffraction (XRD) and UV-vis spectroscopy. Under the same conditions, no bioreduction of silver nitrate was found. According to IR spectra, some functional groups, such as the amide of the proteins, were involved in the processes of biosorption and bioreduction.

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A novel high-throughput strategy was developed to determine the calcium precipitation activity (CPA) of mineralization bacteria used for self-healing of concrete cracks. A bacterial strain designated as H4 with the highest CPA of 94.8 % was screened and identified as a Bacillus species based on 16S rDNA sequence and phylogenetic tree analysis. Furthermore, the effects of certain influential factors on the microbial calcium precipitation process of H4 were evaluated. The results showed that lactate and nitrate are the best carbon and nitrogen sources, with optimal concentrations of approximately 25 and 18 mM, respectively. The H4 strain is able to maintain a high CPA in the pH range of 9.5-11.0, and a suitable initial spore concentration is 4.0 × 10(7) spores/ml. Moreover, an ambient Ca(2+) concentration greater than 60 mM resulted in a serious adverse impact not only on the CPA but also on the growth of H4, suggesting that the maintenance of the Ca(2+) concentration at a low level is necessary for microbial self-healing of concrete cracks.

Genetically engineered E. coli, which express both a Hg2+ transport system and metallothionein, were tested for their ability to remove mercury from wastewater. The wastewater contained more than ten different ions, including 2.58 mg/l mercury, and its pH was 9.6. Mercury uptake was faster from the wastewater than from distilled water, probably because of the higher ionic strength, as the high pH had little effect on mercury accumulation. EDTA also stimulated mercury uptake rather than inhibiting it. A hollow-fiber bioreactor was used to retain induced cells for continuous mercury uptake. The cells removed more than 99% of the mercury in the wastewater and the final amount of mercury accumulated was 26.8 mg/g cell dry weight, while none of the other ions were removed from the water. These results indicated that the induced cells had a high affinity and specificity for mercury.

A strategy to supply molecular oxygen for microbial calcium precipitation was developed for the first time. Firstly, a controlled oxygen-releasing tablet (ORT) containing CaO and lactic acid with a suitable ratio of 9:1 was developed. It can provide a stable oxygen supply and maintain pH in the range of 9.5-11.0 for 45 days while contacting with water. In the presence of oxygen, a self-healing bacterium H4 spores germinated more effectively and maintained high metabolic activity. Furthermore, H4 vegetative cells induced 50 % more calcium precipitation than that obtained without oxygen supply. Finally, a binary self-healing system containing bacterial spores and ORT was established. The calcium precipitation experiments showed that H4 in the binary self-healing system precipitated 27.5 mM calcium with oxygen supply after 32 days and dissolved oxygen (DO) concentration of the solution decreased from 15 to 4 mg l, while only 6.9 mM calcium precipitation was obtained without oxygen supply. This work can disclose the effect of oxygen on microbial calcium precipitation and further lay a foundation for the establishment of ternary self-healing system containing bacteria, ORT, and nutrients, which will be promising for the self-healing of cracks deep inside the concrete structure.

HighlightsIsomaltases (Imap) preferably cleave α-(1,6) bonds, yet show clear substrate ambiguity.With only 3 different aa, Ima3p activities and thermostability diverge from Ima2p.The most distant protein, Ima5p, is extremely sensitive to temperature.Ima5p nevertheless displays most of the same catalytic properties as Ima1p and Ima2p.Ima5p challenges previous conclusions about specific aa needs for the active site.

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