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The present study focuses on an efficient Cr(VI)-reducing bacterial strain (CR-2) isolated from an abandoned chromate plant in Qinghai Province, China. CR-2 was confirmed as Lysinibacillus cavernae using 16S rRNA gene sequencing. CR-2 could survive at 500 mg L−1 Cr(VI) and effectively reduce Cr(VI) at concentrations of <50 mg L−1, a pH of 5–9, a temperature of 20–40 °C, and a salinity of 5–15 g L−1. According to the Box–Behnken experimental design, the maximum Cr(VI) removal efficiency by L. cavernae CR-2 was 76.21% under optimum conditions, which comprised a pH of 6.68, a temperature of 28.90 °C, and a salinity of 9.85 g L−1. With regard to Cr(VI) reduction mediated by L. cavernae CR-2, enhancement in efficiency was observed in the presence of Cu2+ and Ca2+, while significant inhibition in the reduction capacity occurred upon exposure to Mg2+, Ba2+, Ni2+, Pb2+, or Cd2+. Moreover, L. cavernae CR-2 tends to use glucose as an electron donor for the reduction of Cr(VI). Results of cell fraction separation and degeneration indicated that the Cr(VI) removal was primarily due to the reduction of Cr(VI) via chromium reductase in the cytoplasm. In addition, bioanalysis of L. cavernae CR-2 by SEM-EDS and TEM-EDS suggested that Cr was distributed both on the surface and in the cell cytoplasm. FT-IR analyses established that multiple functional groups (hydroxyl, carbonyl, amide, amino, and aldehyde groups) participated in the Cr(VI) biosorption on the cell surface. XPS and HPLC also showed that the Cr(III) end-products could be present as Cr(III) hydroxides or as organic–Cr(III) complexes. This study yields insights into the Cr(VI) bioreduction mechanism of L. cavernae CR-2. [ABSTRACT FROM AUTHOR]

Bioreduction of Cr(VI) is an efficient and environmentally friendly remediation method. In this study, we isolated and screened a strain of Penicillium rubens LR6 that could tolerate to Cr(VI) and investigated its mechanism for removing Cr(VI). We ascertained the factors affecting the ability of strain to remove Cr(VI) through batch experiments. The results revealed that the strain could effectively remove high concentrations of Cr(VI) and exhibit excellent removal efficiency under different environmental conditions. The removal of Cr(VI) by the strain could be accurately explained by the exponential decay equation, where approximately 9.45% of the Cr was immobilized on the microorganisms. We further investigated the ability of different cell fractions to remove Cr(VI) and found that bioreduction was the primary mechanism involved. This was supported by SEM and TEM analyses, which showed the presence of Cr on the surface and inside the cells. Additionally, XPS analysis confirmed the presence of both Cr(VI) and Cr(III) on the cell surface, and FTIR analysis suggested the involvement of amino, carboxyl, and hydroxyl groups in the reduction and fixation of Cr(VI) on the cell surface. The findings offer a novel technique for bioremediation of Cr(VI)-contaminated wastewater in weakly acidic to weakly alkaline and high salinity environments, providing potential solutions for remediating chromium-contaminated environments. [ABSTRACT FROM AUTHOR]

The objective of this study is to demonstrate the basic characteristics of Bacillus SP3 and evaluate its effect on different crude oils. Strain SP3 is a motile, gram-positive, spore-producing rod that was isolated from a reservoir of the Shengli oil field in East China. The cells of strain SP3 grew at high temperatures up to 58°C at the pH range of 5.5–8.5. Strain SP3 grew facultatively and could use different organic substrates, and produce some metabolites such as 4-hydroxy-4-methyl-2-pentanone, methyl-2-nitrogen benzene and 1, 2-benzenedicarboxylic acid bis ester. Laboratory studies have demonstrated that the strain converted and degraded different components and changed the physical and chemical properties of crude oils. Strain SP3 degraded crude oil and the growth of bacteria on crude oil resulted in loss of aromatic hydrocarbons, resins and asphaltenes. The bioconversion of crude oils would lead to an enrichment in lighter hydrocarbons and an overall redistribution of saturate hydrocarbons. The interactions of microorganisms with crude oils are variable, depending on the microbial species and the chemical compositions of crude oils. [ABSTRACT FROM AUTHOR]

An introduction is presented in which the editors discuss various reports within the issue on topics including microbial diversity, implications of microbial cell surfaces' metal sorption in bioremediation, and light fuel cell (LFC) interactions.