Bioleaching of realgar nanoparticles using the extremophilic bacterium Acidithiobacillus ferrooxidans DLC-5

BACKGROUND: This paper presents micro- and nano-fabrication techniques for leachable realgar using the extremophilic bacterium Acidithiobacillus ferrooxidans (A. ferrooxidans) DLC-5. RESULTS: Realgar nanoparticles of size ranging from 120 nm to 200 nm were successfully prepared using the highenergy ball mill instrument. A. ferrooxidans DLC-5 was then used to bioleach the particles. The arsenic concentration in the bioleaching system was found to be increased significantly when compared with that in the sterile control. Furthermore, in the comparison with the bioleaching of raw realgar, nanoparticles could achieve the same effect with only one fifth of the consumption. CONCLUSION: Emphasis was placed on improving the dissolvability of arsenic because of the great potential of leachable realgar drug delivery in both laboratory and industrial settings

Isolation, molecular identification and screening of halophilic and thermophiliclipase producing bacterial strains from extreme environmental conditions

Aims@#The aim of this study was to isolate and screen lipolytic-thermophilic and halophilic strains from extreme environments and at the same time studying the influence of physiological conditions such as temperature and sodium chloride concentrations on growth of the strains.@*Methodology and results@# A total of 45 halophilic bacterial strains and 4 thermophilic bacterial strains were isolated from various saline environments and hot spring respectively, and were screened for lipolytic activity on tributyrincontaining agar. The strains that showed lipolytic potential on the solid agar were further subjected to secondary screening by submerged fermentation using the same substrate (tributyrin). One halophilic (SWJ2) and thermophilic (HS2) strain each with highest extracellular lipase production ability was outsourced for molecular identification. The result from 16S rRNA partial gene sequencing and amplification of the selected isolates designated the halophilic strain SWJ2 as Marinobacter sp. SWJ2 and the thermophilic strain HS2 as Bacillus sp. HS2. Upon screening under submerged fermentation, Bacillus sp. HS2 gave 0.17 U/mL lipase production while Marinobacter sp. SWJ2 had 0.57 U/mL lipase production.@*Conclusion, significance and impact of study@#It could be inferred that the selected strains possess high lipase producing potential with interesting thermal and halophilic properties. Continuous screening of extremophilic environment for strains producing lipases with novel properties will improve their potential industrial and biotechnological applications especially for those processes conducted in harsh reaction conditions.