Biomining

Event Date: 
Wednesday, January 28, 2015 - 18:00 - 18:15
Institution: 
University of New South Wales
Title: 

Biomining and methanogenesis for resource extraction from asteroids

Abstract: 

As spacecraft fuel is a limited resource, creating a readily available source for hydrocarbon-based fuels in space will reduce launch cost and increase operating time of spacecraft. Biomethanation is viable for Earth-based operations, thus applications in space under controlled conditions have potential. This study proposes a sustainable environment for methanogens on Near-Earth Objects. Vacuum and desiccation effects, at 0.025% Earth atmospheric pressure, are conducted on three bacterial and three Archaea strains to test post-exposure viability. Cell degradation and colony size reduction was quantified for aerobic strains. Adverse effects were exhibited more so in gram-negative than gram-positive strains. Archaea showed limited to no cell degradation, providing evidence that vacuum effects, at these pressures, will have minor effects on in-situ biofuel operations. If successful, a sustainable and cost-effective method of metal extraction and producing methane based fuel reservoirs could revolutionise in-situ resource and fuel resupply of spacecraft, thus enhancing spacefaring capabilities.

Event Date: 
Wednesday, March 26, 2014 - 18:00 - 18:15
Institution: 
UNSW
Title: 

Insights into the stress response of the biomining bacterium Acidithiobacillus ferrooxidans using gene expression and proteomic analysis

Abstract: 

Bioleaching is a simple and effective process used for metal extraction from low grade ores and mineral concentrates using microorganisms. The extraction of some metals such as copper from low grade ore is becoming necessary because of gradual depletion of high grade ore. The traditional methods used for extraction of copper are either Pyrometallurgy or Hydrometallurgy. However both the methods are not environmental friendly. There are many techniques proposed to extract metals but these are not practically suitable, as these requires a very high energy input as well as most of them creates environmental pollution problem, that also rises the cost of environmental protection throughout the world. Therefore, bioleaching is recognizable as the most environmentally friendly method of separating metals since it requires less energy and it reduces the amount of greenhouse gasses released to the atmosphere. Bioleaching is also a fairly simple process that does not require a lot of expertise to operate or complicated machinery.
The most commonly used bacterium in bioleaching is Acidithiobacillus ferrooxidans (former Thiobacillus ferrooxidans) and this is due to its capacity to oxidize metal sulphides. A. ferroxidans is a chemolithotrophic bacterium capable of utilizing ferrous iron or reduced sulphur compounds as the sole source of energy for its growth. It thrives optimally around pH 2.0 and 30ºC. During Bioleaching process, A. ferrooxidans is often subject to changes in the ideal growth pH and temperature, and to nutrients starvation. These changes can affect the bacterial physiology and as a consequence, the efficiency of bioleaching. Then, the stress response of this bacterium subject to heat stress and phosphate starvation has been investigated using different approaches, namely, gene expression and proteomic analysis, Fourier transform infrared spectroscopy (FT-IR), as well as morphological analysis by scanning electron microscopy (SEM).
The results showed that under the tested stress conditions A. ferrooxidans cells suffer elongation, a common stress response in bacteria. Alterations in carbohydrates, phospholipids and phosphoproteins were detected by FT-IR. By proteomic analyses (2-DE and tandem mass spectrometry), many differentially expressed protein spots were visualized and identified as proteins belonging to 11 different functional categories. Indeed, the up-regulated proteins were mainly from the protein fate category. Real time quantitative PCR was employed to analyze changes in the expression patterns of heat shock genes, as well as many other genes encoding proteins related to several functional categories in A. ferrooxidans. Cells were submitted to long-term growth and to heat shock, both at 40°C. The results evidenced that heat shock affected the expression levels of most genes while long-term growth at 40°C caused minimal changes in gene expression patterns – with exception of some iron transport related genes, which were strongly down-regulated. Further bioinformatic analysis indicated a putative transcriptional regulation, by the σ32 factor, in most heat-affected genes. These results evidence that A. ferrooxidans has an efficient range of stress-responses, which explains its ability for biotechnological purposes.
 

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