Preservation of Thiobacillus ferroxidans and Thiobacillus thiooxidans with activity check

Abstract

Cultures of Thiobacillus ferrooxidans and Thiobacillus thiooxidans, used in biohydrometallurgical processes of economic importance, are very difficult to preserve by conventional methods. Hence, to preserve the cultures with their activity intact, various techniques were tried, after determining their respective activity in terms of Iron Oxidation Rate (IOR) and Sulfur Oxidation Rate (SOR). Among the methods tested, along with the recommended method of serial transfer in a liquid medium, were methods such as lyophilization, storage in a liquid nitrogen and mixing with sterile, inert carriers like lignite or chalcopyrite ores. After a period check-up at 4 months and 8 months storage, it was found that out of these methods, mixing with sterile ore followed by storage at 8 degrees C, kept both types of activities intact. The temperature of storage was observed to have a definite effect on activity, in that when the preserved cultures were stored at 8 degrees C, the activity was retained, whereas at 28-30 degrees C (RT) storage, the activity of all the cultures preserved by various techniques, dropped significantly.

Metal removal rate of Thiobacillus thiooxidans without pre-secreted metabolite

“…The cells were counted by the optical density (OD) method. The OD of 0.3 at 545 nm corresponded to approximately (6.0-6.3) × 10 8 cells/ml of the culture (Gupta and Agate, 1986). This process was carried out each time after cells were harvested and obtained from this good growth of exponential phase.…”

Biomachining: Preservation of Acidithiobacillus ferrooxidans and treatment of the liquid residue

“…A. ferrooxidans is highly susceptible to cryoinjury and the addition of a suitable protective agent is therefore critical for cell survival or for improving cell viability . In the particular case of A. ferrooxidans , protective agents such as GP (glycerate 3‐phosphate molecule), glycine betaine, skimmed milk, sucrose, sucrose + mannitol, and glycerol have already been tested in the different preservation methods . Preservation in the absence of cryoprotective agents is also possible with the aid of cryoballs, which are now widely used .…”

“…A reliable preservation method that enables long-term storage of A. ferrooxidans while maintaining cell viability would ensure the ready availability of the bacteria and prevent mutations and contamination of cultures [12][13][14][15]. Successful techniques for preserving A. ferrooxidans have already been studied [16][17][18][19]. A. ferrooxidans is highly susceptible to cryoinjury [17] and the addition of a suitable protective agent is therefore critical for cell survival or for improving cell viability [17,[19][20][21].…”

Acidithiobacillus

“…Maintenance: Mineral or elementary sulfur oxidizing strains are maintained quite easily following growth in 9K or GEBS under air using 5 g/L sterile pyrite, chalcopyrite, lignite or roll sulfur as the electron donor. After growth is evident, viability is retained for 2-4 months at 4-10 °C (Gupta and Agate, 1986). Many Acidithiobacillus spp.…”

“…Lyophilization of Acidithiobacillus spp. is not usually very successful (Gupta and Agate, 1986). Enrichment and isolation: For solid samples, 1-2 g soil, corroded concrete, coal or minerals are added directly to 50 mL of the appropriate basal salts, supplemented with the required electron donor in a sterile, wide-mouth Erlenmeyer flask.…”