Dispersion of sulfur creates a valuable new growth medium formulation that enables earlier sulfur oxidation in relation to iron oxidation in Acidithiobacillus ferrooxidans cultures. Issue 8 (16th June 2021)

• Record Type: Journal Article
• Authors: Inaba, Yuta; Kernan, Timothy; West, Alan C.; Banta, Scott
• Is Part Of: Biotechnology and bioengineering. Volume 118:Issue 8(2021)
• Page Start: 3225
• Page End: 3238
• Publication Date: 2021-06-16
• Subjects: acidophile -- dispersed sulfur -- iron oxidation -- substrate utilization -- sulfur oxidation; Biotechnology -- Periodicals; Bioengineering -- Periodicals; 660.6
• DOI: 10.1002/bit.27847
• Languages: English
• ISSNs: 0006-3592

Abstract

Abstract: Acidithiobacillus ferrooxidans is an acidophilic chemolithoautotroph that is commonly reported to exhibit diauxic population growth behavior where ferrous iron is oxidized before elemental sulfur when both are available, despite the higher energy content of sulfur. We have discovered sulfur dispersion formulations that enables sulfur oxidation before ferrous iron oxidation. The oxidation of dispersed sulfur can lower the culture pH within days below the range where aerobic ferrous iron oxidation can occur. Thus, ferric iron reduction can be observed quickly which had previously been reported over extended incubation periods with untreated sulfur. Therefore, we demonstrate that this substrate utilization pattern is strongly dependent on the cell loading in relation to sulfur concentration, sulfur surface hydrophobicity, and the pH of the culture. Our dispersed sulfur formulation, lig‐sulfur, can be used to support the rapid antibiotic selection of plasmid‐transformed cells, which is not possible in liquid cultures where ferrous iron is the main source of energy for these acidophiles. Furthermore, we find that media containing lig‐sulfur supports higher production of green fluorescent protein compared to media containing ferrous iron. The use of dispersed sulfur is a valuable new tool for the development of engineered A. ferrooxidans strains and it provides a new method to control iron and sulfur oxidation behaviors. Abstract : The simple dispersion of sulfur by biocompatible surfactants enables sulfur oxidation to occur more rapidly in Acidithiobacillus ferrooxidans. This dispersed sulfur formulation is effective for observing sulfur‐related phenomena quickly and maintaining selective pressure on engineered strains. Using this information, the authors describe how the apparent substrate utilization of iron and sulfur by the population of cells is affected by medium pH, the relative amount of planktonic cells, and the hydrophobicity of the sulfur.