Identification of sulfur-oxidizing bacteria from fishponds and their performance to remove hydrogen sulfide under aquarium conditions

Abstract

Hydrogen sul de is a highly toxic gas that causes many economic losses in aquaculture ponds. The application of sulfur-oxidizing bacteria (SOB) to remove hydrogen sul de is an eco-friendly approach. This study aimed to isolate and identify the most e cient SOBs from the sediment of warm-water sh farms. Enrichment and isolation were performed in three different culture media (Starkey, Postgate, and H-3) based on both mineral and organic carbon. Overall, 27 isolates (14 autotrophic and 13 heterotrophic isolates) were puri ed based on colony and cell morphology differences. Initial screening was performed based on pH decrease. For nal screening, the isolates were assessed based on their e cacy in thiosulfate oxidation and the sulfate production on Starkey liquid medium. Among isolated strains, 3 strains of Iran 2 (FH-13), Iran 3 (FH-21), and Iran 1 (FH-14) that belonged to the genus Thiobacillus thioparus (identi ed by 16s rRNA) showed the highest ability in thiosulfate oxidation (413.21, 1362.50, and 4188.03 mg l -1 for 14 days) and the highest sulfate production (3350, 2075, and 1600 mg l -1 ). In the nal phase, the performance of these strains under aquarium conditions showed that Iran 1 and Iran 2 had the highest ability in sulfur oxidation. In conclusion, Iran 1 and 2 strains can be used as effective SOB to remove hydrogen sul de in sh farms. It is very important to evaluate strains in an appropriate strategy using a combination of different criteria to ensure optimal performance of SOB in farm conditions.