Exploring the Efficacy of Bacillus oceanisediminis Ba9 from Asian Seabass Cage Sediment in Saline Wastewater Treatment

Abstract

Preventing toxicity in aquaculture systems from ammonia and nitrite is important. This study isolated the salt-tolerant Bacillus sp. strain Ba9 from bottom sediment under an Asian Seabass (Lates calcarifer) cage cultivating at Koh Yor, Songkhla, Thailand. Morphological characteristics showed that strain Ba9 was rod-shaped, endospore-forming, and Gram-positive. Strain Ba9 grew well at a salinity of 1.5 to 4.0% NaCl. The catalase test of the isolate was positive, while the oxidase test was negative. Based on 16S rRNA gene sequencing data and phylogenetic tree analysis, strain Ba9 was identified as B. oceanisediminis with 97% similarity (strain HQB337T). The result showed that the ammonium removal efficiency of Ba9 in a high ammonium medium was 64.24%. The nitrite and nitrate production were 0.10% and 0.08%, respectively. Consequently, sucrose had been the optimal carbon source for Ba9, which showed ammonium removal was 61.05%. Ammonium sulfate is the most suitable for ammonium oxidation, with 50.53% for the nitrogen source. The optimal C/N ratio of strain Ba9 was 8, with 71.15% ammonia removal. For wastewater improvement, strain Ba9 was inoculated into artificial wastewater for 14 days. The result showed that the ammonium removal efficiency of Ba9 was 96.87%. In addition, the biochemical oxygen demand (BOD) removal efficiency of Ba9 was 90.86%. From this result, the salt-tolerant B. oceanisediminis Ba9 has a high potential as a microbial product for water quality management in marine aquaculture.