Journal of Central South University | 2019
Isolation of an acid producing Bacillus sp. EEEL02: Potential for bauxite residue neutralization
Abstract
Bauxite residue deposit area (BRDA) is a typical abandoned mining wasteland representing extreme hostile environment with increased alkalinity. Microbially-driven neutralization of bauxite residue, based on the microbial acid producing metabolisms, is a novel strategy for achieving rapid pH neutralization and thus improving its environmental outcomes. The hypothesis was that these extreme conditions promote microbial communities which are capable of novel ecologically relevant functions. Several alkaliphilic acid producing bacteria were isolated in this study. One strain was selected for its superior growth pattern and acid metabolism (termed EEEL02). Based on the phylogenetic analysis, this strain was identified as Bacillus thuringiensis. The optimized fermentation conditions were as follows: pH 10; NaCl concentration 5%; temperature 25 °C; EEEL02 preferred glucose and peptone as carbon and nitrogen sources, respectively. Based on optimal fermentation conditions, EEEL02 induced a significant pH reduction from 10.26 to 5.62 in 5-day incubation test. Acetic acid, propionic acid and CO2 (g) were the major acid metabolites of fermentation, suggesting that the pH reduction in bauxite residue may be caused by acid neutralization derived from microbial metabolism. This finding provided the basis of a novel strategy for achieving rapid pH neutralization of bauxite residue.摘要赤泥堆场是一种典型矿业废弃地,盐度高,碱性强,对植物生长十分不利。酸碱中和是降低赤 泥碱性的主要方法,对堆场植被重建具有重要意义。本研究从赤泥堆场中筛选出1 株耐碱产酸细菌 EEEL02,经鉴定,该菌株为苏云金芽孢杆菌,从属于芽孢杆菌门。通过单因素试验确定该菌株最佳 产酸条件:初始pH 为10,盐浓度5%,培养温度25 °C;最优发酵培养基组成为葡萄糖2%,蛋白胨 0.5%。将EEEL02 接种于赤泥中,在最佳培养条件下培养5 d 后,赤泥pH 从10.26 降低至5.62。EEEL02 在发酵过程中主要代谢产物为乙酸、丙酸和二氧化碳。微生物发酵产酸过程能有效降低赤泥碱度,为 赤泥碱性调控提出一种新思路。