Abstract:Red mud is a kind of dangerous solid waste produced by the alumina industry and its ecological restoration is a difficult problem. To address limitation of high pH value of high salinity red mud on ecological restoration of red mud yard, a salt-tolerant bacteria strain ZH1 was screened from red mud yard, which could efficiently reduce pH value of red mud and was identified as Bacillus sp. by 16S rDNA analysis. The results show that ZH1 reduces pH value of red mud by producing acid , and its optimal acid-producing medium includes glucose of 8 g/L, yeast extract of 3 g/L, monopotassium phosphate of 0.3 g/L and magnesium chloride of 0.3 g/L. Content of oxalic acid produced by ZH1 is the highest, followed by α-ketoglutaric acid, acetic acid and tartaric acid in shaking culture; while content of oxalic acid produced by ZH1 is the highest, followed by lactate and tartaric acid in static culture, but tartaric acid is only produced under weakly acidic or neutral conditions. pH value of culture medium reduces to about 6.0, but the time required for shaking culture is shorter (about 48 h), which is about 72 h faster than that of static culture. Through correlation test between pH value and organic acid, it is found that drop of pH in shaking culture is mainly caused by oxalic acid and α-ketoglutaric acid, while in static cultivation, it is mainly caused together by oxalic acid, lactic acid and tartaric acid.