Biodegratation of S-heterocyclic compounds in anoxic sediments

• Main Authors: Elaine Lai, 賴伊蓮
• Other Authors: 劉秀美
• Format: Others
• Language: zh-TW
• Published: 2002
• Online Access: http://ndltd.ncl.edu.tw/handle/64832773072190150668

碩士 === 國立海洋大學 === 海洋生物研究所 === 90 === S-heterocyclic compounds in the petroleum products are culprits of the acid rain. In order to upgrade the petroleum products by removing the S-heterocyclic compounds or to clean up petroleum contaminat in environments, it is necessary to understand microbial degradation pathways of the S-heterocyclic compounds. In this study, biodegradabity of thiophene, 2-methylthiophene, 3-methylthiophene, 2,5-dimethythiophene, 2-thiophene carboxylic acid and 3-thiophene carboxylic acid in estuary sediments were investigated under different redox potential (denitrifying, iron-reducing, sulfate-reducing and methanogenic conditions). After incubation for 400 days we found that thiophene, 2-methylthiophene, 3-methylthiophene and 2,5-dimethythiophene were not degraded under any conditions. 2-Thiophene carboxylic acid was degraded under denitrifying, sulfate reducing and methanogenic conditions, but not under iron-reducing conditions. While 3-thiophene carboxylic acid could be degraded under any conditions. Subsequent additions of these compounds to the sediment slurries after its removal enhanced its degradation rate. However, the intermediate product(s) of 2-thiophene carboxylic acid and 3-thiophene carboxylic acid under either condition were not identified. 2-Thiophene carboxylic acid-adapted sediments didn’t enhance biodrgradation of 3-thiophene carboxylic acid, thiophene or 2-methylthiophene, while degradation. 3-thiophene carboxylic acid-adapted sediments didn’t enhance biodegradation of 2-thiophene carboxylic acid, thiophene or 3-methylthiophene degradation. From the detection of methane production we found that 2-thiophene carboxylic acid transformed (mole) and methane produced (mole) was in a stoichiometric ratio of 1:6, while 3-thiophene carboxylic acid transformed and methane produced was 1:1. It seems that 2-thiophene carboxylic acid was degraded completely to methane while only one carbon was transformed during biodegradation of 3-thiophene carboxylic acid. 2-Thiophene carboxylic acid-adapted denitrifying sediment slurries did not degrade 2-thiophene carboxylic acid when changing electron acceptor form nitrate to Fe(Ⅲ), sulfate or CO2. However, 3-thiophene carboxylic acid-adapted sediment slurries could degrade 3-thiophene carboxylic acid when changing electron acceptor from Fe(Ⅲ) to sulfate or from sulfate to sulfite and Fe(Ⅲ). Addition of molybdate (sulfate-reducing bacteria inhibitor) to inhibited biodegradation of 3-thiophene carboxylic acid in 3-thiophene carboxylic acid-adapted sulfate reducing sediment slurries. 2-Thiophene carboxylic acid-adapted denitrifying sediment slurries could degrade 90 mg / L of 2-thiophene carboxylic acid and the maximum velocity was 8.90 mg / L‧day. 3-Thiophene carboxylic acid adapted iron-reducing and sulfate-reducing sediment slurries could degraded 120 mg / L of 3-thiophene carboxylic acid and the maximum velocity was 8.05 mg / L‧day and 12.58 mg / L‧day, respectively. Based to these results, it seems that the 2-thiophene carboxylic acid-and 3-thiophene carboxylic acid was degraded under different pathway. More research is needed in the future to understand the degradation pathways of 2-thiophene carboxylic acid and 3-thiophene carboxylic acid.