Enhanced Mineralization of Amino Acids by Birnessite as Influenced by Pyrogallol
- M. C. Wang and
- Ching-Ho Lin
Dep. of Soil Science, National Chung Hsing Univ., Taichung, Taiwan 40227, Republic of China
Taichung District Agricultural Improvement Stn., Changhua, Taiwan 51501, Republic of China
The structural differences among amino acids influencing mineralization by soil minerals, and the role of phenols in this mineralization, is very important in C turnover and N and S transformations in soil. The objective of this study was thus to investigate the effect of birnessite and pyrogallol on the mineralization of amino acids. Using a specially designed reaction flask, amounts and distribution of CO2 and NH3 released were determined during 90-h reaction periods. The results show that birnessite enhanced the decarboxylation of amino acids. The amount of CO2 released with l-serine, l-phenylalanine, l-proline, dl-methionine, and l-cysteine without birnessite was not detectable, while with birnessite-amino acid, losses were 109 ± 0, 162 ± 3, 145 ± 2, 95 ± 2, and 182 ± 3 µmol, respectively. Since L-cysteine has the strongest reducing power among the amino acids examined, the amount of CO2 released with birnessite-l-cysteine was greatest. Birnessite enhanced the deamination of amino acids. The amounts of NH3 released with l-serine, l-phenylalanine, l-proline, dl-methionine, and l-cysteine without birnessite were not detectable, while those with birnessite-amino acid were 140 ± 4, 145 ± 5, 66 ± 6, 83 ± 2, and 226 ± 8 µmol, respectively. Birnessite enhanced the mineralization of methionine and cysteine to release SO2−4 in the supernatants of the reaction systems. The amounts of SO2−4 released with dl-methionine and l-cysteine without birnessite were 0.1 ± 0.0 and 0.2 ± 0.0 µmol, respectively, while those with birnessite-amino acid were 0.8 ± 0.0 and 112 ± 7 µmol, respectively. In conclusion, the enhancing effects of birnessite play an important role in C turnover and N and S transformations in soil.
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