Enhanced dimethyl phthalate biodegradation by accelerating phthalic acid di-oxygenation

Abstract

The aerobic biodegradation of dimethyl phthalate (DMP) is initiated with two hydrolysis reactions that generate an intermediate, phthalic acid (PA), that is further biodegraded through a two-step di-oxygenation reaction. DMP biodegradation is inhibited when PA accumulates, but DMP's biodegradation can be enhanced by adding an exogenous electron donor. We evaluated the effect of adding succinate, acetate, or formate as an exogenous electron donor. PA removal rates were increased by 15 and 30% for initial PA concentrations of 0.3 and 0.6 mM when 0.15 and 0.30 mM succinate, respectively, were added as exogenous electron donor. The same electron-equivalent additions of acetate and formate had the same acceleration impacts on PA removal. Consequently, the DMP-removal rate, even PA coexisting with DMP simultaneously, was accelerated by 37% by simultaneous addition of 0.3 mM succinate. Thus, lowering the accumulation of PA by addition of an electron increased the rate of DMP biodegradation.

Application of Fungus Enzymes in Spent Mushroom Composts from Edible Mushroom Cultivation for Phthalate Removal

“…The key enzymes of the initial stage are esterases/hydrolases. The second stage of phthalate biodegradation continues with benzene ring cleavage of PA and the metabolites produced from PA and alcohol decomposition [ 31 , 32 , 33 , 34 ]. Dioxygenases and oxidases/dehydrogenases are involved in the second stage of phthalate biodegradation.…”

“…The biodegradation of phthalates has been investigated in several studies [ 31 , 32 , 33 , 34 ]. The main basis of phthalate biodegradation pathways is composed of two stages: The first stage is initiated with ester hydrolysis reactions, which generate phthalic acid (PA) and alcohols.…”

“…The biodegradation is continued with benzene ring cleavage of PA and metabolites produced from the decomposition of PA and alcohol. Several enzymes, including decarboxylases, oxygenases, and oxidases/dehydrogenases may be involved in the second stage [ 31 , 32 , 33 , 34 ]. The genus Pleurotus comprises a group of edible mushrooms with important biotechnological and environmental applications [ 35 ].…”

The role of oxygen and electron donors in indole biodegradation and mineralization

“…However, due to its instability, indoxyl is only a proposed intermediate, 18–20 which is readily oxidized in the presence of oxygen, 11 followed by a fast non‐enzymatic dehydration reaction to get isatin 12 . Next, a series of oxygenation, decarboxylation, and deamination reactions convert isatin to catechol, which is further decomposed into organic acids, 13,21–23 and they can be oxidized to form intracellular electron carriers to prompt the initial mono‐oxygenation step and any other donor‐requiring steps . 24,25…”

“…However, due to its instability, indoxyl is only a proposed intermediate, [18][19][20] which is readily oxidized in the presence of oxygen, 11 followed by a fast non-enzymatic dehydration reaction to get isatin. 12 Next, a series of oxygenation, decarboxylation, and deamination reactions convert isatin to catechol, which is further decomposed into organic acids, 13,[21][22][23] and they can be oxidized to form intracellular electron carriers to prompt the initial monooxygenation step and any other donor-requiring steps . 24,25 For some hydrocarbon compounds, in their aerobic biodegradation, the initial rate-limiting step is catalyzed by a mono-oxygenase and needs two co-substrates: a reduced electron carrier (e.g., NADH + H + , described as 2H in Figure 1) 17,26,27 and molecular oxygen (O 2 ).…”