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Nishi-Tokyo-shi, Japan

Kishi M.,Soka University | Kawai M.,Asian Peoples Exchange | Toda T.,Soka University
Algal Research

This study explored the possibility of heterotrophic algal treatment of waste ethylene glycol (EG) and propylene glycol (PG) with simultaneous biomass production. Five Chlorella species were fed with EG and PG. With glycol-utilizing Chlorella species, the effect of pH was evaluated with pH-static cultures adjusted at pH4.0, 5.5, 7.0, 8.5, and 10. Chlorella protothecoides was found to assimilate both EG and PG. The pH level had greater effects on the treatment of EG than PG, and drastic reduction of pH was observed in cultures with EG, probably owing to proton and organic acid generation during EG degradation. When pH was controlled within the range of 5.5-8.5, high EG removal efficiency (86%) was achieved. Although PG removal efficiency was low (30%), biomass yield from PG (0.52gDWgPG-1) was found to be higher than that from EG (0.081gDWgEG-1). The present study evaluated algal glycol assimilation quantitatively for the first time, and the results suggested potential future application of algal heterotrophic culture on glycol. © 2015 Elsevier B.V. Source

Eio E.J.,Soka University | Kawai M.,Asian Peoples Exchange | Kawai M.,Soka University | Niwa C.,Soka University | And 3 more authors.
Environmental Science and Pollution Research

The degradation of bisphenol A (BPA) by Chlorella sorokiniana and BPA-degrading bacteria was investigated. The results show that BPA was partially removed by a monoculture of C. sorokiniana, but the remaining BPA accounted for 50.2, 56.1, and 60.5 % of the initial BPA concentrations of 10, 20, and 50 mg L−1, respectively. The total algal BPA adsorption and accumulation were less than 1 %. C. sorokiniana-bacterial system effectively removed BPA with photosynthetic oxygen provided by the algae irrespective of the initial BPA concentration. The growth of C. sorokiniana in the algal system was inhibited by BPA concentrations of 20 and 50 mg L−1, but not in the algal-bacterial system. This observation indicates that bacterial growth in the algal-bacterial system reduced the BPA-inhibiting effect on algae. A total of ten BPA biodegradation intermediates were identified by GC-MS. The concentrations of the biodegradation intermediates decreased to a low level at the end of the experiment. The hypothetical carbon mass balance analysis showed that the amounts of oxygen demanded by the bacteria are insufficient for effective BPA degradation. However, adding an external carbon source could compensate for the oxygen shortage. This study demonstrates that the algal-bacterial system has the potential to remove BPA and its biodegradation intermediates. © 2015, Springer-Verlag Berlin Heidelberg. Source

Eio E.J.,Soka University | Kawai M.,Asian Peoples Exchange | Kawai M.,Soka University | Tsuchiya K.,Soka University | And 2 more authors.
International Biodeterioration and Biodegradation

The effect of light on BPA degradation by an adapted bacterial consortium was investigated. BPA was completely degraded up to 50mgl-1, and the degradation followed first-order reaction kinetics both in the light and in the dark. The degradation half-life of BPA when the consortium was grown in presence of light was 21.9, 17.2, and 12.6h for concentrations of 10, 20, and 50mgl-1, respectively; the degradation half-life of BPA in the dark was 13.1, 10.8, and 10.2h for concentrations of 10, 20, and 50mgl-1, respectively. Therefore, light inhibited BPA biodegradation. However, under both conditions, BPA was completely depleted. The bacterial consortium effectively utilised BPA as a growth substrate to sustain a cell yield of 0.95gg-1 and 0.97gg-1 in the light and dark, respectively. A total of ten and nine biodegradation intermediates were detected in the light and dark, respectively. Three bacterial metabolic pathways and one photodegradation pathway were proposed to explain their occurrence. This study demonstrated that bacterial consortia may assemble a wide range of catabolic pathways to allow for efficient degradation of BPA, converting BPA to principally bacterial biomass and metabolites exhibiting low or no oestrogenic activity. © 2014 Elsevier Ltd. Source

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