Factors affecting the selection of PHB accumulating methanotrophs from waste activated sludge while utilizing ammonium as their nitrogen source
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Bibliographic record
Abstract
Abstract BACKGROUND Methanotrophs can offer a long‐term reliable solution to two of the major problems causing environmental pollution. These microorganisms can convert methane, i.e. second major greenhouse gas (GHG), into biodegradable polymers as polyhydroxybutyrate (PHB). In this research, waste activated sludge was used as a seed for cultivating enrichments utilizing methane and ammonium as their sole carbon and nitrogen sources respectively with high PHB accumulation capacity. Moreover, to test the effect of different parameters, such as the initial ratio between the ammonium and the microorganisms (N/M), food to microorganisms ratio (F/M), the solids retention time (SRT), copper elimination and nitrate, on the selection of PHB accumulating, i.e. Type II methanotrophs. RESULTS After establishing a mixed culture dominated by Type II methanotrophs, the enriched culture was kept in the exponential phase of growth and had a stable performance for almost 30 consecutive cycles with a specific growth rate of 0.077 ± 0.005 h ‐1 and biomass yield of 0.81 ± 0.06 mg‐VSS mg ‐1 ‐CH 4 . The PHB accumulation capacity of the enrichment reached 52.9 ± 4% with a yield of 0.54 ± 0.12 mg‐PHB mg ‐1 ‐CH 4 . CONCLUSIONS Increasing the N/M ratio can be employed to ensure the dominance of Type II methanotrophs in mixed cultures having high PHB accumulation capacity while maintaining a high F/M ratio overcomes any inhibition resulting from ammonium co‐metabolism. Despite the dominance of Type II, switching the nitrogen source to nitrate caused an invasion of Type I methanotrophs and a deterioration in the PHB accumulation of the enriched culture. © 2017 Society of Chemical Industry
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.002 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from it