Production and biochemical and molecular characterization of a keratinolytic serine protease from chicken feather-degrading<i>Bacillus licheniformis</i>RPk
Bibliographic record
Abstract
A novel feather-degrading bacterium was isolated from a polluted river and identified as Bacillus licheniformis RPk. The isolate exhibited high proteinase production when grown in chicken-feather media. Complete feather degradation was achieved during cultivation. Maximum protease activity (4150 U/mL with casein as a substrate and 37.35 U/mL with keratin as a substrate) was obtained when the strain was grown in a medium containing 7.5 g/L chicken feathers, 2 g/L yeast extract, 0.5 g/L NaCl, 0.1 g/L MgSO4 x 7H2O, 0.7 g/L KH2PO4, and 1.4 g/L K2HPO4 for 48 h with agitation of 200 rev/min at 37 degrees C. The major protease produced by B. licheniformis RPk was purified to homogeneity by a 3-step procedure. The molecular mass of the purified enzyme was estimated to be 32 kDa by SDS-PAGE and gel filtration. The optimum pH and temperature for the caseinolytic activity were around 11.0 and 65 degrees C, respectively. The optimum pH and temperature for the keratinolytic activity were 9.0 and 60 degrees C, respectively. The activity of the enzyme was totally lost in the presence of phenylmethylsulfonyl fluoride, which suggests that the purified enzyme is a serine protease. The thermostability of the enzyme was considerably enhanced in the presence of Ca2+ at temperatures >50 degrees C. The kerRP gene, which encodes the keratinolytic protease, was isolated, and its DNA sequence was determined. The deduced amino acid sequence revealed that the keratinase KerRP differs from KerA of B. licheniformis PWD-1, subtilisin Carlsberg, and keratinase of B. licheniformis by 2, 4, and 62 amino acids, respectively.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| 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 itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".