Overview
Jaafar isolated a Pediococcus pentosaceus strain from common-carp pond water in Basra, Iraq, confirmed probiotic traits, and tested its tolerance and removal of experimentally added lead and cadmium. This is mitigation and bioremediation evidence, not consumer-product occurrence evidence: the lead (Pb) and cadmium (Cd) values come from spiked laboratory media and fish-pond remediation framing, so they should not enter food, salt, probiotic, or supplement benchmark pools.
Key numbers
The study collected nine water samples from three common-carp ponds during April 2018. Colonies grown on MRS agar were screened by Gram stain, catalase reaction, morphology, biochemical tests, and Vitek II; the selected isolate was identified as P. pentosaceus with 95% confidence.
For probiotic survival, Table 2 reports optical density at 600 nm across pH and bile-salt tests. At pH 3, OD600 declined from 0.564 after 3 hours to 0.327 after 24 hours; at pH 7, OD600 was 1.629 after 3 hours and 1.687 after 24 hours; at pH 9, OD600 was 1.511 after 3 hours and 1.645 after 24 hours. In bile salt, OD600 after 24 hours was 1.557 at 0%, 0.568 at 0.15%, 0.398 at 0.25%, and 0.239 at 0.5%. The gastric and intestinal juice test reported 390 bacteria at pH 3 after 24 hours and 205 bacteria at pH 8 after 24 hours.
For metal tolerance, the minimum inhibitory concentration was 1800 ppm for Pb and 150 ppm for Cd. The authors interpret this as stronger Pb resistance than Cd resistance in the isolated P. pentosaceus strain.
For metal removal, the study incubated bacteria in MRS broth containing 25 ppm or 50 ppm Pb or Cd for 24 hours at 37 C, centrifuged the cultures, and measured residual metal in the supernatant by flame atomic absorption spectrophotometry. Table 3 and the results text report:
| Metal | Initial concentration | Removal after 24 hours |
|---|---|---|
| lead (Pb) | 25 ppm | 62.10% |
| lead (Pb) | 50 ppm | 68.39% |
| cadmium (Cd) | 25 ppm | 52.71% |
| cadmium (Cd) | 50 ppm | 11.25% |
The direction differs by metal: Pb removal increased from 25 ppm to 50 ppm, while Cd fractional removal decreased sharply at 50 ppm.
Methods (brief)
Water samples from carp ponds were serially diluted, plated on MRS agar, incubated at 37 C for 48 hours, and purified. The isolate was characterized by colony morphology, Gram reaction, catalase and biochemical testing, and Vitek II. Probiotic suitability was tested by acid tolerance, bile-salt tolerance, gastric and intestinal juice survival, antimicrobial activity against Salmonella sp., and antibiotic susceptibility.
For the bioremediation assay, Pb(NO3)2 and Cd(NO3)2.H2O were used to prepare spiked metal solutions. MIC testing used MRS agar supplemented with 25, 50, 100, 250, 500, 1000, 1500, 1800, and 2000 ppm Pb or Cd. Removal testing used 25 and 50 ppm Pb or Cd in MRS broth, 24-hour incubation at 37 C, centrifugation, and flame AAS (AAS 6300, Shimadzu, Japan) of the supernatant. The study reports removal percentages rather than sample-level pond-water Pb or Cd occurrence concentrations.
Related evidence
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