I will use the Bacillus subtilis for biodegradation of low-density polyethylene. After I will isolate, I will screen the B. subtilis for biodegradation ability against low-density polyethylene as sole carbon source.
Thank you so much!
The medium is useful for isolating bacteria. For more specific isolation, one can bait the source with medium containing casein or skim milk powder. One can also enrich the soil sample with medium containing skim milk and/ or casein for several transfers in a screw topped culture tube and then plate serial dilutions on medium with agar and skim milk. 1% skim milk powder, skim milk powder + casein mixture should be sufficient. Halos against the white colored medium is a positive test. Purify colonies on medium containing casein and check for subtilisin production. The incubation temperature should be selected between 20 °C to 37 °C, or for thermophiles 50 °C to 70 °C. Please use 2-2.5% agar plates to isolate thermophiles, i.e., incubating at 50 °C to 70 °C.
Happy isolation!
Not easily. "Mineral salt agar" (whatever formula that is) with (assume) LDPE over simplifies the concept. Landfill will offer a diversity of microorganisms including B. subtilis that could grow and "LDPE" is not a readily available substrate - except perhaps as its fillers and plasticizers.
This is why a baiting medium is required. I have suggested for it based on my experience of isolating a variety of Bacillus organisms. Some plasticizers can be hydrolyzed by Bacillus organisms, especially thermophilic Bacillus species. Thermophilic Bacillus spp., are found in both. composts and from Landfill sites. In a broader sense, a landfill is similar to a composting site. Albeit, in a landfill the microenvironment is more anaerobic, again depending on the depth that is sampled.
In my opinion, the Bacillus subtilis can be isolated from landfill soil. There are a number of indications in the literature for it. Furthermore, one has to be cognizant of the fact that the BAcillus organisms can sporulate as endospores and can survive extreme environmental conditions, depending upon nutritional conditions Please see, discussion by Gordon et al., pages 99-109.
Also, The Appendix to the EPA Report 1997 in Table shows that at least 7 trillion B. subtilis CFU/day can be released from landfill.
Please also consult following articles. It is noteworthy that despite the finding of B. subtilis in a number of studies in aerosol, the organisms have to come from the soil dust, especially at an active landfill site.
EPA Report, Attachment I, FINAL RISK ASSESSMENTOF BACILLUS SUBTILIS. 17 Pages. Please note Page 1, Introduction, lines 1-7 and Table I.
Gordon, R. E., et al., 1973. "The Genus Bacillus. Agriculture Handbook No. 427, ARS, USDA.
Kalwasinska, et al., 2014. Clean - Soil, Air, Water, 42(10): 1337-1343.
Lal, et al. 2013. IJAEES, 1(2), 1-7.
Madika et al., 2017. UJMR, 2(2): 82-86. Note that at least 4 isolates from refuse dump site were obtained (Tables, 1-4). Refuse dump may be considered an active landfill site.
Nair, A. 2021. Bioaerosols in the landfill environment: an overview of microbial diversity and potential health hazards. Aerobiologia, 37: 185-203.
Hopefully, information provided would be useful.
I have the copies of articles, but I cannot include a copy because of the potential violation of copyright laws.
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