Enrichment inoculum

Laboratory experiments using natural consortia under defined conditions have particular value from several points of view. They are of direct environmental relevance, and their use minimizes the ambiguities in extrapolation from the results of studies with pure cultures. They provide valuable verification of the results of studies with pure cultures and make it possible to evaluate the extent to which the results of such studies may justifiably be extended to the natural environment. It should be appreciated, however, that in some cases the habitats from which the inoculum was taken might already have been exposed to xenobiotics so that natural enrichment (preexposure) could already have taken place. This has been discussed in Chapter 4. 

Middeldorp PJM, De Wolf J, Zehnder AJB, Schraa G (1997) Enrichment and properties of a 1,2,4-trichlorobenzene-dechlorinating methanogenic microbial consortium. Appl Environ Microbiol 63 1225-1229 Miller ME, Alexander M (1991) Kinetics of bacterial degradation of benzylamine in a montmorillonite suspension. Environ Sci Technol 25 240-245 Montville R, Schaffner DW (2003) Inoculum size influences bacterial cross contamination between surfaces. Appl Environ Microbiol 69 7188-7193 Mortland, MM (1970) Clay-organic complexes and interactions. Advances in Agronomy 22 75-117... 

Figure 3. Autoradiographic detection of naphthalene degradative bacterial colonies from MGP soil enrichments used as inoculum for continuous stirred soil slurry bioreactors.

Proteobacteria, were found to account for up to 50% of the community DNA and up to a third of the total mineralization of lignin in these enrichments (Gonzalez et al., 1999). The community composition varied considerably between the microcosms, which might be attributed to differences in inoculum composition, differences in ecological interactions, or a combination of the two (Gonzalez et al., 1999). 

Regrowth experiments were performed by mixing P. antarctica-den ved organic matter with an inoculum of Antarctic bacteria. Phaeocystis-derived organic matter was prepared from pure cultures of P. antarctica grown under Fe-limiting (LFe) and enriched conditions (HFe). 

Algae are cultured and exposed to the test substance in a nutrient-enriched medium. Tests consistent with OECD Test Guideline 201 (Algal growth inhibition) should be used. Standard test methods employ a cell density in the inoculum in order to ensure exponential growth through the test, usually 3 to 4 days duration. 

Figure 1. Depletion of 2-, 3-, and 4-chlorophenol isomers established in separate enrichment cultures under methanogenic conditions. Inoculum was obtained from the upper Hudson River, near Albany, NY. Data are average of duplicate cultures. Re-addition of substrate is indicated by arrows. (Adapted with permission from reference 34. Copyright 1993 American Society for Microbiology.)...

Figure 4. Depletion of benzene, toluene, and p-, m-, and o-xylenes under denitrifying conditions. All five alkylbenzenes were added together to triplicate enrichment cultures established under denitrifying conditions. Re-addition of toluene is indicated by the arrow. Seven different inocula were used. These results, typical of what was observed, were obtained with an inoculum from a digester at a domestic sewage treatment plant that receives industrial waste. (Adapted with permission from reference 44. Copyright 1993 American Society for...

It should be appreciated, however, that in some cases the habitats from which the inoculum was taken may already have been exposed to xenobiot-ics so that "natural" enrichment may already have taken place this has been discussed briefly in Chapter 4, Section 4.6.4. 

Evaluated the effect of environmental factors on hydrogen production using mixed culture. Successfully enriched naturally available mixed seed to culture hydrogen producing bacteria. Enhanced the hydrogen production through preheat treatment of seed inoculum at 70-90°C for 15 - 20 minutes followed by repeated heat treatment of settled returned sludge. 

Preparation of inoculum by the expansion of mycelial mass on enriched agar media and then on grain. Implantation of grain spawn into composted and uncomposted substrates or the use of grain as a fruiting substrate. 

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