Production of a granular compost carrier for bacterial inoculants
Date
2003-08-01
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Degree Level
Masters
Abstract
Bacterial inoculants play an important role in both agriculture and bioremediation.
The long-term use of Rhizobium inoculants in agriculture has resulted in increased
demands on natural peat reserves (the primary carrier material for these inoculants) and
environmental concerns regarding the sustainable use of our natural resources. Methods
of application of other bacterial inoculants, such as those used in the bioremediation of
petroleum oil-contaminated soil, have been relatively unsuccessful. It is with consideration of these concerns that this study was undertaken to identify and develop
compost as an alternative carrier material for Rhizobium and as an alternative to liquid
bacterial inoculants for bioremediation technologies.
Composted manure was selected as the carrier material in both studies. The survival of Rhizobium and petroleum-hydrocarbon (phenanthrene )-degrading bacteria on
granular compost was examined. In addition, the ability of these newly developed
inoculants to fulfill their expected functions was assessed. For example, delivery of
Rhizobium to leguminous roots and the degradation of phenanthrene in soil by
phenanthrene-degrading bacteria.
Rhizobium leguminosarum bv. viciae bacteria were not detected via standard
plating of non-sterile compost granules after ~30 days of storage for the composted
Saskatoon Zoo waste (SZ) and ~70 days for the composted cattle manures (designated as
EA, PA) at 4°C. However, survival of R. leguminosarum bv. viciae (9.28 x 10⁷ CFU g⁻¹
compost inoculant) inoculated onto sterile granular composted zoo waste was 5.36 x 10⁵ CFU g⁻¹ compost inoculant after 224 days of storage at 4°C. The populations of rhizobia
present on the sterile granular composted zoo waste after 224 days of storage
consistently nodulated field pea (Pisum sativum) roots under sterile conditions.
However, variable nodulation occurred when either non-sterile or sterile, freshly inoculated
compost granules were added to soil prior to seeding pots with peas.
The sterile granulated composts in this study, due to their many similarities to
inoculant-quality peat and their capability of promoting the survival of
R. leguminosarum bv. viciae for an extended period of time, should be further examined
as potential carriers for Rhizobium.
The survival of phenanthrene-degrading strains of Arthrobacter globiformis and
Rahnella aquatilis, inoculated onto granular composted manure, was generally one log
unit higher when stored at 4°C as opposed to 22°C after 240 days of storage. Survival
was relatively consistent between the different composts. When the A. globiformis- inoculated
compost granules were added to 1.0% phenanthrene-spiked soil no significant
phenanthrene degradation occurred, possibly in part due to the lack of bacterial
movement from the granules into the spiked soil environment. However, when crushed
granules inoculated with phenanthrene-degrading A. globiformis, or a liquid broth of the
A. globiformis were added to phenanthrene-spiked soil, a decrease in measurable volatile
phenanthrene was seen.
The inoculant/contaminant contact is a very important aspect of bioremediation
technologies. The use of PAR-degrading bacteria inoculated onto crushed granules by
way of direct incorporation into contaminated soil or application by coating seeds used
to promote phytoremediation should be investigated further.
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Citation
Degree
Master of Science (M.Sc.)
Department
Applied Microbiology and Food Science
Program
Applied Microbiology and Food Science