Inoculant production and formulation of Pseudomonas sp. strain ADP
Thesis DisciplineChemical Engineering
Degree GrantorUniversity of Canterbury
Degree NameDoctor of Philosophy
In this work, a model microbial agent for bioremediation was improved using fermentation and formulation methods. The outcomes of the fermentation work include the development of a new culture medium which increased the cell productivity greater than one order of magnitude. A robust functionality to degrade the herbicide atrazine was expressed. The new medium was scaled-up to a 2L bioreactor.
Liquid bacterial culture was not inherently stable and lost viability at both 4°C and 25°C storage. When liquid bacterial culture was formulated by encapsulation in a biopolymer gel and applied to zeolite the transfer of cells from bacterial culture to formulated carrier was highly efficient. No loss of viability was measured from the immobilization process, and the functionality of the agent was retained. The formulated agent expressed an extended shelf life of at least 10 weeks when stored in ambient (25°C) temperature.
When the formulation granules were inoculated into sterile soil, viability of the granules was stable and also retained the maximum level of functionality for the full test period of 10 weeks. The soil surrounding the formulation granules was also enumerated. The number of cells in the soil increased after a single inoculation of the formulation and the maximum level of functionality was conveyed from the formulation to the surrounding soil.
The formulated inoculant constitutes an improvement for a bioremediation strain to stabilize the agent, produce an extended shelf life at ambient temperatures, and maintain the functionality of a microbe to utilize atrazine. In this thesis we have used a biopolymer formulation in which an inoculum is simply mixed into a gel and applied directly to the surface of the zeolite with no special equipment, drying, temperatures, or secondary re-growth steps required. It is a simple model system consisting of a carrier, and a artificial biofilm. As a technique to produce stable functional inoculants for bioremediation, the work presented here demonstrates an approach that is simple, practical, effective, and robust.