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Title: Evaluation of economically feasible, natural plant extract-based microbiological media for producing biomass of the dry rot biocontrol strain Pseudomonas fluorescens P22Y05 in liquid culture

item KHALIL, SADIA - University Of Karachi
item ALI, TASNEEM - University Of Karachi
item Skory, Christopher - Chris
item Slininger, Patricia - Pat
item Schisler, David

Submitted to: World Journal of Microbiology and Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/21/2015
Publication Date: 1/13/2016
Citation: Khalil, S., Ali, T.A., Skory, C., Slininger, P.J., Schisler, D.A. 2016. Evaluation of economically feasible, natural plant extract-based microbiological media for producing biomass of the dry rot biocontrol strain Pseudomonas fluorescens P22Y05 in liquid culture. World Journal of Microbiology and Biotechnology. 32(2):25. doi: 10.1007/s11274-015-1984-1.

Interpretive Summary: Scientific research on discovering biological control microorganisms to reduce plant diseases requires producing them in liquid media but costs of commercially available media can be a significant hurdle to conducting this research in developing countries. In previous research at the ARS laboratory in Peoria, IL, we found a bacterial isolate of Pseudomonas fluorescens that reduces Fusarium dry rot on stored potato tubers. In these studies, several plant extract-based media from sources ranging from onion bulbs to lentil seeds performed as well as commercial media in producing cells of P. fluorescens in shake flasks and in microbioreactors. Cells grown in these media also reduced dry rot by the same amount as those produced in commercial media. By identifying less costly alternatives to commercially produced liquid growth media, these results provide opportunity for scientists in developing countries to conduct additional research to discover environmentally friendly alternatives for plant disease control.

Technical Abstract: The production of microbial biomass in liquid media often represents an indispensable step in the research and development of bacterial and fungal strains. Costs of commercially prepared nutrient media or purified media components, however, can represent a significant hurdle to conducting research in locations where obtaining these products is difficult. A less expensive option for providing components essential to microbial growth in liquid culture is the use of extracts of fresh or dried plant products obtained by using hot water extraction techniques. A total of 13 plant extract-based media were prepared from a variety of plant fruits, pods or seeds of plant species including Allium cepa (red onion bulb), Phaseolus vulgaris (green bean pods), and Lens culinaris (lentil seeds). In shake flask tests, cell production by potato dry rot antagonist Pseudomonas fluorescens P22Y05 in plant extract-based media was generally statistically indistinguishable from that in commercially produced tryptic soy broth and nutrient broth as measured by optical density and colony forming units/ml produced (P=0.05, Fisher’s protected LSD). The efficacy of biomass produced in the best plant extract-based media or commercial media was equivalent in reducing Fusarium dry rot by 50-96% compared to controls. In studies using a high-throughput microbioreactor, logarithmic growth of P22Y05 in plant extract-based media initiated in 3-5 hours in most cases but specific growth rate and the time of maximum OD varied as did the maximum pH obtained in media. Nutrient analysis of selected media before and after cell growth indicated that nitrogen in the form of NH4 accumulated in culture supernatants, possibly due to unbalanced growth conditions brought on by a scarcity of simple sugars in the media tested. The potential of plant extract-based media to economically produce biomass of microbes active in reducing plant disease is considerable and deserves further research.