David A. Schisler

Cyclic lipopeptide profile of three Bacillus subtilis strains; antagonists of Fusarium head blight

The objective of the study was to identify the lipopetides associated with three Bacillus subtilis strains. The strains are antagonists of Gibberella zeae, and have been shown to be effective in reducing Fusarium head blight in wheat. The lipopeptide profile of three B. subtilis strains (AS43.3, AS43.4, and OH131.1) was determined using mass spectroscopy. Strains AS43.3 and AS43.4 produced the anti-fungal lipopeptides from the iturin and fengycin family during the stationary growth phase. All three strains produced the lipopeptide surfactin at different growth times. Strain OH131.1 only produced surfactin under these conditions. The antifungal activity of the culture supernatant and individual lipopeptides was determined by the inhibition of G. zeae. Cell-free supernatant from strains AS43.3 and AS43.4 demonstrated strong antibiosis of G. zeae, while strain OH131.1 had no antibiosis activity. These results suggest a different mechanism of antagonism for strain OH131.1, relative to AS43.3 and AS43.4.

Discovery and development of biological agents to control crop pests

Thousands of potential microbial biocontrol agents have been isolated from agricultural fields and crops during research over the last 80 years, yet only a few are in commercial use. Recently, public health and safety concerns about the environmental impact of chemical pesticides have led to consideration of biological control as a natural approach to maintaining crop health. Despite environmental incentives and strong research efforts, commercialization of biocontrol agents has been slow to evolve. The momentum of the chemical industry is difficult to shift, and fermentation processes tend to be more expensive to operate than synthetic chemical processes.Yet there is a demand for biological control products, especially in agricultural niche markets, where there is no chemical competitor. However, given this market demand, the fundamental methods of economical large-scale production and application of biological control agents are lacking. Many aspects of biocontrol agent production and development represent untrodden territory in the progression of industrial fermentation technology beyond its well-established food and pharmaceuticals niche. Distinguishing them from traditional fermentation products, biocontrol agents must not only be produced in high yield but must also meet the following quality criteria: high (near 100%) retention of cell viability with maintenance of crop compatibility and consistent bioefficacy during several months of storage. Research examples will be reviewed to illustrate the challenges and strategies of developing processes to manufacture and deliver biological agents for insect, weed, and plant disease control.

Biological Control Agents for Suppression of Post-Harvest Diseases of Potatoes: Strategies on Discovery and Development

As used in plant pathology, the term biological control or its short form “biocontrol” commonly refers to the decrease in the inoculum or the disease-producing activity of a pathogen accomplished through one or more organisms, including the host plant but excluding man (Baker, 1987). Biological control of plant pathogens naturally occurs at some level in all agricultural ecosystems, sometimes to a degree where symptoms of disease are noticeably reduced. Thousands of potential microbial biocontrol agents have been isolated from agricultural fields and crops during research over the last 80 years, yet only a few are in commercial use. Recently, public health and safety concerns about the environmental impact of chemical pesticides have led to consideration of biological control as a natural approach to maintaining crop health. Despite environmental incentives and strong research efforts, commercialization of biocontrol agents has been slow to evolve. The momentum of the chemical industry is difficult to shift, and fermentation processes tend to be more expensive to operate than synthetic chemical processes. Yet there is a demand for biological control products, especially in the organic and agricultural niche markets, where there is no efficient chemical competitor. Indeed, the tide has been turning and a recent story in Chemical and Engineering News (Reisch, 2011) has indicated that during the last decade, the growth in sales of biological pest control agents has significantly outpaced that of chemicals. However, given this market demand, the fundamental methods of economical large-scale production and application of biological control agents are still lacking and need to be developed. Many aspects of biocontrol agent production and development represent untrodden territory in the progression of industrial fermentation technology beyond its well-established food and pharmaceuticals niche. Distinguishing them from traditional fermentation products, biocontrol agents must not only be produced in high yield but must also meet the following quality criteria: high (near 100%) retention of cell viability with maintenance of crop compatibility and consistent bioefficacy during several months of storage.

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

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 (Pxa0≤xa00.05, 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 50–96xa0% compared to controls. In studies using a high-throughput microbioreactor, logarithmic growth of P22Y05 in plant extract-based media initiated in 3–5xa0h 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.