Investigation of Bacillus subtilis as a Biopesticide Against Botrytis cinerea

<p>The objective of this thesis was to investigate BiOWiSH^TM-Aqua, a commercial dry solid formulation containing a consortium of bacteria and yeast, as a biopesticide for treatment of <em>Botrytis cinerea</em>, a gray mold that affects strawberries. BiOWiSH^TM-Aqua was compared with another commercial product specifically used as a fungicide and bacteriocide, Serenade® Garden Disease Control Spray (concentrated <em>Bacillus subtilis</em> strain QST 713). Both laboratory tests as well as <em>in vivo</em> lab tests were conducted. BiOWiSH^TM-Aqua results varied widely from plate to plate, regardless of experimental conditions. In some of these plates, inhibition zones were observed around colonies from BiOWiSH^TM-Aqua, indicating efficacy. The organism responsible for the inhibition zones of <em>B. cinerea</em> growth was isolated from BiOWiSH^TM-Aqua, and 16s rRNA analysis identified this culture as a strain of <em>B. subtilis</em>. This strain was designated as <em>B. subtilis</em> ssp. KLB. The <em>B. subtilis</em> KLB concentration required to completely inhibit <em>B. cinerea</em> was 9.1x10⁴ CFU/mL when <em>B. subtilis</em> KLB was inoculated 48 hours before <em>B. cinerea</em>, 1.3x10⁵ CFU/mL at 24 hours, and 3.2x10⁶ CFU/mL when both were inoculated at the same time. Various preliminary experiments using <em>B. subtilis</em> KLB were also conducted to investigate its economic feasibility, to characterize the organism, and to test its post-harvest <em>in vivo</em> viability. <em>B. subtilis</em> KLB cell concentration was 1.6x10⁹ CFU/mL in a bioreactor with LB at the end of the log growth phase. <em>B. subtilis</em> KLB achieved cell concentrations as high as 5x10⁹ CFU/mL in shake flasks with food-grade tapioca as a carbon source. Inoculation of <em>B. subtilis</em> KLB on post-harvest strawberries did not have an effect on <em>Botrytis</em> infection rates compared to the negative control. These various experiments were the first step in research to potentially produce <em>B. subtilis</em> KLB on a commercial scale.</p>

Name thesis:degree_name

MS in Engineering - Biochemical Engineering

Discipline thesis:degree_discipline

Biomedical and General Engineering

Year dc:date.available

2012

Author dc:creator

• Ng, Kenneth K

Contributors dc:contributor

• Nirupam Pal

• biopesticides
• botrytis
• bacillus subtilis
• Agriculture
• Biochemical and Biomolecular Engineering
• Biotechnology
• Environmental Microbiology and Microbial Ecology

Identifier

10.15368/theses.2012.35

OAI identifier oai:identifier

oai:digitalcommons.calpoly.edu:theses-1758