Alternative low-cost process for large-scale production of Bacillus thuringiensis in a simple and novel culture system

• Published in: Journal of environmental science and health. Part B, Pesticides, food contaminants, and agricultural wastes Pesticides, food contaminants, and agricultural wastes, 2018-01, Vol.53 (11), p.719-728
• Main Authors: Rojas, Natalia L., Lewkowicz, Elizabeth S., Nobile, Matias L.
• Format: Article
• Language: English
• Subjects: Aquatic insects; Bacillus thuringiensis; Bacillus thuringiensis israelensis; Baking yeast; biopesticide; Bioreactors; Culture; Fed batch; fed batch one pot; Glycerol; Inoculation; Insect control; Insecticides; Low cost; Mosquitoes; Saccharomyces cerevisiae; Spores; Strategy; Yeasts
• ISSN: 0360-1234; 1532-4109
• DOI: 10.1080/03601234.2018.1480156

An industrial-scale, profitable method for production of the most widely used bioinsecticide, Bacillus thuringiensis (Bt), is challenging because of its widespread application. The aim of this study is to present a strategy to develop a low-cost, large-scale bioprocess to produce Bt H14. This study was first focused on the design of a culture medium composed of economical and available components, such as glycerol and lysed Saccharomyces cerevisiae. The production goal of 1200 ITU was achieved using a medium composed of 20:20 g L −1 of glycerol:lysed yeast in batch cultures. Efforts were subsequently focused on the design of an appropriate culture system, and an original two-stage culture system was proposed. First, yeast (the primary component of the culture medium) are cultivated using a minimal mineral medium and lysed, and in the second stage, Bt is cultivated in the same bioreactor using the lysed yeasts as culture medium (supplemented with a feeding pulse of 10 g L −1 glycerol). This system was called fed batch one pot (FOP). A new inoculation strategy is also presented in this study, since these Bt cultures were inoculated directly with heat pre-treated spores instead of vegetative bacteria to facilitate the bioprocess. This study was developed from the laboratory to production-scale bioreactors (measuring from 500 mL to 2500 L), and the efficiency of the proposed strategy was evident in LD 50 tests results, achieving 1796 ITU in large-scale processes. Both the use of non-conventional sources and the process development for biomass production are important for cost-effective production of Bt-based insecticides in mosquito control projects.