Main Article Content
Bacillus thuringiensis (Bt) is a significant bioinsecticidal agent that has been solely produced by liquid fermentation. With the increasing demand of bioinsecticides for organic agriculture, solid fermentation is preferred to enable low-cost and large-scale production of Bt. Therefore, in this study, we attempted to develop a solid state fermentation method to produce Bt by testing different solid substrates and also the effects of water percentage, fermentation time, temperature and seeding rate on the productions of biomass and parasporal crystal bodies (crystal proteins) of the Bt strain PAM33. Corn bran, rice bran and soybean meal are suitable to be utilized as substrates for biomass production. However, crystal proteins are only observed in solid fermentation using soybean meal as the substrate after 6 days of culture. The temperature range of 25-30°C and 10% seeding rate are the most suitable conditions for solid fermentation of strain PAM33 to obtain the bacterial density of approximate 109 CFU/g and the highest quantity of crystal proteins. This study shows that solid fermentation of Bt is feasible and effective to obtain bacterial biomass and crytal proteins by using cheap and available agricultural wastes. Thus, it can be a potential approach to produce the important Bt-based insecticide products for use in organic agriculture.
 A. N. Williams, K. S. MacLea, Genome sequence of Bacillus thuringiensis strain MW, a freshwater isolate, Microbiol Resour Announc 9:e01482-19, 2020, https://doi.org/ 10.1128/MRA.01482-19.
 N. Crickmore, Beyond the spore – past and future developments of Bacillus thuringiensis as a biopesticide, Journal of Applied Microbiology, 101, 2006, pp. 616-619, https://doi.org/10.1111/ j.1365-2672.2006.02936.x.
 C. Usta, Microorganisms in Biological Pest Control - A Review (Bacterial Toxin Application and Effect of Environmental Factors), In Current Progress in Biological Research, 2013.
 L. J. Stowell, Submerged Fermentation of Biological Herbicides. In TeBeest D.O. (eds) Microbial Control of Weeds, Springer, Boston, MA, 1991, https://doi.org/10.1007/978-1-4615-9680-6_13
 H. Zou, S. Ding, W. Zhang, J. Yao, L. Jiang, and J. Liang, Study on influence factors in Bacillus Thuringiensis production by semi-solid state fermentation using food waste, Procedia Environmental Sciences. 31, 2016, pp. 127-135.
 D. M. Fontana Capalbo, F. H. Valicente, I. D. Oliveira Moraes, and L. H. Pelizer, Solid-state fermentation of Bacillus thuringiensis tolworthi to control fall armyworm in maize, Electronic journal of Biotechnology, 4(2), 2001, pp. 9-10.
 Y. Içgen, B. Içgen, and G. Özcengiz, Regulation of crystal protein biosynthesis by Bacillus thuringiensis: II. Effects of carbon and nitrogen sources, Research in Microbiology. 153(9), 2002, pp. 605-609.
 E. Aranda, A. Lorence, and M. Del Refugio Trejo, Rural production of Bacillus thuringiensis by solid state fermentation, in Entomopathogenic Bacteria: from Laboratory to Field Application, Springer, 2000, pp. 317-332.