Meios de cultura para produção de endósporos por Bacillus velezensis

Abstract

The control of plant disease is essential to minimze the damage. Among plant disease control measures, biological control is an economically and environmentally viable alternative. The genus Bacillus is recognized for its efficiency in the control plant disease, with several species available on the market. The isolate of Bacillus velezensis AP 3 has been showing promise in the control of diseases, nematodes, seed treatment and as a coinoculant, as it acts through antibiosis, competition and induction of resistance, in addition to promoting plant growth, being a producer of phytohormones. The present work aimed to optimize the mass production of B. velezensis AP 3 and to develop a wettable powder formulation. Optimization was based on endospore production which was evaluated by determining colony forming units. The optimization of liquid fermentation was performed by testing eight different culture media. Soon after, the physical factors aeration, temperature, leaving the Erlenmeyers stationary after a day of fermentation, sonication in an ultrasound bath and the pre-culture volume were evaluated. For the optimization of nutritional factors after testing different media, some were selected for tests with replacement of the nitrogen or carbon source. Subsequently, the isolate was formulated in two different formulations, which were composed of 50% inert 50% of broth fermented with B. velezensis AP-3 and added 5% dispersant after drying. The formulations were evaluated for storage stability and suspension. The agitation of the culture media, the oxygenation stress, the stress in an ultrasound bath and the pre-culture volume tested do not interfere with the production of B. velezensis AP-3 endospores. The best temperature for the production of B. velezensis AP-3 endospores was 34 °C. Chemically defined culture media for bacteria + sucrose + protein hydrolyzate, the one used by a farmer, the one used by a farmer + protein hydrolyzate, the molasses + cottonseed meal, the molasses + soy protein isolate + hylyses yeast and the molasses + protein hydrolyzate produced at least 1x109 endospores mL-1. The wettable powder formulation based on soluble starch had a shelf life of over 114 days when stored at room temperature and also had adequate suspensability.