Development of a novel fermentation and formulation process for an endophytic Beauveria bassiana strain

Abstract: There is an increasing demand for alternative or complementary crop protectionstrategies. A novel approach could be the use of the entomopathogenic and endophytic fungusBeauveria bassiana isolate ATP-04. To use the endophyte as a commercial biocontrol agent, thefungus has to be mass-produced. B. bassiana was raised in shake flask cultures to producesubmerged conidiospores (SCS) which are reported to show a higher shelf life than myceliumand blastospores (BS). It was found that in mineral media with 5% sugar beet molassesB. bassiana produced 0.1 x 1010 SCS g-1 sucrose in 192 h. By adding 50 g l-1 NaCl 48 h afterinoculation the SCS yield increased to 1.4 x 1010 SCS g-1 sucrose. The scale-up to a 2 l stirredtank reactor was carried out at 25°C, 200-600 rpm and 1 vvm at pH 5.5. A total spore yield of 5.2x 1010 spores g-1 sucrose corresponding to a SCS yield of 0.2 x 1010 SCS g-1 sucrose was obtainedafter 216 h. Also the yield of SCS increased to 1.1 x 1010 SCS g-1 sucrose by the addition ofNaCl. After fermentation the B. bassiana was formulated in a novel spray formulation thatdelivers the fungus on oilseed rape leaves, increases persistence, germination and growth onleaves as well as penetration, colonization and efficacy in bioassays with Plutella xylostella.