Optimization of Paenibacillus polymyxa wettable powder based on the extreme vertex mixture design

Wettability is an important quality performance of wettable powder (WP). In this study, 10% (mass fraction) precipitated silica (PS) in light calcium carbonate (LCC) was used to reduce wetting time of Paenibacillus polymyxa WP (PPWP) from 416 s to 54 s. Then, extreme vertex mixture design was used to optimize PPWP formulation. Optimization results showed that suitable LCC mass fraction in PPWP carrier was 90%-92%, suitable PS mass fraction was 7.5%-9.0%. Under these conditions, mixture design predicted that wetting time of PPWP would be 85-117 s, suspensibility of PPWP would be 70.5%-71.7%, and pH value of PPWP would be 9.01-9.05. Verification test results matched well with the predicted results, which will provide reference for optimization of PPWP.