Optimization of fermentation medium for biocontrol strain Pantoea jilinensis D25 and preparation of its microcapsules

Abstract

A newly isolated biocontrol strain, Pantoea jilinensis D25, can effectively inhibit Botrytis cinerea caused tomato gray mold. However, the short shelf-life limits its biopesticide applications. This study optimized the fermentation medium for P. jilinensis D25. Also, the best microencapsulation conditions were determined. P. jilinensis D25 microcapsules (D25Ms) were evaluated for storage stability and biofilm formation ability. The results showed that the optimal medium composition contained sucrose (19.65 g/L), tryptone (2.73 g/L), NaCl (20.71 g/L), and yeast extract (13.00 g/L) at pH 6–8. The optimal fermentation conditions were temperature 25 ℃, inoculation amount 2 %, rotation speed 150 r/min, and liquid volume 75 mL. Maltodextrin was found to be an effective microencapsulation wall material showing a great protective effect on P. jilinensis D25. The bacterial survival rate was the highest (90.83 %) for conditions: maltodextrin 80 %, air-inlet temperature 130 ℃, feed flow rate 500 mL/h, and spray pressure 0.15 MPa. D25Ms were stored at 4 ℃ for 180 days showing the bacterial survival rates of 95.1 %. Compared with free cells, the biofilm formation ability of D25Ms was 1.86 times higher. Overall, D25Ms with good stability and biofilm formation ability can be a potential biocontrol agent.