Abstract
Bacillus cereus strain C1L, screened from the rhizosphere of Lilium formosanum, prevents severe lily leaf blight. The purpose of this study was to formulate a new biopesticide by microencapsulating the C1L strain to enhance residual stability. In addition, since the viable cell number of Bacillus cereus C1L is an important factor affecting the biological effects of this fungicide, this study also used the response surface methodology and sequential quadratic programming methods to optimize the best formula for maximum viability of Bacillus cereus C1L microencapsulated by spray drying. Optimization results revealed that the strain could maintain 42% viability with 18.3% maltodextrin and 12.5% gum arabic as coating materials and spray drying at an outlet temperature of 73.5 oC. A comparison with chemical pesticides showed that maneb was the most efficient disease inhibitor, followed by B. cereus C1L encapsulated by spray drying. The chemical pesticide probenazole and B. cereus C1L encapsulated by extrusion revealed no significant differences in disease control.
Highlights
Bacillus cereus, a large, gram-positive and endospore-forming bacterium, is very common in plants and soils (Martinez, Michaud, Belanger, & Tweddell, 2002; Huang, Wang, Chung, & Chen, 2005)
Since the viable cell number of Bacillus cereus C1L is an important factor affecting the biological effects of this fungicide, this study used the response surface methodology and sequential quadratic programming methods to optimize the best formula for maximum viability of Bacillus cereus C1L microencapsulated by spray drying
A comparison with chemical pesticides showed that maneb was the most efficient disease inhibitor, followed by B. cereus C1L encapsulated by spray drying
Summary
A large, gram-positive and endospore-forming bacterium, is very common in plants and soils (Martinez, Michaud, Belanger, & Tweddell, 2002; Huang, Wang, Chung, & Chen, 2005). Several studies have reported that antifungal compounds of B. cereus strains are beneficial biological control agents in the suppression of crop disease. B. cereus DGA34 naturally produces the antibiotic zwittermicin A, an effective antibiotic against a wide range of bacteria and fungi to reduce symptoms of damping-off disease and root rot (Handelsman, Jacobson & Stabb, 1998). B. cereus UW85, generating two antibiotics (zwittermicin A and antibiotic B) (Silo-Suh, Lethbridge, Raffle, He, Clardy, & Handelsman, 1994), has been proven to be a dependable biocontrol agent, which protects cucumber fruits from rot caused by Pythium aphanidermatum, alfalfa seedlings from dampening off due to Phytophthora medicaginis, tobacco seedlings from Phytophthora nicotianae and peanuts from Sclerotinia minor (Silo-Suh et al, 1994). Only few B. cereus strains have current United States patents as biocontrol agents for crop diseases
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