lpa-14, a gene, involved in the production of lipopeptide antibiotics, regulates the production of a siderophore, 2,3-dihydroxybenzoylglycine, in Bacillus subtilis RB14

Optimization of spore and antifungal lipopeptide production during the solid-state fermentation of Bacillus subtilis

Bacillus subtilis strain TrigoCor 1448 was grown on wheat middlings in 0.5-l solid-state fermentation (SSF) bioreactors for the production of an antifungal biological control agent. Total antifungal activity was quantified using a 96-well microplate bioassay against the plant pathogen Fusarium oxysporum f. sp. melonis. The experimental design for process optimization consisted of a 2(6-1) fractional factorial design followed by a central composite face-centered design. Initial SSF parameters included in the optimization were aeration, fermentation length, pH buffering, peptone addition, nitrate addition, and incubator temperature. Central composite face-centered design parameters included incubator temperature, aeration rate, and initial moisture content (MC). Optimized fermentation conditions were determined with response surface models fitted for both spore concentration and activity of biological control product extracts. Models showed that activity measurements and spore production were most sensitive to substrate MC with highest levels of each response variable occurring at maximum moisture levels. Whereas maximum antifungal activity was seen in a limited area of the design space, spore production was fairly robust with near maximum levels occurring over a wider range of fermentation conditions. Optimization resulted in a 55% increase in inhibition and a 40% increase in spore production over nonoptimized conditions.

Bacterial control of plant diseases

This article focuses on the effective biocontrol of plant diseases by microorganisms, which is attracting attention as an alternative to chemical control methods. As most research has so far been concentrated on fluorescent Pseudomonas species, the use of Bacillus species which has been considered to be less effective compared to that of pseudomonads, has been mainly introduced to demonstrate the effectiveness of the bacteria.