Bacillus subtilis Genome Reduction Improves Surfactin Production

Bacillus subtilis ∆6 is a genome-reduced strain derived from the laboratory strain 168 through deletion of six prophages and AT-rich islands. The parental and the genome-reduced strains were edited to restore the capacity to synthesize surfactin. Although the genome deletions are not directly related to surfactin biosynthesis, the ∆6 strain produces more surfactin while building lower biomass compared to the parental strain. Further editions to ∆6, such as srfA promoter replacement, codY deletion, and comA overexpression, were deleterious to surfactin production. The results showcase that the ∆6 is metabolically distinct from its parental strain and other surfactin-producing strains, as the gene editions made have been previously described to increase surfactin production in these strains. The ∆6 produced the highest surfactin titer, rate, and yield in LB medium enriched with glucose, compared to other commonly used media for B. subtilis. This work demonstrates the enhanced capacity of a genome-reduced strain to produce surfactin compared to the parental strain, as well as the metabolic changes resulting from genome engineering.