Enhanced emulsan production in mutants of Acinetobacter calcoaceticus RAG-1 selected for resistance to cetyltrimethylammonium bromide.

Mutants of Acinetobacter calcoaceticus RAG-1 that produced elevated levels of the polymeric bioemulsifier emulsan were isolated on the basis of their resistance to the cationic surfactant cetyltrimethylammonium bromide (CTAB). Such mutants showed maximum enhancement in both overall yield and specific productivity of some two- to threefold over that of the wild type. In addition, the effect was also observed in a resting cell system in the presence of chloramphenicol, indicating that the mutation is not simply the result of faster growth. When CTAB-tolerant mutants were subjected together with the sensitive parent to the detergent under growing conditions, only the mutants were found to grow. The results suggest that the mutation for CTAB resistance leads to enhanced capsule production. This was confirmed quantitatively by a specific enzyme-linked immunosorbent assay for the cell-bound emulsan minicapsule.