Sigma factors are initiation factors that promote the attachment of RNA polymerase (RNAP) to specific initiation sites and are then released. This sigma factor is responsible for the expression of the levanase operon. The open complex (sigma-54 and core RNA polymerase) serves as the receptor for receipt of the melting signal from the remotely bound activator protein LevR for the expression of the levanase operon. Associates with the RNAP core only in stationary phase cells (PubMed:21710567). Interacts transiently with the RNAP core. Association with RNAP core increases slightly during late sporulation but not tested stresses (at protein level). Belongs to the sigma-54 factor family.