Exploring Levansucrase Operon Regulating Levan-Type Fructooligosaccharides Production in Priestia koreensis HL12.

Levan biopolymer and levan-type fructooligosaccharides (L-FOSs) are β-2,6-linked fructans that have been used as non-digestible dietary fiber and prebiotic oligosaccharides in food and cosmeceutical applications. In this study, we explore the operon responsible for levan and lL-FOSs production in Priestia koreensis HL12. Presented is the first genomic perspective on sucrose utilization and the levan biosynthesis pathway in this bacterium. Regarding sequence annotation, the putative levansucrase operon responsible for β-2,6-linked fructan was identified in the genome of strain HL12, and comprises sacB levansucrase gene belonging to GH68, located adjacent to levB endo-levanase gene, which belongs to GH32. Importantly, sugars related with the levan biosynthesis pathway are proposed to be transported via 3 types of transportation systems, including multiple ABCSugar and glucose/H+ transporters, as well as glucoseand fructose-specific PTS systems. Based on product profile analysis, the HL12 strain exhibited high efficiency in levan production from high sucrose concentration (300 g/l), achieving the highest yield of 127 g/l (equivalent to 55% conversion based on sucrose consumption), together with short-chain L-FOSs (DP3-5) and long-chain L-FOSs with respective size larger than DP6 after 48 h incubation. These findings highlight the potential of P. koreensis HL12 as a whole-cell biocatalyst for producing levan and L-FOSs, and underscore its novelty in converting sugars into high-value-added products for diverse commercial and industrial applications.