Exploring key genes involved in the biosynthesis of gellan in Sphingomonas paucimobilis based on transcriptomic and metabolomic analyses of UV/ARTP-induced mutants

Gellan is a microbial polysaccharide synthesized by Sphingomonas paucimobilis , and is widely utilized in the food and pharmaceutical industries, as well as in other fields. However, much remains unknown about the key genes involved in the gellan synthesis pathway. In this study, ultraviolet (UV) and atmospheric room temperature plasma (ARTP) were employed to induce mutations in S . paucimobilis ATCC31461 (Sp31461 NC), and ultimately resulting a high-yield mutant strain (Sp31461 UA) with a yield increase of 120 % from 3.6 g/L to 8.3 g/L. The growth curve, monosaccharide composition and molecular weight indicated that mutagenesis accelerated the growth of the strain, but did not affect gellan's basic physicochemical property. A combined analysis of transcriptomic and metabolomic demonstrated that the differentially expressed genes and metabolites resulting from mutations were primarily enriched in pathways related to energy metabolism, among which potential key genes such as pgi , clpB , ycaJ associated with gellan yield, were further verified by quantitative reverse transcription polymerase chain reaction (qRT-PCR) and gene overexpression. Notably, the strain overexpression the pgi gene resulted in a 20 % increase in gellan yield compared to the Sp31461 UA strain, reaching 10.0 g/L. In summary, the energy metabolism pathway in S . paucimobilis is closely linked to gellan biosynthesis, and high-yield strains of gellan can be developed through mutagenesis breeding and the overexpression of key genes identified by transcriptomics and metabolomics. This research offers valuable scientific insights for the industrial production and application of gellan.