Genomic and phenotypic analysis unveiling the carbohydrate metabolic characteristics of Leuconostoc citreum SH12 in plant-based fermentation

Abstract

Leuconostoc citreum has been widely utilized for industrial fermentation. Previously, we found Leuc. citreum SH12 as a starter culture, exhibited superior fermentation characteristics in plant-based food, but its genomic, evolutionary and carbohydrate metabolic features remained unclear. This study aimed to reveal the metabolic characteristics of Leuc. citreum SH12 in response to various carbon sources by genomic and phenotypic analysis. By multiple sequencing technology, we assembled the 1.84 Mb complete genome of Leuc. citreum SH12 and identified 193 carbohydrate metabolism genes involved in the KEGG annotation, including 59 carbohydrate-active enzymes (CAZymes) genes. Comparative genome analysis indicated that Leuc. citreum SH12 had carbohydrate metabolism pathways similar to other Leuc. citreum, but it had 27 specific genes annotated as ABC transporters and hypothetical proteins, probably representing great resilience to the environment. The reconstruction of carbohydrate metabolic pathways and carbon utilization tests showed that Leuc. citreum SH12 could metabolize glucose, sucrose, fructose and maltose well, followed by xylose, arabinose, mannose and cellobiose, but could not utilize galactose, lactose, raffinose and stachyose. Soymilk fermentation test indicated that the strain could produce mannitol, and water-soluble and water-insoluble α-glucans. This study provided insights into a deeper understanding of the genomic and carbohydrate metabolic characteristics of Leuc. citreum SH12, and implied its potential application in plant-based fermented food.