The main objective of the present invention is to provide a lactic acid bacterial strain and a composition for improving gut microbiota composition. The composition comprises the lactic acid bacterial strain and/or extracellular vesicles secreted by the lactic acid bacterial strain. Another objective of the present invention is to provide a method for improving gut microbiota composition and products of the lactic acid bacterial strain. Additionally, the composition of the present invention has the capability to influence the growth of Firmicutes and Bacteroidetes, thereby leading to an improvement in gut microbiota composition.