Efficient isolation of new lactobionic acid-producing microorganisms from environmental samples by colloidal calcium carbonate agar plate-based screening.

Lactobionic acid (LBA) has recently emerged as an important substance in various industries, such as cosmetics, foods, and pharmaceuticals. In this study, we developed a simple, efficient, and high-throughput method for screening LBA-producing microorganisms. First, an agar plate was prepared to isolate LBA-producing microorganisms by utilizing the property of LBA to solubilize colloidal calcium carbonate (CaCO), resulting in the formation of a clear halo around colonies on a nutrient broth agar plate containing CaCO. Subsequently, LBA production from the isolated microorganisms was confirmed using high-performance liquid chromatography (HPLC). Approximately 560 colonies from soil samples in Ulsan, Korea were screened and a clear halo was observed around three colonies on the prepared LBA-screening agar plate. The culture supernatants of these three colonies were analyzed by HPLC and it was found that these strains could produce LBA from lactose. Phylogenetic analysis by comparing their 16S rRNA nucleotide sequences revealed that these strains were Pseudomonas spp. and Alcaligenes faecalis. This is the first report highlighting that A. faecalis can produce LBA. As per the aforementioned results, the LBA-screening method that we devised here is highly effective for isolating and identifying new LBA-producing microorganisms.