Bacterial glycolipids in Pediococcus pentosaceus for fermented soybean paste (miso) and Tetragenococcus halophilus for soy sauce

Gram-positive bacterial biomembranes are composed of phosphatidyl glycerol (PG), cardiolipin (CL), and dihexaosyl diglycerides (DH-DG) as the major lipid constituents. The carbohydrate structures of DH-DG are specific to the particular bacterial species and we previously revealed them to have immunologically active properties. To characterize the functional significance of glycolipids in Gram-positive bacteria for fermented foods, the structures of DH-DG in Pediococcus pentosaceus (PP) for producing fermented soybean paste (miso) and Tetragenococcus halophilus (TH) for soy sauce were determined. They were shown to be Glcα1-2Glcα1-3′DG (kojibiosyl DG) with 18:1 and 18:1 for PP, and those with 16:0 and 18:1 for TH, both of which were identical to DH-DG from Streptococcus salivarius , a symbiotic bacterium in the human oral cavity. Additionally, both bacteria contained an acidic glycolipid, in which glycerol phosphate was attached to the 6-position of the nonreducing terminal Glc residue of DH-DG. DH-DG in PP and TH comprised 65.5% and 81.6% of the total glycolipids, respectively, and the ratios of PG and DH-DG to CL were 1.9 and 1.4 for PP, and 2.0 and 1.7 for TH. TLC immunostaining with human sera revealed antibodies for Galα1-2Glcα1-3′DG (LacDH-DG) from Lactobacillus species and Glcβ1-6Glcβ1-3′DG (StaDH-DG) from Staphylococcus species, but not for Glcα1-2Glcα1-3′DG (StrDH-DG) from Streptococcus species, in 2 out of 20 human sera. Given that one serum sample with anti-StaDH-DG antibodies was from a patient who had suffered food poisoning due to Staphylococcus aureus 6 months previously, the antibodies for bacterial DH-DG were thought to have arisen via bacterial infection.