Lactobacillus kosoi sp. nov., a fructophilic species isolated from kôso, a Japanese sugar-vegetable fermented beverage

A novel Gram-positive, fructophilic, catalase negative, and rod-shaped strain, designated strain 10H^T was isolated from kôso, a Japanese sugar-vegetable fermented beverage obtained from a food processing factory in Saku City, Nagano Prefecture, Japan. Phylogenetic analysis based on 16S rRNA gene sequences revealed strain 10H^T to belong to the genus Lactobacillus, with closely related type strains being Lactobacillus kunkeei YH-15^T (95.5% sequence similarity), Lactobacillus ozensis Mizu2-1^T (95.4% sequence similarity), and Lactobacillus apinorum Fhon13N^T (95.3% sequence similarity). The isolate was found to grow at 18–39 °C (optimum 27 °C), pH 4.0–7.0 (optimum pH 6.5) and in the presence of 0–2% NaCl (optimum 0% NaCl). The G + C content of its genomic DNA was determined to be 30.5 mol%. The major fatty acid (≥ 10%) components identified included C_16:0, C_19:0 cyclo ω7c, C_19:0 cyclo ω9c, and C_18:1 ω9c. The polar lipids were identified as lysophosphatidylethanolamine, phosphatidylethanolamine and glycolipids. The predominant isoprenoid quinones (> 10%) were identified as MK-7, MK-8, MK-9 and MK-10. The amino acid composition of the cell wall was detected as comprising Asp, Glu, Ala, and Lys but the strain lacks meso-diaminopimelic acid. As with other fructophilic lactic acid bacteria, such as L. kunkeei and L. apinorum, strain 10H^T was found to prefer d-fructose to d-glucose as a growth substrate. On the basis of these genetic and phenotypic results, the isolate is concluded to represent a novel species, for which the name Lactobacillus kosoi is proposed. The type strain is 10H^T (= NBRC 113063^T = BCRC 81100^T).