Philodulcilactobacillus myokoensis gen. nov., sp. nov., a fructophilic, acidophilic, and agar-phobic lactic acid bacterium isolated from fermented vegetable extracts.

Lactic acid bacteria are commonly in the fermentation industry and pose potential positive effects on health. In this study, a new lactic acid bacterium was isolated from fermented vegetable extracts in Myoko, Niigata, Japan. This bacterium is fructophilic, acidophilic, and hard to grow on agar medium. The isolate is Gram-stain-positive, non-spore-forming, non-motile, rod-shaped, and catalase-negative. Growth occurred at pH 3.5-5.5, with optimal growth at pH 4.5-5.0. The cells formed colonies on a solid MRS medium with 20% (w/v) sucrose and 0.8% (w/v) gellan gum under anaerobic conditions. The bacterium was able to grow on up to 50% (w/v) sucrose but not on d-glucose. Moreover, 16S rRNA gene sequence analysis revealed that the strain was most closely related to Apilactobacillus ozensis (93.1% sequence similarity). The values of average nucleotide identity, digital DNA-DNA hybridization, average amino acid sequence identity, and amino acid identity of conserved genes were calculated between the isolated strain (type strain is WR16-4T = NBRC 115064T = DSM 112857T) and its phylogenetically closest type strains. The average nucleotide identity values (73.36-78.28%) and DNA-DNA hybridization values (16.3-32.9%) were significantly lower than the threshold values for species boundaries. The average amino acid sequence identity values (53.96-60.88%) were significantly below the threshold boundary of genus demarcation (68%). The amino acid identity of conserved genes values compared to strain WR16-4T were the genera Apilactobacillus, Nicoliella spurrieriana SGEP1_A5T, Acetilactobacillus jinshanensis HSLZ-75T, and Fructilactobacillus were 62.51-63.79%, 62.87%, 62.03%, and 58.00-61.04%, respectively. The 16S rRNA gene and core genome phylogenetic trees suggested that this novel strain was most closely related to the type strain of A. jinshanensis HSLZ-75T. Based on the physiological, morphological, and phenotypical characteristics of strain WR16-4T, we propose its classification as a novel genus, Philodulcilactobacillus myokoensis gen. nov., sp. nov.

Effect of steam explosion pretreatment on treatment with Pleurotus ostreatus for the enzymatic hydrolysis of rice straw.

The effects of steam explosion (1.5 MPa, 1 min) on the treatment of rice straw with Pleurotus ostreatus were evaluated in terms of the change in composition of the components and the susceptibility to enzymatic hydrolysis. When rice straw was pretreated with a steam explosion prior to biological treatment, the treatment time required for obtaining a 33% net glucose yield was reduced to 36 days from 60 days. The reduction is probably due to loosening of networks of Klason lignin with sugar moieties and partial collapse of the structure during the biological treatment.