Draft genome sequencing of Sporolactobacillus terrae SBT-1, an efficient bacterium to ferment concentrated sugar to d -lactic acid

Recently, the industrial-scale development of microbial d -lactic acid production has been discussed. In this study, the efficiency of the new isolate Sporolactobacillus terrae SBT-1 for producing d -lactic acid under challenge conditions was investigated. The isolate SBT-1 exhibited superior activity in fermenting a very high glucose or sucrose concentration to d -lactic acid compared to the other S. terrae isolates previously reported in the literature; therefore, SBT-1 could overcome the limitations of effective lactic acid production. In batch cultivation using 360 g/L glucose, SBT-1 produced 290.30 g/L d -lactate with a sufficiently high glucose conversion yield of 86%, volumetric productivity of 3.02 g/L h, and optical purity of 96.80% enantiomer excess. SBT-1 could also effectively utilize 440 g/L sucrose as a sole carbon source to produce 276.50 g/L lactic acid with a conversion yield of 90%, a production rate of 2.88 g/L h, and an optical purity of 98%. d -Lactic acid fermentation by two other related producers, S. inulinus NRIC1133 T and S. terrae NRIC0357 T , was compared with fermentation by isolate SBT-1. The experimental data revealed that SBT-1 possessed the ability to ferment relatively high glucose or sucrose concentrations to d -lactic acid without obvious catabolite repression and byproduct formation compared to the two reference strains. In draft genome sequencing of S. terrae SBT-1, the results provided here can promote further study to overcome the current limitations for the industrial-scale production of d -lactic acid.