Draft Genome Sequence of Sporolactobacillus inulinus Strain CASD, an Efficient d-Lactic Acid-Producing Bacterium with High-Concentration Lactate Tolerance Capability

Abstract

Sporolactobacillus inulinus CASD is an efficient d-lactic acid producer with high optical purity. Here we report for the first time the draft genome sequence of S. inulinus (2,930,096 bp). The large number of annotated two-component system genes makes it possible to explore the mechanism of extraordinary lactate tolerance of S. inulinus CASD.

GENOME ANNOUNCEMENT

Lactic acid, the most important hydroxycarboxylic acid, is regarded as a feedstock for the green chemistry of the future. Besides its versatile applications in the food, pharmaceutical, textile, and leather industries, lactic acid is also a building block for biodegradable plastic, mainly poly(l-lactic acid), which has gained substantial attention in the new wave of industrial biotechnology (7, 4). The development of a stereocomplex of poly(l-lactic acid) and poly(d-lactic acid) is considered an advance in poly(lactic acid) modification, in which the melting point of this stereocomplex could reach the same temperature as that of other petroleum-based polymers (3). Therefore, the potential utilization of d-lactic acid has attracted increased attention to its production by using sustainable bioresource materials (8, 12).

Sporolactobacillus is a genus of anaerobic endospore-forming, Gram-positive, motile, rod-shaped lactic acid bacteria. Sporolactobacillus inulinus, the type species of the genus, was originally named Sporolactobacillus (subgen. Lactobacillus) inulinus (5). Because of its high-optical-purity d-lactic acid-producing capability, Sporolactobacillus inulinus has been suggested to be a better producer of d-lactic acid (2, 12). Sporolactobacillus inulinus CASD, isolated by our group (10), can produce high concentrations of d-lactic acid (207 g/liter) with very high optical purity at 99.3%, which is the highest production titer reported to date (9). The strain has been deposited in the China General Microbiological Culture Collection Center (no. 2185).

Here we report for the first time the draft genome sequence of Sporolactobacillus inulinus, obtained using the Illumina GA system with a paired-end library. The reads were assembled with the VELVET software program (11). The draft genome sequence of S. inulinus CASD was annotated with the Prokaryotic Genomes Automatic Annotation Pipeline (PGAAP) (6). In addition, the contigs were searched against the KEGG, UniProt, and Clusters of Orthologous Groups (COG) databases to annotate the gene descriptions. The G+C mole percent measurements were calculated using the genome sequence.

The draft genome includes 2,930,096 bases with a G+C content of 44.97%, consisting of 674 large contigs (>300 bp in size) and comprised of 3,476 predicted coding sequences (CDSs). According to KEGG pathway analysis, most genes encoding proteins for glycolysis, amino acids, nucleotides, lipids, cofactor/vitamin metabolism, and importantly d-lactic acid formation were successfully annotated. With many fructose- and mannose-metabolizing genes annotated, S. inulinus CASD is predicted to be capable of metabolizing fructose and mannose. Furthermore, two-component systems serve as a basic stimulus-response coupling mechanism to allow organisms to sense and respond to changes in many different environmental conditions, including temperature, osmolarity, chemoattractants, and pH pressure (8, 1). A large number of two-component system genes were annotated from the draft genome sequence, which gives a good chance to explore the mechanism of the extraordinary high-concentration lactate tolerance of S. inulinus CASD.

Nucleotide sequence accession number.

The draft genome sequence of Sporolactobacillus inulinus CASD is available in GenBank under accession number AFVQ00000000. The version described in this article is the first version.