Molecular characterization of Paenibacillus antarcticus IPAC21, a bioemulsifier producer isolated from Antarctic soil

Abstract

Paenibacillus antarcticus IPAC21, an endospore-forming and bioemulsifier-producing strain, was isolated from King George Island, Antarctica. As psychrotolerant/psychrophilic bacteria can be considered promising sources for novel products such as bioactive compounds and other industrially relevant substances/compounds, the IPAC21 genome was sequenced using Illumina Hi-seq, and a search for genes related to the production of bioemulsifiers and other metabolic pathways was performed. The IPAC21 strain has a genome of 5,505,124 bp and a G + C content of 40.5%. Genes related to the biosynthesis of exopolysaccharides, such as the gene that encodes the extracellular enzyme levansucrase responsible for the synthesis of levan, the 2,3-butanediol pathway, PTS sugar transporters, cold-shock proteins, and chaperones were found in its genome. IPAC21 cell-free supernatants obtained after cell growth in trypticase soy broth at different temperatures were evaluated for bioemulsifier production by the emulsification index (EI) using hexadecane, kerosene and diesel. EI values higher than 50% were obtained using the three oil derivatives when IPAC21 was grown at 28°C. The bioemulsifier produced by P. antarcticus IPAC21 was stable at different NaCl concentrations, low temperatures and pH values, suggesting its potential use in lower and moderate temperature processes in the petroleum industry.

Keywords: Antarctica; Paenibacillus antarcticus; bioemulsifier; genome; levan.

Figure 1

Alignment of the 16S rRNA-encoding gene of Paenibacillus antarcticus IPAC21 and related species. The phylogenetic tree was constructed using the maximum likelihood method and the Jukes–Cantor model. The GenBank accession number of each sequence is shown in parentheses. Bootstrap values are expressed as percentages of 1,000 replications and are shown at branch points. Bacillus subtilis RNA40 was used as an outgroup.

Figure 2

Paenibacillus antarcticus strain IPAC21 subsystem features based on the RAST annotation server.

Figure 3

Representation of the metabolic pathway of EPS production found in the IPAC21 genome. The diagram demonstrates the enzymes found using KEGG and Metacyclic annotation programs. Levansucrase (EC 2.4.1.10); sugar PTS (EC 2.7.1.-); phosphoglucomutase (EC 5.4.2.2); UTP-glucose-1-phosphate uridylyltransferase (EC 2.7.7.9); glucose-1-phosphate thymidylyltransferase (EC 2.7.7.24); galactose-1-phosphate uridylyltransferase (EC 2.7.7.12); UDP-glucose-6-dehydrogenase (EC 1.1.1.22); dTDP-glucose-4,6-dehydratase (EC 4.2.1.46); dTDP-4-dehydrorhamnose-3,5-epimerase (EC 5.1.3.13); dTDP-4-dehydrorhamnose reductase (EC 5.1.3.- 1.1.1.-); exopolysaccharide biosynthesis protein; flippase (EC 7.6.2.1).

Figure 4

Circular diagram illustrating the nucleotide similarity between P. antarcticus IPAC21 (in purple, inside the circle) and other Paenibacillus genomes represented by concentric rings.

Figure 5

Emulsifying indexes (E24) of P. antarcticus IPAC21 with different oils (kerosene, n-hexadecane, diesel) after IPAC growth in TSB at 5°C, 15°C, and 28°C. Different letters indicate statistically significant differences (Tukey, p < 0.05).

Figure 6

Stability of the bioemulsifier produced by IPAC21 under different salinity, pH and temperature conditions. (A) NaCl concentrations of 3, 6, 9 and 12%. (B) pH of 2, 4, 10, 12. (C) Temperatures of −20°C, 5°C and 15°C.