Taxonomy of acetic acid bacteria and oxidative products of Acetobacter and Gluconobacter strains

Abstract

One hundred and forty-seven isolates of acetic acid bacteria were isolated from fruits, flowers, and other materials in Thailand. They were divided into 4 genera, Acetobacter (86 isolates), Gluconobacter (42 isolates), Asaia (15 isolates), and Gluconacetobacter (4 isolates) based on their phenotypic and chemotaxonomic characteristics including RFLP-ITS analysis and the 16S rDNA phylogenetic analysis. Acetobacter isolates contained Q-9 as major quinone while the other genera contained Q-10. The DNA G+C contents ranged from isolates 52.2-64.3 mol%. Acetobacter isolates were identified as A. pasteurianus (Group 1, 26 isolates), A. orientalis (Group 2, 13 isolates), A. lovaniensis (Group 3, 10 isolates), A. indonesiensis (Group 4, 13 isolates), A. tropicalis (Group 5, 4 isolates), A. ghanensis (Group 6, 8 isolates), A. orleanensis (Group 7, 4 isolates), A. syzygii (Group 8, 4 isolates) and Acetobacter sp. (Group 9, 3 isolates). Gluconobacter isolates were identified as G. frateurii (Group 10, 8 isolates), G. japonicus (Group 11, 8 isolates), G. thailandicus (Group 12, 6 isolates), G. oxydans (Group 13, 13 isolates), Gluconobacter sp. (Group 14, 3 isolates) and Gluconobacter sp. (Group 15, 4 isolates). Asaia isolates were identified as As. bogorensis (Group 16, 8 isolates), As. siamensis (Group 17, 5 isolates) and As. sphathodeae (Group 18, 2 isolates), and Gluconacetobacter isolates were identified as Ga. liquefaciens (Group 19, 4 isolates). The isolates G360-1, G361-1 and G362-1 (Group 9) showed 99.7% 16S rDNA sequence similarity to A. orleanensis NBRC 13752T and discriminated from known Acetobacter species when digestion with HpaII and AvaII and low DNA-DNA relatedness (15-38%). Therefore, they should be proposed as a new species in the genus Acetobacter. The isolates RBY-1T, PHD-1 and PHD-2 (Group 14) showed 98.1% ITS genes sequence similarity to G. japonicus NBRC 3271T and discriminated from other Gluconobacter species when digestion with TaqI, AluI, HpaII and AvaII and low DNA-DNA relatedness (11-38%) Therefore, the name Gluconobacter nephelii sp. nov. was proposed for them. The isolates ZW160-2, LC155-1, LG156-2 and JJ157-2 (Group 15) showed 97.3% ITS genes sequence similarity to G. oxydans NBRC 14818T and discriminated from other Gluconobacter when digestion with TaqI, AluI, HpaII and AvaII and low DNA-DNA relatedness (11-26%). Therefore, they should be proposed as a new species in the genus Gluconobacter. The isolates GB23-2T and GB23-3 (Group 18) showed 99.9% 16S rDNA sequence similarity to As. siamensis NBRC 16457T and discriminated from other Asaia species when digestion with StyI, BsaJI, SnaBI, HpaII and HpyAV and low DNA-DNA relatedness (21-48%). Therefore, the name Asaia spathodeae sp. nov. was proposed for them. ADH activity was determined in Acetobacter isolates and the activity ranged from 2.05 to 7.52 unit/mg at 30°C. The isolate PHD-23 could produce highest acetic acid when the medium composed of ethanol 4% and with out addition of acetic acid. Forty-two Gluconobacter isolates were screened for DHA and L-sorbose production. The isolates could produce DHA ranged from 20.05 to 42.52 g/l at 30°C. Isolate PHD-27 could produce the DHA with a maximum of 44.08 g/l at 30°C by conversion time of 84 h and generated DHA at a rate of 0.52 g/l/h at 30°C. The tested isolates produced L-sorbose ranged from 19.99 to 48.39 g/l at 30°C and G. frateurii AP59-1 produced the largest amount of L-sorbose.