A novel thermostable dextranase from a Thermoanaerobacter species cultured from the geothermal waters of the Great Artesian Basin of Australia

Abstract

A Gram‐negative sporulating thermophilic anaerobe, designated AB11Ad, was isolated from the heated waters of the Great Artesian Basin of Australia. It grew on a variety of carbohydrates including glucose, starch, and dextran and produced a thermostable and thermoactive extracellular endo‐dextranase. The enzyme was produced more actively under pH controlled continuous culture conditions than under batch conditions. Ammonium sulfate precipitated crude dextranase exhibited a temperature optimum of 70 °C and a pH optimum between 5 and 6. The half life was ~ 6.5 h at 75 °C and 2 h at 80 °C at pH 5.0 and in the absence of added dextran. 16S rRNA sequence analysis indicated that isolate AB1 lAd was a member of the genus Thermoanaerobacter.

Isolation of a new Thermoanaerobacterium thermosaccharolyticum strain (FH1) producing a thermostable dextranase.

“…This is in the same range that was described for other crude thermostable bacterial dextranases, but low in comparison to the crude commercial enzyme of C. gracile (2,750 U/mg at 55°C) (Wynter et al, 1995(Wynter et al, , 1996. The pH optimum of the dextranase of FH1 was determined at 65°C.…”

“…The same problems were observed by measuring dextranase activities in culture supernatants of other bacteria (Wynter et al, 1995(Wynter et al, , 1996. The protein of cell-free culture supernatant (1 L) was therefore concentrated by ammonium sulfate precipitation.…”

Microvirga subterranea gen. nov., sp. nov., a moderate thermophile from a deep subsurface Australian thermal aquifer

“…Anaerobic growth was tested in TYEG medium (Wynter et al, 1996). The presence of photosynthetic pigments and carotenoids was determined by scanning acetone extracts of 10 and 50 ml cultures that had been incubated in the dark and in the light, in a Cintra20 spectrophotometer (GBC Scientific Equipment) at wavelengths between 250 and 900 nm.…”

“…A variety of novel microbial physiologies have been isolated from this environment and include Desulfotomaculum australicum (Love et al, 1993), Desulfovibrio longreachensis (Redburn & Patel, 1994), Fervidobacterium gondwanense (Andrews & Patel, 1996), Thermaerobacter subterraneus (Spanevello et al, 2002) and Bacillus subterraneus (Kanso et al, 2002). In addition, extensive studies on the production of industrially important thermostable enzymes such as amylases and dextranase has been undertaken (Wynter et al, 1996), but the vast majority of these strains have remained taxonomically uncharacterized. Microbial communities observed to thrive along the temperature gradient sometimes as visible mat communities have also been under investigation in our laboratory (Spanevello, 2001).…”

Microvirga guangxiensis sp. nov., a novel alphaproteobacterium from soil, and emended description of the genus Microvirga

“…Growth with various pH, temperature and sodium chloride regimes was determined on LB agar plates incubated for up to 3 days. Anaerobic growth was tested by using TYEG medium (Wynter et al, 1996). Resistance to lysozyme was determined by using the method of Gordon et al (1974).…”