Xylanolytic activities ofSpirochaeta thermophila
Spirochetes capable of degrading xylan or cellulose have not been commonly isolated, nor have their polysaccharolytic activities been characterized.Spirochaeta thermophila strain RI 19.B1 is xylanolytic and grows well at 65°C with oatspelt (OX), birchwood (BX), corncob (CCX-A) xylans, or glucuronoxylan (MGX) as the energy source. All xylans were extensively degraded and utilized during growth. About 72–82% of the initial hexuronic acids and 57–79% of initial pentoses disappeared during growth.S. thermophila possessed xylanase, xylosidase, and arabinofuranosidase enzyme activities. Low levels of these activities were detected with growth on glucose, but high expression of these activities occurred during growth on OX. All three activities were cell-associated and were more stable in cells than cell extracts. Xylan-degrading activities were measured with cells or cell extracts exposed (60 min) to a variety of temperatures (65°–85°C) and pHs (5.0–8.0). More than 50% loss of activities occurred at temperatures above 75°C. Although pH stability was affected by buffer, the optimal range was pH 6.5–7.5. These temperature and pH profiles for xylan-degrading activities coincide with those found for the growth ofS. thermophila.
KeywordsGlucose Enzyme Cellulose Enzyme Activity High Expression
Unable to display preview. Download preview PDF.
- 1.Aksenova HY, Rainey FA, Jassen PH, Zavarzin GA, Morgan HW (1992)Spirochaeta thermophila sp. nov., an obligately anaerobic, polysaccharolytic, extremely thermophilic bacterium. Int J Syst Bacteriol 42:175–177Google Scholar
- 2.Ashwell G (1957) Colorimetric analysis of sugars. Methods Enzymol 3:73–105Google Scholar
- 7.Hespell RB (1992) Fermentation of xylans byButyrivibrio fibrisolvens andThermoanaerobacter strain B6a: utilization of uronic acids and xylanolyytic activities. Curr Microbiol 25:189–195Google Scholar
- 10.Hespell RB, Wolf R, Bothast RJ (1988) Fermentation of xylans byButyrivibrio fibrisolvens and other ruminal bacterial species. Appl Environ Microbiol 53:2849–2853Google Scholar
- 15.Paster BJ, Stackebrandt E, Hespell RB, Hahn CM, Woese CR (1984) The phylogeny of the spirochetes. Syst Appl Microbiol 5:337–351Google Scholar
- 17.Rainey FA, Jansson PH, Wild DJC, Morgan HW (1991) Isolation and characterization of an obligately anaerobic, polysaccharolytic, extremely thermophilic member of the genusSpirochaeta. Arch Microbiol 155:396–401Google Scholar
- 18.Salyers AA, Balascio JR, Palmer JK (1982) Breakdown of xylan by enzymes from human colonic bacteria. J Food Biochem 6:39–55Google Scholar
- 19.Schneider WC (1957) Determination of nucleic acids by pentose analysis. Methods Enzymol 3:374–381Google Scholar
- 20.Scott RW (1979) Colorimetric determination of hexuronic acids in plant materials. Anal Chem 51:936–941Google Scholar
- 24.Thomson JA (1993) Molecular biology of xylan degradation. FEMS Microbiol Rev 104:65–82Google Scholar
- 25.Whitehead TR, Hespell RB (1990) Heterologus expression of theBacteroides ruminicola xylanase gene inBacteroides fragilis andBacteroides uniformis. FEMS Microbiol Lett 66:61–66Google Scholar