Very stable enzymes from extremely thermophilic archaebacteria and eubacteria

Abstract

Thirty-six thermophilic archaebacteria and nine extremely thermophilic eubacteria have been screened on solid media for extracellular amylase, protease, hemicellulase (xylanase), cellulase, pectinase and lipase activities. Extracellular enzymes were detected in 14 archaebacteria belonging to three different orders. Twelve of these were able to degrade starch and casein and the two Thermofilum strains were able to degrade starch, xylan and carboxymethylcellulose. Three of the eubacteria could degrade only starch. The other six (including four Thermotoga strains) all had activity against starch, xylan and carboxymethylcellulose, and one also had activity against casein. Some of the amylolytic archaebacteria released α-glucosidase, β-glucosidase, amylase and transglucosylase activities into liquid media containing starch or maltose. Thermotoga strain FjSS3B.1 released amylase, xylanase, cellulase and β -glucosidase activities into the medium when grown in the presence of substrates. When the partially purified enzymes from Thermotoga and some of the archaebacteria were compared with known thermostable enzymes the majority were found to be the most thermostable of their type. The β-glucosidase, xylanase and cellulase from Thermotoga and two -glucosidases, a β-glucosidase, an amylase and a pullulanase from archaebacteria all have half-lives of at least 15 min at 105°C.