Expression and secretion of a thermostable bacterial xylanase in Kluyveromyces lactis

The xynA structural gene from the extremely thermophilic anaerobe Dictyoglomus thermophilum Rt46B.1 was fused in frame with the secretion signal of the Kluyveromyces lactis killer toxin in episomal expression vectors based on the Kluyveromyces plasmid pKD1. XynA was secreted predominantly as an unglycosylated 35-kDa protein which comprised up to 90% of the total extracellular proteins and reached a concentration of 130 micrograms/ml in shake-flask cultures grown under selective conditions.