The application of a purified alpha-amylase preparation results in sig
nificant improvement in the drainage qualities of backwater from a rec
ycling paper plant. A crude thermostable alpha-amylase preparation was
purified using chromatofocusing to exclude the possible interaction o
f contaminating cellulase and xylanase enzymes. The resultant purified
alpha-amylase, with a molar mass of 66 000 and isoelectric point of 7
.60, demonstrated an activity of 175.6 units/mg against starch and 182
.5 units/mg against amylopectin. Drainage improvements were demonstrat
ed using both the crude and purified forms of the alpha-amylase.