SUMMARYBacillus sp. ATCC 21591, an alkalophilic bacterium, produces 3 enzymes associated with degradation of starch-a-amylase, pullulanase and a-glucosidase. The latter reached a maximum after 24 h growth. Highest activities of a-glucosidase and pullulanase were obtained when the initial pH of the medium was 9.7 and although at pH 10.4 highest biomass was attained after 48 h no a-glucosidase was present. The pH optimum for activity with maltose as substrate was 7.0, which is surprisingly low for an alkalophilic organism. The enzyme was substrate specific for p-nitrophenyl-a-D-glucoside, maltose and maltotriose in that order. Forty eight times the activity was located in the cell-free supernatant, relative to that found intracellulary. Transferase activity was detected -the major end-product formed from maltose was a compound with an Rf-value similar to isomaltose.