The amounts of a 160-kDa amylase and a 140-kDa alpha-amylase (A. Burgess-Cassler and S.H. Imam, Curr. Microbiol. 23:207-213, 1991) secreted into culture medium by the starch-utilizing Lactobacillus amylovorus were enhanced by the use of cyclodextrin (CD) as the carbon source. The levels of total extracellular alpha-amylase obtained with glucose as the carbon source could be boosted severalfold by use of CD. The best enhancer was beta-CD, and the rank order of best to least effective was beta-CD > alpha-CD = gamma-CD > glucose. Another amylase, a 65-kDa alpha-amylase, which degraded para-nitrophenyl-alpha(1,4)-D-glucopyranoside, was also detected in this study. The most effective enhancer in this case was alpha-CD, and the rank order was alpha-C-D > beta-CD > gamma-CD much greater than glucose. Despite its ability to degrade p-nitrophenylated glucose, this enzyme did not convert maltose to glucose. It showed a cleared zone on starch zymograms and did degrade short maltodextrins to maltose. Neither this new alpha-amylase nor the 140-kDa alpha-amylase exhibited any detectable ring-decyclizing (cyclodextrinase) activity against alpha- or beta-CD. Other extracellular amylases (not characterized here) appeared to be similarly enhanced by CDs. Although the precise mechanism by which this effect is accomplished remains undefined, CDs can be useful inducing agents, boosting the expression and/or secretion of otherwise low-level enzymes, either as additives to growth media or as sole carbon source.