The effects of various medium carbon sources and salt solutions on the production of beta-glucosidase (betaG, EC 3.2.1.21) by Aspergillus niger have been studied. Beta-glucosidase productivity was found to be 50 times greater than that reported previously.1 This higher productivity was achieved by employing a mutant strain of the organism, readily available and inexpensive carbon sources, such as cellulose and orange peel, and a simple nutrient salt solution.