The use of salted whey (liquid by-product from the dairy industry containing 7.5% NaCl) as a substrate for either acetic acid or glycerol production was investigated using two yeast strains. One was Kluyveromyces fragilis. The other organism (strain L) can utilize whey lactose that was isolated from waste whey (disposal stream). 8% NaCl, 3% Na2SO3 and pH 8.5 at 32 degreesC were the optimum operating conditions for maximum acetic acid production (25.84 g1(-1)) from salted whey using immobilized cells of yeast strain L. Also, strain L gave a higher yield of acetic acid (0.497 g acetic acid per gram lactose) as compared with K. fragilis (0.322 g acetic acid per gram lactose). 1% Na2SO3 at pH 7 and whey supplemented with peptone and malt extract were the optimal conditions for maximum batch glycerol production (13.2 gl(-1)) from salted whey using immobilized cells of K. fragilis. The extreme values, 18.7 gl(-1) for glycerol concentration and 39,78 for the percent yield of glycerol (based on sugar concentration) in a membrane cell recycle bioreactor were higher than those obtained for the immobilized cell batch reactors (13.2 gl(-1) and 28, respectively). (C) 2001 Elsevier Science Ltd. All rights reserved.