A comparative study of the fermentation of a range of carbohydrate substrates, at various temperatures, was carried out using a commercial Lactobacillus casei strain in a free cell form and immobilised on gluten pellets. This strain required yeast extract, L-cysteine . HCl and Mn2+ at 5, 0.5 and 0.1 g l(-1), respectively, for maximum growth and lactic acid production. Sugar fermentation using free cells showed preference in the order glucose, sucrose, fructose while lactose was poorly utilised. Optimum temperature for growth and lactic acid production over (18-30 h) was 43 degreesC. L. casei was successfully immobilised on gluten pellets and fermented glucose and sucrose in a shorter time (18 h) with increased lactic acid production (42 and 41 g l(-1) on glucose and sucrose, respectively).