OPTIMIZATION OF THE LACTIC-ACID FERMENTATION OF HYDROLYZED COD GURRY WITH MOLASSES

The purpose of this study was to determine the optimum concentration of blackstrap molasses required in conjunction with the use of several species of homofermentative lactic acid bacteria in the fermentation of hydrolyzed cod gurry. Blackstrap molasses at a concentration of 7.5 % was found to be optimum for achieving a successful lactic acid fermentation of hydrolyzed cod gurry. Among the three homofermentative lactic acid bacteria studied (Lactobacillus plantarum, Pediococcus acidilactici and Streptococcus faecium) L. plantarum resulted in the most rapid fementation. S. faecium was the least desirable bacterium on the basis of fermentation rates and extent of pH decrease after 72 h of incubation. All three organisms failed to utilize significantly the sucrose derived from molasses, even though sucrose was the most abundant carbohydrate in the molasses. P. acidilactici was unable to utilize sucrose when present as a sole carbohydrate, while L. plantarum and S. faecium decreased the pH in broth cultures with sucrose as a sole carbohydrate. These results suggest that glucose in molasses functions as a repressor of invertase formation in L. plantarum and S. faecium, and that the use of derepressed mutants should allow a significant decrease in the amount of molasses required for a satisfactory fermentation.