CONTINUOUS PRODUCTION OF AMMONIUM LACTATE BY STREPTOCOCCUS-CREMORIS IN A 3-STAGE REACTOR

Batch and continuous fermentation studies were performed to optimize the production of ammonium lactate from whey permeate. The product known as fermented ammoniated condensed whey permeate (FACWP) is a very promising animal feed. After an initial screening of four strains which produce predominantly L(+)-lactic acid, the desired isomer [D(-)-lactic acid is toxic], Streptococcus cremoris 2487 was chosen for further study. In batch mode, pH between 6.0 and 6.5 and 35-degrees-C provided optimum incubation conditions. To simulate a plug flow reactor, three CSTRs (continuous stirred tank reactors) were connected in tandem. For a 7.5-h retention time, 1.6-fold and 1.3-fold higher productivities were obtained for the three-stage than for the single- and two-stage reactors, respectively. Various retention times were examined (5, 7.5, and 10 h; 5 g/L yeast extract). Although maximum lactate productivity occurred at a 5-h residence time (5.38 g/L H, 75% lactose utilization), lactose utilization was more complete at 7.5 h (4.38 g/L h productivity, 91% lactose utilization). Retention time was increased to 15 h to obtain 95.9% lactose utilization and a productivity of 2.42 g/L h for 2 g/L yeast extract. Based on this lower yeast extract concentration, it was determined that ammonium lactate production and subsequent concentration by 11-fold would yield a product (FACWP) costing 17% more than soybean meal (crude protein contents are equivalent, 440/o) at current market prices.