Continuous production of Ammonium lactate by Streptococccus cremoris in a three‐stage reactor

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Abstract
Batch and continuous fermentation studies were performed to optimize the production of ammonium lactate from whey 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°C provided optimum incubation conditions. To stimulate 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 three‐stage than for the single‐ and two‐stage reactors, respectively. Various retentions times were examined (5, 7.5, and 10 h; 5g/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 and a productivity, 91% lactose utilization). Retention time was increased to 15 h to obtain 95.9% lactose utilization and a productivity of 2.42g/L h for 2g/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) 17% more than soybean meal (crude protein contents are equivalent, 44%) at current market prices.