Abstract: In order to reduce the manufacturing cost of L-lactic acid and increase the compound usage of rape cake, rape cake hydrolysate was used to replace beef extract etc. as nitrogen source. The model of BP neural networks was set up on the basis of uniform experiment along with the results of single-factor tests(%). Then, neural networks was optimized by genetic algorithms. The obtained optimal medium ingredients are (g/L): glucose110.43, rape cake (dry weight)hydrolyzate 87.75, corn liquid 21.18, (NH4)2HC6H5O7 2.85. Under the optimal medium determined, the output is increased by 9.30%.

Key words: rape cake hydrolysate, L-lactic acid, fermentation medium, neural networks, genetic algorithms