Abstract:

The effect of Rhizopus oryzae strain on fermentation intensity of L-lactic acid during repeated intermittent fermentation in a 3 L fermentor were investigated. Results demonstrated that the yields of L-lactic acid were 105.8 g/L and 105.0 g/L through in the first batch fermentation by Rhizopus oryzae strain in flocs-form and pellet-form, and glucose conversion rates were 88.12 % and 87.50%, respectively. The average yield of L-lactic acid fermentation through Rhizopus oryzae strain in pellet-form was more than 80.00 g/L during the first 6 repeated intermittent fermentations. The glucose conversion rate was higher than 87.33%, and the highest L-lactic acid productivity was 4.26 g/(L·h). However, the yield of L-lactic acid was decreased to 78.60 g/L in the 7th batch fermentation. The average yield of L-lactic acid fermentation through Rhizopus oryzae strain in flocs-form was more than 80.00 g/L during the first 4 repeated intermittent fermentations. But the yield of L-lactic acid was decreased to 78.30, 77.40 g/L and 70.20 g/L in the following 3 batches of fermentation. The highest productivity for L-lactic acid reached up to 4.07 g/(L·h).

Key words: L-lactic acid, Rhizopus oryzae, morphology, repeated intermittent fermentation