固定化米根霉发酵制L-乳酸

采用海藻酸钙包埋法固定化米根霉（Ｒｈｉｚｏｐｕｓｏｒｙｚａｅ），菌体在颗粒表面形成一层菌丝膜，有利于氧气和其它营养物质的传递；三相流化床生物反应器结构简单、动力消耗低、反应器内物质混合均匀、氧传递量大于固定化米根霉的需氧量，非常适合好氧的固定化米根霉发酵。利用它进行重复使用固定化米根霉的间歇发酵或连续发酵制备Ｌ 乳酸，整个过程一般可持续两周以上。固定化米根霉的产酸速率达１６～１８ｇ／Ｌ ｂｅａｄ．ｈｒ，得率为７０～８０％，反应器生产能力约为传统搅拌罐的３倍。采用海藻酸钙包埋法固定化米根霉在三相流化床生物反应器中进行发酵可以有效地提高Ｌ 乳酸的生产效率，具有良好的工业应用前景。

L LACTIC ACID FERMENTATION USING IMMOBILIZED RHIZOPUS ORYZAE

The alginate calcium entrapment method was developed to immobilize Rhizopus oryzae . A shell layer of mycelia was formed on the surface of the particle, which was favorable for oxygen and substrates mass transfer. A three phase fluidized bed bioreactor was used to perform L lactic acid fermentation with immobilized R . oryzae , which had the following advantages: simple structure, low energy requirement, well mixing and good mass transfer. The fermentation could be carried out either in repeated batch or in continuous operation mode, with a lifetime of more than two weeks. The productivity of L lactic acid reached 16～18g/(L bead.hr), and glucose to L lactic acid yield was 70～80%. The productivity based on total reactor volume was about 3 times higher than that with free cells in a traditional stirred tank bioreactor. The results indicated that the immobilized cell fermentation in a three phase fluidized bed bioreactor provided an effective alternative method for L lactic acid fermentation and had a good prospect in industrial application.