产L-肉碱的菌种筛选及发酵条件优化

SCREENING AND OPTIMIZING FERMENTATION CONDITIONS OF L-CARNITINE PRODUCING STRAIN

将D ,L 肉碱 (carnitine ,β 羟基 γ 三甲胺丁酸 )用浓硫酸脱水获得反 巴豆甜菜碱 (trans crotonobetaine) ,从本室保藏的菌株中筛选出 1株能将反 巴豆甜菜碱非对称合成L 肉碱的菌株E .coliK74。利用它的休止细胞立体选择性地水合反 巴豆甜菜碱产生L 肉碱 ,起催化作用的酶是L 肉碱脱水酶 ,是一种可诱导的胞内酶 ,当培养基中加入反 巴豆甜菜碱并在部分厌氧条件下可诱导产生。如培养基中含有葡萄糖、硝酸盐或氧时 ,酶的合成受到抑制 ,在磷酸缓冲液中 ,E .coliK74休止细胞的最适反应条件是 :pH为 7.8,温度为 37～ 42℃。

Trans cronobetaine was obtained by concentrated sulfuric acid dehydration of D, L carnitine (β carboxyl γ trimethylamine butyric acid). An E. coli K74 strain screened and collected in our lab, which asymmetrically produces L carnitine and its resting cells has efficient ability to stereo selective hydration of trans cronobetaine, was used to produce L carnitine from trans cronobetaine. An enzyme, L carnitine dehydratase, inducible intracellular enzyme produced under partial anaerobic conditions by adding trans cronobetaine in the medium,was responsible to the catalysis. When glucose, nitrates and oxygen were added to the medium, the synthesis of the enzyme was inhibited. Under phosphoric acid buffer the most suitable reaction condition of E. coli K74 resting cells was pH 7.8 and temperature at 37～42℃.