摘要
目的乙醇脱氢酶(ADH)是米根霉发酵生产L-乳酸代谢途径中的支路关键酶,选育米根霉ADH突变株,降低ADH活力,可以提高乳酸转化率。方法利用亚硝基胍(NTG)诱变米根霉As3.3462,在含丙烯醇的YPD选择培养基上筛选获得ADH突变株,研究了突变菌株在限氧与通氧条件下的乙醇、乳酸、ADH与L-乳酸脱氢酶(LDH)的特性。结果获得11株ADH突变株,其中mut-2突变株在通氧和限氧条件下对乳酸的转化率比出发菌株分别提高了84.6%和175%,而对乙醇的转化分别下降了39.5%和59.8%。mut-2突变株的最大ADH活力在通氧和限氧条件下均比出发菌株降低,而LDH活力在限氧条件下显著增加,通氧条件下变化不明显。结论氧气的供给对米根霉发酵产L-乳酸的产物组成比例影响很大,限氧发酵条件下ADH活力提高,乙醇积累。结果还表明,通过筛选米根霉ADH突变株,是获得L-乳酸高产菌株的一种简单快速的有效手段。
[ Objective ]Ethanol dehydrogenase （ADH） is an important branch pathway enzyme that catalyzes the transformation of ethanol from pyruvate in Rhizopus oryzae, which decrease the conversion rate of glucose to L-lactic acid. So, screening the mutants with lower ADH activity may markedly increase lactate production. [Method] Mutation ofRhizopus oryzae As3.3462 was induced with N-methyl-N＇-nitro-N-nitrosoguanidine （NTG） and mutants with lower ADH activity were screened out, then the characteristics of mutant under aeration and oxygen-limiting fermentations were investigated. [ Result] There were 11 Rhizopus oryzae strains of ADH mutants were obtained. After preliminary fermentation, rout-2 was selected for further study on the fermentation characteristics because of its high lactate conversion rate of 84.6% and 175% as compared with parent strain under aeration and oxygen-limiting fermentation, respectively. The ethanol concentration of rout-2 decreased by 39.5% and 59.8% under aeration and oxygen-limiting fermentation. The ADH specific activities of rout-2 under aeration and oxygen-limiting fermentation were lower than parent strain. The LDH specific activities under oxygen-limiting condition were markedly higher than parent strain, but the difference was not distinct under aeration fermentation. [ Conclusion] The product compositions of Rhizopus oryzae carbon metabolism were remarkably determined by the supply of oxygen. Oxygen-limiting fermentation would result in a higher ADH activity and the accumulation of ethanol. The results also indicated that screening Rhizopus oryzae ADH mutant was an effective method for increase the conversion rate of L-lactic acid.
出处
《中国农业科学》
CAS
CSCD
北大核心
2006年第6期1228-1232,共5页
Scientia Agricultura Sinica
基金
国家教育部高等学校博士点基金项目(20040359008)
教育部"同步辐射博士生创新中心"研究生创新基金资助(20041216S)
关键词
米根霉
ADH
乙醇
L-乳酸
Rhizopus oryzae
ADH
Ethanol
L-lactic acid
