Nagayasu Machiko, Wardani Agustin Krisna, Nagahisa Keisuke, Shimizu Hiroshi, Shioya Suteaki
Department of Biotechnology, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan.
J Biosci Bioeng. 2007 Jun;103(6):529-34. doi: 10.1263/jbb.103.529.
Lactococcus lactis is a facultative anaerobic microorganism that produces lactate as the major product, and acetate and acetoin as by-products; some strains of this species produce an antimicrobial compound, nisin. Lactate has a strong inhibitory effect on L. lactis growth. On the other hand, hemin has a suppressive effect on lactate production during L. lactis growth under aerobic condition. To achieve the optimum effect of hemin on lactate amount reduction in L. lactis ATCC11454, cultures entailing various conditions were performed with and without hemin. In the culture with hemin, L. lactis growth and lactate reduction improved compared with those in the culture without hemin; that is, lactate production was suppressed by 1.8- and 1.3-fold under batch and fed-batch cultures, respectively. In microaerobic fed-batch culture with hemin, lactate production was sufficiently suppressed. This result suggests that microaerobic fed-batch culture could be applied to the maintenance of the low lactate amount. Under this condition, metabolic shift was observed from lactate to acetoin and acetate. However, no increase in nisin production was observed even though lactate production could significantly decrease in L. lactis ATCC11454.
乳酸乳球菌是一种兼性厌氧微生物，其主要产物为乳酸，副产物为乙酸和3-羟基丁酮；该物种的一些菌株会产生一种抗菌化合物——乳链菌肽。乳酸对乳酸乳球菌的生长具有强烈的抑制作用。另一方面，在有氧条件下，血红素对乳酸乳球菌生长过程中的乳酸产生具有抑制作用。为了实现血红素对乳酸乳球菌ATCC11454中乳酸量减少的最佳效果，在有和没有血红素的情况下进行了各种条件的培养。在添加血红素的培养中，与未添加血红素的培养相比，乳酸乳球菌的生长和乳酸减少情况有所改善；也就是说，在分批培养和补料分批培养中，乳酸产量分别被抑制了1.8倍和1.3倍。在添加血红素的微需氧补料分批培养中，乳酸产量得到了充分抑制。这一结果表明，微需氧补料分批培养可应用于维持低乳酸量。在此条件下，观察到代谢从乳酸向3-羟基丁酮和乙酸的转变。然而，尽管乳酸乳球菌ATCC11454中的乳酸产量可显著降低，但未观察到乳链菌肽产量的增加。
