Liu S-Q, Holland R, Crow V L
Fonterra Research Centre, Private Bag 11029, Palmerston North, New Zealand.
Appl Microbiol Biotechnol. 2003 Nov;63(1):81-8. doi: 10.1007/s00253-003-1355-y. Epub 2003 Jun 18.
The ability of Streptococcus thermophilus ST1 and 19 other dairy lactic acid bacteria (LAB) to synthesize esters was investigated in an aqueous environment. These LAB were able to synthesize esters from alcohols and glycerides via a transferase reaction (alcoholysis) in which fatty acyl groups from glycerides were transferred to alcohols. S. thermophilus ST1 was active on tributyrin and on di- or monoglycerides of up to C10 with ethanol as the acyl acceptor. This strain was also active on a diglyceride of C6 and monoglyceride of C8 with 2-phenyl ethanol as the acyl acceptor. Alcoholysis occurred preferentially over hydrolysis. S. thermophilus ST1 had an apparent K(m) value of 250 mM for ethanol and an apparent K(m) value of 1.3 mM for tributyrin, measured against whole cells. Around 80% of both the transferase activity and the esterase activity were detected in the cell-free extract (CFE) of strain ST1. Both activities in the CFEs of five LAB tested were, to a similar degree, enhanced slightly by growth in the presence of ethanol and tributyrin. Using tributyrin and ethanol as substrates, the transferase activities ranged over 0.006-1.37 units/mg cell dry weight among the LAB tested and were both species- and strain-dependent.
在水相环境中研究了嗜热链球菌ST1和其他19种乳源乳酸菌（LAB）合成酯的能力。这些乳酸菌能够通过转移酶反应（醇解）从醇类和甘油酯合成酯，在该反应中甘油酯的脂肪酰基转移到醇类上。嗜热链球菌ST1对三丁酸甘油酯以及以乙醇作为酰基受体的C10以下的甘油二酯或甘油单酯具有活性。该菌株对以2-苯乙醇作为酰基受体的C6甘油二酯和C8甘油单酯也具有活性。醇解比水解更易发生。以全细胞测定，嗜热链球菌ST1对乙醇的表观K(m)值为250 mM，对三丁酸甘油酯的表观K(m)值为1.3 mM。在菌株ST1的无细胞提取物（CFE）中检测到约80%的转移酶活性和酯酶活性。在乙醇和三丁酸甘油酯存在下生长时，所测试的5种乳酸菌CFE中的这两种活性均有相似程度的轻微增强。以三丁酸甘油酯和乙醇为底物，在所测试的乳酸菌中，转移酶活性范围为0.006 - 1.37单位/毫克细胞干重，且具有种属和菌株依赖性。
