Effect of NaCl stress on pyruvate metabolism and enzyme activity in Lactobacillus bulgaricus

• 1、Key Laboratory of Dairy Science, Ministry of Education, College of Food Science, Northeast Agricultural University,Harbin 150030

Abstract：The aim of this study was to investigate the effects of NaCl stress on metabolism of pyruvate and activity of key enzymes in Lactobacillus bulgaricus, and to analyze the relationship between NaCl stress and survival rate of freeze-dried. Glucose, organic acids, acetyl coenzyme A (Acetyl-CoA) and intracellular energy metabolism were analyzed by high performance liquid chromatography (HPLC); Acetaldehyde was determined by headspace gas chromatography (HS-GC); activity of Key enzymes were mearsured by spectrophotometry and colorimetry. Pyruvate metabolism of Lactobacillus bulgaricus was significantly changed by NaCl stress; The utilization rate of glucose and the production rate of lactate were increased by 48.18% and 8.93% respectively (P<0.01), the content of key intermediate metabolite Acetyl-CoA increased 31.35% approximately (P<0.01);the content of acetic acid demonstrated negative growth, and the production rate of acetaldehyde was decreased 22.86% (P<0.05).Changes of intracellular ATP metabolism was contributed to accelerate the utilization of glucose; the activities of lactate dehydrogenase, acetate kinase, and phosphate acetyltransferase were increased by NaCl stress, the activity of aldehyde dehydrogenase was decreased.The results show that，The survival rate of freeze-dried was increased may be related to the increase of glucose utilization, rerouting of pyruvate metabolism, and the changes of the key enzyme activities in Lactobacillus bulgaricu by NaCl stress.

Keywords： Lactobacillus bulgaricus；NaCl stress；pyruvate metabolism；energy metabolism； enzyme activity