Effect of Salt Stress on Acetoin Metabolism of an Aroma-producing Strain Bacillus subtilis

Abstract

An aroma-producing strain B15 was isolated from a spontaneous fermentation culture of traditional Chinese sweet bean sauce (Tian Wei Food Co., Ltd., China), and identified as Bacillus subtilis, exhibiting an ability to synthesize acetoin. In order to better understand the influence of salt stress on acetoin metabolism, a metabolic network of B. subtilis for synthesis of acetoin was established, and the changes in levels of acetoin, glucose, lactic acid, amylase activity, cell dry weight and amino acids were measured during fermentation under 0.5, 5 and 10% NaCl. After the metabolic flux analysis of 3 important metabolite nodes (glucose-6-phosphate, fructose-6-phosphate and pyruvic acid) and the role of amino acids and NADPH in metabolic network, it was found that salt stress greatly affected the metabolic content of pyruvate, and the total carbon flux distribution of amino acids and NADPH decreased in different pathways along with the increase of salt concentration. The results provided a further in-depth investigation of B. subtilis strategies in the struggle for acetoin biosynthesis under salt stress.