Coordination of characteristic cytomembrane and energy metabolism contributes to ethanol-tolerance of Acetobacter pasteurianus

Abstract

Acetic acid bacteria (AAB) are widely used in acetic acid fermentation where the combined action of ethanol and acetic acid disturbs the cell viability. The present study investigated the ethanol resistance mechanisms through the comparisons between a more ethanol-tolerant Acetobacter pasteurianus JZ1601 and a less ethanol-tolerant A. pasteurianus 1.41 by focusing on the early stage of fermentation without acetic acid interference. While the membrane was the primary injury target, optimum membrane stability rather than increased membrane fluidity was demonstrated to be relevant to the ethanol tolerance. The weak membrane permeability entrusted JZ1601 with relatively reduced sublethal injury, low intracellular ethanol, and superior growth throughout the high ethanol challenge. However, the level of fatty acids could not play a direct role in improving the membrane stability. Furthermore, the tricarboxylic acid cycle, pyrroquinoline quinone-dependent alcohol dehydrogenase (PQQ-ADH) and acetaldehyde dehydrogenase (PQQ-ALDH) activities were the potential to adapt to high ethanol challenges, with PQQ-ADH activity contributing more to the ethanol tolerance of JZ1601. These results demonstrated that the characteristic membrane structure, energy metabolism, and their improved adaptive regulation contributed to a high ethanol tolerance of AAB.