The Effect of Ethanol on Bacterial Cellulose Synthesis by Different Bacterial Species and the Sensitivity and Tolerance of High-yield Bacterial Strains to Ethanol

Key words: 
• bacterial cellulose producing bacterial strain /
• improving effect of ethanol /
• Komagataeibacter /
• A. bogorensis /
• sensitivity and tolerance /

Abstract: In order to study the efficient synthesis of bacterial cellulose（BC） and the factors affecting the stable high yielding BC synthesis, 8 cellulose-producing bacterial species were cultured in Asai chemically-defined medium to observe the effects of ethanol on BC synthesis to select highyielding bacterial species. These highyielding species were used as models to analyze their sensitivity and tolerance to ethanol. The results showed that the effects of ethanol on the 8 cellulose-producing species were quite different in BC synthesis. Of the 8 cellulose-producing species, 5 from the genus Komagataeibacter, and Acetobacter bogorensis were improved in BC synthesis, especially K. nataicola and K. xylinus which had most significant improvement（P ＜ 0.05）, while an unknown species from the genus Komagataeibacter was not significantly improved and K. europaeus was inhibited in BC synthesis. A K. nataicola strain Y19 was screened to show high sensitivity and tolerance to ethanol. This strain increased BC yield sharply by 6.6 times in the Asai medium supplemented with 0.5%（similarly hereinafter）ethanol and by 8.3 times to 7.12 g·L^-1 at the presence of 1% ethanol, and then declined gradually the growth rate of BC synthesis with the increase of ethanol in the Asai medium. The BC yield of the strain was 44% lower than that of the control when the Asai medium was added with ethanol by up to 5%. This suggested that K. nataicola Y19 had an improving effect in response to ethanol at a wide range of concentrations from 0.5% to 4%, which would explain the vital significance to the large-scale BC production practice by using natural pre-fermented coconut water. On the other hand, one high yield and one inhibition strain were selected, which would lay good foundation for further mechanism study on ethanol effect.