Function Exploration Of Ethanol,Acetic Acid And Lactic Acid On The Synthesis Of Bacterial Cellulose In Gluconacetobacter Xylinus

Bacterial cellulose(BC)is a kind of macromolecule polymer synthesized by microorganisms using glucose as precursor.It is widely used in various sectors of papermaking,food and medicine because of excellents properties,such as high purity,good mechanical properties.Gluconacetobacter xylinus(G.xylinus)is a Gram-negative aerobic microorganism,which is regarded as a model microorganism in BC production process.Many studies have shown that adding additional substances in the fermentation process can effectively improve BC production.In this study,different concentrations of ethanol,acetic acid and lactie acid were added to explore the effects of different additives on G.xylinus energy metabolism and BC synthesis.In this study,different concentrations of ethanol,acetic acid and lactic acid were added to change the culture conditions.The fermentation characteristics,metabolomics were analysed to reveal the effect and mechanism of different additives on BC production.Fermentation performance test results showed that ethanol and acetic acid had the greatest impact on G.xylinus metabolic process.External addition of ethanol and lactic acid and appropriate concentration of acetic acid could effectively increase BC production rate,while excessive concentration of acetic acid could effectively reduce BC production rate and bacterial growth activity.Under static culture,the logarithmic growth period was reached in the experimental group with ethanol at 4 days,and the experimental group with acetic acid and lactic acid at 6 days.When the culture time reached 14 days,the BC yield of the experimental group reached the maximum and stabilized.Therefore,the fermentation period of static culture was determined to be 14 days.To reveal the influencing mechanism of additives on BC yield and influence mechanism,Metabolomics and Key enzymatic activities were performed.On 4th day,the activity of glycolysis pathway was inhibited,while the energy metabolism and gluconeogenesis were significantly advanced in the ethanol-added experimental group.On 6th day,when the acetic acid content was higher than 4.5 g/L,TCA cycle activity and uridine diphosphate glucose pyrophosphorylase activity were inhibited,and the contents of saturated fatty acid and trehalose were significantly higher than control group.In the experimental group with lactic acid,the key enzymes in TCA cycle,BC synthesis and gluconeogenesis pathway were effectively enhanced,while the glycolysis pathway was inhibited.