Metabolic Analysis And Application:Komagataeibacter Naiaicola Y19 With Enhanced Cellulose Yield By Adding Ethanol

Due to the unique physical and chemical properties,bacterial cellulose(BC)is widely used in food,chemical and medical industries.But because of the low yield,many byproducts and high production cost,it is restricted to the production of high value-added products.In order to increase the yield of BC,a certain amount of ethanol was added in the culture process.Through research on the sensitivity and tolerance of the strains for ethanol,growth metabolism and the key enzyme activity in main metabolic pathways,we analyzed the reason why that ethanol promoted BC production from the metabolic level,and the mechanism and regulation.In addition,based on the theoretical basis and the BC production status,we study on synthesis of BC by co-culturing yeast and the strain,to realize large-scale production laying the theoretical foundation.The main results were as follows:(1)The sensitivity of cellulose producing bacteria to ethanol was related to the species characteristics,which showed that the sensitivity and tolerance of 12 strains of bacteria(8 species)were different,and there was a difference in the production of BC with different concentrations of ethanol.Among them,there were no significant differences between the BC productions by three strains of Komagataeibacter sp.(Y15?WE1?Y2),but these were significantly different by three strains of K.nataicola(Y19,JMG1536,D6).It was also found that K.nataicola Y19 was the most sensitive to ethanol,and the tolerance to ethanol was 0-4%.when ethanol was 1%(v/v),the amount of BC was the highest,7.117g/L,about 9.3 times in the control group.(2)Effect of ethanol on the main metabolic pathways,we found that ethanol could improve the yield of BC though promoting ATP production.Ethanol was oxidized to acetic acid into the cells,and then adjusted the growth and metabolism.That could produce too much ATP that inhibited G6PDH acti-vity,weakening the HMP pathway,but the EMP pathway and BC synthesis pathway were active.At the same time,it could increase the PK,PEPC and PDH activity prompting PEP into OAA directly into the TCA pathway to lead to the accumulation of PYR increased,while bypessed the other circulations to reduce the formation of by-products.PDH prompted the conversion of acetic acid to AcCoA,and then entered the TCA pathway resulting in the production of biomass and BC increased.In addition,ethanol could reduce the formation of byproducts,such as glucose acid and glycerin,to improve the yield of BC.Ethanol could weaken the carbon source flows into gluconic acid formation pathways to increase substrate utilization rate.Carbon source was forced into the EMP pathway and BC synthesis pathway,reducing the inflow of HMP pathway flux to reduce the glycerol accumulation and increase the yield of BC.While the flux of PYR into OAA pathway was increased,on the contrary,the flux of AC into the TCA cycle was reduced,so was the energy flux into other ways.What's more,ethanol could also force the products such as glycerol into gluconeogenesis and provide carbon source.(3)It was feasible to co-culture of yeast and cellulose,which could promote the synthesis of BC,but it didn't affect the microstructure.When the initial pH value was 4,Saccharomyces.cerevisiae DV10,S.cerevisiae D254 and S.cerevisiae EC1118 were inoculated with K.nataicola Y19 in the proportion of 10-3:1 inoculation,and under the condition of 30? for 7 days,the yield of BC reached the maximum,which was 6.12 g/L,6.68 g/L,6.08g/L,respectively.While Metschnikowia agaves P3-3(10-1:1,6,28?),Candida tropicalis P3-4(10-4:1,4,29 ?),Meyerozyma sp.4-17B(10-4:1,6,30?),S.bayanus BV818(10-4:1,4,29 ?)were co-cultured with K nataicola Y19,the yield of BC reached 3.18g/L,5.93g/L,6.35g/L,6.60g,respectively,which increased by 1.8,4.3,4.6,4.8 times compared with CK.It was also found that the promoting effect was related to the characteristics of yeast strains.