Screening Of Cellulose-producing Bacterial Strains And Optimization Of Culture Medium

Bacterial cellulose(BC)and its bacterial producers have advanced the great development and applications in the field of biomaterial,medicine and food industry.In this study,a strain of Acetobacter pasteurianus MGC-N8819 with the ability to produce bacterial cellulose was isolated from Zhejiang traditional rose vinegar fermentation broth.As the same time,this strain as the original strain,the production of bacterial cellulose was improved by optimizing the carbon source type and carbon source concentration of the culture medium for bacterial cellulose production.Then,the effects on bacterial cellulose synthesis were explored by changing the culture methods,that is,expanded culture,intermittent feeding,and the changes in the physicochemical properties of bacterial cellulose were also evaluated.Finally,using agricultural lotus root and its by-products as carbon sources to explore its utilization of waste.It has played a positive role in reducing production costs and recycling waste.The initial bacterial cellulose production of A.pasteurianus MGC-N8819 was 6.6 g/L.Through the comparison of carbon sources such as glucose,glycerol,glucose-glycerol composite and high fructose syrup,found that high fructose syrup was used as substance to produce bacterial cellulose,the yield of bacterial cellulose was the highest(8.1 g/L).The initial concentration of high fructose syrup was optimized.The concentration of high fructose syrup was 40 g/L,the production of bacterial cellulose could be increased to 9.5 g/L.At the same time,the surface area and depth of the medium significantly affect the yield of bacterial cellulose.By exploring the effect of different surface areas on the synthesis of bacterial cellulose,the results showed that the surface area was 698 cm~2,the yield of bacterial cellulose,the productivity of bacterial cellulose,substrate conversion rate,substrate consumption rate was 14.9 g/L,1.86g/L/day,59%and 3.125 g/L/day,respectively.The results of the effect of different V:A on bacterial cellulose synthesis showed that the V:A ratio was 6,the bacterial cellulose yield(19.8g/L),the production efficiency(2.48 g/L/day),the substrate conversion rate(60%),the substrate consumption rate(4.13 g/L/day)was the highest.Taking the volume/surface area ratio of 6 as the expansion reference,after expanding the fermentation volume from 748 cm~3 to 4002cm~3,the bacterial cellulose yield was 10 g/L.However,the bacterial cellulose production was up to 21.8 g/L and the bacterial cellulose productivity was 1.6 g/L/day after the intermittent feeding method.Lotus root is an important agricultural product in Zhejiang Province and is widely cultivated.Agricultural lotus root and its by-products as the carbon source were investigated for bacterial cellulose synthesis,displaying BC yield by 2.1 g/L,BC productivity was 0.26g/L/day and substrate conversion rate was up to 56%.The derive BC exhibited a high crystallinity index up to 90.5%by XRD analysis and high thermal stability by TGA determination,which were consistent with the high tensile strength(82 MPa)and elongation at break(26%).It suggests that A.pasteurianus MGC-N8819 promise a valuable candidate for BC production and lotus root and its by-products be plausible alternative carbon source.