Study On The Process And Characterization Of Bacterial Cellulose Producted By Kombucha

Bacterial cellulose synthesized by microbial metabolism is a kind of biodegradable polymer material which is superior to other types of cellulose unique nature,and can be applied to food,biological,pharmaceutical,papermaking and many other areas.Bacterial cellulose is not widely applicated because of its lower yield and producionhigher costs.It is meaningful to increase production and reduce costs by fermented with the high yield of good bacteria in the cheaper medium.In this study,firstly,high yield of bacterial cellulose strains were separated and filtered from the traditional kombucha gas-liquid surface bacteria film.Secondly,the optimum processes for the production of cellulose by a newly isolated strains were optimized by static and shaken cultures,and the optimal medium for the production of cellulose using corn starch wastewater as raw material were studied preliminarily.And finally,the characterizations of the bacterial cellulose were performed.The main results are as the follows:1.The high-yielding strains of bacterial cellulose isolated from Kombucha pellicle was identified as Gluconobacter oxydans.The microstructural features of the cells which has the ability to produce bacterial cellulose was observed by SEM and AFM.Saccharomycodes ludwigii and Bettanomyces lambicus were also isolated from Kombucha pellicle.2.The optimum processes for the production of cellulose were optimized through single-factor and orthogonal tests.The optimum processes by static cultures were as follows:glucose 30g/L,corn steep liquor 35g/L,ethanol 2.0%(V/V),acetic acid 1.5%(V/V),citric acid 1.8g/L,Na2HPO4·12H2O 4.0g/L,pH4.0,inoculation volume 7.0%(V/V),culture temperature 26℃,fermentation cycle 7d,liquid level 80mL in 250mL triangle bottle,the the yield of bacterial cellulose reached the peak(18.28g/L)at this time.The optimum processes by shaken cultures were as follows:glucose 30g/L,corn steep liquor 37g/L,ethanol 2.0%(V/V),acetic acid 1.5%(V/V),citric acid 1.8g/L,Na2HPO4·12H2O 4.0g/L,pH4.0,inoculation volume 6.0%(V/V),culture temperature 26℃,fermentation cycle 6d,liquid level 120mL in 250mL triangle bottle,shaker revolutions 110r/min,the the yield of bacterial cellulose reached the peak(12.15 g/L)at this time.3.The fesibility of producing bacterial cellulose using corn starch wastewater as raw material was explored.Under optimum conditions,the the yield of bacterial cellulose reached the peak(15.07g/L and 10.47g/L)by static and shaken cultures of the washing wastewater and process wastewater adding to the corn starch in the ratio of 3:7 after mixing wastewater glucose 25g/L.4.The cellulose content of the static and shaker product was 97.67%and 93.74%,respectively.The water holding capacity and moisture content of the product by these two kinds of fermentation were high.The two IR spectra of product and standard were basically consistent,and the product had the characteristic peaks of cellulose.The microstructure of the cross section and surface structure can be observed by SEM.The molecular weight of the product by static culture and shaking culture were 7.514×104g/mol and 6.316×104g/mol,respectively,determined by GPC,and the molecular weight distributed concentrated.Cellulose crystal structure was proved by XRD-ray.Degradability test showed the bacterial cellulose having good biodegradability.