Study On The Co-production Of Bacterial Cellulose And Pear Vinegar Beverage By Pear Residue Fermentation

In this experiment,Shanxi millet vinegar membrane was used as experimental material to isolate and purify acetobacter on the surface of the membrane.Through morphological observation,physiological and biochemical analysis and 16S rDNA gene sequence analysis,strain 6-5 was identified as Komagataeibacter intermedius,and strain M12 was Komagataeibacter rhaeticus.Both strains of acetobacter had the ability to produce acid and bacterial cellulose,and the alcohol tolerance of acetobacter 6-5 was higher than that of acetobacter M12.The infrared spectrum analysis showed that the membrane was bacterial cellulose.Through single factor test and Box-Behnken design optimization,the optimum fermentation conditions were as follows:glucose 35.82 g/L,citric acid 4.47 g/L,inoculation9.21%,fermentation temperature 30?,culture period 7 days,and the predicted yield(dry mass)of bacterial cellulose was 10.97 g/L.Under these conditions,the yield of bacterial cellulose was(11.94±0.42)g/L,which was very close to the predicted value.The relative error was 0.27%.The sensory evaluation of fermentation broth was carried out by means of evaluation test.Five samples were screened out with higher scores.Sample 2>Sample 10>Sample 12>Sample 14>Sample 6.The total acid content of the five fermentation broths were more than 0.3 g/100mL and soluble solids content of the five fermentation broths were more than 3%,which indicated that all the five fermentation broths belonged to pear vinegar beverages.Sample 2 had the highest total acid content and soluble solids,which were 3.48g/100mL and 5.7 g/100mL,respectively.Sample 2 also had a higher BC yield,(10.20±0.02)g/L.The samples of pear vinegar beverage were analyzed by electronic nose,electronic tongue,PCA and DFA.The results showed that there are differences among the five fermentation broths.The volatile constituents of pear vinegar beverage sample 2 were determined by GC-MS.Twenty-three compounds were identified,including acids,alcohols and esters et al.The characteristic aroma components of the pear vinegar beverage are phenylethyl alcohol,ethyl acetate,ethyl phenylacetate,acetic acid and isovaleric acid.BC/1,3-butanediol composite membrane and BC/tremella polysaccharide composite membrane were prepared by adding 1,3-butanediol and tremella polysaccharide to the prepared bacterial cellulose membrane.Through the analysis of bacteriostasis characteristics,it was found that the bacteriostasis effect of the two composite bacteriostasis membranes onStaphylococcus aureus were better.When the mass fraction of 1,3-butanediol was 5%,the bacteriostasis circle of Staphylococcus aureus could reach 2.292 mm.When the mass fraction of tremella polysacc was 0.3%,the absorbance value of Staphylococcus aureus solution was0.045.For 1,3-butanediol of the same concentration,the loading capacity of BC freeze-dried film was the best.When the mass fraction of 1,3-butanediol was 5%,the loading capacity of BC freeze-dried film could reach 5.22 mg/cm~2.The infrared spectra of BC/tremella fuciformis polysaccharide composite membranes were analyzed.It was found that tremella fuciformis polysaccharides do exist in the BC network structure.