Mechanism Of Bacterial Cellulose Memberane In Cantonese-style Vinegar Fermentation By Gluconacetobacter Xylinus And A Design Of A Reactor

Traditional Cantonese-style vinegar fermentating with brown rice as raw material and withGluconacetobacter xylinus as microbe adopts the surface static fermentation method. During thefermentation, the covering of bacterial cellulose membrane which is produced by G. xylinus onthe fermented liquid surface and the integrity of cellulose membrane are both effective on theproduction of total acidity and aroma composition. In this paper, comparison of the acidproductivity by G. xylinus between integrated to smashed bacterial cellulose membrane,comparison of the cell account changing regulation to cellulose membrane and fermentationliquid during the productive peak of acid, comparison of the activity of alcohol dehydrogenase(ADH) in the bacterial cellulose membrane which was on to which was under the air-liquidsurface, observation of the integrate membrane and the smashed membrane with the scanningelectron microscope (SEM), comparison of the utilization rate of oxygen by G.xylinus whichbefore to which after the bacterial cellulose membrane synthesized and comparison of the staticfermentation to the shake method in acid productivity and consumption of the oxygen were made.With the solid phase micro extraction (SPME) combined with gas chromatography and massspectra (GC-MS), composites and the origination of the aroma in Cantonese-style vinegar, andthe effective of bacterial cellulose membrane to the aroma was confirmed. Based on the resultabove, a shelf type membranous aerobic fermentation reactor was designed. The mainconclusions are as follow:1. In static method, G. xylinus produced3.75g/100mL of total acidity on144h with the integratebacterial cellulose membrane, while with the smashed membrane during the fermentation, thetotal acidity was only0.36g/100mL on144h, which mean the integration of bacterial cellulosemembrane was significant in acid production. With sinking the membrane into the liquid duringthe fermentation, the total acidity was1.02g/100mL, which illustrated that the productivity ofacid by G. xylinus would be high when the membrane existed on the air-liquid surface.During the peak period of the acid production (72~216h), the G.xylinus cell accounts (colonycounts (1.34±0.32)E+09CFU/g) in integrate bacterial cellulose membrane was larger than it wasin the liquid of the sample which the membrane was smashed (colony counts (1.97±0.51)E+07CFU/mL), which mean the bacterial cellulose was the main part for G.xylinus’ growthmetabolism.During the fermentation, the ADH activity in the bacterial cellulose membrane which existed onthe air-liquid surface had no distinct difference with the ADH activity in which the membranewas sank to the liquid, which mean the ADH activity was not the key to the acid production by G.xylinus. The result of SEM illustrated the bacterial cellulose appeared a sort of net architecture and the G.xylinus cells were combined in it, while the smashed bacterial cellulose membrane could notmaintain the net structure, and the combined cells were less.40h after that the fermentation, the surface of the liquid began to form an integrate bacterialcellulose membrane, and the oxygen consumption of G. xylinus increased rapidly. While thegroup without bacterial cellulose membrane on the air-liquid surface could not use the oxygen inthe air all along, which mean the reason why bacterial cellulose could affect acid productivity ofG. xyliuns was it could facilitate the cells to utilize the oxygen in the air.The oxygen consumption rate of the G. xylinus in the surface static fermentation method wasabout8.1mg/h and the acid productivity was38mg/100mL·h, while the oxygen consumptionrate of the G. xylinus in the shaking fermentation method was about0.31mg/mL and the acidproductivity was13mg/100mL·h, which mean the surface static method was better for G.xylinus to produce acid and to consume oxygen than the shaking method.2. The main composites of the aroma in Cantonese-style rice vinegar were acetic acid, ethylacetate,3-methyl butanol and3-Hydroxy-2-butanone. The original of these aroma compositeswere mainly from the raw brown rice material and the fermentation process. The flavor ofCantonese-style rice vinegar was stronger than the flavor of normal rice vinegar, and the mainflavor composite the ethyl acetate is much higher.The group with integrate bacterial cellulose membrane on the surface lost less aroma.Accounting as the ethyl acetate, the group with the cellulose membrane integrate was7.14%higher than the group with the smashed membrane, which mean the bacterial cellulose has thefunction of reducing the loss of aroma composites.3. Shelf type membranous aerobic fermentation reactor could maintain the integrity of thebacterial cellulose to avoid it to be smashed, and it could continuously produce, and it shortedthe production cycle, and it facilitated the cleaning and maintain process. It is an available wayfor the traditional static surface fermentation method to continuously mechanized producevinegar.