| Recent study had found the integrality of cellulose membrane on the liquid surface had greatimpacts on acetic acid production in Cantonese-style vinegar produced by surface fermentation. Theproducing acid capacity shut down rapidly as long as cellulose integrality was damaged. Thisresearch invented a packing-tower surface fermentation system to stabilize and integrate cellulosemembrane and to conduct fed-batch fermentation to improve the total acidity. The packing-towersurface fermentation with broth containing ethanol as raw material was conducted to aceticfermentation by G. xylinus. A comparison of total acidity and cellulose production was madebetween packing-tower fermentation and static fermentation, then the parameter of packing-towerfermentation was orthogonal optimized. Secondly, it showed the ethanol concentration affected totalacidity and the balance of product through fed-batch fermentation in packing-tower fermentation.The usage period of packing-tower device in semi-continuous fermentation was also experimented.Finally, the study detected the volatile component in Cantonese-style vinegar made bypacking-tower fermentation and gave improvement measures. All researches provided technologyand parameter support for industrialization and serialization of Cantonese-style vinegar producing.Main results as follows:(1)Comparing total acidity, packing-tower fermentation and static fermentation in single batchwas3.87g/100mLå'Œ3.75g/100mL each, and the former was2d faster than the latter one whichshowed the packing-tower fermentation can basically replace the static fermentation. However, thetotal acidity was not raised obviously; Because the surface membrane obstructed liquid and air, theDO in broth was dropped below2.00mg/L in later fermentation period, while the DO inpacking-tower system stabilized between5.00-6.00mg/L owing to circulation and membrane’smovement. It turned out the raise the degree of DO could be an effective way to shortenfermentation hours. The maximum total acidity in packing-tower fermentation was4.12g/100mL,through5.0%(V/V)alcohol content,10.0mL/min circulating velocity,4.0%(V/V) inoculums sizeand50.0%void fraction by orthogonal optimized.(2)Keeping integrity of cellulose, fed-batch fermentation in packing-tower device was peakedto7.07g/100mL in13d, which was13%higher in total acidity and15%shorter in time than static fed-batch fermentation. It proved fed-batch fermentation in packing-tower device was better thanstatic fed-batch fermentation. In low ethanol concentration, G. xylinus growed faster and tended toproduce more cellulose; while in high concentration, the bacteria preferred to conduct acid,extremely high concentration would also inhibit vinegar production. The max total acidity of7.17g/100mL and cellulose production of0.18g/100mL in constant concentration fed-batchfermentation reached premium ethanol conversion on the view of vinegar production. Improvingthe feeding frequency could stabilize the substrate concentration, results showed feeding frequencyimproved from48h to24h and12h, the time was1d and3d shorter to the max acidity, but hardlyimproving the total acidity. Because shorter the feeding period was good to keep ADH activity inhigh degree, and the total acidity was related to ethanol concentration. In semi-continuousfermentation, the G. xylinus producing acid activity was long as24d.(3)Cantonese-style vinegar made by packing-tower surface fermentation was determined bySPME-GC-MS, the main volatile components were acetic acid, ethyl acetate, benzaldhyde,phenethyl alcohol and phenethyl acetate. Time of packing-tower fermentation was20-30d shorterthan traditional ways, so esterification and ketonization of the acids and the alcohols were notcomplete, butyric acid and hexanoic acid and some flavor precursors were also existed. |
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